[apple/security.git] / libsecurity_asn1 / lib / secasn1d.c

/*
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is the Netscape security libraries.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1994-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s):
 * 
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
 * instead of those above.  If you wish to allow use of your 
 * version of this file only under the terms of the GPL and not to
 * allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by
 * the GPL.  If you do not delete the provisions above, a recipient
 * may use your version of this file under either the MPL or the
 * GPL.
 */

/*
 * Support for DEcoding ASN.1 data based on BER/DER (Basic/Distinguished
 * Encoding Rules).
 *
 * $Id: secasn1d.c,v 1.16 2004/05/13 15:29:13 dmitch Exp $
 */

#include "secasn1.h"
#include "secerr.h"
#include "assert.h"

#ifdef  NDEBUG
#define DEBUG_DECASN1   0
#else
#define DEBUG_DECASN1   1
#endif

#if             DEBUG_DECASN1
#include <stdio.h>
#define dprintf(args...)                        printf(args)
#else
#define dprintf(args...)
#endif  /* DEBUG_DECASN1 */

typedef enum {
    beforeIdentifier,
    duringIdentifier,
    afterIdentifier,
    beforeLength,
    duringLength,
    afterLength,
    beforeBitString,
    duringBitString,
    duringConstructedString,
    duringGroup,
    duringLeaf,
    duringSaveEncoding,
    duringSequence,
    afterConstructedString,
    afterGroup,
    afterExplicit,
    afterImplicit,
    afterInline,
    afterPointer,
    afterSaveEncoding,
    beforeEndOfContents,
    duringEndOfContents,
    afterEndOfContents,
    beforeChoice,
    duringChoice,
    afterChoice,
    notInUse
} sec_asn1d_parse_place;

#ifndef NDEBUG
#define DEBUG_ASN1D_STATES      1
/* tweakable by debugger, debug only */
int doDumpStates = 0;
#else   /* DEBUG_ASN1D_STATES 0 */
#endif  /* DEBUG_ASN1D_STATES */

#if DEBUG_ASN1D_STATES
static const char *place_names[] = {
    "beforeIdentifier",
    "duringIdentifier",
    "afterIdentifier",
    "beforeLength",
    "duringLength",
    "afterLength",
    "beforeBitString",
    "duringBitString",
    "duringConstructedString",
    "duringGroup",
    "duringLeaf",
    "duringSaveEncoding",
    "duringSequence",
    "afterConstructedString",
    "afterGroup",
    "afterExplicit",
    "afterImplicit",
    "afterInline",
    "afterPointer",
    "afterSaveEncoding",
    "beforeEndOfContents",
    "duringEndOfContents",
    "afterEndOfContents",
    "beforeChoice",
    "duringChoice",
    "afterChoice",
    "notInUse"
};

static const char * const class_names[] = {
    "UNIVERSAL",
    "APPLICATION",
    "CONTEXT_SPECIFIC",
    "PRIVATE"
};

static const char * const method_names[] = { "PRIMITIVE", "CONSTRUCTED" };

static const char * const type_names[] = {
    "END_OF_CONTENTS",
    "BOOLEAN",
    "INTEGER",
    "BIT_STRING",
    "OCTET_STRING",
    "NULL",
    "OBJECT_ID",
    "OBJECT_DESCRIPTOR",
    "(type 08)",
    "REAL",
    "ENUMERATED",
    "EMBEDDED",
    "UTF8_STRING",
    "(type 0d)",
    "(type 0e)",
    "(type 0f)",
    "SEQUENCE",
    "SET",
    "NUMERIC_STRING",
    "PRINTABLE_STRING",
    "T61_STRING",
    "VIDEOTEXT_STRING",
    "IA5_STRING",
    "UTC_TIME",
    "GENERALIZED_TIME",
    "GRAPHIC_STRING",
    "VISIBLE_STRING",
    "GENERAL_STRING",
    "UNIVERSAL_STRING",
    "(type 1d)",
    "BMP_STRING",
    "HIGH_TAG_VALUE"
};

static const char * const flag_names[] = { /* flags, right to left */
    "OPTIONAL",
    "EXPLICIT",
    "ANY",
    "INLINE",
    "POINTER",
    "GROUP",
    "DYNAMIC",
    "SKIP",
    "INNER",
    "SAVE",
    "",            /* decoder ignores "MAY_STREAM", */
    "SKIP_REST",
    "CHOICE",
    "NO_STREAM",
    "DEBUG_BREAK",
    "unknown 08",
    "unknown 10",
    "unknown 20",
    "unknown 40",
    "unknown 80"
};

static int /* bool */
formatKind(unsigned long kind, char * buf)
{
    int i;
    unsigned long k = kind & SEC_ASN1_TAGNUM_MASK;
    unsigned long notag = kind & (SEC_ASN1_CHOICE | SEC_ASN1_POINTER |
        SEC_ASN1_INLINE | SEC_ASN1_ANY | SEC_ASN1_SAVE);

    buf[0] = 0;
    if ((kind & SEC_ASN1_CLASS_MASK) != SEC_ASN1_UNIVERSAL) {
        sprintf(buf, " %s", class_names[(kind & SEC_ASN1_CLASS_MASK) >> 6] );
        buf += strlen(buf);
    }
    if (kind & SEC_ASN1_METHOD_MASK) {
        sprintf(buf, " %s", method_names[1]);
        buf += strlen(buf);
    }
    if ((kind & SEC_ASN1_CLASS_MASK) == SEC_ASN1_UNIVERSAL) {
        if (k || !notag) {
            sprintf(buf, " %s", type_names[k] );
            if ((k == SEC_ASN1_SET || k == SEC_ASN1_SEQUENCE) &&
                (kind & SEC_ASN1_GROUP)) {
                buf += strlen(buf);
                sprintf(buf, "_OF");
            }
        }
    } else {
        sprintf(buf, " [%lu]", k);
    }
    buf += strlen(buf);

    for (k = kind >> 8, i = 0; k; k >>= 1, ++i) {
        if (k & 1) {
            sprintf(buf, " %s", flag_names[i]);
            buf += strlen(buf);
        }
    }
    return notag != 0;
}

#endif /* DEBUG_ASN1D_STATES */

typedef enum {
    allDone,
    decodeError,
    keepGoing,
    needBytes
} sec_asn1d_parse_status;

struct subitem {
    const void *data;
    unsigned long len;          /* only used for substrings */
    struct subitem *next;
};

typedef struct sec_asn1d_state_struct {
    SEC_ASN1DecoderContext *top;
    const SecAsn1Template *theTemplate;
    void *dest;

    void *our_mark;     /* free on completion */

    struct sec_asn1d_state_struct *parent;      /* aka prev */
    struct sec_asn1d_state_struct *child;       /* aka next */

    sec_asn1d_parse_place place;

    /*
     * XXX explain the next fields as clearly as possible...
     */
    unsigned char found_tag_modifiers;
    unsigned char expect_tag_modifiers;
    unsigned long check_tag_mask;
    unsigned long found_tag_number;
    unsigned long expect_tag_number;
    unsigned long underlying_kind;

    unsigned long contents_length;
    unsigned long pending;
    unsigned long consumed;

    int depth;

    /*
     * Bit strings have their length adjusted -- the first octet of the
     * contents contains a value between 0 and 7 which says how many bits
     * at the end of the octets are not actually part of the bit string;
     * when parsing bit strings we put that value here because we need it
     * later, for adjustment of the length (when the whole string is done).
     */
    unsigned int bit_string_unused_bits;

    /*
     * The following are used for indefinite-length constructed strings.
     */
    struct subitem *subitems_head;
    struct subitem *subitems_tail;

    PRPackedBool
        allocate,       /* when true, need to allocate the destination */
        endofcontents,  /* this state ended up parsing end-of-contents octets */
        explicit,       /* we are handling an explicit header */
        indefinite,     /* the current item has indefinite-length encoding */
        missing,        /* an optional field that was not present */
        optional,       /* the template says this field may be omitted */
        substring;      /* this is a substring of a constructed string */
} sec_asn1d_state;

#define IS_HIGH_TAG_NUMBER(n)   ((n) == SEC_ASN1_HIGH_TAG_NUMBER)
#define LAST_TAG_NUMBER_BYTE(b) (((b) & 0x80) == 0)
#define TAG_NUMBER_BITS         7
#define TAG_NUMBER_MASK         0x7f

#define LENGTH_IS_SHORT_FORM(b) (((b) & 0x80) == 0)
#define LONG_FORM_LENGTH(b)     ((b) & 0x7f)

#define HIGH_BITS(field,cnt)    ((field) >> ((sizeof(field) * 8) - (cnt)))


/*
 * An "outsider" will have an opaque pointer to this, created by calling
 * SEC_ASN1DecoderStart().  It will be passed back in to all subsequent
 * calls to SEC_ASN1DecoderUpdate(), and when done it is passed to
 * SEC_ASN1DecoderFinish().
 */
struct sec_DecoderContext_struct {
    PRArenaPool *our_pool;              /* for our internal allocs */
    PRArenaPool *their_pool;            /* for destination structure allocs */
#ifdef SEC_ASN1D_FREE_ON_ERROR          /*
                                         * XXX see comment below (by same
                                         * ifdef) that explains why this
                                         * does not work (need more smarts
                                         * in order to free back to mark)
                                         */
    /*
     * XXX how to make their_mark work in the case where they do NOT
     * give us a pool pointer?
     */
    void *their_mark;                   /* free on error */
#endif

    sec_asn1d_state *current;
    sec_asn1d_parse_status status;

    SEC_ASN1NotifyProc notify_proc;     /* call before/after handling field */
    void *notify_arg;                   /* argument to notify_proc */
    PRBool during_notify;               /* true during call to notify_proc */

    SEC_ASN1WriteProc filter_proc;      /* pass field bytes to this  */
    void *filter_arg;                   /* argument to that function */
    PRBool filter_only;                 /* do not allocate/store fields */
};


/*
 * XXX this is a fairly generic function that may belong elsewhere
 */
static void *
sec_asn1d_alloc (PRArenaPool *poolp, unsigned long len)
{
    void *thing;

    if (poolp != NULL) {
                /*
                * Allocate from the pool.
                */
                thing = PORT_ArenaAlloc (poolp, len);
    } else {
                /*
                * Allocate generically.
                */
                thing = PORT_Alloc (len);
    }

    return thing;
}


/*
 * XXX this is a fairly generic function that may belong elsewhere
 */
static void *
sec_asn1d_zalloc (PRArenaPool *poolp, unsigned long len)
{
    void *thing;

    thing = sec_asn1d_alloc (poolp, len);
    if (thing != NULL)
        PORT_Memset (thing, 0, len);
    return thing;
}


static sec_asn1d_state *
sec_asn1d_push_state (SEC_ASN1DecoderContext *cx,
                      const SecAsn1Template *theTemplate,
                      void *dest, PRBool new_depth)
{
    sec_asn1d_state *state, *new_state;

    state = cx->current;

    PORT_Assert (state == NULL || state->child == NULL);

    if (state != NULL) {
                PORT_Assert (state->our_mark == NULL);
                state->our_mark = PORT_ArenaMark (cx->our_pool);
    }

    new_state = (sec_asn1d_state*)sec_asn1d_zalloc (cx->our_pool, 
                                                    sizeof(*new_state));
    if (new_state == NULL) {
        dprintf("decodeError: zalloc failure\n");
        goto loser;
    }

    new_state->top         = cx;
    new_state->parent      = state;
    new_state->theTemplate = theTemplate;
    new_state->place       = notInUse;
    if (dest != NULL)
                new_state->dest = (char *)dest + theTemplate->offset;

    if (state != NULL) {
        new_state->depth = state->depth;
        if (new_depth) {
            if (++new_state->depth > SEC_ASN1D_MAX_DEPTH) {
                PORT_SetError (SEC_ERROR_BAD_DER);
                goto loser;
            }
        }
        state->child = new_state;
    }

    cx->current = new_state;
    return new_state;

loser:
    cx->status = decodeError;
    if (state != NULL) {
        PORT_ArenaRelease(cx->our_pool, state->our_mark);
        state->our_mark = NULL;
    }
    return NULL;
}


static void
sec_asn1d_scrub_state (sec_asn1d_state *state)
{
    /*
     * Some default "scrubbing".
     * XXX right set of initializations?
     */
    state->place = beforeIdentifier;
    state->endofcontents = PR_FALSE;
    state->indefinite = PR_FALSE;
    state->missing = PR_FALSE;
        
    PORT_Assert (state->consumed == 0);
}


static sec_asn1d_state *
sec_asn1d_get_enclosing_construct(sec_asn1d_state *state)
{
    for (state = state->parent; state; state = state->parent) {
        sec_asn1d_parse_place place = state->place;
        if (place != afterImplicit      &&
            place != afterPointer       &&
            place != afterInline        &&
            place != afterSaveEncoding  &&
            place != duringSaveEncoding &&
            place != duringChoice) {
            
            /* we've walked up the stack to a state that represents
            ** the enclosing construct.  
            */
            break;
        }
    }
    return state;
}


static PRBool
sec_asn1d_parent_allows_EOC(sec_asn1d_state *state)
{
    /* get state of enclosing construct. */
    state = sec_asn1d_get_enclosing_construct(state);
    if (state) {
        sec_asn1d_parse_place place = state->place;
        /* Is it one of the types that permits an unexpected EOC? */
        int eoc_permitted = 
            (place == duringGroup ||
             place == duringConstructedString ||
             state->child->optional);
        return (state->indefinite && eoc_permitted) ? PR_TRUE : PR_FALSE;
    }
    return PR_FALSE;
}


static void
sec_asn1d_notify_before (SEC_ASN1DecoderContext *cx, void *dest, int depth)
{
    if (cx->notify_proc == NULL)
        return;

    cx->during_notify = PR_TRUE;
    (* cx->notify_proc) (cx->notify_arg, PR_TRUE, dest, depth);
    cx->during_notify = PR_FALSE;
}


static void
sec_asn1d_notify_after (SEC_ASN1DecoderContext *cx, void *dest, int depth)
{
    if (cx->notify_proc == NULL)
        return;

    cx->during_notify = PR_TRUE;
    (* cx->notify_proc) (cx->notify_arg, PR_FALSE, dest, depth);
    cx->during_notify = PR_FALSE;
}


static sec_asn1d_state *
sec_asn1d_init_state_based_on_template (sec_asn1d_state *state,
        #ifdef  __APPLE__
        const char *buf         /* for SEC_ASN1GetSubtemplate() */
        #endif
        )
{
    PRBool explicit, optional, universal;
    unsigned char expect_tag_modifiers;
    unsigned long encode_kind, under_kind;
    unsigned long check_tag_mask, expect_tag_number;
        #ifdef  __APPLE__
        unsigned long dynamic;
        #endif


    /* XXX Check that both of these tests are really needed/appropriate. */
    if (state == NULL || state->top->status == decodeError)
                return state;

    encode_kind = state->theTemplate->kind;

    if (encode_kind & SEC_ASN1_SAVE) {
                /*
                * This is a "magic" field that saves away all bytes, allowing
                * the immediately following field to still be decoded from this
                * same spot -- sort of a fork.
                */
                /* check that there are no extraneous bits */
                PORT_Assert (encode_kind == SEC_ASN1_SAVE);
                if (state->top->filter_only) {
                        /*
                        * If we are not storing, then we do not do the SAVE field
                        * at all.  Just move ahead to the "real" field instead,
                        * doing the appropriate notify calls before and after.
                        */
                        sec_asn1d_notify_after (state->top, state->dest, state->depth);
                        /*
                        * Since we are not storing, allow for our current dest value
                        * to be NULL.  (This might not actually occur, but right now I
                        * cannot convince myself one way or the other.)  If it is NULL,
                        * assume that our parent dest can help us out.
                        */
                        if (state->dest == NULL)
                                state->dest = state->parent->dest;
                        else
                                state->dest = 
                                        (char *)state->dest - state->theTemplate->offset;
                        state->theTemplate++;
                        if (state->dest != NULL)
                                state->dest = 
                                        (char *)state->dest + state->theTemplate->offset;
                        sec_asn1d_notify_before (state->top, state->dest, state->depth);
                        encode_kind = state->theTemplate->kind;
                        PORT_Assert ((encode_kind & SEC_ASN1_SAVE) == 0);
                } else {
                        sec_asn1d_scrub_state (state);
                        state->place = duringSaveEncoding;
                        state = sec_asn1d_push_state (state->top, kSecAsn1AnyTemplate,
                                                state->dest, PR_FALSE);
                        if (state != NULL)
                                state = sec_asn1d_init_state_based_on_template (state,
                                        buf /* __APPLE__ */);
                        return state;
                }
    }


    universal = ((encode_kind & SEC_ASN1_CLASS_MASK) == SEC_ASN1_UNIVERSAL)
                ? PR_TRUE : PR_FALSE;

    explicit = (encode_kind & SEC_ASN1_EXPLICIT) ? PR_TRUE : PR_FALSE;
    encode_kind &= ~SEC_ASN1_EXPLICIT;

    optional = (encode_kind & SEC_ASN1_OPTIONAL) ? PR_TRUE : PR_FALSE;
    encode_kind &= ~SEC_ASN1_OPTIONAL;

        #ifdef  __APPLE__
        dynamic = (encode_kind & SEC_ASN1_DYNAMIC) ? PR_TRUE : PR_FALSE;
    encode_kind &= ~SEC_ASN1_DYNAMIC;
        #endif

    PORT_Assert (!(explicit && universal));     /* bad templates */

    encode_kind &= ~SEC_ASN1_DYNAMIC;
    encode_kind &= ~SEC_ASN1_MAY_STREAM;

    if( encode_kind & SEC_ASN1_CHOICE ) {
#if 0   /* XXX remove? */
      sec_asn1d_state *child = sec_asn1d_push_state(state->top, state->theTemplate, state->dest, PR_FALSE);
      if( (sec_asn1d_state *)NULL == child ) {
        return (sec_asn1d_state *)NULL;
      }

      child->allocate = state->allocate;
      child->place = beforeChoice;
      return child;
#else
      state->place = beforeChoice;
      return state;
#endif
    }

    if ((encode_kind & (SEC_ASN1_POINTER | SEC_ASN1_INLINE)) || (!universal
                                                              && !explicit)) {
                const SecAsn1Template *subt;
                void *dest;
                PRBool child_allocate;
                void *subDest;
                
                PORT_Assert ((encode_kind & (SEC_ASN1_ANY | SEC_ASN1_SKIP)) == 0);
        
                sec_asn1d_scrub_state (state);
                child_allocate = PR_FALSE;
        
                if (encode_kind & SEC_ASN1_POINTER) {
                        /*
                        * A POINTER means we need to allocate the destination for
                        * this field.  But, since it may also be an optional field,
                        * we defer the allocation until later; we just record that
                        * it needs to be done.
                        *
                        * There are two possible scenarios here -- one is just a
                        * plain POINTER (kind of like INLINE, except with allocation)
                        * and the other is an implicitly-tagged POINTER.  We don't
                        * need to do anything special here for the two cases, but
                        * since the template definition can be tricky, we do check
                        * that there are no extraneous bits set in encode_kind.
                        *
                        * XXX The same conditions which assert should set an error.
                        */
                        if (universal) {
                                /*
                                 * "universal" means this entry is a standalone POINTER;
                                 * there should be no other bits set in encode_kind.
                                 */
                                PORT_Assert (encode_kind == SEC_ASN1_POINTER);
                        } else {
                                /*
                                 * If we get here we have an implicitly-tagged field
                                 * that needs to be put into a POINTER.  The subtemplate
                                 * will determine how to decode the field, but encode_kind
                                 * describes the (implicit) tag we are looking for.
                                 * The non-tag bits of encode_kind will be ignored by
                                 * the code below; none of them should be set, however,
                                 * except for the POINTER bit itself -- so check that.
                                 */
                                PORT_Assert ((encode_kind & ~SEC_ASN1_TAG_MASK)
                                                == SEC_ASN1_POINTER);
                        }
                        if (!state->top->filter_only)
                                child_allocate = PR_TRUE;
                        dest = NULL;
                        state->place = afterPointer;
                } else {
                        dest = state->dest;
                        if (encode_kind & SEC_ASN1_INLINE) {
                                /* check that there are no extraneous bits */
                                /* FIXME - why are optional and inline mutually 
                                 * exclusive? Delete this assert and see what happens...
                                PORT_Assert (encode_kind == SEC_ASN1_INLINE && !optional);
                                */
                                state->place = afterInline;
                        } else {
                                state->place = afterImplicit;
                        }
                }
        
                state->optional = optional;
                
                subDest = state->dest;
                #if defined(__APPLE__)
                /*
                 * We might be starting the processing of a group or a
                 * set, in which case state->dest is NULL. Get parent's dest,
                 * or grandparent's, etc... just for the use by 
                 * SEC_ASN1GetSubtemplate (specifically, by dynamic
                 * choosers)
                 */
                sec_asn1d_state *tempState = state;
                while(subDest == NULL) {
                        sec_asn1d_state *parent = tempState->parent;
                        if(parent == NULL) {
                                /* Oh well. Not going to work for this template. */
                                break;
                        }
                        subDest = parent->dest;
                        tempState = parent;
                }
                #endif  /* __APPLE__ */
                subt = SEC_ASN1GetSubtemplate (state->theTemplate, subDest,
                        PR_FALSE, buf /* __APPLE__ */);
                state = sec_asn1d_push_state (state->top, subt, dest, PR_FALSE);
                if (state == NULL)
                        return NULL;
        
                state->allocate = child_allocate;
        
                if (universal
                        #ifdef  __APPLE__
                        /* Dynamic: restart with new template */
                        || dynamic
                        #endif
                        ) {
                        state = sec_asn1d_init_state_based_on_template (state,
                                buf /* __APPLE__ */);
                        if (state != NULL) {
                                /*
                                 * If this field is optional, we need to record that on
                                 * the pushed child so it won't fail if the field isn't
                                 * found.  I can't think of a way that this new state
                                 * could already have optional set (which we would wipe
                                 * out below if our local optional is not set) -- but
                                 * just to be sure, assert that it isn't set.
                                 */
                                PORT_Assert (!state->optional);
                                state->optional = optional;
                        }
                        return state;
                }
        
                under_kind = state->theTemplate->kind;
                under_kind &= ~SEC_ASN1_MAY_STREAM;
    } else if (explicit) {
                /*
                 * For explicit, we only need to match the encoding tag next,
                 * then we will push another state to handle the entire inner
                 * part.  In this case, there is no underlying kind which plays
                 * any part in the determination of the outer, explicit tag.
                 * So we just set under_kind to 0, which is not a valid tag,
                 * and the rest of the tag matching stuff should be okay.
                 */
                under_kind = 0;
    } else {
                /*
                * Nothing special; the underlying kind and the given encoding
                * information are the same.
                */
                under_kind = encode_kind;
    }

    /* XXX is this the right set of bits to test here? */
    PORT_Assert ((under_kind & (SEC_ASN1_EXPLICIT 
                                | SEC_ASN1_MAY_STREAM
                                | SEC_ASN1_INLINE | SEC_ASN1_POINTER)) == 0);

    if (encode_kind & (SEC_ASN1_ANY | SEC_ASN1_SKIP)) {
                PORT_Assert (encode_kind == under_kind);
                if (encode_kind & SEC_ASN1_SKIP) {
                        PORT_Assert (!optional);
                        PORT_Assert (encode_kind == SEC_ASN1_SKIP);
                        state->dest = NULL;
                }
                check_tag_mask = 0;
                expect_tag_modifiers = 0;
                expect_tag_number = 0;
    } else {
                check_tag_mask = SEC_ASN1_TAG_MASK;
                expect_tag_modifiers = (unsigned char)encode_kind & SEC_ASN1_TAG_MASK
                                        & ~SEC_ASN1_TAGNUM_MASK;
                /*
                 * XXX This assumes only single-octet identifiers.  To handle
                 * the HIGH TAG form we would need to do some more work, especially
                 * in how to specify them in the template, because right now we
                 * do not provide a way to specify more *tag* bits in encode_kind.
                 */
                expect_tag_number = encode_kind & SEC_ASN1_TAGNUM_MASK;
        
                switch (under_kind & SEC_ASN1_TAGNUM_MASK) {
                case SEC_ASN1_SET:
                        /*
                         * XXX A plain old SET (as opposed to a SET OF) is not 
                         * implemented.
                         * If it ever is, remove this assert...
                         */
                        PORT_Assert ((under_kind & SEC_ASN1_GROUP) != 0);
                        /* fallthru */
                case SEC_ASN1_SEQUENCE:
                        expect_tag_modifiers |= SEC_ASN1_CONSTRUCTED;
                        break;
                case SEC_ASN1_BIT_STRING:
                case SEC_ASN1_BMP_STRING:
                case SEC_ASN1_GENERALIZED_TIME:
                case SEC_ASN1_IA5_STRING:
                case SEC_ASN1_OCTET_STRING:
                case SEC_ASN1_PRINTABLE_STRING:
                case SEC_ASN1_T61_STRING:
                case SEC_ASN1_UNIVERSAL_STRING:
                case SEC_ASN1_UTC_TIME:
                case SEC_ASN1_UTF8_STRING:
                case SEC_ASN1_VISIBLE_STRING:
                        check_tag_mask &= ~SEC_ASN1_CONSTRUCTED;
                        break;
                }
    }

    state->check_tag_mask = check_tag_mask;
    state->expect_tag_modifiers = expect_tag_modifiers;
    state->expect_tag_number = expect_tag_number;
    state->underlying_kind = under_kind;
    state->explicit = explicit;
    state->optional = optional;
    sec_asn1d_scrub_state (state);

    return state;
}


static unsigned long
sec_asn1d_parse_identifier (sec_asn1d_state *state,
                            const char *buf, unsigned long len)
{
    unsigned char byte;
    unsigned char tag_number;

    PORT_Assert (state->place == beforeIdentifier);

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    byte = (unsigned char) *buf;
#ifdef DEBUG_ASN1D_STATES
        if (doDumpStates > 0) {
        char kindBuf[256];
        formatKind(byte, kindBuf);
        printf("Found tag %02x %s\n", byte, kindBuf);
    }
#endif
    tag_number = byte & SEC_ASN1_TAGNUM_MASK;

    if (IS_HIGH_TAG_NUMBER (tag_number)) {
                state->place = duringIdentifier;
                state->found_tag_number = 0;
                /*
                 * Actually, we have no idea how many bytes are pending, but we
                 * do know that it is at least 1.  That is all we know; we have
                 * to look at each byte to know if there is another, etc.
                 */
                state->pending = 1;
    } else {
                if (byte == 0 && sec_asn1d_parent_allows_EOC(state)) {
                        /*
                         * Our parent has indefinite-length encoding, and the
                         * entire tag found is 0, so it seems that we have hit the
                         * end-of-contents octets.  To handle this, we just change
                         * our state to that which expects to get the bytes of the
                         * end-of-contents octets and let that code re-read this byte
                         * so that our categorization of field types is correct.
                         * After that, our parent will then deal with everything else.
                         */
                        state->place = duringEndOfContents;
                        state->pending = 2;
                        state->found_tag_number = 0;
                        state->found_tag_modifiers = 0;
                        /*
                         * We might be an optional field that is, as we now find out,
                         * missing.  Give our parent a clue that this happened.
                         */
                        if (state->optional)
                                state->missing = PR_TRUE;
                        return 0;
                }
                state->place = afterIdentifier;
                state->found_tag_number = tag_number;
    }
    state->found_tag_modifiers = byte & ~SEC_ASN1_TAGNUM_MASK;

    return 1;
}


static unsigned long
sec_asn1d_parse_more_identifier (sec_asn1d_state *state,
                                 const char *buf, unsigned long len)
{
    unsigned char byte;
    int count;

    PORT_Assert (state->pending == 1);
    PORT_Assert (state->place == duringIdentifier);

    if (len == 0) {
        state->top->status = needBytes;
        return 0;
    }

    count = 0;

    while (len && state->pending) {
        if (HIGH_BITS (state->found_tag_number, TAG_NUMBER_BITS) != 0) {
            /*
             * The given high tag number overflows our container;
             * just give up.  This is not likely to *ever* happen.
             */
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
                dprintf("decodeError: parse_more_id high bits oflow\n");
            return 0;
        }

        state->found_tag_number <<= TAG_NUMBER_BITS;

        byte = (unsigned char) buf[count++];
        state->found_tag_number |= (byte & TAG_NUMBER_MASK);

        len--;
        if (LAST_TAG_NUMBER_BYTE (byte))
            state->pending = 0;
    }

    if (state->pending == 0)
        state->place = afterIdentifier;

    return count;
}


static void
sec_asn1d_confirm_identifier (sec_asn1d_state *state)
{
    PRBool match;

    PORT_Assert (state->place == afterIdentifier);

    match = (PRBool)(((state->found_tag_modifiers & state->check_tag_mask)
             == state->expect_tag_modifiers)
            && ((state->found_tag_number & state->check_tag_mask)
                == state->expect_tag_number));
    if (match) {
                state->place = beforeLength;
    } else {
                if (state->optional) {
                        state->missing = PR_TRUE;
                        state->place = afterEndOfContents;
                } else {
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
                        //dprintf("decodeError: sec_asn1d_confirm_identifier\n");
                }
    }
}


static unsigned long
sec_asn1d_parse_length (sec_asn1d_state *state,
                        const char *buf, unsigned long len)
{
    unsigned char byte;

    PORT_Assert (state->place == beforeLength);

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    /*
     * The default/likely outcome.  It may get adjusted below.
     */
    state->place = afterLength;

    byte = (unsigned char) *buf;

    if (LENGTH_IS_SHORT_FORM (byte)) {
                state->contents_length = byte;
    } else {
                state->contents_length = 0;
                state->pending = LONG_FORM_LENGTH (byte);
                if (state->pending == 0) {
                        state->indefinite = PR_TRUE;
                } else {
                        state->place = duringLength;
                }
    }

    /* If we're parsing an ANY, SKIP, or SAVE template, and 
        ** the object being saved is definite length encoded and constructed, 
        ** there's no point in decoding that construct's members.
        ** So, just forget it's constructed and treat it as primitive.
        ** (SAVE appears as an ANY at this point)
        */
    if (!state->indefinite &&
        (state->underlying_kind & (SEC_ASN1_ANY | SEC_ASN1_SKIP))) {
        state->found_tag_modifiers &= ~SEC_ASN1_CONSTRUCTED;
    }
    
    return 1;
}


static unsigned long
sec_asn1d_parse_more_length (sec_asn1d_state *state,
                             const char *buf, unsigned long len)
{
    int count;

    PORT_Assert (state->pending > 0);
    PORT_Assert (state->place == duringLength);

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    count = 0;

    while (len && state->pending) {
                if (HIGH_BITS (state->contents_length, 9) != 0) {
                        /*
                        * The given full content length overflows our container;
                        * just give up.
                        */
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
                        dprintf("decodeError: sec_asn1d_parse_more_length\n");
                        return 0;
                }
        
                state->contents_length <<= 8;
                state->contents_length |= (unsigned char) buf[count++];
        
                len--;
                state->pending--;
    }

    if (state->pending == 0)
                state->place = afterLength;

    return count;
}


static void
sec_asn1d_prepare_for_contents (sec_asn1d_state *state,
        #ifdef  __APPLE__
        const char *buf         /* needed for SEC_ASN1GetSubtemplate */
        #endif
        )
{
    SecAsn1Item *item;
    PRArenaPool *poolp;
    unsigned long alloc_len;

#ifdef DEBUG_ASN1D_STATES
        if (doDumpStates > 0) {
        printf("Found Length %lu %s\n", state->contents_length,
               state->indefinite ? "indefinite" : "");
    }
#endif

    /*
     * XXX I cannot decide if this allocation should exclude the case
     *     where state->endofcontents is true -- figure it out!
     */
    if (state->allocate) {
                void *dest;
        
                PORT_Assert (state->dest == NULL);
                /*
                * We are handling a POINTER or a member of a GROUP, and need to
                * allocate for the data structure.
                */
                dest = sec_asn1d_zalloc (state->top->their_pool,
                                        state->theTemplate->size);
                if (dest == NULL) {
                        dprintf("decodeError: sec_asn1d_prepare_for_contents zalloc\n");
                        state->top->status = decodeError;
                        return;
                }
                /* FIXME _ we're losing the dest pointer after this! */
                state->dest = (char *)dest + state->theTemplate->offset;
        
                /*
                * For a member of a GROUP, our parent will later put the
                * pointer wherever it belongs.  But for a POINTER, we need
                * to record the destination now, in case notify or filter
                * procs need access to it -- they cannot find it otherwise,
                * until it is too late (for one-pass processing).
                */
                if (state->parent->place == afterPointer) {
                        void **placep;
        
                        placep = state->parent->dest;
                        *placep = dest;
                }
    }

    /*
     * Remember, length may be indefinite here!  In that case,
     * both contents_length and pending will be zero.
     */
    state->pending = state->contents_length;

    /* If this item has definite length encoding, and 
    ** is enclosed by a definite length constructed type,
    ** make sure it isn't longer than the remaining space in that 
    ** constructed type.  
    */
    if (state->contents_length > 0) {
        sec_asn1d_state *parent = sec_asn1d_get_enclosing_construct(state);
        if (parent && !parent->indefinite && 
            state->consumed + state->contents_length > parent->pending) {
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
            return;
        }
    }
    
    /*
     * An EXPLICIT is nothing but an outer header, which we have
     * already parsed and accepted.  Now we need to do the inner
     * header and its contents.
     */
    if (state->explicit) {
                state->place = afterExplicit;
                state = sec_asn1d_push_state (state->top,
                                      SEC_ASN1GetSubtemplate(state->theTemplate,
                                                             state->dest,
                                                             PR_FALSE,
                                                                 buf /* __APPLE__ */),
                                      state->dest, PR_TRUE);
                if (state != NULL)
                        state = sec_asn1d_init_state_based_on_template (state,
                                buf /* __APPLE__ */);
                return;
    }

    /*
     * For GROUP (SET OF, SEQUENCE OF), even if we know the length here
     * we cannot tell how many items we will end up with ... so push a
     * state that can keep track of "children" (the individual members
     * of the group; we will allocate as we go and put them all together
     * at the end.
     */
    if (state->underlying_kind & SEC_ASN1_GROUP) {
        /* XXX If this assertion holds (should be able to confirm it via
         * inspection, too) then move this code into the switch statement
         * below under cases SET_OF and SEQUENCE_OF; it will be cleaner.
         */
        PORT_Assert (state->underlying_kind == SEC_ASN1_SET_OF
           || state->underlying_kind == SEC_ASN1_SEQUENCE_OF
           || state->underlying_kind == (SEC_ASN1_SEQUENCE_OF|SEC_ASN1_DYNAMIC)
           || state->underlying_kind == (SEC_ASN1_SET_OF|SEC_ASN1_DYNAMIC)
                     );
        if (state->contents_length != 0 || state->indefinite) {
            const SecAsn1Template *subt;

            state->place = duringGroup;
            subt = SEC_ASN1GetSubtemplate (state->theTemplate, state->dest,
                                           PR_FALSE, buf /* __APPLE__ */);
            state = sec_asn1d_push_state (state->top, subt, NULL, PR_TRUE);
            if (state != NULL) {
                        if (!state->top->filter_only)
                                state->allocate = PR_TRUE;      /* XXX propogate this? */
                        /*
                        * Do the "before" field notification for next in group.
                        */
                        sec_asn1d_notify_before (state->top, state->dest, state->depth);
                        state = sec_asn1d_init_state_based_on_template (state,
                                buf /* __APPLE__ */);
            }
        } else {
            /*
             * A group of zero; we are done.
             * Set state to afterGroup and let that code plant the NULL.
             */
            state->place = afterGroup;
        }
        return;
    }

    switch (state->underlying_kind) {
      case SEC_ASN1_SEQUENCE:
        /*
         * We need to push a child to handle the individual fields.
         */
        state->place = duringSequence;
        state = sec_asn1d_push_state (state->top, state->theTemplate + 1,
                                      state->dest, PR_TRUE);
        if (state != NULL) {
            /*
             * Do the "before" field notification.
             */
            sec_asn1d_notify_before (state->top, state->dest, state->depth);
            state = sec_asn1d_init_state_based_on_template (state,
                        buf /* __APPLE__ */);
        }
        break;

      case SEC_ASN1_SET:        /* XXX SET is not really implemented */
        /*
         * XXX A plain SET requires special handling; scanning of a
         * template to see where a field should go (because by definition,
         * they are not in any particular order, and you have to look at
         * each tag to disambiguate what the field is).  We may never
         * implement this because in practice, it seems to be unused.
         */
        dprintf("decodeError: prepare for contents SEC_ASN1_SET\n");
        PORT_Assert(0);
        PORT_SetError (SEC_ERROR_BAD_DER); /* XXX */
        state->top->status = decodeError;
        break;

      case SEC_ASN1_NULL:
        /*
         * The NULL type, by definition, is "nothing", content length of zero.
         * An indefinite-length encoding is not alloweed.
         */
        if (state->contents_length || state->indefinite) {
            dprintf("decodeError: prepare for contents indefinite NULL\n");
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
            break;
        }
        if (state->dest != NULL) {
            item = (SecAsn1Item *)(state->dest);
            item->Data = NULL;
            item->Length = 0;
        }
        state->place = afterEndOfContents;
        break;

      case SEC_ASN1_BMP_STRING:
        /* Error if length is not divisable by 2 */
        if (state->contents_length % 2) {
           dprintf("decodeError: prepare for contents odd length BMP_STRING\n");
           PORT_SetError (SEC_ERROR_BAD_DER);
           state->top->status = decodeError;
           break;
        }   
        /* otherwise, handle as other string types */
        goto regular_string_type;

      case SEC_ASN1_UNIVERSAL_STRING:
        /* Error if length is not divisable by 4 */
        if (state->contents_length % 4) {
           dprintf("decodeError: prepare for contents odd length UNIV_STRING\n");
           PORT_SetError (SEC_ERROR_BAD_DER);
           state->top->status = decodeError;
           break;
        }   
        /* otherwise, handle as other string types */
        goto regular_string_type;

      case SEC_ASN1_SKIP:
      case SEC_ASN1_ANY:
      case SEC_ASN1_ANY_CONTENTS:
        /*
         * These are not (necessarily) strings, but they need nearly
         * identical handling (especially when we need to deal with
         * constructed sub-pieces), so we pretend they are.
         */
        /* fallthru */
regular_string_type:
      case SEC_ASN1_BIT_STRING:
      case SEC_ASN1_IA5_STRING:
      case SEC_ASN1_OCTET_STRING:
      case SEC_ASN1_PRINTABLE_STRING:
      case SEC_ASN1_T61_STRING:
      case SEC_ASN1_UTC_TIME:
      case SEC_ASN1_UTF8_STRING:
      case SEC_ASN1_VISIBLE_STRING:
        /*
         * We are allocating for a primitive or a constructed string.
         * If it is a constructed string, it may also be indefinite-length.
         * If it is primitive, the length can (legally) be zero.
         * Our first order of business is to allocate the memory for
         * the string, if we can (if we know the length).
         */
        item = (SecAsn1Item *)(state->dest);

        /*
         * If the item is a definite-length constructed string, then
         * the contents_length is actually larger than what we need
         * (because it also counts each intermediate header which we
         * will be throwing away as we go), but it is a perfectly good
         * upper bound that we just allocate anyway, and then concat
         * as we go; we end up wasting a few extra bytes but save a
         * whole other copy.
         */
        alloc_len = state->contents_length;
        poolp = NULL;   /* quiet compiler warnings about unused... */

        if (item == NULL || state->top->filter_only) {
            if (item != NULL) {
                        item->Data = NULL;
                        item->Length = 0;
            }
            alloc_len = 0;
        } else if (state->substring) {
            /*
             * If we are a substring of a constructed string, then we may
             * not have to allocate anything (because our parent, the
             * actual constructed string, did it for us).  If we are a
             * substring and we *do* have to allocate, that means our
             * parent is an indefinite-length, so we allocate from our pool;
             * later our parent will copy our string into the aggregated
             * whole and free our pool allocation.
             */
            if (item->Data == NULL) {
                        PORT_Assert (item->Length == 0);
                        poolp = state->top->our_pool;
            } else {
                        alloc_len = 0;
            }
        } else {
            item->Length = 0;
            item->Data = NULL;
            poolp = state->top->their_pool;
        }

        if (alloc_len || ((! state->indefinite)
                          && (state->subitems_head != NULL))) {
            struct subitem *subitem;
            unsigned long len;

            PORT_Assert (item->Length == 0 && item->Data == NULL);
            /*
             * Check for and handle an ANY which has stashed aside the
             * header (identifier and length) bytes for us to include
             * in the saved contents.
             */
            if (state->subitems_head != NULL) {
                PORT_Assert (state->underlying_kind == SEC_ASN1_ANY);
                for (subitem = state->subitems_head;
                     subitem != NULL; subitem = subitem->next)
                    alloc_len += subitem->len;
            }

            item->Data = (unsigned char*)sec_asn1d_zalloc (poolp, alloc_len);
            if (item->Data == NULL) {
                    dprintf("decodeError: prepare for contents zalloc\n");
                        state->top->status = decodeError;
                        break;
            }

            len = 0;
            for (subitem = state->subitems_head;
                 subitem != NULL; subitem = subitem->next) {
                PORT_Memcpy (item->Data + len, subitem->data, subitem->len);
                len += subitem->len;
            }
            item->Length = len;

            /*
             * Because we use arenas and have a mark set, we later free
             * everything we have allocated, so this does *not* present
             * a memory leak (it is just temporarily left dangling).
             */
            state->subitems_head = state->subitems_tail = NULL;
        }

        if (state->contents_length == 0 && (! state->indefinite)) {
            /*
             * A zero-length simple or constructed string; we are done.
             */
            state->place = afterEndOfContents;
        } else if (state->found_tag_modifiers & SEC_ASN1_CONSTRUCTED) {
            const SecAsn1Template *sub;

            switch (state->underlying_kind) {
              case SEC_ASN1_ANY:
              case SEC_ASN1_ANY_CONTENTS:
                sub = kSecAsn1AnyTemplate;
                break;
              case SEC_ASN1_BIT_STRING:
                sub = kSecAsn1BitStringTemplate;
                break;
              case SEC_ASN1_BMP_STRING:
                sub = kSecAsn1BMPStringTemplate;
                break;
              case SEC_ASN1_GENERALIZED_TIME:
                sub = kSecAsn1GeneralizedTimeTemplate;
                break;
              case SEC_ASN1_IA5_STRING:
                sub = kSecAsn1IA5StringTemplate;
                break;
              case SEC_ASN1_OCTET_STRING:
                sub = kSecAsn1OctetStringTemplate;
                break;
              case SEC_ASN1_PRINTABLE_STRING:
                sub = kSecAsn1PrintableStringTemplate;
                break;
              case SEC_ASN1_T61_STRING:
                sub = kSecAsn1T61StringTemplate;
                break;
              case SEC_ASN1_UNIVERSAL_STRING:
                sub = kSecAsn1UniversalStringTemplate;
                break;
              case SEC_ASN1_UTC_TIME:
                sub = kSecAsn1UTCTimeTemplate;
                break;
              case SEC_ASN1_UTF8_STRING:
                sub = kSecAsn1UTF8StringTemplate;
                break;
              case SEC_ASN1_VISIBLE_STRING:
                sub = kSecAsn1VisibleStringTemplate;
                break;
              case SEC_ASN1_SKIP:
                sub = kSecAsn1SkipTemplate;
                break;
              default:          /* redundant given outer switch cases, but */
                PORT_Assert(0); /* the compiler does not seem to know that, */
                sub = NULL;     /* so just do enough to quiet it. */
                break;
            }

            state->place = duringConstructedString;
            state = sec_asn1d_push_state (state->top, sub, item, PR_TRUE);
            if (state != NULL) {
                state->substring = PR_TRUE;     /* XXX propogate? */
                state = sec_asn1d_init_state_based_on_template (state,
                        buf /* __APPLE__ */);
            }
        } else if (state->indefinite) {
            /*
             * An indefinite-length string *must* be constructed!
             */
            dprintf("decodeError: prepare for contents indefinite not construncted\n");
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
        } else {
            /*
             * A non-zero-length simple string.
             */
            if (state->underlying_kind == SEC_ASN1_BIT_STRING)
                state->place = beforeBitString;
            else
                state->place = duringLeaf;
        }
        break;

      default:
        /*
         * We are allocating for a simple leaf item.
         */
        if (state->contents_length) {
            if (state->dest != NULL) {
                        item = (SecAsn1Item *)(state->dest);
                        item->Length = 0;
                        if (state->top->filter_only) {
                                item->Data = NULL;
                        } else {
                                item->Data = (unsigned char*)
                                                        sec_asn1d_zalloc (state->top->their_pool,
                                                        state->contents_length);
                                if (item->Data == NULL) {
                                        dprintf("decodeError: prepare for contents zalloc\n");
                                        state->top->status = decodeError;
                                        return;
                                }
                        }
            }
            state->place = duringLeaf;
        } else {
            /*
             * An indefinite-length or zero-length item is not allowed.
             * (All legal cases of such were handled above.)
             */
                dprintf("decodeError: prepare for contents indefinite zero len \n");
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
        }
    }
}


static void
sec_asn1d_free_child (sec_asn1d_state *state, PRBool error)
{
    if (state->child != NULL) {
        PORT_Assert (error || state->child->consumed == 0);
        PORT_Assert (state->our_mark != NULL);
        PORT_ArenaRelease (state->top->our_pool, state->our_mark);
        if (error && state->top->their_pool == NULL) {
            /*
             * XXX We need to free anything allocated.
             * At this point, we failed in the middle of decoding. But we
             * can't free the data we previously allocated with PR_Malloc
             * unless we keep track of every pointer. So instead we have a
             * memory leak when decoding fails half-way, unless an arena is
             * used. See bug 95311 .
             */
        }
        state->child = NULL;
        state->our_mark = NULL;
    } else {
        /*
         * It is important that we do not leave a mark unreleased/unmarked.
         * But I do not think we should ever have one set in this case, only
         * if we had a child (handled above).  So check for that.  If this
         * assertion should ever get hit, then we probably need to add code
         * here to release back to our_mark (and then set our_mark to NULL).
         */
        PORT_Assert (state->our_mark == NULL);
    }
    state->place = beforeEndOfContents;
}


/* We have just saved an entire encoded ASN.1 object (type) for a SAVE 
** template, and now in the next template, we are going to decode that 
** saved data  by calling SEC_ASN1DecoderUpdate recursively.
** If that recursive call fails with needBytes, it is a fatal error,
** because the encoded object should have been complete.
** If that recursive call fails with decodeError, it will have already
** cleaned up the state stack, so we must bail out quickly.
**
** These checks of the status returned by the recursive call are now
** done in the caller of this function, immediately after it returns.
*/
static void
sec_asn1d_reuse_encoding (sec_asn1d_state *state)
{
    sec_asn1d_state *child;
    unsigned long consumed;
    SecAsn1Item *item;
    void *dest;


    child = state->child;
    PORT_Assert (child != NULL);

    consumed = child->consumed;
    child->consumed = 0;

    item = (SecAsn1Item *)(state->dest);
    PORT_Assert (item != NULL);

    PORT_Assert (item->Length == consumed);

    /*
     * Free any grandchild.
     */
    sec_asn1d_free_child (child, PR_FALSE);

    /*
     * Notify after the SAVE field.
     */
    sec_asn1d_notify_after (state->top, state->dest, state->depth);

    /*
     * Adjust to get new dest and move forward.
     */
    dest = (char *)state->dest - state->theTemplate->offset;
    state->theTemplate++;
    child->dest = (char *)dest + state->theTemplate->offset;
    child->theTemplate = state->theTemplate;

    /*
     * Notify before the "real" field.
     */
    PORT_Assert (state->depth == child->depth);
    sec_asn1d_notify_before (state->top, child->dest, child->depth);

    /*
     * This will tell DecoderUpdate to return when it is done.
     */
    state->place = afterSaveEncoding;

    /*
     * We already have a child; "push" it by making it current.
     */
    state->top->current = child;

    /*
     * And initialize it so it is ready to parse.
     */
    (void) sec_asn1d_init_state_based_on_template(child,
                (char *) item->Data /* __APPLE__ */);

    /*
     * Now parse that out of our data.
     */
    if (SEC_ASN1DecoderUpdate (state->top,
                               (char *) item->Data, item->Length) != SECSuccess)
        return;
    if (state->top->status == needBytes) {
        return;
    }
    
    PORT_Assert (state->top->current == state);
    PORT_Assert (state->child == child);

    /*
     * That should have consumed what we consumed before.
     */
    PORT_Assert (consumed == child->consumed);
    child->consumed = 0;

    /*
     * Done.
     */
    state->consumed += consumed;
    child->place = notInUse;
    state->place = afterEndOfContents;
}


static unsigned long
sec_asn1d_parse_leaf (sec_asn1d_state *state,
                      const char *buf, unsigned long len)
{
    SecAsn1Item *item;
    unsigned long bufLen;

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    if (state->pending < len)
                len = state->pending;

    bufLen = len;

    item = (SecAsn1Item *)(state->dest);
    if (item != NULL && item->Data != NULL) {
                /* Strip leading zeroes when target is unsigned integer */
                if (state->underlying_kind == SEC_ASN1_INTEGER && /* INTEGER   */
                        item->Length == 0 &&                          /* MSB       */
                        #ifdef  __APPLE__
                        !(state->underlying_kind & SEC_ASN1_SIGNED_INT))
                        #else
                        item->type == siUnsignedInteger)              /* unsigned  */
                        #endif
                {
                        while (len > 1 && buf[0] == 0) {              /* leading 0 */
                                buf++;
                                len--;
                        }
                }
                PORT_Memcpy (item->Data + item->Length, buf, len);
                item->Length += len;
    }
    state->pending -= bufLen;
    if (state->pending == 0)
                state->place = beforeEndOfContents;

    return bufLen;
}


static unsigned long
sec_asn1d_parse_bit_string (sec_asn1d_state *state,
                            const char *buf, unsigned long len)
{
    unsigned char byte;

    /*PORT_Assert (state->pending > 0); */
    PORT_Assert (state->place == beforeBitString);

    if ((state->pending == 0) || (state->contents_length == 1)) {
                if (state->dest != NULL) {
                        SecAsn1Item *item = (SecAsn1Item *)(state->dest);
                        item->Data = NULL;
                        item->Length = 0;
                        state->place = beforeEndOfContents;
                }
                if(state->contents_length == 1) {
                        /* skip over (unused) remainder byte */
                        return 1;
                }
                else {
                        return 0;
                }
    }

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    byte = (unsigned char) *buf;
    if (byte > 7) {
                dprintf("decodeError: parse_bit_string remainder oflow\n");
                PORT_SetError (SEC_ERROR_BAD_DER);
                state->top->status = decodeError;
                return 0;
    }

    state->bit_string_unused_bits = byte;
    state->place = duringBitString;
    state->pending -= 1;

    return 1;
}


static unsigned long
sec_asn1d_parse_more_bit_string (sec_asn1d_state *state,
                                 const char *buf, unsigned long len)
{
    PORT_Assert (state->place == duringBitString);
    if (state->pending == 0) {
        /* An empty bit string with some unused bits is invalid. */
        if (state->bit_string_unused_bits) {
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
        } else {
            /* An empty bit string with no unused bits is OK. */
            state->place = beforeEndOfContents;
        }
        return 0;
    }

    len = sec_asn1d_parse_leaf (state, buf, len);
    if (state->place == beforeEndOfContents && state->dest != NULL) {
        SecAsn1Item *item;

        item = (SecAsn1Item *)(state->dest);
        if (item->Length)
            item->Length = (item->Length << 3) - state->bit_string_unused_bits;
    }

    return len;
}


/*
 * XXX All callers should be looking at return value to detect
 * out-of-memory errors (and stop!).
 */
static struct subitem *
sec_asn1d_add_to_subitems (sec_asn1d_state *state,
                           const void *data, unsigned long len,
                           PRBool copy_data)
{
    struct subitem *thing;

    thing = (struct subitem*)sec_asn1d_zalloc (state->top->our_pool,
                                sizeof (struct subitem));
    if (thing == NULL) {
                dprintf("decodeError: zalloc\n");       
                state->top->status = decodeError;
                return NULL;
    }

    if (copy_data) {
        void *copy;
        copy = sec_asn1d_alloc (state->top->our_pool, len);
        if (copy == NULL) {
                dprintf("decodeError: alloc\n");        
            state->top->status = decodeError;
            return NULL;
        }
        PORT_Memcpy (copy, data, len);
        thing->data = copy;
    } else {
        thing->data = data;
    }
    thing->len = len;
    thing->next = NULL;

    if (state->subitems_head == NULL) {
        PORT_Assert (state->subitems_tail == NULL);
        state->subitems_head = state->subitems_tail = thing;
    } else {
        state->subitems_tail->next = thing;
        state->subitems_tail = thing;
    }

    return thing;
}


static void
sec_asn1d_record_any_header (sec_asn1d_state *state,
                             const char *buf,
                             unsigned long len)
{
    SecAsn1Item *item;

    item = (SecAsn1Item *)(state->dest);
    if (item != NULL && item->Data != NULL) {
        PORT_Assert (state->substring);
        PORT_Memcpy (item->Data + item->Length, buf, len);
        item->Length += len;
    } else {
        sec_asn1d_add_to_subitems (state, buf, len, PR_TRUE);
    }
}


/*
 * We are moving along through the substrings of a constructed string,
 * and have just finished parsing one -- we need to save our child data
 * (if the child was not already writing directly into the destination)
 * and then move forward by one.
 *
 * We also have to detect when we are done:
 *      - a definite-length encoding stops when our pending value hits 0
 *      - an indefinite-length encoding stops when our child is empty
 *        (which means it was the end-of-contents octets)
 */
static void
sec_asn1d_next_substring (sec_asn1d_state *state)
{
    sec_asn1d_state *child;
    SecAsn1Item *item;
    unsigned long child_consumed;
    PRBool done;

    PORT_Assert (state->place == duringConstructedString);
    PORT_Assert (state->child != NULL);

    child = state->child;

    child_consumed = child->consumed;
    child->consumed = 0;
    state->consumed += child_consumed;

    done = PR_FALSE;

    if (state->pending) {
        PORT_Assert (!state->indefinite);
        if( child_consumed > state->pending ) {
                dprintf("decodeError: next_substring consumed > pend\n");       
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
            return;
        }

        state->pending -= child_consumed;
        if (state->pending == 0)
            done = PR_TRUE;
    } else {
        PORT_Assert (state->indefinite);

        item = (SecAsn1Item *)(child->dest);
        if (item != NULL && item->Data != NULL) {
            /*
             * Save the string away for later concatenation.
             */
            PORT_Assert (item->Data != NULL);
            sec_asn1d_add_to_subitems (state, item->Data, item->Length, PR_FALSE);
            /*
             * Clear the child item for the next round.
             */
            item->Data = NULL;
            item->Length = 0;
        }

        /*
         * If our child was just our end-of-contents octets, we are done.
         */
        if (child->endofcontents)
            done = PR_TRUE;
    }

    /*
     * Stop or do the next one.
     */
    if (done) {
        child->place = notInUse;
        state->place = afterConstructedString;
    } else {
        sec_asn1d_scrub_state (child);
        state->top->current = child;
    }
}


/*
 * We are doing a SET OF or SEQUENCE OF, and have just finished an item.
 */
static void
sec_asn1d_next_in_group (sec_asn1d_state *state,
        const char *buf         /* __APPLE__ */)
{
    sec_asn1d_state *child;
    unsigned long child_consumed;

    PORT_Assert (state->place == duringGroup);
    PORT_Assert (state->child != NULL);

    child = state->child;

    child_consumed = child->consumed;
    child->consumed = 0;
    state->consumed += child_consumed;

    /*
     * If our child was just our end-of-contents octets, we are done.
     */
        #ifdef  __APPLE__
        /* 
         * Without the check for !child->indefinite, this path could
         * be taken erroneously if the child is indefinite!
         */
        if(child->endofcontents && !child->indefinite) {
        #else
    if (child->endofcontents) {
        #endif  /* __APPLE__ */
        /* XXX I removed the PORT_Assert (child->dest == NULL) because there
         * was a bug in that a template that was a sequence of which also had
         * a child of a sequence of, in an indefinite group was not working 
         * properly.  This fix seems to work, (added the if statement below),
         * and nothing appears broken, but I am putting this note here just
         * in case. */
        /*
         * XXX No matter how many times I read that comment,
         * I cannot figure out what case he was fixing.  I believe what he
         * did was deliberate, so I am loathe to touch it.  I need to
         * understand how it could ever be that child->dest != NULL but
         * child->endofcontents is true, and why it is important to check
         * that state->subitems_head is NULL.  This really needs to be
         * figured out, as I am not sure if the following code should be
         * compensating for "offset", as is done a little farther below
         * in the more normal case.
         */
        PORT_Assert (state->indefinite);
        PORT_Assert (state->pending == 0);
        if(child->dest && !state->subitems_head) {
            sec_asn1d_add_to_subitems (state, child->dest, 0, PR_FALSE);
            child->dest = NULL;
        }

        child->place = notInUse;
        state->place = afterGroup;
        return;
    }

    /* 
     * Do the "after" field notification for next in group.
     */
    sec_asn1d_notify_after (state->top, child->dest, child->depth);

    /*
     * Save it away (unless we are not storing).
     */
    if (child->dest != NULL) {
        void *dest;

        dest = child->dest;
        dest = (char *)dest - child->theTemplate->offset;
        sec_asn1d_add_to_subitems (state, dest, 0, PR_FALSE);
        child->dest = NULL;
    }

    /*
     * Account for those bytes; see if we are done.
     */
    if (state->pending) {
        PORT_Assert (!state->indefinite);
        if( child_consumed > state->pending ) {
                dprintf("decodeError: next_in_group consumed > pend\n");        
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
            return;
        }

        state->pending -= child_consumed;
        if (state->pending == 0) {
            child->place = notInUse;
            state->place = afterGroup;
            return;
        }
    }

    /*
     * Do the "before" field notification for next item in group.
     */
    sec_asn1d_notify_before (state->top, child->dest, child->depth);

    /*
     * Now we do the next one.
     */
    sec_asn1d_scrub_state (child);

    /* Initialize child state from the template */
    sec_asn1d_init_state_based_on_template(child, buf /* __APPLE__ */);

    state->top->current = child;
}


/*
 * We are moving along through a sequence; move forward by one,
 * (detecting end-of-sequence when it happens).
 * XXX The handling of "missing" is ugly.  Fix it.
 */
static void
sec_asn1d_next_in_sequence (sec_asn1d_state *state,
        const char *buf /* __APPLE__ */)
{
    sec_asn1d_state *child;
    unsigned long child_consumed;
    PRBool child_missing;

    PORT_Assert (state->place == duringSequence);
    PORT_Assert (state->child != NULL);

    child = state->child;

    /*
     * Do the "after" field notification.
     */
    sec_asn1d_notify_after (state->top, child->dest, child->depth);

    child_missing = (PRBool) child->missing;
    child_consumed = child->consumed;
    child->consumed = 0;

    /*
     * Take care of accounting.
     */
    if (child_missing) {
                PORT_Assert (child->optional);
    } else {
                state->consumed += child_consumed;
                /*
                 * Free any grandchild.
                 */
                sec_asn1d_free_child (child, PR_FALSE);
                if (state->pending) {
                        PORT_Assert (!state->indefinite);
                        if( child_consumed > state->pending ) {
                                dprintf("decodeError: next_in_seq consumed > pend\n");  
                                PORT_SetError (SEC_ERROR_BAD_DER);
                                state->top->status = decodeError;
                                return;
                        }
                        state->pending -= child_consumed;
                        if (state->pending == 0) {
                        child->theTemplate++;
                        while (child->theTemplate->kind != 0) {
                                if ((child->theTemplate->kind & SEC_ASN1_OPTIONAL) == 0) {
                                        dprintf("decodeError: next_in_seq child not opt\n");    
                                        PORT_SetError (SEC_ERROR_BAD_DER);
                                        state->top->status = decodeError;
                                        return;
                                }
                                child->theTemplate++;
                        }
                        child->place = notInUse;
                        state->place = afterEndOfContents;
                        return;
                        }
                }
    }

    /*
     * Move forward.
     */
    child->theTemplate++;
    if (child->theTemplate->kind == 0) {
        /*
         * We are done with this sequence.
         */
        child->place = notInUse;
        if (state->pending) {
                dprintf("decodeError: next_in_seq notInUse still pending\n");   
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
        } else if (child_missing) {
            /*
             * We got to the end, but have a child that started parsing
             * and ended up "missing".  The only legitimate reason for
             * this is that we had one or more optional fields at the
             * end of our sequence, and we were encoded indefinite-length,
             * so when we went looking for those optional fields we
             * found our end-of-contents octets instead.
             * (Yes, this is ugly; dunno a better way to handle it.)
             * So, first confirm the situation, and then mark that we
             * are done.
             */
            if (state->indefinite && child->endofcontents) {
                PORT_Assert (child_consumed == 2);
                if( child_consumed != 2 ) {
                        dprintf("decodeError: next_in_seq indef len != 2\n");   
                    PORT_SetError (SEC_ERROR_BAD_DER);
                    state->top->status = decodeError;
                } else {
                    state->consumed += child_consumed;
                    state->place = afterEndOfContents;
                }
            } else {
                        dprintf("decodeError: next_in_seq !indef, child missing\n");    
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
            }
        } else {
            /*
             * We have to finish out, maybe reading end-of-contents octets;
             * let the normal logic do the right thing.
             */
            state->place = beforeEndOfContents;
        }
    } else {
        unsigned char child_found_tag_modifiers = 0;
        unsigned long child_found_tag_number = 0;

        /*
         * Reset state and push.
         */
        if (state->dest != NULL)
            child->dest = (char *)state->dest + child->theTemplate->offset;

        /*
         * Do the "before" field notification.
         */
        sec_asn1d_notify_before (state->top, child->dest, child->depth);

        if (child_missing) { /* if previous child was missing, copy the tag data we already have */
            child_found_tag_modifiers = child->found_tag_modifiers;
            child_found_tag_number = child->found_tag_number;
        }
        state->top->current = child;
        child = sec_asn1d_init_state_based_on_template (child, 
                buf /* __APPLE__ */);
        if (child_missing) {
            child->place = afterIdentifier;
            child->found_tag_modifiers = child_found_tag_modifiers;
            child->found_tag_number = child_found_tag_number;
            child->consumed = child_consumed;
            if (child->underlying_kind == SEC_ASN1_ANY
                && !child->top->filter_only) {
                /*
                 * If the new field is an ANY, and we are storing, then
                 * we need to save the tag out.  We would have done this
                 * already in the normal case, but since we were looking
                 * for an optional field, and we did not find it, we only
                 * now realize we need to save the tag.
                 */
                unsigned char identifier;

                /*
                 * Check that we did not end up with a high tag; for that
                 * we need to re-encode the tag into multiple bytes in order
                 * to store it back to look like what we parsed originally.
                 * In practice this does not happen, but for completeness
                 * sake it should probably be made to work at some point.
                 */
                PORT_Assert (child_found_tag_number < SEC_ASN1_HIGH_TAG_NUMBER);
                identifier = (unsigned char)(child_found_tag_modifiers | child_found_tag_number);
                sec_asn1d_record_any_header (child, (char *) &identifier, 1);
            }
        }
    }
}


static void
sec_asn1d_concat_substrings (sec_asn1d_state *state)
{
    PORT_Assert (state->place == afterConstructedString);

    if (state->subitems_head != NULL) {
        struct subitem *substring;
        unsigned long alloc_len, item_len;
        unsigned char *where;
        SecAsn1Item *item;
        PRBool is_bit_string;

        item_len = 0;
        is_bit_string = (state->underlying_kind == SEC_ASN1_BIT_STRING)
                        ? PR_TRUE : PR_FALSE;

        substring = state->subitems_head;
        while (substring != NULL) {
            /*
             * All bit-string substrings except the last one should be
             * a clean multiple of 8 bits.
             */
            if (is_bit_string && (substring->next == NULL)
                              && (substring->len & 0x7)) {
                        dprintf("decodeError: sec_asn1d_concat_substrings align\n");    
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
                        return;
            }
            item_len += substring->len;
            substring = substring->next;
        }

        if (is_bit_string) {
#ifdef XP_WIN16         /* win16 compiler gets an internal error otherwise */
            alloc_len = (((long)item_len + 7) / 8);
#else
            alloc_len = ((item_len + 7) >> 3);
#endif
        } else {
            /*
             * Add 2 for the end-of-contents octets of an indefinite-length
             * ANY that is *not* also an INNER.  Because we zero-allocate
             * below, all we need to do is increase the length here.
             */
            if (state->underlying_kind == SEC_ASN1_ANY && state->indefinite)
                item_len += 2; 
            alloc_len = item_len;
        }

        item = (SecAsn1Item *)(state->dest);
        PORT_Assert (item != NULL);
        PORT_Assert (item->Data == NULL);
        item->Data = (unsigned char*)sec_asn1d_zalloc (state->top->their_pool, 
                                                       alloc_len);
        if (item->Data == NULL) {
                dprintf("decodeError: zalloc\n");       
            state->top->status = decodeError;
            return;
        }
        item->Length = item_len;

        where = item->Data;
        substring = state->subitems_head;
        while (substring != NULL) {
            if (is_bit_string)
                item_len = (substring->len + 7) >> 3;
            else
                item_len = substring->len;
            PORT_Memcpy (where, substring->data, item_len);
            where += item_len;
            substring = substring->next;
        }

        /*
         * Because we use arenas and have a mark set, we later free
         * everything we have allocated, so this does *not* present
         * a memory leak (it is just temporarily left dangling).
         */
        state->subitems_head = state->subitems_tail = NULL;
    }

    state->place = afterEndOfContents;
}


static void
sec_asn1d_concat_group (sec_asn1d_state *state)
{
    const void ***placep;

    PORT_Assert (state->place == afterGroup);

    placep = (const void***)state->dest;
    PORT_Assert(state->subitems_head == NULL || placep != NULL);
    if (placep != NULL) {
        struct subitem *item;
        const void **group;
        int count;

        count = 0;
        item = state->subitems_head;
        while (item != NULL) {
            PORT_Assert (item->next != NULL || item == state->subitems_tail);
            count++;
            item = item->next;
        }

        group = (const void**)sec_asn1d_zalloc (state->top->their_pool,
                                  (count + 1) * (sizeof(void *)));
        if (group == NULL) {
                dprintf("decodeError: zalloc\n");       
            state->top->status = decodeError;
            return;
        }

        *placep = group;

        item = state->subitems_head;
        while (item != NULL) {
            *group++ = item->data;
            item = item->next;
        }
        *group = NULL;

        /*
         * Because we use arenas and have a mark set, we later free
         * everything we have allocated, so this does *not* present
         * a memory leak (it is just temporarily left dangling).
         */
        state->subitems_head = state->subitems_tail = NULL;
    }

    state->place = afterEndOfContents;
}

/*
 * For those states that push a child to handle a subtemplate,
 * "absorb" that child (transfer necessary information).
 */
static void
sec_asn1d_absorb_child (sec_asn1d_state *state)
{
    /*
     * There is absolutely supposed to be a child there.
     */
    PORT_Assert (state->child != NULL);

    /*
     * Inherit the missing status of our child, and do the ugly
     * backing-up if necessary.
     */
    state->missing = state->child->missing;
    if (state->missing) {
        state->found_tag_number = state->child->found_tag_number;
        state->found_tag_modifiers = state->child->found_tag_modifiers;
        state->endofcontents = state->child->endofcontents;
    }

    /*
     * Add in number of bytes consumed by child.
     * (Only EXPLICIT should have already consumed bytes itself.)
     */
    PORT_Assert (state->place == afterExplicit || state->consumed == 0);
    state->consumed += state->child->consumed;

    /*
     * Subtract from bytes pending; this only applies to a definite-length
     * EXPLICIT field.
     */
    if (state->pending) {
        PORT_Assert (!state->indefinite);
        PORT_Assert (state->place == afterExplicit);

        /*
         * If we had a definite-length explicit, then what the child
         * consumed should be what was left pending.
         */
        if (state->pending != state->child->consumed) {
            if (state->pending < state->child->consumed) {
                        dprintf("decodeError: absorb_child pending < consumed\n");      
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
                        return;
            }
            /*
             * Okay, this is a hack.  It *should* be an error whether
             * pending is too big or too small, but it turns out that
             * we had a bug in our *old* DER encoder that ended up
             * counting an explicit header twice in the case where
             * the underlying type was an ANY.  So, because we cannot
             * prevent receiving these (our own certificate server can
             * send them to us), we need to be lenient and accept them.
             * To do so, we need to pretend as if we read all of the
             * bytes that the header said we would find, even though
             * we actually came up short.
             */
            state->consumed += (state->pending - state->child->consumed);
        }
        state->pending = 0;
    }

    /*
     * Indicate that we are done with child.
     */
    state->child->consumed = 0;

    /*
     * And move on to final state.
     * (Technically everybody could move to afterEndOfContents except
     * for an indefinite-length EXPLICIT; for simplicity though we assert
     * that but let the end-of-contents code do the real determination.)
     */
    PORT_Assert (state->place == afterExplicit || (! state->indefinite));
    state->place = beforeEndOfContents;
}


static void
sec_asn1d_prepare_for_end_of_contents (sec_asn1d_state *state)
{
    PORT_Assert (state->place == beforeEndOfContents);

    if (state->indefinite) {
        state->place = duringEndOfContents;
        state->pending = 2;
    } else {
        state->place = afterEndOfContents;
    }
}


static unsigned long
sec_asn1d_parse_end_of_contents (sec_asn1d_state *state,
                                 const char *buf, unsigned long len)
{
    unsigned int i;

    PORT_Assert (state->pending <= 2);
    PORT_Assert (state->place == duringEndOfContents);

    if (len == 0) {
                state->top->status = needBytes;
                return 0;
    }

    if (state->pending < len)
        len = state->pending;

    for (i = 0; i < len; i++) {
        if (buf[i] != 0) {
            /*
             * We expect to find only zeros; if not, just give up.
             */
                dprintf("decodeError: end of contents non zero\n");     
            PORT_SetError (SEC_ERROR_BAD_DER);
            state->top->status = decodeError;
            return 0;
        }
    }

    state->pending -= len;

    if (state->pending == 0) {
        state->place = afterEndOfContents;
        state->endofcontents = PR_TRUE;
    }

    return len;
}


static void
sec_asn1d_pop_state (sec_asn1d_state *state)
{
#if 0   /* XXX I think this should always be handled explicitly by parent? */
    /*
     * Account for our child.
     */
    if (state->child != NULL) {
        state->consumed += state->child->consumed;
        if (state->pending) {
            PORT_Assert (!state->indefinite);
            if( state->child->consumed > state->pending ) {
                        dprintf("decodeError: pop_state pending < consumed\n"); 
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
            } else {
                        state->pending -= state->child->consumed;
            }
        }
        state->child->consumed = 0;
    }
#endif  /* XXX */

    /*
     * Free our child.
     */
    sec_asn1d_free_child (state, PR_FALSE);

    /*
     * Just make my parent be the current state.  It will then clean
     * up after me and free me (or reuse me).
     */
    state->top->current = state->parent;
}

static sec_asn1d_state *
sec_asn1d_before_choice (sec_asn1d_state *state, const char *buf /* __APPLE__ */)
{
        sec_asn1d_state *child;

        if( state->allocate ) {
                void *dest;
        
                dest = sec_asn1d_zalloc(state->top->their_pool, 
                        state->theTemplate->size);
                if( (void *)NULL == dest ) {
                        dprintf("decodeError: zalloc\n");       
                        state->top->status = decodeError;
                        return (sec_asn1d_state *)NULL;
                }
        
                state->dest = (char *)dest + state->theTemplate->offset;
        }

        child = sec_asn1d_push_state(state->top, state->theTemplate + 1, 
                                     (char *)state->dest - state->theTemplate->offset, 
                                     PR_FALSE);
        if( (sec_asn1d_state *)NULL == child ) {
                return (sec_asn1d_state *)NULL;
        }
        
        sec_asn1d_scrub_state(child);
        child = sec_asn1d_init_state_based_on_template(child, 
                buf /* __APPLE__ */);
        if( (sec_asn1d_state *)NULL == child ) {
                return (sec_asn1d_state *)NULL;
        }
        
        child->optional = PR_TRUE;
        
        state->place = duringChoice;
        
        return child;
}

static sec_asn1d_state *
sec_asn1d_during_choice (sec_asn1d_state *state, const char *buf /* __APPLE__ */)
{
  sec_asn1d_state *child = state->child;
  
  PORT_Assert((sec_asn1d_state *)NULL != child);

  if( child->missing ) {
    unsigned char child_found_tag_modifiers = 0;
    unsigned long child_found_tag_number = 0;
    void *        dest;
    
    state->consumed += child->consumed;

    if (child->endofcontents) {
        /* This choice is probably the first item in a GROUP
        ** (e.g. SET_OF) that was indefinite-length encoded.
        ** We're actually at the end of that GROUP.
        ** We look up the stack to be sure that we find
        ** a state with indefinite length encoding before we
        ** find a state (like a SEQUENCE) that is definite.
        */
        child->place = notInUse;
        state->place = afterChoice;
        state->endofcontents = PR_TRUE;  /* propagate this up */
        if (sec_asn1d_parent_allows_EOC(state))
            return state;
        dprintf("decodeError: during_choice child at EOC by parent does not allow EOC\n");      
        PORT_SetError(SEC_ERROR_BAD_DER);
        state->top->status = decodeError;
        return NULL;
    }

    dest = (char *)child->dest - child->theTemplate->offset;    
    child->theTemplate++;

    if( 0 == child->theTemplate->kind ) {
      /* Ran out of choices */
          dprintf("decodeError: during_choice ran out of choice\n");    
      PORT_SetError(SEC_ERROR_BAD_DER);
      state->top->status = decodeError;
      return (sec_asn1d_state *)NULL;
    }
    child->dest = (char *)dest + child->theTemplate->offset;

    /* cargo'd from next_in_sequence innards */
    if( state->pending ) {
      PORT_Assert(!state->indefinite);
      if( child->consumed > state->pending ) {
                        dprintf("decodeError: during_choice consumed > pending\n");     
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        state->top->status = decodeError;
                        return NULL;
      }
      state->pending -= child->consumed;
      if( 0 == state->pending ) {
        /* XXX uh.. not sure if I should have stopped this
         * from happening before. */
        PORT_Assert(0);
        PORT_SetError(SEC_ERROR_BAD_DER);
                dprintf("decodeError: during_choice !pending\n");       
        state->top->status = decodeError;
        return (sec_asn1d_state *)NULL;
      }
    }

    child->consumed = 0;
    sec_asn1d_scrub_state(child);

    /* move it on top again */
    state->top->current = child;

    child_found_tag_modifiers = child->found_tag_modifiers;
    child_found_tag_number = child->found_tag_number;

    child = sec_asn1d_init_state_based_on_template(child, buf /* __APPLE__*/);
    if( (sec_asn1d_state *)NULL == child ) {
      return (sec_asn1d_state *)NULL;
    }

    /* copy our findings to the new top */
    child->found_tag_modifiers = child_found_tag_modifiers;
    child->found_tag_number = child_found_tag_number;

    child->optional = PR_TRUE;
    child->place = afterIdentifier;

    return child;
  }
  if( (void *)NULL != state->dest ) {
      /* Store the enum */
      int *which = (int *)state->dest;
      *which = (int)child->theTemplate->size;
  }

  child->place = notInUse;

  state->place = afterChoice;
  return state;
}

static void
sec_asn1d_after_choice (sec_asn1d_state *state)
{
  state->consumed += state->child->consumed;
  state->child->consumed = 0;
  state->place = afterEndOfContents;
  sec_asn1d_pop_state(state);
}

#if 0
unsigned long
sec_asn1d_uinteger(SecAsn1Item *src)
{
    unsigned long value;
    int len;

    if (src->Length > 5 || (src->Length > 4 && src->Data[0] == 0))
        return 0;

    value = 0;
    len = src->Length;
    while (len) {
        value <<= 8;
        value |= src->Data[--len];
    }
    return value;
}
#endif

SECStatus
SEC_ASN1DecodeInteger(SecAsn1Item *src, unsigned long *value)
{
    unsigned long v;
    unsigned int i;
    
    if (src == NULL) {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        return SECFailure;
    }

    if (src->Length > sizeof(unsigned long)) {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        return SECFailure;
    }

    if (src->Data == NULL) {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        return SECFailure;
    }

    if (src->Data[0] & 0x80)
        v = -1;         /* signed and negative - start with all 1's */
    else
        v = 0;

    for (i= 0; i < src->Length; i++) {
        /* shift in next byte */
        v <<= 8;
        v |= src->Data[i];
    }
    *value = v;
    return SECSuccess;
}

#ifdef DEBUG_ASN1D_STATES
static void
dump_states(SEC_ASN1DecoderContext *cx)
{
    sec_asn1d_state *state;
    char kindBuf[256];
    
    for (state = cx->current; state->parent; state = state->parent) {
        ;
    }
    
    for (; state; state = state->child) {
        int i;
        for (i = 0; i < state->depth; i++) {
            printf("  ");
        }
        
        i = formatKind(state->theTemplate->kind, kindBuf);
        printf("%s: tmpl %p, kind%s",
               (state == cx->current) ? "STATE" : "State",
               state->theTemplate,
               kindBuf);
        printf(" %s", (state->place <= notInUse)
               ? place_names[ state->place ]
               : "(undefined)");
        if (!i)
            printf(", expect 0x%02lx",
                   state->expect_tag_number | state->expect_tag_modifiers);
        
        printf("%s%s%s %lu\n",
               state->indefinite    ? ", indef"   : "",
               state->missing       ? ", miss"    : "",
               state->endofcontents ? ", EOC"     : "",
               state->pending
               );
    }
    
    return;
}
#endif /* DEBUG_ASN1D_STATES */

SECStatus
SEC_ASN1DecoderUpdate (SEC_ASN1DecoderContext *cx,
                       const char *buf, size_t len)
{
    sec_asn1d_state *state = NULL;
    unsigned long consumed;
    SEC_ASN1EncodingPart what;
    sec_asn1d_state *stateEnd = cx->current;

    if (cx->status == needBytes)
                cx->status = keepGoing;

    while (cx->status == keepGoing) {
                state = cx->current;
                what = SEC_ASN1_Contents;
                consumed = 0;
                #if DEBUG_ASN1D_STATES
                if (doDumpStates > 1) {
                    printf("\nPLACE = %s, next byte = 0x%02x, %p[%lu]\n",
                           (state->place <= notInUse) ?
                           place_names[ state->place ] : "(undefined)",
                           (unsigned int)((unsigned char *)buf)[ consumed ],
                           buf, consumed);
                    dump_states(cx);
                }
                #endif /* DEBUG_ASN1D_STATES */
                switch (state->place) {
                case beforeIdentifier:
                        consumed = sec_asn1d_parse_identifier (state, buf, len);
                        what = SEC_ASN1_Identifier;
                        break;
                case duringIdentifier:
                        consumed = sec_asn1d_parse_more_identifier (state, buf, len);
                        what = SEC_ASN1_Identifier;
                        break;
                case afterIdentifier:
                        sec_asn1d_confirm_identifier (state);
                        break;
                case beforeLength:
                        consumed = sec_asn1d_parse_length (state, buf, len);
                        what = SEC_ASN1_Length;
                        break;
                case duringLength:
                        consumed = sec_asn1d_parse_more_length (state, buf, len);
                        what = SEC_ASN1_Length;
                        break;
                case afterLength:
                        sec_asn1d_prepare_for_contents (state, buf);
                        break;
                case beforeBitString:
                        consumed = sec_asn1d_parse_bit_string (state, buf, len);
                        break;
                case duringBitString:
                        consumed = sec_asn1d_parse_more_bit_string (state, buf, len);
                        break;
                case duringConstructedString:
                        sec_asn1d_next_substring (state);
                        break;
                case duringGroup:
                        sec_asn1d_next_in_group (state, buf);
                        break;
                case duringLeaf:
                        consumed = sec_asn1d_parse_leaf (state, buf, len);
                        break;
                case duringSaveEncoding:
                        sec_asn1d_reuse_encoding (state);
                        if (cx->status == decodeError) {
                            /* recursive call has already popped all states from stack.
                            ** Bail out quickly.
                            */
                            return SECFailure;
                        }
                        if (cx->status == needBytes) {
                            /* recursive call wanted more data. Fatal. Clean up below. */
                            PORT_SetError (SEC_ERROR_BAD_DER);
                            cx->status = decodeError;
                        }
                        break;
                case duringSequence:
                        sec_asn1d_next_in_sequence (state, buf);
                        break;
                case afterConstructedString:
                        sec_asn1d_concat_substrings (state);
                        break;
                case afterExplicit:
                case afterImplicit:
                case afterInline:
                case afterPointer:
                        sec_asn1d_absorb_child (state);
                        break;
                case afterGroup:
                        sec_asn1d_concat_group (state);
                        break;
                case afterSaveEncoding:
                        /* SEC_ASN1DecoderUpdate has called itself recursively to 
                        ** decode SAVEd encoded data, and now is done decoding that.
                        ** Return to the calling copy of SEC_ASN1DecoderUpdate.
                        */
                        return SECSuccess;
                case beforeEndOfContents:
                        sec_asn1d_prepare_for_end_of_contents (state);
                        break;
                case duringEndOfContents:
                        consumed = sec_asn1d_parse_end_of_contents (state, buf, len);
                        what = SEC_ASN1_EndOfContents;
                        break;
                case afterEndOfContents:
                        sec_asn1d_pop_state (state);
                        break;
                        case beforeChoice:
                                state = sec_asn1d_before_choice(state, buf);
                                break;
                        case duringChoice:
                                state = sec_asn1d_during_choice(state, buf);
                                break;
                        case afterChoice:
                                sec_asn1d_after_choice(state);
                                break;
                case notInUse:
                default:
                        /* This is not an error, but rather a plain old BUG! */
                        PORT_Assert (0);
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        dprintf("decodeError: decoder update bad state->place\n");      
                        cx->status = decodeError;
                        break;
                }
        
                if (cx->status == decodeError)
                        break;
        
                /* We should not consume more than we have.  */
                PORT_Assert (consumed <= len);
                if( consumed > len ) {
                        dprintf("decodeError: decoder update consumed > len\n");        
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        cx->status = decodeError;
                        break;
                }
        
                /* It might have changed, so we have to update our local copy.  */
                state = cx->current;
        
                /* If it is NULL, we have popped all the way to the top.  */
                if (state == NULL) {
                        PORT_Assert (consumed == 0);
        #if 0   
                /* XXX I want this here, but it seems that we have situations (like
                 * downloading a pkcs7 cert chain from some issuers) that give us a
                 * length which is greater than the entire encoding.  So, we cannot
                 * have this be an error.
                 */
                        if (len > 0) {
                                dprintf("decodeError: decoder update nonzero len\n");   
                                PORT_SetError (SEC_ERROR_BAD_DER);
                                cx->status = decodeError;
                        }
                        else
        #endif
                        cx->status = allDone;
                        break;
                }
                else if (state->theTemplate->kind == SEC_ASN1_SKIP_REST) {
                        cx->status = allDone;
                        break;
                }
                
                if (consumed == 0)
                        continue;
        
                /*
                 * The following check is specifically looking for an ANY
                 * that is *not* also an INNER, because we need to save aside
                 * all bytes in that case -- the contents parts will get
                 * handled like all other contents, and the end-of-contents
                 * bytes are added by the concat code, but the outer header
                 * bytes need to get saved too, so we do them explicitly here.
                 */
                if (state->underlying_kind == SEC_ASN1_ANY
                        && !cx->filter_only && (what == SEC_ASN1_Identifier
                                                || what == SEC_ASN1_Length)) {
                        sec_asn1d_record_any_header (state, buf, consumed);
                }
        
                /*
                 * We had some number of good, accepted bytes.  If the caller
                 * has registered to see them, pass them along.
                 */
                if (state->top->filter_proc != NULL) {
                        int depth;
        
                        depth = state->depth;
                        if (what == SEC_ASN1_EndOfContents && !state->indefinite) {
                                PORT_Assert (state->parent != NULL
                                                && state->parent->indefinite);
                                depth--;
                                PORT_Assert (depth == state->parent->depth);
                        }
                        (* state->top->filter_proc) (state->top->filter_arg,
                                                buf, consumed, depth, what);
                }
        
                state->consumed += consumed;
                buf += consumed;
                len -= consumed;
    }   /* main decode loop */

    if (cx->status == decodeError) {
                while (state != NULL && stateEnd->parent!=state) {
                        sec_asn1d_free_child (state, PR_TRUE);
                        state = state->parent;
                }
#ifdef SEC_ASN1D_FREE_ON_ERROR  /*
                                 * XXX This does not work because we can
                                 * end up leaving behind dangling pointers
                                 * to stuff that was allocated.  In order
                                 * to make this really work (which would
                                 * be a good thing, I think), we need to
                                 * keep track of every place/pointer that
                                 * was allocated and make sure to NULL it
                                 * out before we then free back to the mark.    
                                 */
                if (cx->their_pool != NULL) {
                        PORT_Assert (cx->their_mark != NULL);
                        PORT_ArenaRelease (cx->their_pool, cx->their_mark);
                }
#endif
                return SECFailure;
    }

#if 0   
        /* XXX This is what I want, but cannot have because it seems we
         * have situations (like when downloading a pkcs7 cert chain from
         * some issuers) that give us a total length which is greater than
         * the entire encoding.  So, we have to allow allDone to have a
         * remaining length greater than zero.  I wanted to catch internal
         * bugs with this, noticing when we do not have the right length.
         * Oh well.
         */
    PORT_Assert (len == 0
                 && (cx->status == needBytes || cx->status == allDone));
#else
    PORT_Assert ((len == 0 && cx->status == needBytes)
                 || cx->status == allDone);
#endif
    return SECSuccess;
}


SECStatus
SEC_ASN1DecoderFinish (SEC_ASN1DecoderContext *cx)
{
    SECStatus rv;

    if (cx->status == needBytes) {
                #ifdef  __APPLE__
                /*
                 * Special case: need more bytes, but this field and all
                 * subsequent fields are optional. I'm surprised this case is
                 * not handled in the original NSS code, and this workaround
                 * is a bit of a hack...
                 */
                sec_asn1d_state *state = cx->current;
                assert(state != NULL);
                if(state->place == beforeIdentifier) {
                        int allOptional = 1;
                        const SecAsn1Template *templ = state->theTemplate;
                        while(templ->kind != 0) {
                                if(!(templ->kind & SEC_ASN1_OPTIONAL)) {
                                        allOptional = 0;
                                        break;
                                }
                                templ++;
                        }
                        if(allOptional) {
                                /* letting this one slide */
                                rv = SECSuccess;
                        }
                        else {
                                PORT_SetError (SEC_ERROR_BAD_DER);
                                rv = SECFailure;
                        }
                }
                else {
                        PORT_SetError (SEC_ERROR_BAD_DER);
                        rv = SECFailure;
                }
                #else
                PORT_SetError (SEC_ERROR_BAD_DER);
                rv = SECFailure;
                #endif  /* __APPLE__ */
    } else {
                rv = SECSuccess;
    }

    /*
     * XXX anything else that needs to be finished?
     */

    PORT_FreeArena (cx->our_pool, PR_FALSE);

    return rv;
}


SEC_ASN1DecoderContext *
SEC_ASN1DecoderStart (PRArenaPool *their_pool, void *dest,
                      const SecAsn1Template *theTemplate
                          #ifdef        __APPLE__
                          ,
                          /* only needed if first element will be SEC_ASN1_DYNAMIC */
                          const char *buf
                          #endif        
                          )
{
    PRArenaPool *our_pool;
    SEC_ASN1DecoderContext *cx;

    our_pool = PORT_NewArena (SEC_ASN1_DEFAULT_ARENA_SIZE);
    if (our_pool == NULL)
        return NULL;

    cx = (SEC_ASN1DecoderContext*)PORT_ArenaZAlloc (our_pool, sizeof(*cx));
    if (cx == NULL) {
        PORT_FreeArena (our_pool, PR_FALSE);
        return NULL;
    }

    cx->our_pool = our_pool;
    if (their_pool != NULL) {
        cx->their_pool = their_pool;
#ifdef SEC_ASN1D_FREE_ON_ERROR
        cx->their_mark = PORT_ArenaMark (their_pool);
#endif
    }

    cx->status = needBytes;

    if (sec_asn1d_push_state(cx, theTemplate, dest, PR_FALSE) == NULL
           || sec_asn1d_init_state_based_on_template (cx->current, 
                        buf /* __APPLE__ */) == NULL) {
                /*
                 * Trouble initializing (probably due to failed allocations)
                 * requires that we just give up.
                 */
                PORT_FreeArena (our_pool, PR_FALSE);
                return NULL;
    }

    return cx;
}


void
SEC_ASN1DecoderSetFilterProc (SEC_ASN1DecoderContext *cx,
                              SEC_ASN1WriteProc fn, void *arg,
                              PRBool only)
{
    /* check that we are "between" fields here */
    PORT_Assert (cx->during_notify);

    cx->filter_proc = fn;
    cx->filter_arg = arg;
    cx->filter_only = only;
}


void
SEC_ASN1DecoderClearFilterProc (SEC_ASN1DecoderContext *cx)
{
    /* check that we are "between" fields here */
    PORT_Assert (cx->during_notify);

    cx->filter_proc = NULL;
    cx->filter_arg = NULL;
    cx->filter_only = PR_FALSE;
}


void
SEC_ASN1DecoderSetNotifyProc (SEC_ASN1DecoderContext *cx,
                              SEC_ASN1NotifyProc fn, void *arg)
{
    cx->notify_proc = fn;
    cx->notify_arg = arg;
}


void
SEC_ASN1DecoderClearNotifyProc (SEC_ASN1DecoderContext *cx)
{
    cx->notify_proc = NULL;
    cx->notify_arg = NULL;      /* not necessary; just being clean */
}


void
SEC_ASN1DecoderAbort(SEC_ASN1DecoderContext *cx, int error)
{
    PORT_Assert(cx);
    PORT_SetError(error);
    cx->status = decodeError;
}


SECStatus
SEC_ASN1Decode (PRArenaPool *poolp, void *dest,
                const SecAsn1Template *theTemplate,
                const char *buf, size_t len)
{
    SEC_ASN1DecoderContext *dcx;
    SECStatus urv, frv;

    dcx = SEC_ASN1DecoderStart (poolp, dest, theTemplate,
                buf /* __APPLE__ */);
    if (dcx == NULL)
        return SECFailure;

    urv = SEC_ASN1DecoderUpdate (dcx, buf, len);
    frv = SEC_ASN1DecoderFinish (dcx);

    if (urv != SECSuccess)
        return urv;

    return frv;
}


SECStatus
SEC_ASN1DecodeItem (PRArenaPool *poolp, void *dest,
                    const SecAsn1Template *theTemplate,
                    const SecAsn1Item *item)
{
    return SEC_ASN1Decode (poolp, dest, theTemplate,
                           (const char *) item->Data, item->Length);
}