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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include <errno.h>
     18 #include <libgen.h>
     19 #include <stdio.h>
     20 #include <stdlib.h>
     21 #include <string.h>
     22 #include <sys/stat.h>
     23 #include <sys/statfs.h>
     24 #include <sys/types.h>
     25 #include <fcntl.h>
     26 #include <unistd.h>
     27 
     28 #include "mincrypt/sha.h"
     29 #include "applypatch.h"
     30 #include "mtdutils/mtdutils.h"
     31 #include "edify/expr.h"
     32 
     33 static int LoadPartitionContents(const char* filename, FileContents* file);
     34 static ssize_t FileSink(unsigned char* data, ssize_t len, void* token);
     35 static int GenerateTarget(FileContents* source_file,
     36                           const Value* source_patch_value,
     37                           FileContents* copy_file,
     38                           const Value* copy_patch_value,
     39                           const char* source_filename,
     40                           const char* target_filename,
     41                           const uint8_t target_sha1[SHA_DIGEST_SIZE],
     42                           size_t target_size,
     43                           const Value* bonus_data);
     44 
     45 static int mtd_partitions_scanned = 0;
     46 
     47 // Read a file into memory; optionally (retouch_flag == RETOUCH_DO_MASK) mask
     48 // the retouched entries back to their original value (such that SHA-1 checks
     49 // don't fail due to randomization); store the file contents and associated
     50 // metadata in *file.
     51 //
     52 // Return 0 on success.
     53 int LoadFileContents(const char* filename, FileContents* file,
     54                      int retouch_flag) {
     55     file->data = NULL;
     56 
     57     // A special 'filename' beginning with "MTD:" or "EMMC:" means to
     58     // load the contents of a partition.
     59     if (strncmp(filename, "MTD:", 4) == 0 ||
     60         strncmp(filename, "EMMC:", 5) == 0) {
     61         return LoadPartitionContents(filename, file);
     62     }
     63 
     64     if (stat(filename, &file->st) != 0) {
     65         printf("failed to stat \"%s\": %s\n", filename, strerror(errno));
     66         return -1;
     67     }
     68 
     69     file->size = file->st.st_size;
     70     file->data = malloc(file->size);
     71 
     72     FILE* f = fopen(filename, "rb");
     73     if (f == NULL) {
     74         printf("failed to open \"%s\": %s\n", filename, strerror(errno));
     75         free(file->data);
     76         file->data = NULL;
     77         return -1;
     78     }
     79 
     80     ssize_t bytes_read = fread(file->data, 1, file->size, f);
     81     if (bytes_read != file->size) {
     82         printf("short read of \"%s\" (%ld bytes of %ld)\n",
     83                filename, (long)bytes_read, (long)file->size);
     84         free(file->data);
     85         file->data = NULL;
     86         return -1;
     87     }
     88     fclose(f);
     89 
     90     // apply_patch[_check] functions are blind to randomization. Randomization
     91     // is taken care of in [Undo]RetouchBinariesFn. If there is a mismatch
     92     // within a file, this means the file is assumed "corrupt" for simplicity.
     93     if (retouch_flag) {
     94         int32_t desired_offset = 0;
     95         if (retouch_mask_data(file->data, file->size,
     96                               &desired_offset, NULL) != RETOUCH_DATA_MATCHED) {
     97             printf("error trying to mask retouch entries\n");
     98             free(file->data);
     99             file->data = NULL;
    100             return -1;
    101         }
    102     }
    103 
    104     SHA(file->data, file->size, file->sha1);
    105     return 0;
    106 }
    107 
    108 static size_t* size_array;
    109 // comparison function for qsort()ing an int array of indexes into
    110 // size_array[].
    111 static int compare_size_indices(const void* a, const void* b) {
    112     int aa = *(int*)a;
    113     int bb = *(int*)b;
    114     if (size_array[aa] < size_array[bb]) {
    115         return -1;
    116     } else if (size_array[aa] > size_array[bb]) {
    117         return 1;
    118     } else {
    119         return 0;
    120     }
    121 }
    122 
    123 // Load the contents of an MTD or EMMC partition into the provided
    124 // FileContents.  filename should be a string of the form
    125 // "MTD:<partition_name>:<size_1>:<sha1_1>:<size_2>:<sha1_2>:..."  (or
    126 // "EMMC:<partition_device>:...").  The smallest size_n bytes for
    127 // which that prefix of the partition contents has the corresponding
    128 // sha1 hash will be loaded.  It is acceptable for a size value to be
    129 // repeated with different sha1s.  Will return 0 on success.
    130 //
    131 // This complexity is needed because if an OTA installation is
    132 // interrupted, the partition might contain either the source or the
    133 // target data, which might be of different lengths.  We need to know
    134 // the length in order to read from a partition (there is no
    135 // "end-of-file" marker), so the caller must specify the possible
    136 // lengths and the hash of the data, and we'll do the load expecting
    137 // to find one of those hashes.
    138 enum PartitionType { MTD, EMMC };
    139 
    140 static int LoadPartitionContents(const char* filename, FileContents* file) {
    141     char* copy = strdup(filename);
    142     const char* magic = strtok(copy, ":");
    143 
    144     enum PartitionType type;
    145 
    146     if (strcmp(magic, "MTD") == 0) {
    147         type = MTD;
    148     } else if (strcmp(magic, "EMMC") == 0) {
    149         type = EMMC;
    150     } else {
    151         printf("LoadPartitionContents called with bad filename (%s)\n",
    152                filename);
    153         return -1;
    154     }
    155     const char* partition = strtok(NULL, ":");
    156 
    157     int i;
    158     int colons = 0;
    159     for (i = 0; filename[i] != '\0'; ++i) {
    160         if (filename[i] == ':') {
    161             ++colons;
    162         }
    163     }
    164     if (colons < 3 || colons%2 == 0) {
    165         printf("LoadPartitionContents called with bad filename (%s)\n",
    166                filename);
    167     }
    168 
    169     int pairs = (colons-1)/2;     // # of (size,sha1) pairs in filename
    170     int* index = malloc(pairs * sizeof(int));
    171     size_t* size = malloc(pairs * sizeof(size_t));
    172     char** sha1sum = malloc(pairs * sizeof(char*));
    173 
    174     for (i = 0; i < pairs; ++i) {
    175         const char* size_str = strtok(NULL, ":");
    176         size[i] = strtol(size_str, NULL, 10);
    177         if (size[i] == 0) {
    178             printf("LoadPartitionContents called with bad size (%s)\n", filename);
    179             return -1;
    180         }
    181         sha1sum[i] = strtok(NULL, ":");
    182         index[i] = i;
    183     }
    184 
    185     // sort the index[] array so it indexes the pairs in order of
    186     // increasing size.
    187     size_array = size;
    188     qsort(index, pairs, sizeof(int), compare_size_indices);
    189 
    190     MtdReadContext* ctx = NULL;
    191     FILE* dev = NULL;
    192 
    193     switch (type) {
    194         case MTD:
    195             if (!mtd_partitions_scanned) {
    196                 mtd_scan_partitions();
    197                 mtd_partitions_scanned = 1;
    198             }
    199 
    200             const MtdPartition* mtd = mtd_find_partition_by_name(partition);
    201             if (mtd == NULL) {
    202                 printf("mtd partition \"%s\" not found (loading %s)\n",
    203                        partition, filename);
    204                 return -1;
    205             }
    206 
    207             ctx = mtd_read_partition(mtd);
    208             if (ctx == NULL) {
    209                 printf("failed to initialize read of mtd partition \"%s\"\n",
    210                        partition);
    211                 return -1;
    212             }
    213             break;
    214 
    215         case EMMC:
    216             dev = fopen(partition, "rb");
    217             if (dev == NULL) {
    218                 printf("failed to open emmc partition \"%s\": %s\n",
    219                        partition, strerror(errno));
    220                 return -1;
    221             }
    222     }
    223 
    224     SHA_CTX sha_ctx;
    225     SHA_init(&sha_ctx);
    226     uint8_t parsed_sha[SHA_DIGEST_SIZE];
    227 
    228     // allocate enough memory to hold the largest size.
    229     file->data = malloc(size[index[pairs-1]]);
    230     char* p = (char*)file->data;
    231     file->size = 0;                // # bytes read so far
    232 
    233     for (i = 0; i < pairs; ++i) {
    234         // Read enough additional bytes to get us up to the next size
    235         // (again, we're trying the possibilities in order of increasing
    236         // size).
    237         size_t next = size[index[i]] - file->size;
    238         size_t read = 0;
    239         if (next > 0) {
    240             switch (type) {
    241                 case MTD:
    242                     read = mtd_read_data(ctx, p, next);
    243                     break;
    244 
    245                 case EMMC:
    246                     read = fread(p, 1, next, dev);
    247                     break;
    248             }
    249             if (next != read) {
    250                 printf("short read (%d bytes of %d) for partition \"%s\"\n",
    251                        read, next, partition);
    252                 free(file->data);
    253                 file->data = NULL;
    254                 return -1;
    255             }
    256             SHA_update(&sha_ctx, p, read);
    257             file->size += read;
    258         }
    259 
    260         // Duplicate the SHA context and finalize the duplicate so we can
    261         // check it against this pair's expected hash.
    262         SHA_CTX temp_ctx;
    263         memcpy(&temp_ctx, &sha_ctx, sizeof(SHA_CTX));
    264         const uint8_t* sha_so_far = SHA_final(&temp_ctx);
    265 
    266         if (ParseSha1(sha1sum[index[i]], parsed_sha) != 0) {
    267             printf("failed to parse sha1 %s in %s\n",
    268                    sha1sum[index[i]], filename);
    269             free(file->data);
    270             file->data = NULL;
    271             return -1;
    272         }
    273 
    274         if (memcmp(sha_so_far, parsed_sha, SHA_DIGEST_SIZE) == 0) {
    275             // we have a match.  stop reading the partition; we'll return
    276             // the data we've read so far.
    277             printf("partition read matched size %d sha %s\n",
    278                    size[index[i]], sha1sum[index[i]]);
    279             break;
    280         }
    281 
    282         p += read;
    283     }
    284 
    285     switch (type) {
    286         case MTD:
    287             mtd_read_close(ctx);
    288             break;
    289 
    290         case EMMC:
    291             fclose(dev);
    292             break;
    293     }
    294 
    295 
    296     if (i == pairs) {
    297         // Ran off the end of the list of (size,sha1) pairs without
    298         // finding a match.
    299         printf("contents of partition \"%s\" didn't match %s\n",
    300                partition, filename);
    301         free(file->data);
    302         file->data = NULL;
    303         return -1;
    304     }
    305 
    306     const uint8_t* sha_final = SHA_final(&sha_ctx);
    307     for (i = 0; i < SHA_DIGEST_SIZE; ++i) {
    308         file->sha1[i] = sha_final[i];
    309     }
    310 
    311     // Fake some stat() info.
    312     file->st.st_mode = 0644;
    313     file->st.st_uid = 0;
    314     file->st.st_gid = 0;
    315 
    316     free(copy);
    317     free(index);
    318     free(size);
    319     free(sha1sum);
    320 
    321     return 0;
    322 }
    323 
    324 
    325 // Save the contents of the given FileContents object under the given
    326 // filename.  Return 0 on success.
    327 int SaveFileContents(const char* filename, const FileContents* file) {
    328     int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
    329     if (fd < 0) {
    330         printf("failed to open \"%s\" for write: %s\n",
    331                filename, strerror(errno));
    332         return -1;
    333     }
    334 
    335     ssize_t bytes_written = FileSink(file->data, file->size, &fd);
    336     if (bytes_written != file->size) {
    337         printf("short write of \"%s\" (%ld bytes of %ld) (%s)\n",
    338                filename, (long)bytes_written, (long)file->size,
    339                strerror(errno));
    340         close(fd);
    341         return -1;
    342     }
    343     fsync(fd);
    344     close(fd);
    345 
    346     if (chmod(filename, file->st.st_mode) != 0) {
    347         printf("chmod of \"%s\" failed: %s\n", filename, strerror(errno));
    348         return -1;
    349     }
    350     if (chown(filename, file->st.st_uid, file->st.st_gid) != 0) {
    351         printf("chown of \"%s\" failed: %s\n", filename, strerror(errno));
    352         return -1;
    353     }
    354 
    355     return 0;
    356 }
    357 
    358 // Write a memory buffer to 'target' partition, a string of the form
    359 // "MTD:<partition>[:...]" or "EMMC:<partition_device>:".  Return 0 on
    360 // success.
    361 int WriteToPartition(unsigned char* data, size_t len,
    362                         const char* target) {
    363     char* copy = strdup(target);
    364     const char* magic = strtok(copy, ":");
    365 
    366     enum PartitionType type;
    367     if (strcmp(magic, "MTD") == 0) {
    368         type = MTD;
    369     } else if (strcmp(magic, "EMMC") == 0) {
    370         type = EMMC;
    371     } else {
    372         printf("WriteToPartition called with bad target (%s)\n", target);
    373         return -1;
    374     }
    375     const char* partition = strtok(NULL, ":");
    376 
    377     if (partition == NULL) {
    378         printf("bad partition target name \"%s\"\n", target);
    379         return -1;
    380     }
    381 
    382     switch (type) {
    383         case MTD:
    384             if (!mtd_partitions_scanned) {
    385                 mtd_scan_partitions();
    386                 mtd_partitions_scanned = 1;
    387             }
    388 
    389             const MtdPartition* mtd = mtd_find_partition_by_name(partition);
    390             if (mtd == NULL) {
    391                 printf("mtd partition \"%s\" not found for writing\n",
    392                        partition);
    393                 return -1;
    394             }
    395 
    396             MtdWriteContext* ctx = mtd_write_partition(mtd);
    397             if (ctx == NULL) {
    398                 printf("failed to init mtd partition \"%s\" for writing\n",
    399                        partition);
    400                 return -1;
    401             }
    402 
    403             size_t written = mtd_write_data(ctx, (char*)data, len);
    404             if (written != len) {
    405                 printf("only wrote %d of %d bytes to MTD %s\n",
    406                        written, len, partition);
    407                 mtd_write_close(ctx);
    408                 return -1;
    409             }
    410 
    411             if (mtd_erase_blocks(ctx, -1) < 0) {
    412                 printf("error finishing mtd write of %s\n", partition);
    413                 mtd_write_close(ctx);
    414                 return -1;
    415             }
    416 
    417             if (mtd_write_close(ctx)) {
    418                 printf("error closing mtd write of %s\n", partition);
    419                 return -1;
    420             }
    421             break;
    422 
    423         case EMMC:
    424         {
    425             size_t start = 0;
    426             int success = 0;
    427             int fd = open(partition, O_RDWR | O_SYNC);
    428             if (fd < 0) {
    429                 printf("failed to open %s: %s\n", partition, strerror(errno));
    430                 return -1;
    431             }
    432             int attempt;
    433 
    434             for (attempt = 0; attempt < 10; ++attempt) {
    435                 size_t next_sync = start + (1<<20);
    436                 printf("raw O_SYNC write %s attempt %d start at %d\n", partition, attempt+1, start);
    437                 lseek(fd, start, SEEK_SET);
    438                 while (start < len) {
    439                     size_t to_write = len - start;
    440                     if (to_write > 4096) to_write = 4096;
    441 
    442                     ssize_t written = write(fd, data+start, to_write);
    443                     if (written < 0) {
    444                         if (errno == EINTR) {
    445                             written = 0;
    446                         } else {
    447                             printf("failed write writing to %s (%s)\n",
    448                                    partition, strerror(errno));
    449                             return -1;
    450                         }
    451                     }
    452                     start += written;
    453                     if (start >= next_sync) {
    454                         fsync(fd);
    455                         next_sync = start + (1<<20);
    456                     }
    457                 }
    458                 fsync(fd);
    459 
    460                 // drop caches so our subsequent verification read
    461                 // won't just be reading the cache.
    462                 sync();
    463                 int dc = open("/proc/sys/vm/drop_caches", O_WRONLY);
    464                 write(dc, "3\n", 2);
    465                 close(dc);
    466                 sleep(1);
    467                 printf("  caches dropped\n");
    468 
    469                 // verify
    470                 lseek(fd, 0, SEEK_SET);
    471                 unsigned char buffer[4096];
    472                 start = len;
    473                 size_t p;
    474                 for (p = 0; p < len; p += sizeof(buffer)) {
    475                     size_t to_read = len - p;
    476                     if (to_read > sizeof(buffer)) to_read = sizeof(buffer);
    477 
    478                     size_t so_far = 0;
    479                     while (so_far < to_read) {
    480                         ssize_t read_count = read(fd, buffer+so_far, to_read-so_far);
    481                         if (read_count < 0) {
    482                             if (errno == EINTR) {
    483                                 read_count = 0;
    484                             } else {
    485                                 printf("verify read error %s at %d: %s\n",
    486                                        partition, p, strerror(errno));
    487                                 return -1;
    488                             }
    489                         }
    490                         if ((size_t)read_count < to_read) {
    491                             printf("short verify read %s at %d: %d %d %s\n",
    492                                    partition, p, read_count, to_read, strerror(errno));
    493                         }
    494                         so_far += read_count;
    495                     }
    496 
    497                     if (memcmp(buffer, data+p, to_read)) {
    498                         printf("verification failed starting at %d\n", p);
    499                         start = p;
    500                         break;
    501                     }
    502                 }
    503 
    504                 if (start == len) {
    505                     printf("verification read succeeded (attempt %d)\n", attempt+1);
    506                     success = true;
    507                     break;
    508                 }
    509 
    510                 sleep(2);
    511             }
    512 
    513             if (!success) {
    514                 printf("failed to verify after all attempts\n");
    515                 return -1;
    516             }
    517 
    518             if (close(fd) != 0) {
    519                 printf("error closing %s (%s)\n", partition, strerror(errno));
    520                 return -1;
    521             }
    522             // hack: sync and sleep after closing in hopes of getting
    523             // the data actually onto flash.
    524             printf("sleeping after close\n");
    525             sync();
    526             sleep(5);
    527             break;
    528         }
    529     }
    530 
    531     free(copy);
    532     return 0;
    533 }
    534 
    535 
    536 // Take a string 'str' of 40 hex digits and parse it into the 20
    537 // byte array 'digest'.  'str' may contain only the digest or be of
    538 // the form "<digest>:<anything>".  Return 0 on success, -1 on any
    539 // error.
    540 int ParseSha1(const char* str, uint8_t* digest) {
    541     int i;
    542     const char* ps = str;
    543     uint8_t* pd = digest;
    544     for (i = 0; i < SHA_DIGEST_SIZE * 2; ++i, ++ps) {
    545         int digit;
    546         if (*ps >= '0' && *ps <= '9') {
    547             digit = *ps - '0';
    548         } else if (*ps >= 'a' && *ps <= 'f') {
    549             digit = *ps - 'a' + 10;
    550         } else if (*ps >= 'A' && *ps <= 'F') {
    551             digit = *ps - 'A' + 10;
    552         } else {
    553             return -1;
    554         }
    555         if (i % 2 == 0) {
    556             *pd = digit << 4;
    557         } else {
    558             *pd |= digit;
    559             ++pd;
    560         }
    561     }
    562     if (*ps != '\0') return -1;
    563     return 0;
    564 }
    565 
    566 // Search an array of sha1 strings for one matching the given sha1.
    567 // Return the index of the match on success, or -1 if no match is
    568 // found.
    569 int FindMatchingPatch(uint8_t* sha1, char* const * const patch_sha1_str,
    570                       int num_patches) {
    571     int i;
    572     uint8_t patch_sha1[SHA_DIGEST_SIZE];
    573     for (i = 0; i < num_patches; ++i) {
    574         if (ParseSha1(patch_sha1_str[i], patch_sha1) == 0 &&
    575             memcmp(patch_sha1, sha1, SHA_DIGEST_SIZE) == 0) {
    576             return i;
    577         }
    578     }
    579     return -1;
    580 }
    581 
    582 // Returns 0 if the contents of the file (argv[2]) or the cached file
    583 // match any of the sha1's on the command line (argv[3:]).  Returns
    584 // nonzero otherwise.
    585 int applypatch_check(const char* filename,
    586                      int num_patches, char** const patch_sha1_str) {
    587     FileContents file;
    588     file.data = NULL;
    589 
    590     // It's okay to specify no sha1s; the check will pass if the
    591     // LoadFileContents is successful.  (Useful for reading
    592     // partitions, where the filename encodes the sha1s; no need to
    593     // check them twice.)
    594     if (LoadFileContents(filename, &file, RETOUCH_DO_MASK) != 0 ||
    595         (num_patches > 0 &&
    596          FindMatchingPatch(file.sha1, patch_sha1_str, num_patches) < 0)) {
    597         printf("file \"%s\" doesn't have any of expected "
    598                "sha1 sums; checking cache\n", filename);
    599 
    600         free(file.data);
    601         file.data = NULL;
    602 
    603         // If the source file is missing or corrupted, it might be because
    604         // we were killed in the middle of patching it.  A copy of it
    605         // should have been made in CACHE_TEMP_SOURCE.  If that file
    606         // exists and matches the sha1 we're looking for, the check still
    607         // passes.
    608 
    609         if (LoadFileContents(CACHE_TEMP_SOURCE, &file, RETOUCH_DO_MASK) != 0) {
    610             printf("failed to load cache file\n");
    611             return 1;
    612         }
    613 
    614         if (FindMatchingPatch(file.sha1, patch_sha1_str, num_patches) < 0) {
    615             printf("cache bits don't match any sha1 for \"%s\"\n", filename);
    616             free(file.data);
    617             return 1;
    618         }
    619     }
    620 
    621     free(file.data);
    622     return 0;
    623 }
    624 
    625 int ShowLicenses() {
    626     ShowBSDiffLicense();
    627     return 0;
    628 }
    629 
    630 ssize_t FileSink(unsigned char* data, ssize_t len, void* token) {
    631     int fd = *(int *)token;
    632     ssize_t done = 0;
    633     ssize_t wrote;
    634     while (done < (ssize_t) len) {
    635         wrote = write(fd, data+done, len-done);
    636         if (wrote <= 0) {
    637             printf("error writing %d bytes: %s\n", (int)(len-done), strerror(errno));
    638             return done;
    639         }
    640         done += wrote;
    641     }
    642     return done;
    643 }
    644 
    645 typedef struct {
    646     unsigned char* buffer;
    647     ssize_t size;
    648     ssize_t pos;
    649 } MemorySinkInfo;
    650 
    651 ssize_t MemorySink(unsigned char* data, ssize_t len, void* token) {
    652     MemorySinkInfo* msi = (MemorySinkInfo*)token;
    653     if (msi->size - msi->pos < len) {
    654         return -1;
    655     }
    656     memcpy(msi->buffer + msi->pos, data, len);
    657     msi->pos += len;
    658     return len;
    659 }
    660 
    661 // Return the amount of free space (in bytes) on the filesystem
    662 // containing filename.  filename must exist.  Return -1 on error.
    663 size_t FreeSpaceForFile(const char* filename) {
    664     struct statfs sf;
    665     if (statfs(filename, &sf) != 0) {
    666         printf("failed to statfs %s: %s\n", filename, strerror(errno));
    667         return -1;
    668     }
    669     return sf.f_bsize * sf.f_bfree;
    670 }
    671 
    672 int CacheSizeCheck(size_t bytes) {
    673     if (MakeFreeSpaceOnCache(bytes) < 0) {
    674         printf("unable to make %ld bytes available on /cache\n", (long)bytes);
    675         return 1;
    676     } else {
    677         return 0;
    678     }
    679 }
    680 
    681 static void print_short_sha1(const uint8_t sha1[SHA_DIGEST_SIZE]) {
    682     int i;
    683     const char* hex = "0123456789abcdef";
    684     for (i = 0; i < 4; ++i) {
    685         putchar(hex[(sha1[i]>>4) & 0xf]);
    686         putchar(hex[sha1[i] & 0xf]);
    687     }
    688 }
    689 
    690 // This function applies binary patches to files in a way that is safe
    691 // (the original file is not touched until we have the desired
    692 // replacement for it) and idempotent (it's okay to run this program
    693 // multiple times).
    694 //
    695 // - if the sha1 hash of <target_filename> is <target_sha1_string>,
    696 //   does nothing and exits successfully.
    697 //
    698 // - otherwise, if the sha1 hash of <source_filename> is one of the
    699 //   entries in <patch_sha1_str>, the corresponding patch from
    700 //   <patch_data> (which must be a VAL_BLOB) is applied to produce a
    701 //   new file (the type of patch is automatically detected from the
    702 //   blob daat).  If that new file has sha1 hash <target_sha1_str>,
    703 //   moves it to replace <target_filename>, and exits successfully.
    704 //   Note that if <source_filename> and <target_filename> are not the
    705 //   same, <source_filename> is NOT deleted on success.
    706 //   <target_filename> may be the string "-" to mean "the same as
    707 //   source_filename".
    708 //
    709 // - otherwise, or if any error is encountered, exits with non-zero
    710 //   status.
    711 //
    712 // <source_filename> may refer to a partition to read the source data.
    713 // See the comments for the LoadPartition Contents() function above
    714 // for the format of such a filename.
    715 
    716 int applypatch(const char* source_filename,
    717                const char* target_filename,
    718                const char* target_sha1_str,
    719                size_t target_size,
    720                int num_patches,
    721                char** const patch_sha1_str,
    722                Value** patch_data,
    723                Value* bonus_data) {
    724     printf("patch %s: ", source_filename);
    725 
    726     if (target_filename[0] == '-' &&
    727         target_filename[1] == '\0') {
    728         target_filename = source_filename;
    729     }
    730 
    731     uint8_t target_sha1[SHA_DIGEST_SIZE];
    732     if (ParseSha1(target_sha1_str, target_sha1) != 0) {
    733         printf("failed to parse tgt-sha1 \"%s\"\n", target_sha1_str);
    734         return 1;
    735     }
    736 
    737     FileContents copy_file;
    738     FileContents source_file;
    739     copy_file.data = NULL;
    740     source_file.data = NULL;
    741     const Value* source_patch_value = NULL;
    742     const Value* copy_patch_value = NULL;
    743 
    744     // We try to load the target file into the source_file object.
    745     if (LoadFileContents(target_filename, &source_file,
    746                          RETOUCH_DO_MASK) == 0) {
    747         if (memcmp(source_file.sha1, target_sha1, SHA_DIGEST_SIZE) == 0) {
    748             // The early-exit case:  the patch was already applied, this file
    749             // has the desired hash, nothing for us to do.
    750             printf("already ");
    751             print_short_sha1(target_sha1);
    752             putchar('\n');
    753             free(source_file.data);
    754             return 0;
    755         }
    756     }
    757 
    758     if (source_file.data == NULL ||
    759         (target_filename != source_filename &&
    760          strcmp(target_filename, source_filename) != 0)) {
    761         // Need to load the source file:  either we failed to load the
    762         // target file, or we did but it's different from the source file.
    763         free(source_file.data);
    764         source_file.data = NULL;
    765         LoadFileContents(source_filename, &source_file,
    766                          RETOUCH_DO_MASK);
    767     }
    768 
    769     if (source_file.data != NULL) {
    770         int to_use = FindMatchingPatch(source_file.sha1,
    771                                        patch_sha1_str, num_patches);
    772         if (to_use >= 0) {
    773             source_patch_value = patch_data[to_use];
    774         }
    775     }
    776 
    777     if (source_patch_value == NULL) {
    778         free(source_file.data);
    779         source_file.data = NULL;
    780         printf("source file is bad; trying copy\n");
    781 
    782         if (LoadFileContents(CACHE_TEMP_SOURCE, &copy_file,
    783                              RETOUCH_DO_MASK) < 0) {
    784             // fail.
    785             printf("failed to read copy file\n");
    786             return 1;
    787         }
    788 
    789         int to_use = FindMatchingPatch(copy_file.sha1,
    790                                        patch_sha1_str, num_patches);
    791         if (to_use >= 0) {
    792             copy_patch_value = patch_data[to_use];
    793         }
    794 
    795         if (copy_patch_value == NULL) {
    796             // fail.
    797             printf("copy file doesn't match source SHA-1s either\n");
    798             free(copy_file.data);
    799             return 1;
    800         }
    801     }
    802 
    803     int result = GenerateTarget(&source_file, source_patch_value,
    804                                 &copy_file, copy_patch_value,
    805                                 source_filename, target_filename,
    806                                 target_sha1, target_size, bonus_data);
    807     free(source_file.data);
    808     free(copy_file.data);
    809 
    810     return result;
    811 }
    812 
    813 static int GenerateTarget(FileContents* source_file,
    814                           const Value* source_patch_value,
    815                           FileContents* copy_file,
    816                           const Value* copy_patch_value,
    817                           const char* source_filename,
    818                           const char* target_filename,
    819                           const uint8_t target_sha1[SHA_DIGEST_SIZE],
    820                           size_t target_size,
    821                           const Value* bonus_data) {
    822     int retry = 1;
    823     SHA_CTX ctx;
    824     int output;
    825     MemorySinkInfo msi;
    826     FileContents* source_to_use;
    827     char* outname;
    828     int made_copy = 0;
    829 
    830     // assume that target_filename (eg "/system/app/Foo.apk") is located
    831     // on the same filesystem as its top-level directory ("/system").
    832     // We need something that exists for calling statfs().
    833     char target_fs[strlen(target_filename)+1];
    834     char* slash = strchr(target_filename+1, '/');
    835     if (slash != NULL) {
    836         int count = slash - target_filename;
    837         strncpy(target_fs, target_filename, count);
    838         target_fs[count] = '\0';
    839     } else {
    840         strcpy(target_fs, target_filename);
    841     }
    842 
    843     do {
    844         // Is there enough room in the target filesystem to hold the patched
    845         // file?
    846 
    847         if (strncmp(target_filename, "MTD:", 4) == 0 ||
    848             strncmp(target_filename, "EMMC:", 5) == 0) {
    849             // If the target is a partition, we're actually going to
    850             // write the output to /tmp and then copy it to the
    851             // partition.  statfs() always returns 0 blocks free for
    852             // /tmp, so instead we'll just assume that /tmp has enough
    853             // space to hold the file.
    854 
    855             // We still write the original source to cache, in case
    856             // the partition write is interrupted.
    857             if (MakeFreeSpaceOnCache(source_file->size) < 0) {
    858                 printf("not enough free space on /cache\n");
    859                 return 1;
    860             }
    861             if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
    862                 printf("failed to back up source file\n");
    863                 return 1;
    864             }
    865             made_copy = 1;
    866             retry = 0;
    867         } else {
    868             int enough_space = 0;
    869             if (retry > 0) {
    870                 size_t free_space = FreeSpaceForFile(target_fs);
    871                 enough_space =
    872                     (free_space > (256 << 10)) &&          // 256k (two-block) minimum
    873                     (free_space > (target_size * 3 / 2));  // 50% margin of error
    874                 if (!enough_space) {
    875                     printf("target %ld bytes; free space %ld bytes; retry %d; enough %d\n",
    876                            (long)target_size, (long)free_space, retry, enough_space);
    877                 }
    878             }
    879 
    880             if (!enough_space) {
    881                 retry = 0;
    882             }
    883 
    884             if (!enough_space && source_patch_value != NULL) {
    885                 // Using the original source, but not enough free space.  First
    886                 // copy the source file to cache, then delete it from the original
    887                 // location.
    888 
    889                 if (strncmp(source_filename, "MTD:", 4) == 0 ||
    890                     strncmp(source_filename, "EMMC:", 5) == 0) {
    891                     // It's impossible to free space on the target filesystem by
    892                     // deleting the source if the source is a partition.  If
    893                     // we're ever in a state where we need to do this, fail.
    894                     printf("not enough free space for target but source "
    895                            "is partition\n");
    896                     return 1;
    897                 }
    898 
    899                 if (MakeFreeSpaceOnCache(source_file->size) < 0) {
    900                     printf("not enough free space on /cache\n");
    901                     return 1;
    902                 }
    903 
    904                 if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
    905                     printf("failed to back up source file\n");
    906                     return 1;
    907                 }
    908                 made_copy = 1;
    909                 unlink(source_filename);
    910 
    911                 size_t free_space = FreeSpaceForFile(target_fs);
    912                 printf("(now %ld bytes free for target) ", (long)free_space);
    913             }
    914         }
    915 
    916         const Value* patch;
    917         if (source_patch_value != NULL) {
    918             source_to_use = source_file;
    919             patch = source_patch_value;
    920         } else {
    921             source_to_use = copy_file;
    922             patch = copy_patch_value;
    923         }
    924 
    925         if (patch->type != VAL_BLOB) {
    926             printf("patch is not a blob\n");
    927             return 1;
    928         }
    929 
    930         SinkFn sink = NULL;
    931         void* token = NULL;
    932         output = -1;
    933         outname = NULL;
    934         if (strncmp(target_filename, "MTD:", 4) == 0 ||
    935             strncmp(target_filename, "EMMC:", 5) == 0) {
    936             // We store the decoded output in memory.
    937             msi.buffer = malloc(target_size);
    938             if (msi.buffer == NULL) {
    939                 printf("failed to alloc %ld bytes for output\n",
    940                        (long)target_size);
    941                 return 1;
    942             }
    943             msi.pos = 0;
    944             msi.size = target_size;
    945             sink = MemorySink;
    946             token = &msi;
    947         } else {
    948             // We write the decoded output to "<tgt-file>.patch".
    949             outname = (char*)malloc(strlen(target_filename) + 10);
    950             strcpy(outname, target_filename);
    951             strcat(outname, ".patch");
    952 
    953             output = open(outname, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
    954             if (output < 0) {
    955                 printf("failed to open output file %s: %s\n",
    956                        outname, strerror(errno));
    957                 return 1;
    958             }
    959             sink = FileSink;
    960             token = &output;
    961         }
    962 
    963         char* header = patch->data;
    964         ssize_t header_bytes_read = patch->size;
    965 
    966         SHA_init(&ctx);
    967 
    968         int result;
    969 
    970         if (header_bytes_read >= 8 &&
    971             memcmp(header, "BSDIFF40", 8) == 0) {
    972             result = ApplyBSDiffPatch(source_to_use->data, source_to_use->size,
    973                                       patch, 0, sink, token, &ctx);
    974         } else if (header_bytes_read >= 8 &&
    975                    memcmp(header, "IMGDIFF2", 8) == 0) {
    976             result = ApplyImagePatch(source_to_use->data, source_to_use->size,
    977                                      patch, sink, token, &ctx, bonus_data);
    978         } else {
    979             printf("Unknown patch file format\n");
    980             return 1;
    981         }
    982 
    983         if (output >= 0) {
    984             fsync(output);
    985             close(output);
    986         }
    987 
    988         if (result != 0) {
    989             if (retry == 0) {
    990                 printf("applying patch failed\n");
    991                 return result != 0;
    992             } else {
    993                 printf("applying patch failed; retrying\n");
    994             }
    995             if (outname != NULL) {
    996                 unlink(outname);
    997             }
    998         } else {
    999             // succeeded; no need to retry
   1000             break;
   1001         }
   1002     } while (retry-- > 0);
   1003 
   1004     const uint8_t* current_target_sha1 = SHA_final(&ctx);
   1005     if (memcmp(current_target_sha1, target_sha1, SHA_DIGEST_SIZE) != 0) {
   1006         printf("patch did not produce expected sha1\n");
   1007         return 1;
   1008     } else {
   1009         printf("now ");
   1010         print_short_sha1(target_sha1);
   1011         putchar('\n');
   1012     }
   1013 
   1014     if (output < 0) {
   1015         // Copy the temp file to the partition.
   1016         if (WriteToPartition(msi.buffer, msi.pos, target_filename) != 0) {
   1017             printf("write of patched data to %s failed\n", target_filename);
   1018             return 1;
   1019         }
   1020         free(msi.buffer);
   1021     } else {
   1022         // Give the .patch file the same owner, group, and mode of the
   1023         // original source file.
   1024         if (chmod(outname, source_to_use->st.st_mode) != 0) {
   1025             printf("chmod of \"%s\" failed: %s\n", outname, strerror(errno));
   1026             return 1;
   1027         }
   1028         if (chown(outname, source_to_use->st.st_uid,
   1029                   source_to_use->st.st_gid) != 0) {
   1030             printf("chown of \"%s\" failed: %s\n", outname, strerror(errno));
   1031             return 1;
   1032         }
   1033 
   1034         // Finally, rename the .patch file to replace the target file.
   1035         if (rename(outname, target_filename) != 0) {
   1036             printf("rename of .patch to \"%s\" failed: %s\n",
   1037                    target_filename, strerror(errno));
   1038             return 1;
   1039         }
   1040     }
   1041 
   1042     // If this run of applypatch created the copy, and we're here, we
   1043     // can delete it.
   1044     if (made_copy) unlink(CACHE_TEMP_SOURCE);
   1045 
   1046     // Success!
   1047     return 0;
   1048 }
   1049