mDNSShared/dnssd_clientlib.c

   1 /* -*- Mode: C; tab-width: 4 -*-
   2  *
   3  * Copyright (c) 2004, Apple Computer, Inc. All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright notice,
   9  *     this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright notice,
  11  *     this list of conditions and the following disclaimer in the documentation
  12  *     and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of its
  14  *     contributors may be used to endorse or promote products derived from this
  15  *     software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  26  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include <stdlib.h>
  30 #include <string.h>
  31
  32 #include "dns_sd.h"
  33
  34 #if MDNS_BUILDINGSHAREDLIBRARY || MDNS_BUILDINGSTUBLIBRARY
  35 #pragma export on
  36 #endif
  37
  38 #if defined(_WIN32)
  39 // disable warning "conversion from <data> to uint16_t"
  40 #pragma warning(disable:4244)
  41 #define strncasecmp _strnicmp
  42 #define strcasecmp _stricmp
  43 #endif
  44
  45 /*********************************************************************************************
  46 *
  47 *  Supporting Functions
  48 *
  49 *********************************************************************************************/
  50
  51 #define mDNSIsDigit(X)     ((X) >= '0' && (X) <= '9')
  52
  53 // DomainEndsInDot returns 1 if name ends with a dot, 0 otherwise
  54 // (DNSServiceConstructFullName depends this returning 1 for true, rather than any non-zero value meaning true)
  55
  56 static int DomainEndsInDot(const char *dom)
  57 {
  58     while (dom[0] && dom[1])
  59     {
  60         if (dom[0] == '\\') // advance past escaped byte sequence
  61         {
  62             if (mDNSIsDigit(dom[1]) && mDNSIsDigit(dom[2]) && mDNSIsDigit(dom[3]))
  63                 dom += 4;           // If "\ddd"    then skip four
  64             else dom += 2;          // else if "\x" then skip two
  65         }
  66         else dom++;                 // else goto next character
  67     }
  68     return (dom[0] == '.');
  69 }
  70
  71 static uint8_t *InternalTXTRecordSearch
  72 (
  73     uint16_t txtLen,
  74     const void       *txtRecord,
  75     const char       *key,
  76     unsigned long    *keylen
  77 )
  78 {
  79     uint8_t *p = (uint8_t*)txtRecord;
  80     uint8_t *e = p + txtLen;
  81     *keylen = (unsigned long) strlen(key);
  82     while (p<e)
  83     {
  84         uint8_t *x = p;
  85         p += 1 + p[0];
  86         if (p <= e && *keylen <= x[0] && !strncasecmp(key, (char*)x+1, *keylen))
  87             if (*keylen == x[0] || x[1+*keylen] == '=') return(x);
  88     }
  89     return(NULL);
  90 }
  91
  92 /*********************************************************************************************
  93 *
  94 *  General Utility Functions
  95 *
  96 *********************************************************************************************/
  97
  98 // Note: Need to make sure we don't write more than kDNSServiceMaxDomainName (1009) bytes to fullName
  99 // In earlier builds this constant was defined to be 1005, so to avoid buffer overruns on clients
 100 // compiled with that constant we'll actually limit the output to 1005 bytes.
 101
 102 DNSServiceErrorType DNSSD_API DNSServiceConstructFullName
 103 (
 104     char       *const fullName,
 105     const char *const service,      // May be NULL
 106     const char *const regtype,
 107     const char *const domain
 108 )
 109 {
 110     const size_t len = !regtype ? 0 : strlen(regtype) - DomainEndsInDot(regtype);
 111     char       *fn   = fullName;
 112     char *const lim  = fullName + 1005;
 113     const char *s    = service;
 114     const char *r    = regtype;
 115     const char *d    = domain;
 116
 117     // regtype must be at least "x._udp" or "x._tcp"
 118     if (len < 6 || !domain || !domain[0]) return kDNSServiceErr_BadParam;
 119     if (strncasecmp((regtype + len - 4), "_tcp", 4) && strncasecmp((regtype + len - 4), "_udp", 4)) return kDNSServiceErr_BadParam;
 120
 121     if (service && *service)
 122     {
 123         while (*s)
 124         {
 125             unsigned char c = *s++;             // Needs to be unsigned, or values like 0xFF will be interpreted as < 32
 126             if (c <= ' ')                       // Escape non-printable characters
 127             {
 128                 if (fn+4 >= lim) goto fail;
 129                 *fn++ = '\\';
 130                 *fn++ = '0' + (c / 100);
 131                 *fn++ = '0' + (c /  10) % 10;
 132                 c     = '0' + (c      ) % 10;
 133             }
 134             else if (c == '.' || (c == '\\'))   // Escape dot and backslash literals
 135             {
 136                 if (fn+2 >= lim) goto fail;
 137                 *fn++ = '\\';
 138             }
 139             else
 140             if (fn+1 >= lim) goto fail;
 141             *fn++ = (char)c;
 142         }
 143         *fn++ = '.';
 144     }
 145
 146     while (*r) if (fn+1 >= lim) goto fail;else *fn++ = *r++;
 147     if (!DomainEndsInDot(regtype)) { if (fn+1 >= lim) goto fail;else *fn++ = '.';}
 148
 149     while (*d) if (fn+1 >= lim) goto fail;else *fn++ = *d++;
 150     if (!DomainEndsInDot(domain)) { if (fn+1 >= lim) goto fail;else *fn++ = '.';}
 151
 152     *fn = '\0';
 153     return kDNSServiceErr_NoError;
 154
 155 fail:
 156     *fn = '\0';
 157     return kDNSServiceErr_BadParam;
 158 }
 159
 160 /*********************************************************************************************
 161 *
 162 *   TXT Record Construction Functions
 163 *
 164 *********************************************************************************************/
 165
 166 typedef struct _TXTRecordRefRealType
 167 {
 168     uint8_t  *buffer;       // Pointer to data
 169     uint16_t buflen;        // Length of buffer
 170     uint16_t datalen;       // Length currently in use
 171     uint16_t malloced;  // Non-zero if buffer was allocated via malloc()
 172 } TXTRecordRefRealType;
 173
 174 #define txtRec ((TXTRecordRefRealType*)txtRecord)
 175
 176 // The opaque storage defined in the public dns_sd.h header is 16 bytes;
 177 // make sure we don't exceed that.
 178 struct CompileTimeAssertionCheck_dnssd_clientlib
 179 {
 180     char assert0[(sizeof(TXTRecordRefRealType) <= 16) ? 1 : -1];
 181 };
 182
 183 void DNSSD_API TXTRecordCreate
 184 (
 185     TXTRecordRef     *txtRecord,
 186     uint16_t bufferLen,
 187     void             *buffer
 188 )
 189 {
 190     txtRec->buffer   = buffer;
 191     txtRec->buflen   = buffer ? bufferLen : (uint16_t)0;
 192     txtRec->datalen  = 0;
 193     txtRec->malloced = 0;
 194 }
 195
 196 void DNSSD_API TXTRecordDeallocate(TXTRecordRef *txtRecord)
 197 {
 198     if (txtRec->malloced) free(txtRec->buffer);
 199 }
 200
 201 DNSServiceErrorType DNSSD_API TXTRecordSetValue
 202 (
 203     TXTRecordRef     *txtRecord,
 204     const char       *key,
 205     uint8_t valueSize,
 206     const void       *value
 207 )
 208 {
 209     uint8_t *start, *p;
 210     const char *k;
 211     unsigned long keysize, keyvalsize;
 212
 213     for (k = key; *k; k++) if (*k < 0x20 || *k > 0x7E || *k == '=') return(kDNSServiceErr_Invalid);
 214     keysize = (unsigned long)(k - key);
 215     keyvalsize = 1 + keysize + (value ? (1 + valueSize) : 0);
 216     if (keysize < 1 || keyvalsize > 255) return(kDNSServiceErr_Invalid);
 217     (void)TXTRecordRemoveValue(txtRecord, key);
 218     if (txtRec->datalen + keyvalsize > txtRec->buflen)
 219     {
 220         unsigned char *newbuf;
 221         unsigned long newlen = txtRec->datalen + keyvalsize;
 222         if (newlen > 0xFFFF) return(kDNSServiceErr_Invalid);
 223         newbuf = malloc((size_t)newlen);
 224         if (!newbuf) return(kDNSServiceErr_NoMemory);
 225         memcpy(newbuf, txtRec->buffer, txtRec->datalen);
 226         if (txtRec->malloced) free(txtRec->buffer);
 227         txtRec->buffer = newbuf;
 228         txtRec->buflen = (uint16_t)(newlen);
 229         txtRec->malloced = 1;
 230     }
 231     start = txtRec->buffer + txtRec->datalen;
 232     p = start + 1;
 233     memcpy(p, key, keysize);
 234     p += keysize;
 235     if (value)
 236     {
 237         *p++ = '=';
 238         memcpy(p, value, valueSize);
 239         p += valueSize;
 240     }
 241     *start = (uint8_t)(p - start - 1);
 242     txtRec->datalen += p - start;
 243     return(kDNSServiceErr_NoError);
 244 }
 245
 246 DNSServiceErrorType DNSSD_API TXTRecordRemoveValue
 247 (
 248     TXTRecordRef     *txtRecord,
 249     const char       *key
 250 )
 251 {
 252     unsigned long keylen, itemlen, remainder;
 253     uint8_t *item = InternalTXTRecordSearch(txtRec->datalen, txtRec->buffer, key, &keylen);
 254     if (!item) return(kDNSServiceErr_NoSuchKey);
 255     itemlen   = (unsigned long)(1 + item[0]);
 256     remainder = (unsigned long)((txtRec->buffer + txtRec->datalen) - (item + itemlen));
 257     // Use memmove because memcpy behaviour is undefined for overlapping regions
 258     memmove(item, item + itemlen, remainder);
 259     txtRec->datalen -= itemlen;
 260     return(kDNSServiceErr_NoError);
 261 }
 262
 263 uint16_t DNSSD_API TXTRecordGetLength  (const TXTRecordRef *txtRecord) { return(txtRec->datalen); }
 264 const void * DNSSD_API TXTRecordGetBytesPtr(const TXTRecordRef *txtRecord) { return(txtRec->buffer); }
 265
 266 /*********************************************************************************************
 267 *
 268 *   TXT Record Parsing Functions
 269 *
 270 *********************************************************************************************/
 271
 272 int DNSSD_API TXTRecordContainsKey
 273 (
 274     uint16_t txtLen,
 275     const void       *txtRecord,
 276     const char       *key
 277 )
 278 {
 279     unsigned long keylen;
 280     return (InternalTXTRecordSearch(txtLen, txtRecord, key, &keylen) ? 1 : 0);
 281 }
 282
 283 const void * DNSSD_API TXTRecordGetValuePtr
 284 (
 285     uint16_t txtLen,
 286     const void       *txtRecord,
 287     const char       *key,
 288     uint8_t          *valueLen
 289 )
 290 {
 291     unsigned long keylen;
 292     uint8_t *item = InternalTXTRecordSearch(txtLen, txtRecord, key, &keylen);
 293     if (!item || item[0] <= keylen) return(NULL);   // If key not found, or found with no value, return NULL
 294     *valueLen = (uint8_t)(item[0] - (keylen + 1));
 295     return (item + 1 + keylen + 1);
 296 }
 297
 298 uint16_t DNSSD_API TXTRecordGetCount
 299 (
 300     uint16_t txtLen,
 301     const void       *txtRecord
 302 )
 303 {
 304     uint16_t count = 0;
 305     uint8_t *p = (uint8_t*)txtRecord;
 306     uint8_t *e = p + txtLen;
 307     while (p<e) { p += 1 + p[0]; count++; }
 308     return((p>e) ? (uint16_t)0 : count);
 309 }
 310
 311 DNSServiceErrorType DNSSD_API TXTRecordGetItemAtIndex
 312 (
 313     uint16_t txtLen,
 314     const void       *txtRecord,
 315     uint16_t itemIndex,
 316     uint16_t keyBufLen,
 317     char             *key,
 318     uint8_t          *valueLen,
 319     const void       **value
 320 )
 321 {
 322     uint16_t count = 0;
 323     uint8_t *p = (uint8_t*)txtRecord;
 324     uint8_t *e = p + txtLen;
 325     while (p<e && count<itemIndex) { p += 1 + p[0]; count++; }  // Find requested item
 326     if (p<e && p + 1 + p[0] <= e)   // If valid
 327     {
 328         uint8_t *x = p+1;
 329         unsigned long len = 0;
 330         e = p + 1 + p[0];
 331         while (x+len<e && x[len] != '=') len++;
 332         if (len >= keyBufLen) return(kDNSServiceErr_NoMemory);
 333         memcpy(key, x, len);
 334         key[len] = 0;
 335         if (x+len<e)        // If we found '='
 336         {
 337             *value = x + len + 1;
 338             *valueLen = (uint8_t)(p[0] - (len + 1));
 339         }
 340         else
 341         {
 342             *value = NULL;
 343             *valueLen = 0;
 344         }
 345         return(kDNSServiceErr_NoError);
 346     }
 347     return(kDNSServiceErr_Invalid);
 348 }
 349
 350 /*********************************************************************************************
 351 *
 352 *   SCCS-compatible version string
 353 *
 354 *********************************************************************************************/
 355
 356 // For convenience when using the "strings" command, this is the last thing in the file
 357
 358 // Note: The C preprocessor stringify operator ('#') makes a string from its argument, without macro expansion
 359 // e.g. If "version" is #define'd to be "4", then STRINGIFY_AWE(version) will return the string "version", not "4"
 360 // To expand "version" to its value before making the string, use STRINGIFY(version) instead
 361 #define STRINGIFY_ARGUMENT_WITHOUT_EXPANSION(s) # s
 362 #define STRINGIFY(s) STRINGIFY_ARGUMENT_WITHOUT_EXPANSION(s)
 363
 364 // NOT static -- otherwise the compiler may optimize it out
 365 // The "@(#) " pattern is a special prefix the "what" command looks for
 366 const char VersionString_SCCS_libdnssd[] = "@(#) libdns_sd " STRINGIFY(mDNSResponderVersion) " (" __DATE__ " " __TIME__ ")";