diff options
Diffstat (limited to 'common')
| -rw-r--r-- | common/auth/polarssl/polarssl.c | 108 |
1 files changed, 84 insertions, 24 deletions
diff --git a/common/auth/polarssl/polarssl.c b/common/auth/polarssl/polarssl.c index e099f50c..82c8b331 100644 --- a/common/auth/polarssl/polarssl.c +++ b/common/auth/polarssl/polarssl.c @@ -51,8 +51,8 @@ * during the Trusted Boot process. */ -/* SHA256 algorithm */ -#define SHA_BYTES 32 +/* Maximum OID string length ("a.b.c.d.e.f ...") */ +#define MAX_OID_STR_LEN 64 /* * An 8 KB stack has been proven to be enough for the current Trusted Boot @@ -79,6 +79,18 @@ static unsigned char heap[POLARSSL_HEAP_SIZE]; #define RSA_PUB_DER_MAX_BYTES 38 + 2 * POLARSSL_MPI_MAX_SIZE /* + * SHA256: + * DigestInfo ::= SEQUENCE { 1 + 1 + * digestAlgorithm AlgorithmIdentifier, + 1 + 1 (sequence) + * + 1 + 1 + 9 (sha256 oid) + * + 1 + 1 (params null) + * digest OCTET STRING + 1 + 1 + 32 (sha256) + * } + */ +#define SHA256_BYTES 32 +#define SHA256_DER_BYTES (19 + SHA256_BYTES) + +/* * Buffer for storing public keys extracted from certificates while they are * verified */ @@ -89,13 +101,13 @@ static x509_crt cert; /* BL specific variables */ #if IMAGE_BL1 -static unsigned char sha_bl2[SHA_BYTES]; +static unsigned char sha_bl2[SHA256_DER_BYTES]; #elif IMAGE_BL2 /* Buffers to store the hash of BL3-x images */ -static unsigned char sha_bl30[SHA_BYTES]; -static unsigned char sha_bl31[SHA_BYTES]; -static unsigned char sha_bl32[SHA_BYTES]; -static unsigned char sha_bl33[SHA_BYTES]; +static unsigned char sha_bl30[SHA256_DER_BYTES]; +static unsigned char sha_bl31[SHA256_DER_BYTES]; +static unsigned char sha_bl32[SHA256_DER_BYTES]; +static unsigned char sha_bl33[SHA256_DER_BYTES]; /* Buffers to store the Trusted and Non-Trusted world public keys */ static unsigned char tz_world_pk[RSA_PUB_DER_MAX_BYTES]; static unsigned char ntz_world_pk[RSA_PUB_DER_MAX_BYTES]; @@ -111,12 +123,12 @@ static int x509_get_crt_ext_data(const unsigned char **ext_data, x509_crt *crt, const char *oid) { - int ret; + int ret, oid_len; size_t len; unsigned char *end_ext_data, *end_ext_octet; unsigned char *p; const unsigned char *end; - char oid_str[64]; + char oid_str[MAX_OID_STR_LEN]; p = crt->v3_ext.p; end = crt->v3_ext.p + crt->v3_ext.len; @@ -177,8 +189,12 @@ static int x509_get_crt_ext_data(const unsigned char **ext_data, POLARSSL_ERR_ASN1_LENGTH_MISMATCH; /* Detect requested extension */ - oid_get_numeric_string(oid_str, 64, &extn_oid); - if (memcmp(oid, oid_str, sizeof(oid)) == 0) { + oid_len = oid_get_numeric_string(oid_str, + MAX_OID_STR_LEN, &extn_oid); + if (oid_len == POLARSSL_ERR_OID_BUF_TOO_SMALL) + return POLARSSL_ERR_X509_INVALID_EXTENSIONS + + POLARSSL_ERR_ASN1_BUF_TOO_SMALL; + if ((oid_len == strlen(oid_str)) && !strcmp(oid, oid_str)) { *ext_data = p; *ext_len = len; return 0; @@ -251,11 +267,8 @@ static int check_bl2_cert(unsigned char *buf, size_t len) goto error; } - assert(sz == SHA_BYTES + 2); - - /* Skip the tag and length bytes and copy the hash */ - p += 2; - memcpy(sha_bl2, p, SHA_BYTES); + assert(sz == SHA256_DER_BYTES); + memcpy(sha_bl2, p, SHA256_DER_BYTES); error: x509_crt_free(&cert); @@ -433,11 +446,8 @@ static int check_bl3x_cert(unsigned char *buf, size_t len, goto error; } - assert(sz == SHA_BYTES + 2); - - /* Skip the tag and length bytes and copy the hash */ - p += 2; - memcpy(sha, p, SHA_BYTES); + assert(sz == SHA256_DER_BYTES); + memcpy(sha, p, SHA256_DER_BYTES); error: x509_crt_free(&cert); @@ -460,18 +470,68 @@ error: static int check_bl_img(unsigned char *buf, size_t len, const unsigned char *sha) { - unsigned char img_sha[SHA_BYTES]; + asn1_buf md_oid, params; + md_type_t md_alg; + int err; + unsigned char *p = NULL; + const unsigned char *end = NULL; + size_t sz; + unsigned char img_sha[SHA256_BYTES]; + + /* + * Extract the image hash from the ASN.1 structure: + * + * DigestInfo ::= SEQUENCE { + * digestAlgorithm AlgorithmIdentifier, + * digest OCTET STRING + * } + */ + + p = (unsigned char *)sha; + end = sha + SHA256_DER_BYTES; + err = asn1_get_tag(&p, end, &sz, ASN1_CONSTRUCTED | ASN1_SEQUENCE); + if (err != 0) { + ERROR("Malformed image hash extension\n"); + goto error; + } + + err = asn1_get_alg(&p, end, &md_oid, ¶ms); + if (err != 0) { + ERROR("Malformed image hash algorithm\n"); + goto error; + } + + err = oid_get_md_alg(&md_oid, &md_alg); + if (err != 0) { + ERROR("Unknown image hash algorithm\n"); + goto error; + } + + /* Only SHA256 is supported */ + if (md_alg != POLARSSL_MD_SHA256) { + ERROR("Only SHA256 is supported as image hash algorithm\n"); + err = 1; + goto error; + } + + /* Get the hash */ + err = asn1_get_tag(&p, end, &sz, ASN1_OCTET_STRING); + if (err != 0) { + ERROR("Image hash not found in extension\n"); + goto error; + } /* Calculate the hash of the image */ sha256(buf, len, img_sha, 0); /* Match the hash with the one extracted from the certificate */ - if (memcmp(img_sha, sha, SHA_BYTES)) { + if (memcmp(img_sha, p, SHA256_BYTES)) { ERROR("Image hash mismatch\n"); return 1; } - return 0; +error: + return err; } /* |