diff options
| -rw-r--r-- | gcm.c | 78 | ||||
| -rw-r--r-- | gcm.h | 3 |
2 files changed, 49 insertions, 32 deletions
@@ -347,30 +347,6 @@ gcm_set_key(struct gcm_key *key, #endif } -/* - * @length: The size of the iv (fixed for now to GCM_NONCE_SIZE) - * @iv: The iv - */ -void -gcm_set_iv(struct gcm_ctx *ctx, unsigned length, const uint8_t* iv) -{ - /* FIXME: remove the iv size limitation */ - assert (length == GCM_IV_SIZE); - - memcpy (ctx->iv.b, iv, GCM_BLOCK_SIZE - 4); - ctx->iv.b[GCM_BLOCK_SIZE - 4] = 0; - ctx->iv.b[GCM_BLOCK_SIZE - 3] = 0; - ctx->iv.b[GCM_BLOCK_SIZE - 2] = 0; - ctx->iv.b[GCM_BLOCK_SIZE - 1] = 1; - - memcpy (ctx->ctr.b, ctx->iv.b, GCM_BLOCK_SIZE); - INC32 (ctx->ctr); - - /* Reset the rest of the message-dependent state. */ - memset(ctx->x.b, 0, sizeof(ctx->x)); - ctx->auth_size = ctx->data_size = 0; -} - static void gcm_hash(const struct gcm_key *key, union gcm_block *x, unsigned length, const uint8_t *data) @@ -388,6 +364,52 @@ gcm_hash(const struct gcm_key *key, union gcm_block *x, } } +static void +gcm_hash_sizes(const struct gcm_key *key, union gcm_block *x, + uint64_t auth_size, uint64_t data_size) +{ + uint8_t buffer[GCM_BLOCK_SIZE]; + + data_size *= 8; + auth_size *= 8; + + WRITE_UINT64 (buffer, auth_size); + WRITE_UINT64 (buffer + 8, data_size); + + gcm_hash(key, x, GCM_BLOCK_SIZE, buffer); +} + +/* + * @length: The size of the iv (fixed for now to GCM_NONCE_SIZE) + * @iv: The iv + */ +void +gcm_set_iv(struct gcm_ctx *ctx, const struct gcm_key *key, + unsigned length, const uint8_t *iv) +{ + if (length == GCM_IV_SIZE) + { + memcpy (ctx->iv.b, iv, GCM_BLOCK_SIZE - 4); + ctx->iv.b[GCM_BLOCK_SIZE - 4] = 0; + ctx->iv.b[GCM_BLOCK_SIZE - 3] = 0; + ctx->iv.b[GCM_BLOCK_SIZE - 2] = 0; + ctx->iv.b[GCM_BLOCK_SIZE - 1] = 1; + } + else + { + memset(ctx->iv.b, 0, GCM_BLOCK_SIZE); + gcm_hash(key, &ctx->iv, length, iv); + gcm_hash_sizes(key, &ctx->iv, 0, length); + } + + memcpy (ctx->ctr.b, ctx->iv.b, GCM_BLOCK_SIZE); + INC32 (ctx->ctr); + + /* Reset the rest of the message-dependent state. */ + memset(ctx->x.b, 0, sizeof(ctx->x)); + ctx->auth_size = ctx->data_size = 0; +} + void gcm_auth(struct gcm_ctx *ctx, const struct gcm_key *key, unsigned length, const uint8_t *data) @@ -472,13 +494,7 @@ gcm_digest(struct gcm_ctx *ctx, const struct gcm_key *key, assert (length <= GCM_BLOCK_SIZE); - ctx->data_size *= 8; - ctx->auth_size *= 8; - - WRITE_UINT64 (buffer, ctx->auth_size); - WRITE_UINT64 (buffer + 8, ctx->data_size); - - gcm_hash(key, &ctx->x, GCM_BLOCK_SIZE, buffer); + gcm_hash_sizes(key, &ctx->x, ctx->auth_size, ctx->data_size); f (cipher, GCM_BLOCK_SIZE, buffer, ctx->iv.b); memxor3 (digest, ctx->x.b, buffer, length); @@ -93,7 +93,8 @@ gcm_set_key(struct gcm_key *key, void *cipher, nettle_crypt_func *f); void -gcm_set_iv(struct gcm_ctx *ctx, unsigned length, const uint8_t *iv); +gcm_set_iv(struct gcm_ctx *ctx, const struct gcm_key *key, + unsigned length, const uint8_t *iv); void gcm_auth(struct gcm_ctx *ctx, const struct gcm_key *key, |