src/commonlib/bsd/cbfs_private.c

   1 /* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-or-later */
   2
   3 #include <commonlib/bsd/cbfs_private.h>
   4 #include <assert.h>
   5
   6 static enum cb_err read_next_header(cbfs_dev_t dev, size_t *offset, struct cbfs_file *buffer,
   7                                     const size_t devsize)
   8 {
   9         DEBUG("Looking for next file @%#zx...\n", *offset);
  10         *offset = ALIGN_UP(*offset, CBFS_ALIGNMENT);
  11         while (*offset + sizeof(*buffer) < devsize) {
  12                 if (cbfs_dev_read(dev, buffer, *offset, sizeof(*buffer)) != sizeof(*buffer))
  13                         return CB_CBFS_IO;
  14
  15                 if (memcmp(buffer->magic, CBFS_FILE_MAGIC, sizeof(buffer->magic)) == 0)
  16                         return CB_SUCCESS;
  17
  18                 *offset += CBFS_ALIGNMENT;
  19         }
  20
  21         DEBUG("End of CBFS reached\n");
  22         return CB_CBFS_NOT_FOUND;
  23 }
  24
  25 enum cb_err cbfs_walk(cbfs_dev_t dev, enum cb_err (*walker)(cbfs_dev_t dev, size_t offset,
  26                                                             const union cbfs_mdata *mdata,
  27                                                             size_t already_read, void *arg),
  28                       void *arg, struct vb2_hash *metadata_hash, enum cbfs_walk_flags flags)
  29 {
  30         const bool do_hash = CBFS_ENABLE_HASHING && metadata_hash;
  31         const size_t devsize = cbfs_dev_size(dev);
  32         struct vb2_digest_context dc;
  33
  34         assert(CBFS_ENABLE_HASHING || (!metadata_hash && !(flags & CBFS_WALK_WRITEBACK_HASH)));
  35         if (do_hash && vb2_digest_init(&dc, CBFS_HASH_HWCRYPTO, metadata_hash->algo, 0))
  36                 return CB_ERR_ARG;
  37
  38         size_t offset = 0;
  39         enum cb_err ret_header;
  40         enum cb_err ret_walker = CB_CBFS_NOT_FOUND;
  41         union cbfs_mdata mdata;
  42         while ((ret_header = read_next_header(dev, &offset, &mdata.h, devsize)) == CB_SUCCESS) {
  43                 const uint32_t attr_offset = be32toh(mdata.h.attributes_offset);
  44                 const uint32_t data_offset = be32toh(mdata.h.offset);
  45                 const uint32_t data_length = be32toh(mdata.h.len);
  46                 const uint32_t type = be32toh(mdata.h.type);
  47                 const bool empty = (type == CBFS_TYPE_DELETED || type == CBFS_TYPE_NULL);
  48
  49                 DEBUG("Found CBFS header @%#zx (type %d, attr +%#x, data +%#x, length %#x)\n",
  50                       offset, type, attr_offset, data_offset, data_length);
  51                 if (data_offset > sizeof(mdata) || data_length > devsize ||
  52                     offset + data_offset + data_length > devsize) {
  53                         ERROR("File @%#zx too large\n", offset);
  54                         offset += CBFS_ALIGNMENT;
  55                         continue;
  56                 }
  57
  58                 if (empty && !(flags & CBFS_WALK_INCLUDE_EMPTY))
  59                         goto next_file;
  60
  61                 /* When hashing we need to read everything. Otherwise skip the attributes.
  62                    attr_offset may be 0, which means there are no attributes. */
  63                 ssize_t todo;
  64                 if (do_hash || attr_offset == 0)
  65                         todo = data_offset - sizeof(mdata.h);
  66                 else
  67                         todo = attr_offset - sizeof(mdata.h);
  68                 if (todo <= 0 || data_offset < attr_offset) {
  69                         ERROR("Corrupt file header @%#zx\n", offset);
  70                         goto next_file;
  71                 }
  72
  73                 /* Read the rest of the metadata (filename, and possibly attributes). */
  74                 assert(todo > 0 && todo <= sizeof(mdata) - sizeof(mdata.h));
  75                 if (cbfs_dev_read(dev, mdata.raw + sizeof(mdata.h),
  76                                   offset + sizeof(mdata.h), todo) != todo)
  77                         return CB_CBFS_IO;
  78                 /* Force filename null-termination, just in case. */
  79                 mdata.raw[attr_offset ? attr_offset - 1 : data_offset - 1] = '\0';
  80                 DEBUG("File name: '%s'\n", mdata.h.filename);
  81
  82                 if (do_hash && !empty && vb2_digest_extend(&dc, mdata.raw, data_offset))
  83                         return CB_ERR;
  84
  85                 if (walker && ret_walker == CB_CBFS_NOT_FOUND)
  86                         ret_walker = walker(dev, offset, &mdata, sizeof(mdata.h) + todo, arg);
  87
  88                 /* Return IO errors immediately. For others, finish the hash first if needed. */
  89                 if (ret_walker == CB_CBFS_IO || (ret_walker != CB_CBFS_NOT_FOUND && !do_hash))
  90                         return ret_walker;
  91
  92 next_file:
  93                 offset += data_offset + data_length;
  94         }
  95
  96         if (ret_header != CB_CBFS_NOT_FOUND)
  97                 return ret_header;
  98
  99         if (do_hash) {
 100                 uint8_t real_hash[VB2_MAX_DIGEST_SIZE];
 101                 size_t hash_size = vb2_digest_size(metadata_hash->algo);
 102                 if (vb2_digest_finalize(&dc, real_hash, hash_size))
 103                         return CB_ERR;
 104                 if (flags & CBFS_WALK_WRITEBACK_HASH)
 105                         memcpy(metadata_hash->raw, real_hash, hash_size);
 106                 else if (memcmp(metadata_hash->raw, real_hash, hash_size) != 0)
 107                         return CB_CBFS_HASH_MISMATCH;
 108         }
 109
 110         return ret_walker;
 111 }
 112
 113 enum cb_err cbfs_copy_fill_metadata(union cbfs_mdata *dst, const union cbfs_mdata *src,
 114                                     size_t already_read, cbfs_dev_t dev, size_t offset)
 115 {
 116         /* First, copy the stuff that cbfs_walk() already read for us. */
 117         memcpy(dst, src, already_read);
 118
 119         /* Then read in whatever metadata may be left (will only happen in non-hashing case). */
 120         const size_t todo = be32toh(src->h.offset) - already_read;
 121         assert(todo <= sizeof(*dst) - already_read);
 122         if (todo && cbfs_dev_read(dev, dst->raw + already_read, offset + already_read,
 123                                   todo) != todo)
 124                 return CB_CBFS_IO;
 125         return CB_SUCCESS;
 126 }
 127
 128 struct cbfs_lookup_args {
 129         union cbfs_mdata *mdata_out;
 130         const char *name;
 131         size_t namesize;
 132         size_t *data_offset_out;
 133 };
 134
 135 static enum cb_err lookup_walker(cbfs_dev_t dev, size_t offset, const union cbfs_mdata *mdata,
 136                                  size_t already_read, void *arg)
 137 {
 138         struct cbfs_lookup_args *args = arg;
 139         /* Check if the name we're looking for could fit, then we can safely memcmp() it. */
 140         if (args->namesize > already_read - offsetof(union cbfs_mdata, h.filename) ||
 141             memcmp(args->name, mdata->h.filename, args->namesize) != 0)
 142                 return CB_CBFS_NOT_FOUND;
 143
 144         LOG("Found '%s' @%#zx size %#x\n", args->name, offset, be32toh(mdata->h.len));
 145         if (cbfs_copy_fill_metadata(args->mdata_out, mdata, already_read, dev, offset))
 146                 return CB_CBFS_IO;
 147
 148         *args->data_offset_out = offset + be32toh(mdata->h.offset);
 149         return CB_SUCCESS;
 150 }
 151
 152 enum cb_err cbfs_lookup(cbfs_dev_t dev, const char *name, union cbfs_mdata *mdata_out,
 153                         size_t *data_offset_out, struct vb2_hash *metadata_hash)
 154 {
 155         struct cbfs_lookup_args args = {
 156                 .mdata_out = mdata_out,
 157                 .name = name,
 158                 .namesize = strlen(name) + 1,   /* Count trailing \0 so we can memcmp() it. */
 159                 .data_offset_out = data_offset_out,
 160         };
 161         return cbfs_walk(dev, lookup_walker, &args, metadata_hash, 0);
 162 }
 163
 164 const void *cbfs_find_attr(const union cbfs_mdata *mdata, uint32_t attr_tag, size_t size_check)
 165 {
 166         uint32_t offset = be32toh(mdata->h.attributes_offset);
 167         uint32_t end = be32toh(mdata->h.offset);
 168
 169         if (!offset)
 170                 return NULL;
 171
 172         while (offset + sizeof(struct cbfs_file_attribute) <= end) {
 173                 const struct cbfs_file_attribute *attr = (const void *)mdata->raw + offset;
 174                 const uint32_t tag = be32toh(attr->tag);
 175                 const uint32_t len = be32toh(attr->len);
 176
 177                 if (len < sizeof(struct cbfs_file_attribute) || len > end - offset) {
 178                         ERROR("Attribute %s[%x] invalid length: %u\n",
 179                               mdata->h.filename, tag, len);
 180                         return NULL;
 181                 }
 182                 if (tag == attr_tag) {
 183                         if (size_check && len != size_check) {
 184                                 ERROR("Attribute %s[%x] size mismatch: %u != %zu\n",
 185                                       mdata->h.filename, tag, len, size_check);
 186                                 return NULL;
 187                         }
 188                         return attr;
 189                 }
 190                 offset += len;
 191         }
 192
 193         return NULL;
 194 }
 195
 196 const struct vb2_hash *cbfs_file_hash(const union cbfs_mdata *mdata)
 197 {
 198         /* Hashes are variable-length attributes, so need to manually check the length. */
 199         const struct cbfs_file_attr_hash *attr =
 200                 cbfs_find_attr(mdata, CBFS_FILE_ATTR_TAG_HASH, 0);
 201         if (!attr)
 202                 return NULL;    /* no hash */
 203         const size_t asize = be32toh(attr->len);
 204
 205         const struct vb2_hash *hash = &attr->hash;
 206         const size_t hsize = vb2_digest_size(hash->algo);
 207         if (!hsize) {
 208                 ERROR("Hash algo %u for '%s' unsupported.\n", hash->algo, mdata->h.filename);
 209                 return NULL;
 210         }
 211         if (hsize != asize - offsetof(struct cbfs_file_attr_hash, hash.raw)) {
 212                 ERROR("Hash attribute size for '%s' (%zu) incorrect for algo %u.\n",
 213                       mdata->h.filename, asize, hash->algo);
 214                 return NULL;
 215         }
 216         return hash;
 217 }