diff options
Diffstat (limited to 'hash.c')
| -rw-r--r-- | hash.c | 184 |
1 files changed, 173 insertions, 11 deletions
@@ -45,8 +45,19 @@ #include "cryptech.h" -/* Longest digest block we support at the moment */ +/* + * Longest block and digest we support at the moment. + */ + #define MAX_BLOCK_LEN SHA512_BLOCK_LEN +#define MAX_DIGEST_LEN SHA512_DIGEST_LEN + +/* + * HMAC magic numbers. + */ + +#define HMAC_IPAD 0x36 +#define HMAC_OPAD 0x5c /* * Driver. This encapsulates whatever per-algorithm voodoo we need @@ -87,10 +98,22 @@ typedef struct { } internal_hash_state_t; /* - * Drivers and descriptors for known digest algorithms. + * HMAC state. */ -/* Drivers */ +typedef struct { + internal_hash_state_t hash_state; /* Hash state */ + uint8_t keybuf[MAX_BLOCK_LEN]; /* HMAC key */ + size_t keylen; /* Length of HMAC key */ +} internal_hmac_state_t; + +/* + * Drivers for known digest algorithms. + * + * Initialization of the core_name field is not a typo, we're + * concatenating two string constants and trusting the compiler to + * whine if the resulting string doesn't fit into the field. + */ static const driver_t sha1_driver = { SHA1_LENGTH_LEN, @@ -134,41 +157,46 @@ static const driver_t sha512_driver = { MODE_SHA_512 }; -/* Descriptors */ +/* + * Descriptors. Yes, the {hash,hmac}_state_length fields are a bit + * repetitive given that they (currently) have the same value + * regardless of algorithm, but we don't want to wire in that + * assumption, so it's simplest to be explicit. + */ const hal_hash_descriptor_t hal_hash_sha1 = { SHA1_BLOCK_LEN, SHA1_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha1_driver }; const hal_hash_descriptor_t hal_hash_sha256 = { SHA256_BLOCK_LEN, SHA256_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha256_driver }; const hal_hash_descriptor_t hal_hash_sha512_224 = { SHA512_BLOCK_LEN, SHA512_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha512_224_driver }; const hal_hash_descriptor_t hal_hash_sha512_256 = { SHA512_BLOCK_LEN, SHA512_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha512_256_driver }; const hal_hash_descriptor_t hal_hash_sha384 = { SHA512_BLOCK_LEN, SHA512_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha384_driver }; const hal_hash_descriptor_t hal_hash_sha512 = { SHA512_BLOCK_LEN, SHA512_DIGEST_LEN, - sizeof(internal_hash_state_t), 0, + sizeof(internal_hash_state_t), sizeof(internal_hmac_state_t), &sha512_driver }; @@ -292,7 +320,7 @@ static hal_error_t hash_read_digest(const driver_t * const driver, */ hal_error_t hal_hash_update(hal_hash_state_t opaque_state, /* Opaque state block */ - const uint8_t * const data_buffer, /* Data to be hashed */ + const uint8_t * const data_buffer, /* Data to be hashed */ size_t data_buffer_length) /* Length of data_buffer */ { internal_hash_state_t *state = opaque_state.state; @@ -424,6 +452,140 @@ hal_error_t hal_hash_finalize(hal_hash_state_t opaque_state, /* Opaqu } /* + * Initialize HMAC state. + */ + +hal_error_t hal_hmac_initialize(const hal_hash_descriptor_t * const descriptor, + hal_hmac_state_t *opaque_state, + void *state_buffer, const size_t state_length, + const uint8_t * const key, const size_t key_length) +{ + const driver_t * const driver = check_driver(descriptor); + internal_hmac_state_t *state = state_buffer; + internal_hash_state_t *h = &state->hash_state; + hal_hash_state_t oh; + hal_error_t err; + int i; + + if (descriptor == NULL || driver == NULL || state == NULL || opaque_state == NULL || + state_length < descriptor->hmac_state_length) + return HAL_ERROR_BAD_ARGUMENTS; + + /* + * RFC 2104 frowns upon keys shorter than the digest length. + */ + + if (key_length < descriptor->digest_length) + return HAL_ERROR_UNSUPPORTED_KEY; + + if ((err = hal_hash_initialize(descriptor, &oh, h, sizeof(*h))) != HAL_OK) + return err; + + memset(state->keybuf, 0, sizeof(state->keybuf)); + + /* + * If the supplied HMAC key is longer than the hash block length, we + * need to hash the supplied HMAC key to get the real HMAC key. + * Otherwise, we just use the supplied HMAC key directly. + */ + + if (key_length > descriptor->block_length) { + if ((err = hal_hash_update(oh, key, key_length)) != HAL_OK || + (err = hal_hash_finalize(oh, state->keybuf, sizeof(state->keybuf))) != HAL_OK || + (err = hal_hash_initialize(descriptor, &oh, h, sizeof(*h))) != HAL_OK) + return err; + state->keylen = descriptor->digest_length; + } + + else { + memcpy(state->keybuf, key, key_length); + state->keylen = key_length; + } + + /* + * XOR the key with the IPAD value, then start the inner hash. + */ + + for (i = 0; i < state->keylen; i++) + state->keybuf[i] ^= HMAC_IPAD; + + if ((err = hal_hash_update(oh, state->keybuf, state->keylen)) != HAL_OK) + return err; + + /* + * Prepare the key for the final hash. Since we just XORed key with + * IPAD, we need to XOR with both IPAD and OPAD to get key XOR OPAD. + */ + + for (i = 0; i < state->keylen; i++) + state->keybuf[i] ^= HMAC_IPAD ^ HMAC_OPAD; + + /* + * If we had some good way of saving all of our state (including + * state internal to the hash core), this would be a good place to + * do it, since it might speed up algorithms like PBKDF2 which do + * repeated HMAC operations using the same key. Revisit this if and + * when the hash cores support such a thing. + */ + + opaque_state->state = state; + + return HAL_OK; +} + +/* + * Add data to HMAC. + */ + +hal_error_t hal_hmac_update(const hal_hmac_state_t opaque_state, + const uint8_t * data, const size_t length) +{ + internal_hmac_state_t *state = opaque_state.state; + internal_hash_state_t *h = &state->hash_state; + hal_hash_state_t oh = { h }; + + if (state == NULL || data == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + return hal_hash_update(oh, data, length); +} + +/* + * Finish and return HMAC. + */ + +hal_error_t hal_hmac_finalize(const hal_hmac_state_t opaque_state, + uint8_t *hmac, const size_t length) +{ + internal_hmac_state_t *state = opaque_state.state; + internal_hash_state_t *h = &state->hash_state; + const hal_hash_descriptor_t *descriptor; + hal_hash_state_t oh = { h }; + uint8_t d[MAX_DIGEST_LEN]; + hal_error_t err; + + if (state == NULL || hmac == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + descriptor = h->descriptor; + assert(descriptor != NULL && descriptor->digest_length <= sizeof(d)); + + /* + * Finish up inner hash and extract digest, then perform outer hash + * to get HMAC. Key was prepared for this in hal_hmac_initialize(). + */ + + if ((err = hal_hash_finalize(oh, d, sizeof(d))) != HAL_OK || + (err = hal_hash_initialize(descriptor, &oh, h, sizeof(*h))) != HAL_OK || + (err = hal_hash_update(oh, state->keybuf, state->keylen)) != HAL_OK || + (err = hal_hash_update(oh, d, descriptor->digest_length)) != HAL_OK || + (err = hal_hash_finalize(oh, hmac, length)) != HAL_OK) + return err; + + return HAL_OK; +} + +/* * "Any programmer who fails to comply with the standard naming, formatting, * or commenting conventions should be shot. If it so happens that it is * inconvenient to shoot him, then he is to be politely requested to recode |