diff options
Diffstat (limited to 'crypto/asymmetric_keys/verify_pefile.c')
| -rw-r--r-- | crypto/asymmetric_keys/verify_pefile.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index b975918..029a365 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -185,6 +185,192 @@ static int pefile_strip_sig_wrapper(const void *pebuf, return -ELIBBAD; } +/* + * Compare two sections for canonicalisation. + */ +static int pefile_compare_shdrs(const void *a, const void *b) +{ + const struct section_header *shdra = a; + const struct section_header *shdrb = b; + int rc; + + if (shdra->data_addr > shdrb->data_addr) + return 1; + if (shdrb->data_addr > shdra->data_addr) + return -1; + + if (shdra->virtual_address > shdrb->virtual_address) + return 1; + if (shdrb->virtual_address > shdra->virtual_address) + return -1; + + rc = strcmp(shdra->name, shdrb->name); + if (rc != 0) + return rc; + + if (shdra->virtual_size > shdrb->virtual_size) + return 1; + if (shdrb->virtual_size > shdra->virtual_size) + return -1; + + if (shdra->raw_data_size > shdrb->raw_data_size) + return 1; + if (shdrb->raw_data_size > shdra->raw_data_size) + return -1; + + return 0; +} + +/* + * Load the contents of the PE binary into the digest, leaving out the image + * checksum and the certificate data block. + */ +static int pefile_digest_pe_contents(const void *pebuf, unsigned int pelen, + struct pefile_context *ctx, + struct shash_desc *desc) +{ + unsigned *canon, tmp, loop, i, hashed_bytes; + int ret; + + /* Digest the header and data directory, but leave out the image + * checksum and the data dirent for the signature. + */ + ret = crypto_shash_update(desc, pebuf, ctx->image_checksum_offset); + if (ret < 0) + return ret; + + tmp = ctx->image_checksum_offset + sizeof(uint32_t); + ret = crypto_shash_update(desc, pebuf + tmp, + ctx->cert_dirent_offset - tmp); + if (ret < 0) + return ret; + + tmp = ctx->cert_dirent_offset + sizeof(struct data_dirent); + ret = crypto_shash_update(desc, pebuf + tmp, ctx->header_size - tmp); + if (ret < 0) + return ret; + + canon = kcalloc(ctx->n_sections, sizeof(unsigned), GFP_KERNEL); + if (!canon) + return -ENOMEM; + + /* We have to canonicalise the section table, so we perform an + * insertion sort. + */ + canon[0] = 0; + for (loop = 1; loop < ctx->n_sections; loop++) { + for (i = 0; i < loop; i++) { + if (pefile_compare_shdrs(&ctx->secs[canon[i]], + &ctx->secs[loop]) > 0) { + memmove(&canon[i + 1], &canon[i], + (loop - i) * sizeof(canon[0])); + break; + } + } + canon[i] = loop; + } + + hashed_bytes = ctx->header_size; + for (loop = 0; loop < ctx->n_sections; loop++) { + i = canon[loop]; + if (ctx->secs[i].raw_data_size == 0) + continue; + ret = crypto_shash_update(desc, + pebuf + ctx->secs[i].data_addr, + ctx->secs[i].raw_data_size); + if (ret < 0) { + kfree(canon); + return ret; + } + hashed_bytes += ctx->secs[i].raw_data_size; + } + kfree(canon); + + if (pelen > hashed_bytes) { + tmp = hashed_bytes + ctx->certs_size; + ret = crypto_shash_update(desc, + pebuf + hashed_bytes, + pelen - tmp); + if (ret < 0) + return ret; + } + + return 0; +} + +/* + * Digest the contents of the PE binary, leaving out the image checksum and the + * certificate data block. + */ +static int pefile_digest_pe(const void *pebuf, unsigned int pelen, + struct pefile_context *ctx) +{ + struct crypto_shash *tfm; + struct shash_desc *desc; + size_t digest_size, desc_size; + void *digest; + int ret; + + kenter(",%u", ctx->digest_algo); + + /* Allocate the hashing algorithm we're going to need and find out how + * big the hash operational data will be. + */ + tfm = crypto_alloc_shash(hash_algo_name[ctx->digest_algo], 0, 0); + if (IS_ERR(tfm)) + return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm); + + desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); + digest_size = crypto_shash_digestsize(tfm); + + if (digest_size != ctx->digest_len) { + pr_debug("Digest size mismatch (%zx != %x)\n", + digest_size, ctx->digest_len); + ret = -EBADMSG; + goto error_no_desc; + } + pr_debug("Digest: desc=%zu size=%zu\n", desc_size, digest_size); + + ret = -ENOMEM; + desc = kzalloc(desc_size + digest_size, GFP_KERNEL); + if (!desc) + goto error_no_desc; + + desc->tfm = tfm; + desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; + ret = crypto_shash_init(desc); + if (ret < 0) + goto error; + + ret = pefile_digest_pe_contents(pebuf, pelen, ctx, desc); + if (ret < 0) + goto error; + + digest = (void *)desc + desc_size; + ret = crypto_shash_final(desc, digest); + if (ret < 0) + goto error; + + pr_debug("Digest calc = [%*ph]\n", ctx->digest_len, digest); + + /* Check that the PE file digest matches that in the MSCODE part of the + * PKCS#7 certificate. + */ + if (memcmp(digest, ctx->digest, ctx->digest_len) != 0) { + pr_debug("Digest mismatch\n"); + ret = -EKEYREJECTED; + } else { + pr_debug("The digests match!\n"); + } + +error: + kfree(desc); +error_no_desc: + crypto_free_shash(tfm); + kleave(" = %d", ret); + return ret; +} + /** * verify_pefile_signature - Verify the signature on a PE binary image * @pebuf: Buffer containing the PE binary image @@ -252,6 +438,17 @@ int verify_pefile_signature(const void *pebuf, unsigned pelen, pr_debug("Digest: %u [%*ph]\n", ctx.digest_len, ctx.digest_len, ctx.digest); + /* Generate the digest and check against the PKCS7 certificate + * contents. + */ + ret = pefile_digest_pe(pebuf, pelen, &ctx); + if (ret < 0) + goto error; + + ret = pkcs7_verify(pkcs7); + if (ret < 0) + goto error; + ret = -ENOANO; // Not yet complete error: |
