a12da4e238cad6981507a96576bcf5cfad359f6b
   1/*
   2 * GIT - The information manager from hell
   3 *
   4 * Copyright (C) Linus Torvalds, 2005
   5 *
   6 * This handles basic git sha1 object files - packing, unpacking,
   7 * creation etc.
   8 */
   9#include "cache.h"
  10
  11#ifndef O_NOATIME
  12#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  13#define O_NOATIME 01000000
  14#else
  15#define O_NOATIME 0
  16#endif
  17#endif
  18
  19static unsigned int sha1_file_open_flag = O_NOATIME;
  20
  21static unsigned hexval(char c)
  22{
  23        if (c >= '0' && c <= '9')
  24                return c - '0';
  25        if (c >= 'a' && c <= 'f')
  26                return c - 'a' + 10;
  27        if (c >= 'A' && c <= 'F')
  28                return c - 'A' + 10;
  29        return ~0;
  30}
  31
  32int get_sha1_hex(const char *hex, unsigned char *sha1)
  33{
  34        int i;
  35        for (i = 0; i < 20; i++) {
  36                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  37                if (val & ~0xff)
  38                        return -1;
  39                *sha1++ = val;
  40                hex += 2;
  41        }
  42        return 0;
  43}
  44
  45static int get_sha1_file(const char *path, unsigned char *result)
  46{
  47        char buffer[60];
  48        int fd = open(path, O_RDONLY);
  49        int len;
  50
  51        if (fd < 0)
  52                return -1;
  53        len = read(fd, buffer, sizeof(buffer));
  54        close(fd);
  55        if (len < 40)
  56                return -1;
  57        return get_sha1_hex(buffer, result);
  58}
  59
  60static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir;
  61static void setup_git_env(void)
  62{
  63        git_dir = gitenv(GIT_DIR_ENVIRONMENT);
  64        if (!git_dir)
  65                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  66        git_object_dir = gitenv(DB_ENVIRONMENT);
  67        if (!git_object_dir) {
  68                git_object_dir = xmalloc(strlen(git_dir) + 9);
  69                sprintf(git_object_dir, "%s/objects", git_dir);
  70        }
  71        git_refs_dir = xmalloc(strlen(git_dir) + 6);
  72        sprintf(git_refs_dir, "%s/refs", git_dir);
  73        git_index_file = gitenv(INDEX_ENVIRONMENT);
  74        if (!git_index_file) {
  75                git_index_file = xmalloc(strlen(git_dir) + 7);
  76                sprintf(git_index_file, "%s/index", git_dir);
  77        }
  78}
  79
  80char *get_object_directory(void)
  81{
  82        if (!git_object_dir)
  83                setup_git_env();
  84        return git_object_dir;
  85}
  86
  87char *get_refs_directory(void)
  88{
  89        if (!git_refs_dir)
  90                setup_git_env();
  91        return git_refs_dir;
  92}
  93
  94char *get_index_file(void)
  95{
  96        if (!git_index_file)
  97                setup_git_env();
  98        return git_index_file;
  99}
 100
 101int get_sha1(const char *str, unsigned char *sha1)
 102{
 103        static char pathname[PATH_MAX];
 104        static const char *prefix[] = {
 105                "",
 106                "refs",
 107                "refs/tags",
 108                "refs/heads",
 109                "refs/snap",
 110                NULL
 111        };
 112        const char **p;
 113
 114        if (!get_sha1_hex(str, sha1))
 115                return 0;
 116
 117        if (!git_dir)
 118                setup_git_env();
 119        for (p = prefix; *p; p++) {
 120                snprintf(pathname, sizeof(pathname), "%s/%s/%s",
 121                         git_dir, *p, str);
 122                if (!get_sha1_file(pathname, sha1))
 123                        return 0;
 124        }
 125
 126        return -1;
 127}
 128
 129char * sha1_to_hex(const unsigned char *sha1)
 130{
 131        static char buffer[50];
 132        static const char hex[] = "0123456789abcdef";
 133        char *buf = buffer;
 134        int i;
 135
 136        for (i = 0; i < 20; i++) {
 137                unsigned int val = *sha1++;
 138                *buf++ = hex[val >> 4];
 139                *buf++ = hex[val & 0xf];
 140        }
 141        return buffer;
 142}
 143
 144static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 145{
 146        int i;
 147        for (i = 0; i < 20; i++) {
 148                static char hex[] = "0123456789abcdef";
 149                unsigned int val = sha1[i];
 150                char *pos = pathbuf + i*2 + (i > 0);
 151                *pos++ = hex[val >> 4];
 152                *pos = hex[val & 0xf];
 153        }
 154}
 155
 156/*
 157 * NOTE! This returns a statically allocated buffer, so you have to be
 158 * careful about using it. Do a "strdup()" if you need to save the
 159 * filename.
 160 *
 161 * Also note that this returns the location for creating.  Reading
 162 * SHA1 file can happen from any alternate directory listed in the
 163 * DB_ENVIRONMENT environment variable if it is not found in
 164 * the primary object database.
 165 */
 166char *sha1_file_name(const unsigned char *sha1)
 167{
 168        static char *name, *base;
 169
 170        if (!base) {
 171                const char *sha1_file_directory = get_object_directory();
 172                int len = strlen(sha1_file_directory);
 173                base = xmalloc(len + 60);
 174                memcpy(base, sha1_file_directory, len);
 175                memset(base+len, 0, 60);
 176                base[len] = '/';
 177                base[len+3] = '/';
 178                name = base + len + 1;
 179        }
 180        fill_sha1_path(name, sha1);
 181        return base;
 182}
 183
 184static struct alternate_object_database {
 185        char *base;
 186        char *name;
 187} *alt_odb;
 188
 189/*
 190 * Prepare alternate object database registry.
 191 * alt_odb points at an array of struct alternate_object_database.
 192 * This array is terminated with an element that has both its base
 193 * and name set to NULL.  alt_odb[n] comes from n'th non-empty
 194 * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
 195 * variable, and its base points at a statically allocated buffer
 196 * that contains "/the/directory/corresponding/to/.git/objects/...",
 197 * while its name points just after the slash at the end of
 198 * ".git/objects/" in the example above, and has enough space to hold
 199 * 40-byte hex SHA1, an extra slash for the first level indirection,
 200 * and the terminating NUL.
 201 * This function allocates the alt_odb array and all the strings
 202 * pointed by base fields of the array elements with one xmalloc();
 203 * the string pool immediately follows the array.
 204 */
 205static void prepare_alt_odb(void)
 206{
 207        int pass, totlen, i;
 208        const char *cp, *last;
 209        char *op = NULL;
 210        const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
 211
 212        /* The first pass counts how large an area to allocate to
 213         * hold the entire alt_odb structure, including array of
 214         * structs and path buffers for them.  The second pass fills
 215         * the structure and prepares the path buffers for use by
 216         * fill_sha1_path().
 217         */
 218        for (totlen = pass = 0; pass < 2; pass++) {
 219                last = alt;
 220                i = 0;
 221                do {
 222                        cp = strchr(last, ':') ? : last + strlen(last);
 223                        if (last != cp) {
 224                                /* 43 = 40-byte + 2 '/' + terminating NUL */
 225                                int pfxlen = cp - last;
 226                                int entlen = pfxlen + 43;
 227                                if (pass == 0)
 228                                        totlen += entlen;
 229                                else {
 230                                        alt_odb[i].base = op;
 231                                        alt_odb[i].name = op + pfxlen + 1;
 232                                        memcpy(op, last, pfxlen);
 233                                        op[pfxlen] = op[pfxlen + 3] = '/';
 234                                        op[entlen-1] = 0;
 235                                        op += entlen;
 236                                }
 237                                i++;
 238                        }
 239                        while (*cp && *cp == ':')
 240                                cp++;
 241                        last = cp;
 242                } while (*cp);
 243                if (pass)
 244                        break;
 245                alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
 246                alt_odb[i].base = alt_odb[i].name = NULL;
 247                op = (char*)(&alt_odb[i+1]);
 248        }
 249}
 250
 251static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 252{
 253        int i;
 254        char *name = sha1_file_name(sha1);
 255
 256        if (!stat(name, st))
 257                return name;
 258        if (!alt_odb)
 259                prepare_alt_odb();
 260        for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
 261                fill_sha1_path(name, sha1);
 262                if (!stat(alt_odb[i].base, st))
 263                        return alt_odb[i].base;
 264        }
 265        return NULL;
 266}
 267
 268int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 269{
 270        char header[100];
 271        unsigned char real_sha1[20];
 272        SHA_CTX c;
 273
 274        SHA1_Init(&c);
 275        SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 276        SHA1_Update(&c, map, size);
 277        SHA1_Final(real_sha1, &c);
 278        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 279}
 280
 281void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 282{
 283        struct stat st;
 284        void *map;
 285        int fd;
 286        char *filename = find_sha1_file(sha1, &st);
 287
 288        if (!filename) {
 289                error("cannot map sha1 file %s", sha1_to_hex(sha1));
 290                return NULL;
 291        }
 292
 293        fd = open(filename, O_RDONLY | sha1_file_open_flag);
 294        if (fd < 0) {
 295                /* See if it works without O_NOATIME */
 296                switch (sha1_file_open_flag) {
 297                default:
 298                        fd = open(filename, O_RDONLY);
 299                        if (fd >= 0)
 300                                break;
 301                /* Fallthrough */
 302                case 0:
 303                        perror(filename);
 304                        return NULL;
 305                }
 306
 307                /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 308                sha1_file_open_flag = 0;
 309        }
 310        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 311        close(fd);
 312        if (-1 == (int)(long)map)
 313                return NULL;
 314        *size = st.st_size;
 315        return map;
 316}
 317
 318int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 319{
 320        /* Get the data stream */
 321        memset(stream, 0, sizeof(*stream));
 322        stream->next_in = map;
 323        stream->avail_in = mapsize;
 324        stream->next_out = buffer;
 325        stream->avail_out = size;
 326
 327        inflateInit(stream);
 328        return inflate(stream, 0);
 329}
 330
 331void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 332{
 333        int bytes = strlen(buffer) + 1;
 334        unsigned char *buf = xmalloc(1+size);
 335
 336        memcpy(buf, buffer + bytes, stream->total_out - bytes);
 337        bytes = stream->total_out - bytes;
 338        if (bytes < size) {
 339                stream->next_out = buf + bytes;
 340                stream->avail_out = size - bytes;
 341                while (inflate(stream, Z_FINISH) == Z_OK)
 342                        /* nothing */;
 343        }
 344        buf[size] = 0;
 345        inflateEnd(stream);
 346        return buf;
 347}
 348
 349/*
 350 * We used to just use "sscanf()", but that's actually way
 351 * too permissive for what we want to check. So do an anal
 352 * object header parse by hand.
 353 */
 354int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 355{
 356        int i;
 357        unsigned long size;
 358
 359        /*
 360         * The type can be at most ten bytes (including the 
 361         * terminating '\0' that we add), and is followed by
 362         * a space. 
 363         */
 364        i = 10;
 365        for (;;) {
 366                char c = *hdr++;
 367                if (c == ' ')
 368                        break;
 369                if (!--i)
 370                        return -1;
 371                *type++ = c;
 372        }
 373        *type = 0;
 374
 375        /*
 376         * The length must follow immediately, and be in canonical
 377         * decimal format (ie "010" is not valid).
 378         */
 379        size = *hdr++ - '0';
 380        if (size > 9)
 381                return -1;
 382        if (size) {
 383                for (;;) {
 384                        unsigned long c = *hdr - '0';
 385                        if (c > 9)
 386                                break;
 387                        hdr++;
 388                        size = size * 10 + c;
 389                }
 390        }
 391        *sizep = size;
 392
 393        /*
 394         * The length must be followed by a zero byte
 395         */
 396        return *hdr ? -1 : 0;
 397}
 398
 399void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 400{
 401        int ret;
 402        z_stream stream;
 403        char hdr[8192];
 404
 405        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 406        if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 407                return NULL;
 408
 409        return unpack_sha1_rest(&stream, hdr, *size);
 410}
 411
 412int sha1_file_size(const unsigned char *sha1, unsigned long *sizep)
 413{
 414        int ret, status;
 415        unsigned long mapsize, size;
 416        void *map;
 417        z_stream stream;
 418        char hdr[64], type[20];
 419
 420        map = map_sha1_file(sha1, &mapsize);
 421        if (!map)
 422                return -1;
 423        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 424        if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0)
 425                status = -1;
 426        else {
 427                status = 0;
 428                *sizep = size;
 429        }
 430        inflateEnd(&stream);
 431        munmap(map, mapsize);
 432        return status;
 433}
 434
 435void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 436{
 437        unsigned long mapsize;
 438        void *map, *buf;
 439
 440        map = map_sha1_file(sha1, &mapsize);
 441        if (map) {
 442                buf = unpack_sha1_file(map, mapsize, type, size);
 443                munmap(map, mapsize);
 444                return buf;
 445        }
 446        return NULL;
 447}
 448
 449void *read_object_with_reference(const unsigned char *sha1,
 450                                 const char *required_type,
 451                                 unsigned long *size,
 452                                 unsigned char *actual_sha1_return)
 453{
 454        char type[20];
 455        void *buffer;
 456        unsigned long isize;
 457        unsigned char actual_sha1[20];
 458
 459        memcpy(actual_sha1, sha1, 20);
 460        while (1) {
 461                int ref_length = -1;
 462                const char *ref_type = NULL;
 463
 464                buffer = read_sha1_file(actual_sha1, type, &isize);
 465                if (!buffer)
 466                        return NULL;
 467                if (!strcmp(type, required_type)) {
 468                        *size = isize;
 469                        if (actual_sha1_return)
 470                                memcpy(actual_sha1_return, actual_sha1, 20);
 471                        return buffer;
 472                }
 473                /* Handle references */
 474                else if (!strcmp(type, "commit"))
 475                        ref_type = "tree ";
 476                else if (!strcmp(type, "tag"))
 477                        ref_type = "object ";
 478                else {
 479                        free(buffer);
 480                        return NULL;
 481                }
 482                ref_length = strlen(ref_type);
 483
 484                if (memcmp(buffer, ref_type, ref_length) ||
 485                    get_sha1_hex(buffer + ref_length, actual_sha1)) {
 486                        free(buffer);
 487                        return NULL;
 488                }
 489                /* Now we have the ID of the referred-to object in
 490                 * actual_sha1.  Check again. */
 491        }
 492}
 493
 494int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 495{
 496        int size;
 497        unsigned char *compressed;
 498        z_stream stream;
 499        unsigned char sha1[20];
 500        SHA_CTX c;
 501        char *filename;
 502        static char tmpfile[PATH_MAX];
 503        unsigned char hdr[50];
 504        int fd, hdrlen, ret;
 505
 506        /* Generate the header */
 507        hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
 508
 509        /* Sha1.. */
 510        SHA1_Init(&c);
 511        SHA1_Update(&c, hdr, hdrlen);
 512        SHA1_Update(&c, buf, len);
 513        SHA1_Final(sha1, &c);
 514
 515        if (returnsha1)
 516                memcpy(returnsha1, sha1, 20);
 517
 518        filename = sha1_file_name(sha1);
 519        fd = open(filename, O_RDONLY);
 520        if (fd >= 0) {
 521                /*
 522                 * FIXME!!! We might do collision checking here, but we'd
 523                 * need to uncompress the old file and check it. Later.
 524                 */
 525                close(fd);
 526                return 0;
 527        }
 528
 529        if (errno != ENOENT) {
 530                fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
 531                return -1;
 532        }
 533
 534        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 535
 536        fd = mkstemp(tmpfile);
 537        if (fd < 0) {
 538                fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
 539                return -1;
 540        }
 541
 542        /* Set it up */
 543        memset(&stream, 0, sizeof(stream));
 544        deflateInit(&stream, Z_BEST_COMPRESSION);
 545        size = deflateBound(&stream, len+hdrlen);
 546        compressed = xmalloc(size);
 547
 548        /* Compress it */
 549        stream.next_out = compressed;
 550        stream.avail_out = size;
 551
 552        /* First header.. */
 553        stream.next_in = hdr;
 554        stream.avail_in = hdrlen;
 555        while (deflate(&stream, 0) == Z_OK)
 556                /* nothing */;
 557
 558        /* Then the data itself.. */
 559        stream.next_in = buf;
 560        stream.avail_in = len;
 561        while (deflate(&stream, Z_FINISH) == Z_OK)
 562                /* nothing */;
 563        deflateEnd(&stream);
 564        size = stream.total_out;
 565
 566        if (write(fd, compressed, size) != size)
 567                die("unable to write file");
 568        fchmod(fd, 0444);
 569        close(fd);
 570        free(compressed);
 571
 572        ret = link(tmpfile, filename);
 573        if (ret < 0) {
 574                ret = errno;
 575
 576                /*
 577                 * Coda hack - coda doesn't like cross-directory links,
 578                 * so we fall back to a rename, which will mean that it
 579                 * won't be able to check collisions, but that's not a
 580                 * big deal.
 581                 *
 582                 * When this succeeds, we just return 0. We have nothing
 583                 * left to unlink.
 584                 */
 585                if (ret == EXDEV && !rename(tmpfile, filename))
 586                        return 0;
 587        }
 588        unlink(tmpfile);
 589        if (ret) {
 590                if (ret != EEXIST) {
 591                        fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
 592                        return -1;
 593                }
 594                /* FIXME!!! Collision check here ? */
 595        }
 596
 597        return 0;
 598}
 599
 600int write_sha1_from_fd(const unsigned char *sha1, int fd)
 601{
 602        char *filename = sha1_file_name(sha1);
 603
 604        int local;
 605        z_stream stream;
 606        unsigned char real_sha1[20];
 607        unsigned char buf[4096];
 608        unsigned char discard[4096];
 609        int ret;
 610        SHA_CTX c;
 611
 612        local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 613
 614        if (local < 0)
 615                return error("Couldn't open %s\n", filename);
 616
 617        memset(&stream, 0, sizeof(stream));
 618
 619        inflateInit(&stream);
 620
 621        SHA1_Init(&c);
 622
 623        do {
 624                ssize_t size;
 625                size = read(fd, buf, 4096);
 626                if (size <= 0) {
 627                        close(local);
 628                        unlink(filename);
 629                        if (!size)
 630                                return error("Connection closed?");
 631                        perror("Reading from connection");
 632                        return -1;
 633                }
 634                write(local, buf, size);
 635                stream.avail_in = size;
 636                stream.next_in = buf;
 637                do {
 638                        stream.next_out = discard;
 639                        stream.avail_out = sizeof(discard);
 640                        ret = inflate(&stream, Z_SYNC_FLUSH);
 641                        SHA1_Update(&c, discard, sizeof(discard) -
 642                                    stream.avail_out);
 643                } while (stream.avail_in && ret == Z_OK);
 644                
 645        } while (ret == Z_OK);
 646        inflateEnd(&stream);
 647
 648        close(local);
 649        SHA1_Final(real_sha1, &c);
 650        if (ret != Z_STREAM_END) {
 651                unlink(filename);
 652                return error("File %s corrupted", sha1_to_hex(sha1));
 653        }
 654        if (memcmp(sha1, real_sha1, 20)) {
 655                unlink(filename);
 656                return error("File %s has bad hash\n", sha1_to_hex(sha1));
 657        }
 658        
 659        return 0;
 660}
 661
 662int has_sha1_file(const unsigned char *sha1)
 663{
 664        struct stat st;
 665        return !!find_sha1_file(sha1, &st);
 666}
 667
 668int index_fd(unsigned char *sha1, int fd, struct stat *st)
 669{
 670        unsigned long size = st->st_size;
 671        void *buf;
 672        int ret;
 673
 674        buf = "";
 675        if (size)
 676                buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 677        close(fd);
 678        if ((int)(long)buf == -1)
 679                return -1;
 680
 681        ret = write_sha1_file(buf, size, "blob", sha1);
 682        if (size)
 683                munmap(buf, size);
 684        return ret;
 685}