hash.h

   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
  40 #  else
  41 #    define platform_SHA_CTX_unsafe SHA_CTX
  42 #    define platform_SHA1_Init_unsafe SHA1_Init
  43 #    define platform_SHA1_Update_unsafe SHA1_Update
  44 #    define platform_SHA1_Final_unsafe SHA1_Final
  45 #  endif
  46 #elif defined(SHA1_BLK_UNSAFE)
  47 #  define SHA1_UNSAFE_BACKEND "SHA1_BLK_UNSAFE"
  48 #  include "block-sha1/sha1.h"
  49 #  define platform_SHA_CTX_unsafe blk_SHA_CTX
  50 #  define platform_SHA1_Init_unsafe blk_SHA1_Init
  51 #  define platform_SHA1_Update_unsafe blk_SHA1_Update
  52 #  define platform_SHA1_Final_unsafe blk_SHA1_Final
  53 #endif
  54
  55 #if defined(SHA256_NETTLE)
  56 #define SHA256_BACKEND "SHA256_NETTLE"
  57 #include "sha256/nettle.h"
  58 #elif defined(SHA256_GCRYPT)
  59 #define SHA256_BACKEND "SHA256_GCRYPT"
  60 #define SHA256_NEEDS_CLONE_HELPER
  61 #include "sha256/gcrypt.h"
  62 #elif defined(SHA256_OPENSSL)
  63 #  define SHA256_BACKEND "SHA256_OPENSSL"
  64 #  include <openssl/sha.h>
  65 #  if defined(OPENSSL_API_LEVEL) && OPENSSL_API_LEVEL >= 3
  66 #    define SHA256_NEEDS_CLONE_HELPER
  67 #    include "sha256/openssl.h"
  68 #  endif
  69 #else
  70 #define SHA256_BACKEND "SHA256_BLK"
  71 #include "sha256/block/sha256.h"
  72 #endif
  73
  74 #ifndef platform_SHA_CTX
  75 /*
  76  * platform's underlying implementation of SHA-1; could be OpenSSL,
  77  * blk_SHA, Apple CommonCrypto, etc...  Note that the relevant
  78  * SHA-1 header may have already defined platform_SHA_CTX for our
  79  * own implementations like block-sha1, so we list
  80  * the default for OpenSSL compatible SHA-1 implementations here.
  81  */
  82 #define platform_SHA_CTX        SHA_CTX
  83 #define platform_SHA1_Init      SHA1_Init
  84 #define platform_SHA1_Update    SHA1_Update
  85 #define platform_SHA1_Final     SHA1_Final
  86 #endif
  87
  88 #ifndef platform_SHA_CTX_unsafe
  89 #  define platform_SHA_CTX_unsafe      platform_SHA_CTX
  90 #  define platform_SHA1_Init_unsafe    platform_SHA1_Init
  91 #  define platform_SHA1_Update_unsafe  platform_SHA1_Update
  92 #  define platform_SHA1_Final_unsafe   platform_SHA1_Final
  93 #  ifdef platform_SHA1_Clone
  94 #    define platform_SHA1_Clone_unsafe platform_SHA1_Clone
  95 #  endif
  96 #  ifdef SHA1_NEEDS_CLONE_HELPER
  97 #    define SHA1_NEEDS_CLONE_HELPER_UNSAFE
  98 #  endif
  99 #endif
 100
 101 #define git_SHA_CTX             platform_SHA_CTX
 102 #define git_SHA1_Init           platform_SHA1_Init
 103 #define git_SHA1_Update         platform_SHA1_Update
 104 #define git_SHA1_Final          platform_SHA1_Final
 105
 106 #define git_SHA_CTX_unsafe      platform_SHA_CTX_unsafe
 107 #define git_SHA1_Init_unsafe    platform_SHA1_Init_unsafe
 108 #define git_SHA1_Update_unsafe  platform_SHA1_Update_unsafe
 109 #define git_SHA1_Final_unsafe   platform_SHA1_Final_unsafe
 110
 111 #ifdef platform_SHA1_Clone
 112 #define git_SHA1_Clone  platform_SHA1_Clone
 113 #endif
 114 #ifdef platform_SHA1_Clone_unsafe
 115 #  define git_SHA1_Clone_unsafe platform_SHA1_Clone_unsafe
 116 #endif
 117
 118 #ifndef platform_SHA256_CTX
 119 #define platform_SHA256_CTX     SHA256_CTX
 120 #define platform_SHA256_Init    SHA256_Init
 121 #define platform_SHA256_Update  SHA256_Update
 122 #define platform_SHA256_Final   SHA256_Final
 123 #endif
 124
 125 #define git_SHA256_CTX          platform_SHA256_CTX
 126 #define git_SHA256_Init         platform_SHA256_Init
 127 #define git_SHA256_Update       platform_SHA256_Update
 128 #define git_SHA256_Final        platform_SHA256_Final
 129
 130 #ifdef platform_SHA256_Clone
 131 #define git_SHA256_Clone        platform_SHA256_Clone
 132 #endif
 133
 134 #ifdef SHA1_MAX_BLOCK_SIZE
 135 #include "compat/sha1-chunked.h"
 136 #undef git_SHA1_Update
 137 #define git_SHA1_Update         git_SHA1_Update_Chunked
 138 #endif
 139
 140 #ifndef SHA1_NEEDS_CLONE_HELPER
 141 static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
 142 {
 143         memcpy(dst, src, sizeof(*dst));
 144 }
 145 #endif
 146 #ifndef SHA1_NEEDS_CLONE_HELPER_UNSAFE
 147 static inline void git_SHA1_Clone_unsafe(git_SHA_CTX_unsafe *dst,
 148                                        const git_SHA_CTX_unsafe *src)
 149 {
 150         memcpy(dst, src, sizeof(*dst));
 151 }
 152 #endif
 153
 154 #ifndef SHA256_NEEDS_CLONE_HELPER
 155 static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src)
 156 {
 157         memcpy(dst, src, sizeof(*dst));
 158 }
 159 #endif
 160
 161 /*
 162  * Note that these constants are suitable for indexing the hash_algos array and
 163  * comparing against each other, but are otherwise arbitrary, so they should not
 164  * be exposed to the user or serialized to disk.  To know whether a
 165  * git_hash_algo struct points to some usable hash function, test the format_id
 166  * field for being non-zero.  Use the name field for user-visible situations and
 167  * the format_id field for fixed-length fields on disk.
 168  */
 169 /* An unknown hash function. */
 170 #define GIT_HASH_UNKNOWN 0
 171 /* SHA-1 */
 172 #define GIT_HASH_SHA1 1
 173 /* SHA-256  */
 174 #define GIT_HASH_SHA256 2
 175 /* Number of algorithms supported (including unknown). */
 176 #define GIT_HASH_NALGOS (GIT_HASH_SHA256 + 1)
 177
 178 /* Default hash algorithm if unspecified. */
 179 #ifdef WITH_BREAKING_CHANGES
 180 # define GIT_HASH_DEFAULT GIT_HASH_SHA256
 181 #else
 182 # define GIT_HASH_DEFAULT GIT_HASH_SHA1
 183 #endif
 184
 185 /* Legacy hash algorithm. Implied for older data formats which don't specify. */
 186 #define GIT_HASH_SHA1_LEGACY GIT_HASH_SHA1
 187
 188 /* "sha1", big-endian */
 189 #define GIT_SHA1_FORMAT_ID 0x73686131
 190
 191 /* The length in bytes and in hex digits of an object name (SHA-1 value). */
 192 #define GIT_SHA1_RAWSZ 20
 193 #define GIT_SHA1_HEXSZ (2 * GIT_SHA1_RAWSZ)
 194 /* The block size of SHA-1. */
 195 #define GIT_SHA1_BLKSZ 64
 196
 197 /* "s256", big-endian */
 198 #define GIT_SHA256_FORMAT_ID 0x73323536
 199
 200 /* The length in bytes and in hex digits of an object name (SHA-256 value). */
 201 #define GIT_SHA256_RAWSZ 32
 202 #define GIT_SHA256_HEXSZ (2 * GIT_SHA256_RAWSZ)
 203 /* The block size of SHA-256. */
 204 #define GIT_SHA256_BLKSZ 64
 205
 206 /* The length in byte and in hex digits of the largest possible hash value. */
 207 #define GIT_MAX_RAWSZ GIT_SHA256_RAWSZ
 208 #define GIT_MAX_HEXSZ GIT_SHA256_HEXSZ
 209 /* The largest possible block size for any supported hash. */
 210 #define GIT_MAX_BLKSZ GIT_SHA256_BLKSZ
 211
 212 struct object_id {
 213         unsigned char hash[GIT_MAX_RAWSZ];
 214         int algo;       /* XXX requires 4-byte alignment */
 215 };
 216
 217 #define GET_OID_QUIETLY                  01
 218 #define GET_OID_COMMIT                   02
 219 #define GET_OID_COMMITTISH               04
 220 #define GET_OID_TREE                    010
 221 #define GET_OID_TREEISH                 020
 222 #define GET_OID_BLOB                    040
 223 #define GET_OID_FOLLOW_SYMLINKS        0100
 224 #define GET_OID_RECORD_PATH            0200
 225 #define GET_OID_ONLY_TO_DIE           04000
 226 #define GET_OID_REQUIRE_PATH         010000
 227 #define GET_OID_HASH_ANY             020000
 228 #define GET_OID_SKIP_AMBIGUITY_CHECK 040000
 229 #define GET_OID_GENTLY              0100000
 230
 231 #define GET_OID_DISAMBIGUATORS \
 232         (GET_OID_COMMIT | GET_OID_COMMITTISH | \
 233         GET_OID_TREE | GET_OID_TREEISH | \
 234         GET_OID_BLOB)
 235
 236 enum get_oid_result {
 237         FOUND = 0,
 238         MISSING_OBJECT = -1, /* The requested object is missing */
 239         SHORT_NAME_AMBIGUOUS = -2,
 240         /* The following only apply when symlinks are followed */
 241         DANGLING_SYMLINK = -4, /*
 242                                 * The initial symlink is there, but
 243                                 * (transitively) points to a missing
 244                                 * in-tree file
 245                                 */
 246         SYMLINK_LOOP = -5,
 247         NOT_DIR = -6, /*
 248                        * Somewhere along the symlink chain, a path is
 249                        * requested which contains a file as a
 250                        * non-final element.
 251                        */
 252 };
 253
 254 #ifdef USE_THE_REPOSITORY_VARIABLE
 255 # include "repository.h"
 256 # define the_hash_algo the_repository->hash_algo
 257 #endif
 258
 259 /* A suitably aligned type for stack allocations of hash contexts. */
 260 struct git_hash_ctx {
 261         const struct git_hash_algo *algop;
 262         union {
 263                 git_SHA_CTX sha1;
 264                 git_SHA_CTX_unsafe sha1_unsafe;
 265                 git_SHA256_CTX sha256;
 266         } state;
 267 };
 268
 269 typedef void (*git_hash_init_fn)(struct git_hash_ctx *ctx);
 270 typedef void (*git_hash_clone_fn)(struct git_hash_ctx *dst, const struct git_hash_ctx *src);
 271 typedef void (*git_hash_update_fn)(struct git_hash_ctx *ctx, const void *in, size_t len);
 272 typedef void (*git_hash_final_fn)(unsigned char *hash, struct git_hash_ctx *ctx);
 273 typedef void (*git_hash_final_oid_fn)(struct object_id *oid, struct git_hash_ctx *ctx);
 274
 275 struct git_hash_algo {
 276         /*
 277          * The name of the algorithm, as appears in the config file and in
 278          * messages.
 279          */
 280         const char *name;
 281
 282         /* A four-byte version identifier, used in pack indices. */
 283         uint32_t format_id;
 284
 285         /* The length of the hash in binary. */
 286         size_t rawsz;
 287
 288         /* The length of the hash in hex characters. */
 289         size_t hexsz;
 290
 291         /* The block size of the hash. */
 292         size_t blksz;
 293
 294         /* The hash initialization function. */
 295         git_hash_init_fn init_fn;
 296
 297         /* The hash context cloning function. */
 298         git_hash_clone_fn clone_fn;
 299
 300         /* The hash update function. */
 301         git_hash_update_fn update_fn;
 302
 303         /* The hash finalization function. */
 304         git_hash_final_fn final_fn;
 305
 306         /* The hash finalization function for object IDs. */
 307         git_hash_final_oid_fn final_oid_fn;
 308
 309         /* The OID of the empty tree. */
 310         const struct object_id *empty_tree;
 311
 312         /* The OID of the empty blob. */
 313         const struct object_id *empty_blob;
 314
 315         /* The all-zeros OID. */
 316         const struct object_id *null_oid;
 317
 318         /* The unsafe variant of this hash function, if one exists. */
 319         const struct git_hash_algo *unsafe;
 320 };
 321 extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
 322
 323 static inline void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
 324 {
 325         src->algop->clone_fn(dst, src);
 326 }
 327
 328 static inline void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len)
 329 {
 330         ctx->algop->update_fn(ctx, in, len);
 331 }
 332
 333 static inline void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx)
 334 {
 335         ctx->algop->final_fn(hash, ctx);
 336 }
 337
 338 static inline void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
 339 {
 340         ctx->algop->final_oid_fn(oid, ctx);
 341 }
 342
 343 /*
 344  * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
 345  * the name doesn't match a known algorithm.
 346  */
 347 int hash_algo_by_name(const char *name);
 348 /* Identical, except based on the format ID. */
 349 int hash_algo_by_id(uint32_t format_id);
 350 /* Identical, except based on the length. */
 351 int hash_algo_by_length(size_t len);
 352 /* Identical, except for a pointer to struct git_hash_algo. */
 353 static inline int hash_algo_by_ptr(const struct git_hash_algo *p)
 354 {
 355         size_t i;
 356         for (i = 0; i < GIT_HASH_NALGOS; i++) {
 357                 const struct git_hash_algo *algop = &hash_algos[i];
 358                 if (p == algop)
 359                         return i;
 360         }
 361         return GIT_HASH_UNKNOWN;
 362 }
 363
 364 const struct git_hash_algo *unsafe_hash_algo(const struct git_hash_algo *algop);
 365
 366 const struct object_id *null_oid(const struct git_hash_algo *algop);
 367
 368 static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
 369 {
 370         /*
 371          * Teach the compiler that there are only two possibilities of hash size
 372          * here, so that it can optimize for this case as much as possible.
 373          */
 374         if (algop->rawsz == GIT_MAX_RAWSZ)
 375                 return memcmp(sha1, sha2, GIT_MAX_RAWSZ);
 376         return memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
 377 }
 378
 379 static inline int hasheq(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
 380 {
 381         /*
 382          * We write this here instead of deferring to hashcmp so that the
 383          * compiler can properly inline it and avoid calling memcmp.
 384          */
 385         if (algop->rawsz == GIT_MAX_RAWSZ)
 386                 return !memcmp(sha1, sha2, GIT_MAX_RAWSZ);
 387         return !memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
 388 }
 389
 390 static inline void hashcpy(unsigned char *sha_dst, const unsigned char *sha_src,
 391                            const struct git_hash_algo *algop)
 392 {
 393         memcpy(sha_dst, sha_src, algop->rawsz);
 394 }
 395
 396 static inline void hashclr(unsigned char *hash, const struct git_hash_algo *algop)
 397 {
 398         memset(hash, 0, algop->rawsz);
 399 }
 400
 401 static inline int oidcmp(const struct object_id *oid1, const struct object_id *oid2)
 402 {
 403         return memcmp(oid1->hash, oid2->hash, GIT_MAX_RAWSZ);
 404 }
 405
 406 static inline int oideq(const struct object_id *oid1, const struct object_id *oid2)
 407 {
 408         return !memcmp(oid1->hash, oid2->hash, GIT_MAX_RAWSZ);
 409 }
 410
 411 static inline void oidcpy(struct object_id *dst, const struct object_id *src)
 412 {
 413         memcpy(dst->hash, src->hash, GIT_MAX_RAWSZ);
 414         dst->algo = src->algo;
 415 }
 416
 417 static inline void oidread(struct object_id *oid, const unsigned char *hash,
 418                            const struct git_hash_algo *algop)
 419 {
 420         memcpy(oid->hash, hash, algop->rawsz);
 421         if (algop->rawsz < GIT_MAX_RAWSZ)
 422                 memset(oid->hash + algop->rawsz, 0, GIT_MAX_RAWSZ - algop->rawsz);
 423         oid->algo = hash_algo_by_ptr(algop);
 424 }
 425
 426 static inline void oidclr(struct object_id *oid,
 427                           const struct git_hash_algo *algop)
 428 {
 429         memset(oid->hash, 0, GIT_MAX_RAWSZ);
 430         oid->algo = hash_algo_by_ptr(algop);
 431 }
 432
 433 static inline struct object_id *oiddup(const struct object_id *src)
 434 {
 435         struct object_id *dst = xmalloc(sizeof(struct object_id));
 436         oidcpy(dst, src);
 437         return dst;
 438 }
 439
 440 static inline void oid_set_algo(struct object_id *oid, const struct git_hash_algo *algop)
 441 {
 442         oid->algo = hash_algo_by_ptr(algop);
 443 }
 444
 445 /*
 446  * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code
 447  * for use in hash tables. Cryptographic hashes are supposed to have
 448  * uniform distribution, so in contrast to `memhash()`, this just copies
 449  * the first `sizeof(int)` bytes without shuffling any bits. Note that
 450  * the results will be different on big-endian and little-endian
 451  * platforms, so they should not be stored or transferred over the net.
 452  */
 453 static inline unsigned int oidhash(const struct object_id *oid)
 454 {
 455         /*
 456          * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on
 457          * platforms that don't support unaligned reads.
 458          */
 459         unsigned int hash;
 460         memcpy(&hash, oid->hash, sizeof(hash));
 461         return hash;
 462 }
 463
 464 static inline int is_null_oid(const struct object_id *oid)
 465 {
 466         static const unsigned char null_hash[GIT_MAX_RAWSZ];
 467         return !memcmp(oid->hash, null_hash, GIT_MAX_RAWSZ);
 468 }
 469
 470 const char *empty_tree_oid_hex(const struct git_hash_algo *algop);
 471
 472 static inline int is_empty_blob_oid(const struct object_id *oid,
 473                                     const struct git_hash_algo *algop)
 474 {
 475         return oideq(oid, algop->empty_blob);
 476 }
 477
 478 static inline int is_empty_tree_oid(const struct object_id *oid,
 479                                     const struct git_hash_algo *algop)
 480 {
 481         return oideq(oid, algop->empty_tree);
 482 }
 483
 484 #endif