diff options
Diffstat (limited to 'bdb/bdb.c')
-rw-r--r-- | bdb/bdb.c | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/bdb/bdb.c b/bdb/bdb.c new file mode 100644 index 00000000..d3327a51 --- /dev/null +++ b/bdb/bdb.c @@ -0,0 +1,398 @@ +/* Copyright (c) 2015 The Chromium OS Authors. All rights reserved. + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + * + * Boot descriptor block firmware functions + */ + +#include <string.h> +#include "bdb.h" + +/*****************************************************************************/ + +/** + * Check if string contains a null terminator. + * + * Bytes after the null terminator do not need to be null. + * + * @param s String to check + * @param size Size of string buffer in characters + * @return 1 if string has a null terminator, 0 if not + */ +int string_has_null(const char *s, size_t size) +{ + for (; size; size--) { + if (*s++ == 0) + return 1; + } + return 0; +} + +int bdb_check_header(const struct bdb_header *p, size_t size) +{ + if (size < sizeof(*p) || size < p->struct_size) + return BDB_ERROR_BUF_SIZE; + + if (p->struct_magic != BDB_HEADER_MAGIC) + return BDB_ERROR_STRUCT_MAGIC; + + if (p->struct_major_version != BDB_HEADER_VERSION_MAJOR) + return BDB_ERROR_STRUCT_VERSION; + + /* Note that minor version doesn't matter yet */ + + if (p->struct_size < sizeof(*p)) + return BDB_ERROR_STRUCT_SIZE; + + if (p->oem_area_0_size & 3) + return BDB_ERROR_OEM_AREA_SIZE; /* Not 32-bit aligned */ + + /* + * Make sure the BDB is at least big enough for us. At this point, all + * the caller may have loaded is this header We'll check if there's + * space for everything else after we load it. + */ + if (p->bdb_size < sizeof(*p)) + return BDB_ERROR_BDB_SIZE; + + /* + * The rest of the fields don't matter yet; we'll check them when we + * check the BDB itself. + */ + return BDB_SUCCESS; +} + +int bdb_check_key(const struct bdb_key *p, size_t size) +{ + size_t expect_key_size = 0; + + if (size < sizeof(*p) || size < p->struct_size) + return BDB_ERROR_BUF_SIZE; + + if (p->struct_magic != BDB_KEY_MAGIC) + return BDB_ERROR_STRUCT_MAGIC; + + if (p->struct_major_version != BDB_KEY_VERSION_MAJOR) + return BDB_ERROR_STRUCT_VERSION; + + /* Note that minor version doesn't matter yet */ + + if (!string_has_null(p->description, sizeof(p->description))) + return BDB_ERROR_DESCRIPTION; + + /* We currently only support SHA-256 */ + if (p->hash_alg != BDB_HASH_ALG_SHA256) + return BDB_ERROR_HASH_ALG; + + /* Make sure signature algorithm and size are correct */ + switch (p->sig_alg) { + case BDB_SIG_ALG_RSA4096: + expect_key_size = BDB_RSA4096_KEY_DATA_SIZE; + break; + case BDB_SIG_ALG_ECSDSA521: + expect_key_size = BDB_ECDSA521_KEY_DATA_SIZE; + break; + case BDB_SIG_ALG_RSA3072B: + expect_key_size = BDB_RSA3072B_KEY_DATA_SIZE; + break; + default: + return BDB_ERROR_SIG_ALG; + } + + if (p->struct_size < sizeof(*p) + expect_key_size) + return BDB_ERROR_STRUCT_SIZE; + + return BDB_SUCCESS; +} + +int bdb_check_sig(const struct bdb_sig *p, size_t size) +{ + size_t expect_sig_size = 0; + + if (size < sizeof(*p) || size < p->struct_size) + return BDB_ERROR_BUF_SIZE; + + if (p->struct_magic != BDB_SIG_MAGIC) + return BDB_ERROR_STRUCT_MAGIC; + + if (p->struct_major_version != BDB_SIG_VERSION_MAJOR) + return BDB_ERROR_STRUCT_VERSION; + + /* Note that minor version doesn't matter yet */ + + if (!string_has_null(p->description, sizeof(p->description))) + return BDB_ERROR_DESCRIPTION; + + /* We currently only support SHA-256 */ + if (p->hash_alg != BDB_HASH_ALG_SHA256) + return BDB_ERROR_HASH_ALG; + + /* Make sure signature algorithm and size are correct */ + switch (p->sig_alg) { + case BDB_SIG_ALG_RSA4096: + expect_sig_size = BDB_RSA4096_SIG_SIZE; + break; + case BDB_SIG_ALG_ECSDSA521: + expect_sig_size = BDB_ECDSA521_SIG_SIZE; + break; + case BDB_SIG_ALG_RSA3072B: + expect_sig_size = BDB_RSA3072B_SIG_SIZE; + break; + default: + return BDB_ERROR_SIG_ALG; + } + + if (p->struct_size < sizeof(*p) + expect_sig_size) + return BDB_ERROR_STRUCT_SIZE; + + return BDB_SUCCESS; +} + +int bdb_check_data(const struct bdb_data *p, size_t size) +{ + size_t need_size; + + if (size < sizeof(*p) || size < p->signed_size) + return BDB_ERROR_BUF_SIZE; + + if (p->struct_magic != BDB_DATA_MAGIC) + return BDB_ERROR_STRUCT_MAGIC; + + if (p->struct_major_version != BDB_DATA_VERSION_MAJOR) + return BDB_ERROR_STRUCT_VERSION; + + /* Note that minor version doesn't matter yet */ + + if (!string_has_null(p->description, sizeof(p->description))) + return BDB_ERROR_DESCRIPTION; + + if (p->struct_size < sizeof(*p)) + return BDB_ERROR_STRUCT_SIZE; + + if (p->hash_entry_size < sizeof(struct bdb_hash)) + return BDB_ERROR_HASH_ENTRY_SIZE; + + /* Calculate expected size */ + need_size = p->struct_size + p->num_hashes * p->hash_entry_size; + + /* Make sure OEM area size doesn't cause wraparound */ + if (need_size + p->oem_area_1_size < need_size) + return BDB_ERROR_OEM_AREA_SIZE; + if (p->oem_area_1_size & 3) + return BDB_ERROR_OEM_AREA_SIZE; /* Not 32-bit aligned */ + need_size += p->oem_area_1_size; + + if (p->signed_size < need_size) + return BDB_ERROR_SIGNED_SIZE; + + return BDB_SUCCESS; +} + +/*****************************************************************************/ + +const struct bdb_header *bdb_get_header(const void *buf) +{ + return buf; +} + +const struct bdb_key *bdb_get_bdbkey(const void *buf) +{ + const struct bdb_header *h = bdb_get_header(buf); + const uint8_t *b8 = buf; + + /* BDB key follows header */ + return (const struct bdb_key *)(b8 + h->struct_size); +} + +const void *bdb_get_oem_area_0(const void *buf) +{ + const struct bdb_key *k = bdb_get_bdbkey(buf); + const uint8_t *b8 = (const uint8_t *)k; + + /* OEM area 0 follows BDB key */ + return b8 + k->struct_size; +} + +const struct bdb_key *bdb_get_subkey(const void *buf) +{ + const struct bdb_header *h = bdb_get_header(buf); + const uint8_t *b8 = bdb_get_oem_area_0(buf); + + /* Subkey follows OEM area 0 */ + return (const struct bdb_key *)(b8 + h->oem_area_0_size); +} + +const struct bdb_sig *bdb_get_header_sig(const void *buf) +{ + const struct bdb_header *h = bdb_get_header(buf); + const uint8_t *b8 = bdb_get_oem_area_0(buf); + + /* Header signature starts after signed data */ + return (const struct bdb_sig *)(b8 + h->signed_size); +} + +const struct bdb_data *bdb_get_data(const void *buf) +{ + const struct bdb_sig *s = bdb_get_header_sig(buf); + const uint8_t *b8 = (const uint8_t *)s; + + /* Data follows header signature */ + return (const struct bdb_data *)(b8 + s->struct_size); +} + +const void *bdb_get_oem_area_1(const void *buf) +{ + const struct bdb_data *p = bdb_get_data(buf); + const uint8_t *b8 = (const uint8_t *)p; + + /* OEM area 1 follows BDB data */ + return b8 + p->struct_size; +} + +const struct bdb_hash *bdb_get_hash(const void *buf, enum bdb_data_type type) +{ + const struct bdb_data *data = bdb_get_data(buf); + const uint8_t *b8 = bdb_get_oem_area_1(buf); + int i; + + /* Hashes follow OEM area 0 */ + b8 += data->oem_area_1_size; + + /* Search for a matching hash */ + for (i = 0; i < data->num_hashes; i++, b8 += data->hash_entry_size) { + const struct bdb_hash *h = (const struct bdb_hash *)b8; + + if (h->type == type) + return h; + } + + return NULL; +} + +const struct bdb_sig *bdb_get_data_sig(const void *buf) +{ + const struct bdb_data *data = bdb_get_data(buf); + const uint8_t *b8 = (const uint8_t *)data; + + /* Data signature starts after signed data */ + return (const struct bdb_sig *)(b8 + data->signed_size); +} + +/*****************************************************************************/ + +int bdb_verify_sig(const struct bdb_key *key, + const struct bdb_sig *sig, + const uint8_t *digest) +{ + /* Key and signature algorithms must match */ + if (key->sig_alg != sig->sig_alg) + return BDB_ERROR_SIG_ALG; + + switch (key->sig_alg) { + case BDB_SIG_ALG_RSA4096: + if (bdb_rsa4096_verify(key->key_data, sig->sig_data, digest)) + return BDB_ERROR_VERIFY_SIG; + break; + case BDB_SIG_ALG_ECSDSA521: + if (bdb_ecdsa521_verify(key->key_data, sig->sig_data, digest)) + return BDB_ERROR_VERIFY_SIG; + break; + case BDB_SIG_ALG_RSA3072B: + if (bdb_rsa3072b_verify(key->key_data, sig->sig_data, digest)) + return BDB_ERROR_VERIFY_SIG; + break; + default: + return BDB_ERROR_VERIFY_SIG; + } + + return BDB_SUCCESS; +} + +int bdb_verify(const void *buf, size_t size, const uint8_t *bdb_key_digest) +{ + const uint8_t *end = (const uint8_t *)buf + size; + const struct bdb_header *h; + const struct bdb_key *bdbkey, *subkey; + const struct bdb_sig *sig; + const struct bdb_data *data; + const void *oem; + uint8_t digest[BDB_SHA256_DIGEST_SIZE]; + int bdb_digest_mismatch; + + /* Make sure buffer doesn't wrap around address space */ + if (end < (const uint8_t *)buf) + return BDB_ERROR_BUF_SIZE; + + /* + * Check header now that we've actually loaded it. We can't guarantee + * this is the same header which was checked before. + */ + h = bdb_get_header(buf); + if (bdb_check_header(h, size)) + return BDB_ERROR_HEADER; + + /* Sanity-check BDB key */ + bdbkey = bdb_get_bdbkey(buf); + if (bdb_check_key(bdbkey, end - (const uint8_t *)bdbkey)) + return BDB_ERROR_BDBKEY; + + /* Calculate BDB key digest and compare with expected */ + if (bdb_sha256(digest, bdbkey, bdbkey->struct_size)) + return BDB_ERROR_DIGEST; + + bdb_digest_mismatch = memcmp(digest, bdb_key_digest, sizeof(digest)); + + /* Make sure OEM area 0 fits */ + oem = bdb_get_oem_area_0(buf); + if (h->oem_area_0_size > end - (const uint8_t *)oem) + return BDB_ERROR_OEM_AREA_0; + + /* Sanity-check subkey */ + subkey = bdb_get_subkey(buf); + if (bdb_check_key(subkey, end - (const uint8_t *)subkey)) + return BDB_ERROR_SUBKEY; + + /* Make sure enough data was signed, and the signed data fits */ + if (h->oem_area_0_size + subkey->struct_size > h->signed_size || + h->signed_size > end - (const uint8_t *)oem) + return BDB_ERROR_BDB_SIGNED_SIZE; + + /* Sanity-check header signature */ + sig = bdb_get_header_sig(buf); + if (bdb_check_sig(sig, end - (const uint8_t *)sig)) + return BDB_ERROR_HEADER_SIG; + + /* Make sure it signed the right amount of data */ + if (sig->signed_size != h->signed_size) + return BDB_ERROR_HEADER_SIG; + + /* Calculate header digest and compare with expected signature */ + if (bdb_sha256(digest, oem, h->signed_size)) + return BDB_ERROR_DIGEST; + if (bdb_verify_sig(bdbkey, sig, digest)) + return BDB_ERROR_HEADER_SIG; + + /* + * Sanity-check data struct. This also checks that OEM area 1 and the + * hashes fit in the remaining buffer. + */ + data = bdb_get_data(buf); + if (bdb_check_data(data, end - (const uint8_t *)data)) + return BDB_ERROR_DATA; + + /* Sanity-check data signature */ + sig = bdb_get_data_sig(buf); + if (bdb_check_sig(sig, end - (const uint8_t *)sig)) + return BDB_ERROR_DATA_SIG; + if (sig->signed_size != data->signed_size) + return BDB_ERROR_DATA_SIG; + + /* Calculate data digest and compare with expected signature */ + if (bdb_sha256(digest, data, data->signed_size)) + return BDB_ERROR_DIGEST; + if (bdb_verify_sig(subkey, sig, digest)) + return BDB_ERROR_DATA_SIG; + + /* Return success or success-other-than-BDB-key-mismatch */ + return bdb_digest_mismatch ? BDB_GOOD_OTHER_THAN_KEY : BDB_SUCCESS; +} |