[apple/security.git] / libsecurity_codesigning / lib / codedirectory.cpp

/*
 * Copyright (c) 2006-2010 Apple Inc. All Rights Reserved.
 * 
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
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 * @APPLE_LICENSE_HEADER_END@
 */

//
// codedirectory - format and operations for code signing "code directory" structures
//
#include "codedirectory.h"
#include "csutilities.h"
#include "CSCommonPriv.h"

using namespace UnixPlusPlus;


namespace Security {
namespace CodeSigning {


//
// Highest understood special slot in this CodeDirectory.
//
CodeDirectory::SpecialSlot CodeDirectory::maxSpecialSlot() const
{
        SpecialSlot slot = this->nSpecialSlots;
        if (slot > cdSlotMax)
                slot = cdSlotMax;
        return slot;
}


//
// Canonical filesystem names for select slot numbers.
// These are variously used for filenames, extended attribute names, etc.
// to get some consistency in naming. These are for storing signing-related
// data; they have no bearing on the actual hash slots in the CodeDirectory.
//
const char *CodeDirectory::canonicalSlotName(SpecialSlot slot)
{
        switch (slot) {
        case cdRequirementsSlot:
                return kSecCS_REQUIREMENTSFILE;
        case cdResourceDirSlot:
                return kSecCS_RESOURCEDIRFILE;
        case cdCodeDirectorySlot:
                return kSecCS_CODEDIRECTORYFILE;
        case cdSignatureSlot:
                return kSecCS_SIGNATUREFILE;
        case cdApplicationSlot:
                return kSecCS_APPLICATIONFILE;
        case cdEntitlementSlot:
                return kSecCS_ENTITLEMENTFILE;
        default:
                return NULL;
        }
}


//
// Canonical attributes of SpecialSlots.
//
unsigned CodeDirectory::slotAttributes(SpecialSlot slot)
{
        switch (slot) {
        case cdRequirementsSlot:
                return cdComponentIsBlob; // global
        case cdCodeDirectorySlot:
                return cdComponentPerArchitecture | cdComponentIsBlob;
        case cdSignatureSlot:
                return cdComponentPerArchitecture; // raw
        case cdEntitlementSlot:
                return cdComponentIsBlob; // global
        case cdIdentificationSlot:
                return cdComponentPerArchitecture; // raw
        default:
                return 0; // global, raw
        }
}


//
// Symbolic names for code directory special slots.
// These are only used for debug output. They are not API-official.
// Needs to be coordinated with the cd*Slot enumeration in codedirectory.h.
//
#if !defined(NDEBUG)
const char * const CodeDirectory::debugSlotName[] = {
        "codedirectory",
        "info",
        "requirements",
        "resources",
        "application",
        "entitlement"
};
#endif //NDEBUG


//
// Check a CodeDirectory for basic integrity. This should ensure that the
// version is understood by our code, and that the internal structure
// (offsets etc.) is intact. In particular, it must make sure that no offsets
// point outside the CodeDirectory.
// Throws if the directory is corrupted or out of versioning bounds.
// Returns if the version is usable (perhaps with degraded features due to
// compatibility hacks).
//
// Note: There are some things we don't bother checking because they won't
// cause crashes, and will just be flagged as nonsense later. For example,
// a Bad Guy could overlap the identifier and hash fields, which is nonsense
// but not dangerous.
//
void CodeDirectory::checkIntegrity() const
{
        // check version for support
        if (!this->validateBlob())
                MacOSError::throwMe(errSecCSSignatureInvalid);  // busted
        if (version > compatibilityLimit)
                MacOSError::throwMe(errSecCSSignatureUnsupported);      // too new - no clue
        if (version < earliestVersion)
                MacOSError::throwMe(errSecCSSignatureUnsupported);      // too old - can't support
        if (version > currentVersion)
                secdebug("codedir", "%p version 0x%x newer than current 0x%x",
                        this, uint32_t(version), currentVersion);
        
        // now check interior offsets for validity
        if (!stringAt(identOffset))
                MacOSError::throwMe(errSecCSSignatureFailed); // identifier out of blob range
        if (!contains(hashOffset - int64_t(hashSize) * nSpecialSlots, hashSize * (int64_t(nSpecialSlots) + nCodeSlots)))
                MacOSError::throwMe(errSecCSSignatureFailed); // hash array out of blob range
        if (const Scatter *scatter = this->scatterVector()) {
                // the optional scatter vector is terminated with an element having (count == 0)
                unsigned int pagesConsumed = 0;
                for (;; scatter++) {
                        if (!contains(scatter, sizeof(Scatter)))
                                MacOSError::throwMe(errSecCSSignatureFailed);
                        if (scatter->count == 0)
                                break;
                        pagesConsumed += scatter->count;
                }
                if (!contains((*this)[pagesConsumed-1], hashSize))      // referenced too many main hash slots
                        MacOSError::throwMe(errSecCSSignatureFailed);
        }
}


//
// Validate a slot against data in memory.
//
bool CodeDirectory::validateSlot(const void *data, size_t length, Slot slot) const
{
        secdebug("codedir", "%p validating slot %d", this, int(slot));
        MakeHash<CodeDirectory> hasher(this);
        Hashing::Byte digest[hasher->digestLength()];
        generateHash(hasher, data, length, digest);
        return memcmp(digest, (*this)[slot], hasher->digestLength()) == 0;
}


//
// Validate a slot against the contents of an open file. At most 'length' bytes
// will be read from the file.
//
bool CodeDirectory::validateSlot(FileDesc fd, size_t length, Slot slot) const
{
        MakeHash<CodeDirectory> hasher(this);
        Hashing::Byte digest[hasher->digestLength()];
        generateHash(hasher, fd, digest, length);
        return memcmp(digest, (*this)[slot], hasher->digestLength()) == 0;
}


//
// Check whether a particular slot is present.
// Absense is indicated by either a zero hash, or by lying outside
// the slot range.
//
bool CodeDirectory::slotIsPresent(Slot slot) const
{
        if (slot >= -Slot(nSpecialSlots) && slot < Slot(nCodeSlots)) {
                const Hashing::Byte *digest = (*this)[slot];
                for (unsigned n = 0; n < hashSize; n++)
                        if (digest[n])
                                return true;    // non-zero digest => present
        }
        return false;   // absent
}


//
// Given a hash type code, create an appropriate subclass of DynamicHash
// and return it. The caller owns the object and  must delete it when done.
// This function never returns NULL. It throws if the hashType is unsuupported,
// or if there's an error creating the hasher.
//
DynamicHash *CodeDirectory::hashFor(HashAlgorithm hashType)
{
        CCDigestAlg alg;
        switch (hashType) {
        case kSecCodeSignatureHashSHA1:                                         alg = kCCDigestSHA1; break;
        case kSecCodeSignatureHashSHA256:                                       alg = kCCDigestSHA256; break;
        default:
                MacOSError::throwMe(errSecCSSignatureUnsupported);
        }
        return new CCHashInstance(alg);
}


//
// Hash the next limit bytes of a file and return the digest.
// If the file is shorter, hash as much as you can.
// Limit==0 means unlimited (to end of file).
// Return how many bytes were actually hashed.
// Throw on any errors.
//
size_t CodeDirectory::generateHash(DynamicHash *hasher, FileDesc fd, Hashing::Byte *digest, size_t limit)
{
        size_t size = hashFileData(fd, hasher, limit);
        hasher->finish(digest);
        return size;
}


//
// Ditto, but hash a memory buffer instead.
//
size_t CodeDirectory::generateHash(DynamicHash *hasher, const void *data, size_t length, Hashing::Byte *digest)
{
        hasher->update(data, length);
        hasher->finish(digest);
        return length;
}


//
// Turn a hash of canonical type into a hex string
//
std::string CodeDirectory::hexHash(const unsigned char *hash) const
{
        size_t size = this->hashSize;
        char result[2*size+1];
        for (unsigned n = 0; n < size; n++)
                sprintf(result+2*n, "%02.2x", hash[n]);
        return result;
}


//
// Generate a screening code string from a (complete) CodeDirectory.
// This can be used to make a lightweight pre-screening code from (just) a CodeDirectory.
//
std::string CodeDirectory::screeningCode() const
{
        if (slotIsPresent(-cdInfoSlot))         // has Info.plist
                return "I" + hexHash((*this)[-cdInfoSlot]); // use Info.plist hash
        if (pageSize == 0)                                      // good-enough proxy for "not a Mach-O file"
                return "M" + hexHash((*this)[0]); // use hash of main executable
        return "N";                                                     // no suitable screening code
}


}       // CodeSigning
}       // Security


//
// Canonical text form for user-settable code directory flags.
// Note: This table is actually exported from Security.framework.
//
const SecCodeDirectoryFlagTable kSecCodeDirectoryFlagTable[] = {
        { "host",               kSecCodeSignatureHost,                  true },
        { "adhoc",              kSecCodeSignatureAdhoc,                 false },
        { "hard",               kSecCodeSignatureForceHard,             true },
        { "kill",               kSecCodeSignatureForceKill,             true },
        { "expires",            kSecCodeSignatureForceExpiration,       true },
        { "restrict",           kSecCodeSignatureRestrict,              true },
        { "enforcement",        kSecCodeSignatureEnforcement,           true },
        { NULL }
};