/src/git/hash.h

Source
#ifndef HASH_H
#define HASH_H

#if defined(SHA1_APPLE)
#define SHA1_BACKEND "SHA1_APPLE (No collision detection)"
#include <CommonCrypto/CommonDigest.h>
#elif defined(SHA1_OPENSSL)
#  define SHA1_BACKEND "SHA1_OPENSSL (No collision detection)"
#  include <openssl/sha.h>
#  if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
#    define SHA1_NEEDS_CLONE_HELPER
#    include "sha1/openssl.h"
#  endif
#elif defined(SHA1_DC)
#define SHA1_BACKEND "SHA1_DC"
#include "sha1dc_git.h"
#else /* SHA1_BLK */
#define SHA1_BACKEND "SHA1_BLK (No collision detection)"
#include "block-sha1/sha1.h"
#endif

#if defined(SHA1_APPLE_UNSAFE)
#  define SHA1_UNSAFE_BACKEND "SHA1_APPLE_UNSAFE"
#  include <CommonCrypto/CommonDigest.h>
#  define platform_SHA_CTX_unsafe CC_SHA1_CTX
#  define platform_SHA1_Init_unsafe CC_SHA1_Init
#  define platform_SHA1_Update_unsafe CC_SHA1_Update
#  define platform_SHA1_Final_unsafe CC_SHA1_Final
#elif defined(SHA1_OPENSSL_UNSAFE)
#  define SHA1_UNSAFE_BACKEND "SHA1_OPENSSL_UNSAFE"
#  include <openssl/sha.h>
#  if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
#    define SHA1_NEEDS_CLONE_HELPER_UNSAFE
#    include "sha1/openssl.h"
#    define platform_SHA_CTX_unsafe openssl_SHA1_CTX
#    define platform_SHA1_Init_unsafe openssl_SHA1_Init
#    define platform_SHA1_Clone_unsafe openssl_SHA1_Clone
#    define platform_SHA1_Update_unsafe openssl_SHA1_Update
#    define platform_SHA1_Final_unsafe openssl_SHA1_Final
#  else
#    define platform_SHA_CTX_unsafe SHA_CTX
#    define platform_SHA1_Init_unsafe SHA1_Init
#    define platform_SHA1_Update_unsafe SHA1_Update
#    define platform_SHA1_Final_unsafe SHA1_Final
#  endif
#elif defined(SHA1_BLK_UNSAFE)
#  define SHA1_UNSAFE_BACKEND "SHA1_BLK_UNSAFE"
#  include "block-sha1/sha1.h"
#  define platform_SHA_CTX_unsafe blk_SHA_CTX
#  define platform_SHA1_Init_unsafe blk_SHA1_Init
#  define platform_SHA1_Update_unsafe blk_SHA1_Update
#  define platform_SHA1_Final_unsafe blk_SHA1_Final
#endif

#if defined(SHA256_NETTLE)
#define SHA256_BACKEND "SHA256_NETTLE"
#include "sha256/nettle.h"
#elif defined(SHA256_GCRYPT)
#define SHA256_BACKEND "SHA256_GCRYPT"
#define SHA256_NEEDS_CLONE_HELPER
#include "sha256/gcrypt.h"
#elif defined(SHA256_OPENSSL)
#  define SHA256_BACKEND "SHA256_OPENSSL"
#  include <openssl/sha.h>
#  if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
#    define SHA256_NEEDS_CLONE_HELPER
#    include "sha256/openssl.h"
#  endif
#else
#define SHA256_BACKEND "SHA256_BLK"
#include "sha256/block/sha256.h"
#endif

#ifndef platform_SHA_CTX
/*
 * platform's underlying implementation of SHA-1; could be OpenSSL,
 * blk_SHA, Apple CommonCrypto, etc...  Note that the relevant
 * SHA-1 header may have already defined platform_SHA_CTX for our
 * own implementations like block-sha1, so we list
 * the default for OpenSSL compatible SHA-1 implementations here.
 */
#define platform_SHA_CTX  SHA_CTX
#define platform_SHA1_Init  SHA1_Init
#define platform_SHA1_Update  SHA1_Update
#define platform_SHA1_Final     SHA1_Final
#endif

#ifndef platform_SHA_CTX_unsafe
#  define platform_SHA_CTX_unsafe      platform_SHA_CTX
#  define platform_SHA1_Init_unsafe    platform_SHA1_Init
#  define platform_SHA1_Update_unsafe  platform_SHA1_Update
#  define platform_SHA1_Final_unsafe   platform_SHA1_Final
#  ifdef platform_SHA1_Clone
#    define platform_SHA1_Clone_unsafe platform_SHA1_Clone
#  endif
#  ifdef SHA1_NEEDS_CLONE_HELPER
#    define SHA1_NEEDS_CLONE_HELPER_UNSAFE
#  endif
#endif

#define git_SHA_CTX   platform_SHA_CTX
#define git_SHA1_Init   platform_SHA1_Init
#define git_SHA1_Update   platform_SHA1_Update
#define git_SHA1_Final    platform_SHA1_Final

#define git_SHA_CTX_unsafe  platform_SHA_CTX_unsafe
#define git_SHA1_Init_unsafe  platform_SHA1_Init_unsafe
#define git_SHA1_Update_unsafe  platform_SHA1_Update_unsafe
#define git_SHA1_Final_unsafe platform_SHA1_Final_unsafe

#ifdef platform_SHA1_Clone
#define git_SHA1_Clone  platform_SHA1_Clone
#endif
#ifdef platform_SHA1_Clone_unsafe
#  define git_SHA1_Clone_unsafe platform_SHA1_Clone_unsafe
#endif

#ifndef platform_SHA256_CTX
#define platform_SHA256_CTX SHA256_CTX
#define platform_SHA256_Init  SHA256_Init
#define platform_SHA256_Update  SHA256_Update
#define platform_SHA256_Final SHA256_Final
#endif

#define git_SHA256_CTX    platform_SHA256_CTX
#define git_SHA256_Init   platform_SHA256_Init
#define git_SHA256_Update platform_SHA256_Update
#define git_SHA256_Final  platform_SHA256_Final

#ifdef platform_SHA256_Clone
#define git_SHA256_Clone  platform_SHA256_Clone
#endif

#ifdef SHA1_MAX_BLOCK_SIZE
#include "compat/sha1-chunked.h"
#undef git_SHA1_Update
#define git_SHA1_Update   git_SHA1_Update_Chunked
#endif

#ifndef SHA1_NEEDS_CLONE_HELPER
static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
{
  memcpy(dst, src, sizeof(*dst));
}
#endif
#ifndef SHA1_NEEDS_CLONE_HELPER_UNSAFE
static inline void git_SHA1_Clone_unsafe(git_SHA_CTX_unsafe *dst,
               const git_SHA_CTX_unsafe *src)
{
  memcpy(dst, src, sizeof(*dst));
}
#endif

#ifndef SHA256_NEEDS_CLONE_HELPER
static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src)
{
  memcpy(dst, src, sizeof(*dst));
}
#endif

/*
 * Note that these constants are suitable for indexing the hash_algos array and
 * comparing against each other, but are otherwise arbitrary, so they should not
 * be exposed to the user or serialized to disk.  To know whether a
 * git_hash_algo struct points to some usable hash function, test the format_id
 * field for being non-zero.  Use the name field for user-visible situations and
 * the format_id field for fixed-length fields on disk.
 */
/* An unknown hash function. */
#define GIT_HASH_UNKNOWN 0
/* SHA-1 */
#define GIT_HASH_SHA1 1
/* SHA-256  */
#define GIT_HASH_SHA256 2
/* Number of algorithms supported (including unknown). */
#define GIT_HASH_NALGOS (GIT_HASH_SHA256 + 1)

/* Default hash algorithm if unspecified. */
#ifdef WITH_BREAKING_CHANGES
# define GIT_HASH_DEFAULT GIT_HASH_SHA256
#else
# define GIT_HASH_DEFAULT GIT_HASH_SHA1
#endif

/* Legacy hash algorithm. Implied for older data formats which don't specify. */
#define GIT_HASH_SHA1_LEGACY GIT_HASH_SHA1

/* "sha1", big-endian */
#define GIT_SHA1_FORMAT_ID 0x73686131

/* The length in bytes and in hex digits of an object name (SHA-1 value). */
#define GIT_SHA1_RAWSZ 20
#define GIT_SHA1_HEXSZ (2 * GIT_SHA1_RAWSZ)
/* The block size of SHA-1. */
#define GIT_SHA1_BLKSZ 64

/* "s256", big-endian */
#define GIT_SHA256_FORMAT_ID 0x73323536

/* The length in bytes and in hex digits of an object name (SHA-256 value). */
#define GIT_SHA256_RAWSZ 32
#define GIT_SHA256_HEXSZ (2 * GIT_SHA256_RAWSZ)
/* The block size of SHA-256. */
#define GIT_SHA256_BLKSZ 64

/* The length in byte and in hex digits of the largest possible hash value. */
#define GIT_MAX_RAWSZ GIT_SHA256_RAWSZ
#define GIT_MAX_HEXSZ GIT_SHA256_HEXSZ
/* The largest possible block size for any supported hash. */
#define GIT_MAX_BLKSZ GIT_SHA256_BLKSZ

struct object_id {
  unsigned char hash[GIT_MAX_RAWSZ];
  int algo; /* XXX requires 4-byte alignment */
};

#define GET_OID_QUIETLY                  01
#define GET_OID_COMMIT                   02
#define GET_OID_COMMITTISH               04
#define GET_OID_TREE                    010
#define GET_OID_TREEISH                 020
#define GET_OID_BLOB                    040
#define GET_OID_FOLLOW_SYMLINKS        0100
#define GET_OID_RECORD_PATH            0200
#define GET_OID_ONLY_TO_DIE           04000
#define GET_OID_REQUIRE_PATH         010000
#define GET_OID_HASH_ANY             020000
#define GET_OID_SKIP_AMBIGUITY_CHECK 040000
#define GET_OID_GENTLY              0100000

#define GET_OID_DISAMBIGUATORS \
  (GET_OID_COMMIT | GET_OID_COMMITTISH | \
  GET_OID_TREE | GET_OID_TREEISH | \
  GET_OID_BLOB)

enum get_oid_result {
  FOUND = 0,
  MISSING_OBJECT = -1, /* The requested object is missing */
  SHORT_NAME_AMBIGUOUS = -2,
  /* The following only apply when symlinks are followed */
  DANGLING_SYMLINK = -4, /*
        * The initial symlink is there, but
        * (transitively) points to a missing
        * in-tree file
        */
  SYMLINK_LOOP = -5,
  NOT_DIR = -6, /*
           * Somewhere along the symlink chain, a path is
           * requested which contains a file as a
           * non-final element.
           */
};

#ifdef USE_THE_REPOSITORY_VARIABLE
# include "repository.h"
# define the_hash_algo the_repository->hash_algo
#endif

/* A suitably aligned type for stack allocations of hash contexts. */
struct git_hash_ctx {
  const struct git_hash_algo *algop;
  union {
    git_SHA_CTX sha1;
    git_SHA_CTX_unsafe sha1_unsafe;
    git_SHA256_CTX sha256;
  } state;
};

typedef void (*git_hash_init_fn)(struct git_hash_ctx *ctx);
typedef void (*git_hash_clone_fn)(struct git_hash_ctx *dst, const struct git_hash_ctx *src);
typedef void (*git_hash_update_fn)(struct git_hash_ctx *ctx, const void *in, size_t len);
typedef void (*git_hash_final_fn)(unsigned char *hash, struct git_hash_ctx *ctx);
typedef void (*git_hash_final_oid_fn)(struct object_id *oid, struct git_hash_ctx *ctx);

struct git_hash_algo {
  /*
   * The name of the algorithm, as appears in the config file and in
   * messages.
   */
  const char *name;

  /* A four-byte version identifier, used in pack indices. */
  uint32_t format_id;

  /* The length of the hash in binary. */
  size_t rawsz;

  /* The length of the hash in hex characters. */
  size_t hexsz;

  /* The block size of the hash. */
  size_t blksz;

  /* The hash initialization function. */
  git_hash_init_fn init_fn;

  /* The hash context cloning function. */
  git_hash_clone_fn clone_fn;

  /* The hash update function. */
  git_hash_update_fn update_fn;

  /* The hash finalization function. */
  git_hash_final_fn final_fn;

  /* The hash finalization function for object IDs. */
  git_hash_final_oid_fn final_oid_fn;

  /* The OID of the empty tree. */
  const struct object_id *empty_tree;

  /* The OID of the empty blob. */
  const struct object_id *empty_blob;

  /* The all-zeros OID. */
  const struct object_id *null_oid;

  /* The unsafe variant of this hash function, if one exists. */
  const struct git_hash_algo *unsafe;
};
extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];

static inline void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
{
  src->algop->clone_fn(dst, src);
}

static inline void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len)
{
  ctx->algop->update_fn(ctx, in, len);
}

static inline void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx)
{
  ctx->algop->final_fn(hash, ctx);
}

static inline void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
{
  ctx->algop->final_oid_fn(oid, ctx);
}

/*
 * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
 * the name doesn't match a known algorithm.
 */
int hash_algo_by_name(const char *name);
/* Identical, except based on the format ID. */
int hash_algo_by_id(uint32_t format_id);
/* Identical, except based on the length. */
int hash_algo_by_length(size_t len);
/* Identical, except for a pointer to struct git_hash_algo. */
static inline int hash_algo_by_ptr(const struct git_hash_algo *p)
{
  size_t i;
  for (i = 0; i < GIT_HASH_NALGOS; i++) {
    const struct git_hash_algo *algop = &hash_algos[i];
    if (p == algop)
      return i;
  }
  return GIT_HASH_UNKNOWN;
}

const struct git_hash_algo *unsafe_hash_algo(const struct git_hash_algo *algop);

const struct object_id *null_oid(const struct git_hash_algo *algop);

static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
{
  /*
   * Teach the compiler that there are only two possibilities of hash size
   * here, so that it can optimize for this case as much as possible.
   */
  if (algop->rawsz == GIT_MAX_RAWSZ)
    return memcmp(sha1, sha2, GIT_MAX_RAWSZ);
  return memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
}

static inline int hasheq(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
{
  /*
   * We write this here instead of deferring to hashcmp so that the
   * compiler can properly inline it and avoid calling memcmp.
   */
  if (algop->rawsz == GIT_MAX_RAWSZ)
    return !memcmp(sha1, sha2, GIT_MAX_RAWSZ);
  return !memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
}

static inline void hashcpy(unsigned char *sha_dst, const unsigned char *sha_src,
         const struct git_hash_algo *algop)
{
  memcpy(sha_dst, sha_src, algop->rawsz);
}

static inline void hashclr(unsigned char *hash, const struct git_hash_algo *algop)
{
  memset(hash, 0, algop->rawsz);
}

static inline int oidcmp(const struct object_id *oid1, const struct object_id *oid2)
{
  return memcmp(oid1->hash, oid2->hash, GIT_MAX_RAWSZ);
}

static inline int oideq(const struct object_id *oid1, const struct object_id *oid2)
{
  return !memcmp(oid1->hash, oid2->hash, GIT_MAX_RAWSZ);
}

static inline void oidcpy(struct object_id *dst, const struct object_id *src)
{
  memcpy(dst->hash, src->hash, GIT_MAX_RAWSZ);
  dst->algo = src->algo;
}

static inline void oidread(struct object_id *oid, const unsigned char *hash,
         const struct git_hash_algo *algop)
{
  memcpy(oid->hash, hash, algop->rawsz);
  if (algop->rawsz < GIT_MAX_RAWSZ)
    memset(oid->hash + algop->rawsz, 0, GIT_MAX_RAWSZ - algop->rawsz);
  oid->algo = hash_algo_by_ptr(algop);
}

static inline void oidclr(struct object_id *oid,
        const struct git_hash_algo *algop)
{
  memset(oid->hash, 0, GIT_MAX_RAWSZ);
  oid->algo = hash_algo_by_ptr(algop);
}

static inline struct object_id *oiddup(const struct object_id *src)
{
  struct object_id *dst = xmalloc(sizeof(struct object_id));
  oidcpy(dst, src);
  return dst;
}

static inline void oid_set_algo(struct object_id *oid, const struct git_hash_algo *algop)
{
  oid->algo = hash_algo_by_ptr(algop);
}

/*
 * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code
 * for use in hash tables. Cryptographic hashes are supposed to have
 * uniform distribution, so in contrast to `memhash()`, this just copies
 * the first `sizeof(int)` bytes without shuffling any bits. Note that
 * the results will be different on big-endian and little-endian
 * platforms, so they should not be stored or transferred over the net.
 */
static inline unsigned int oidhash(const struct object_id *oid)
{
  /*
   * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on
   * platforms that don't support unaligned reads.
   */
  unsigned int hash;
  memcpy(&hash, oid->hash, sizeof(hash));
  return hash;
}

static inline int is_null_oid(const struct object_id *oid)
{
  static const unsigned char null_hash[GIT_MAX_RAWSZ];
  return !memcmp(oid->hash, null_hash, GIT_MAX_RAWSZ);
}

const char *empty_tree_oid_hex(const struct git_hash_algo *algop);

static inline int is_empty_blob_oid(const struct object_id *oid,
            const struct git_hash_algo *algop)
{
  return oideq(oid, algop->empty_blob);
}

static inline int is_empty_tree_oid(const struct object_id *oid,
            const struct git_hash_algo *algop)
{
  return oideq(oid, algop->empty_tree);
}

#endif

Coverage Report

Created: 2025-12-31 07:01

Line	Count	Source
1		#ifndef HASH_H
2		#define HASH_H
3
4		#if defined(SHA1_APPLE)
5		#define SHA1_BACKEND "SHA1_APPLE (No collision detection)"
6		#include <CommonCrypto/CommonDigest.h>
7		#elif defined(SHA1_OPENSSL)
8		# define SHA1_BACKEND "SHA1_OPENSSL (No collision detection)"
9		# include <openssl/sha.h>
10		# if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
11		# define SHA1_NEEDS_CLONE_HELPER
12		# include "sha1/openssl.h"
13		# endif
14		#elif defined(SHA1_DC)
15		#define SHA1_BACKEND "SHA1_DC"
16		#include "sha1dc_git.h"
17		#else /* SHA1_BLK */
18		#define SHA1_BACKEND "SHA1_BLK (No collision detection)"
19		#include "block-sha1/sha1.h"
20		#endif
21
22		#if defined(SHA1_APPLE_UNSAFE)
23		# define SHA1_UNSAFE_BACKEND "SHA1_APPLE_UNSAFE"
24		# include <CommonCrypto/CommonDigest.h>
25		# define platform_SHA_CTX_unsafe CC_SHA1_CTX
26		# define platform_SHA1_Init_unsafe CC_SHA1_Init
27		# define platform_SHA1_Update_unsafe CC_SHA1_Update
28		# define platform_SHA1_Final_unsafe CC_SHA1_Final
29		#elif defined(SHA1_OPENSSL_UNSAFE)
30		# define SHA1_UNSAFE_BACKEND "SHA1_OPENSSL_UNSAFE"
31		# include <openssl/sha.h>
32		# if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
33		# define SHA1_NEEDS_CLONE_HELPER_UNSAFE
34		# include "sha1/openssl.h"
35		# define platform_SHA_CTX_unsafe openssl_SHA1_CTX
36		# define platform_SHA1_Init_unsafe openssl_SHA1_Init
37		# define platform_SHA1_Clone_unsafe openssl_SHA1_Clone
38		# define platform_SHA1_Update_unsafe openssl_SHA1_Update
39		# define platform_SHA1_Final_unsafe openssl_SHA1_Final