/* * aes_icm_mbedtls.c * * AES Integer Counter Mode * * YongCheng Yang */ /* * * Copyright (c) 2013-2017, Cisco Systems, Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * Neither the name of the Cisco Systems, Inc. nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. * */ #ifdef HAVE_CONFIG_H #include #endif #include #include "aes_icm_ext.h" #include "crypto_types.h" #include "err.h" /* for srtp_debug */ #include "alloc.h" #include "cipher_types.h" #include "cipher_test_cases.h" srtp_debug_module_t srtp_mod_aes_icm = { 0, /* debugging is off by default */ "aes icm mbedtls" /* printable module name */ }; /* * integer counter mode works as follows: * * https://tools.ietf.org/html/rfc3711#section-4.1.1 * * E(k, IV) || E(k, IV + 1 mod 2^128) || E(k, IV + 2 mod 2^128) ... * IV = (k_s * 2^16) XOR (SSRC * 2^64) XOR (i * 2^16) * * IV SHALL be defined by the SSRC, the SRTP packet index i, * and the SRTP session salting key k_s. * * SSRC: 32bits. * Sequence number: 16bits. * nonce is 64bits. . * packet index = ROC || SEQ. (ROC: Rollover counter) * * 16 bits * <-----> * +------+------+------+------+------+------+------+------+ * | nonce | packet index | ctr |---+ * +------+------+------+------+------+------+------+------+ | * | * +------+------+------+------+------+------+------+------+ v * | salt |000000|->(+) * +------+------+------+------+------+------+------+------+ | * | * +---------+ * | encrypt | * +---------+ * | * +------+------+------+------+------+------+------+------+ | * | keystream block |<--+ * +------+------+------+------+------+------+------+------+ * * All fields are big-endian * * ctr is the block counter, which increments from zero for * each packet (16 bits wide) * * packet index is distinct for each packet (48 bits wide) * * nonce can be distinct across many uses of the same key, or * can be a fixed value per key, or can be per-packet randomness * (64 bits) * */ /* * This function allocates a new instance of this crypto engine. * The key_len parameter should be one of 30, 38, or 46 for * AES-128, AES-192, and AES-256 respectively. Note, this key_len * value is inflated, as it also accounts for the 112 bit salt * value. The tlen argument is for the AEAD tag length, which * isn't used in counter mode. */ static srtp_err_status_t srtp_aes_icm_mbedtls_alloc(srtp_cipher_t **c, int key_len, int tlen) { srtp_aes_icm_ctx_t *icm; (void)tlen; debug_print(srtp_mod_aes_icm, "allocating cipher with key length %d", key_len); /* * Verify the key_len is valid for one of: AES-128/192/256 */ if (key_len != SRTP_AES_ICM_128_KEY_LEN_WSALT && key_len != SRTP_AES_ICM_192_KEY_LEN_WSALT && key_len != SRTP_AES_ICM_256_KEY_LEN_WSALT) { return srtp_err_status_bad_param; } /* allocate memory a cipher of type aes_icm */ *c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t)); if (*c == NULL) { return srtp_err_status_alloc_fail; } icm = (srtp_aes_icm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_icm_ctx_t)); if (icm == NULL) { srtp_crypto_free(*c); *c = NULL; return srtp_err_status_alloc_fail; } icm->ctx = (mbedtls_aes_context *)srtp_crypto_alloc(sizeof(mbedtls_aes_context)); if (icm->ctx == NULL) { srtp_crypto_free(icm); srtp_crypto_free(*c); *c = NULL; return srtp_err_status_alloc_fail; } mbedtls_aes_init(icm->ctx); /* set pointers */ (*c)->state = icm; /* setup cipher parameters */ switch (key_len) { case SRTP_AES_ICM_128_KEY_LEN_WSALT: (*c)->algorithm = SRTP_AES_ICM_128; (*c)->type = &srtp_aes_icm_128; icm->key_size = SRTP_AES_128_KEY_LEN; break; case SRTP_AES_ICM_192_KEY_LEN_WSALT: (*c)->algorithm = SRTP_AES_ICM_192; (*c)->type = &srtp_aes_icm_192; icm->key_size = SRTP_AES_192_KEY_LEN; break; case SRTP_AES_ICM_256_KEY_LEN_WSALT: (*c)->algorithm = SRTP_AES_ICM_256; (*c)->type = &srtp_aes_icm_256; icm->key_size = SRTP_AES_256_KEY_LEN; break; } /* set key size */ (*c)->key_len = key_len; return srtp_err_status_ok; } /* * This function deallocates an instance of this engine */ static srtp_err_status_t srtp_aes_icm_mbedtls_dealloc(srtp_cipher_t *c) { srtp_aes_icm_ctx_t *ctx; if (c == NULL) { return srtp_err_status_bad_param; } /* * Free the aes context */ ctx = (srtp_aes_icm_ctx_t *)c->state; if (ctx != NULL) { mbedtls_aes_free(ctx->ctx); srtp_crypto_free(ctx->ctx); /* zeroize the key material */ octet_string_set_to_zero(ctx, sizeof(srtp_aes_icm_ctx_t)); srtp_crypto_free(ctx); } /* free memory */ srtp_crypto_free(c); return srtp_err_status_ok; } static srtp_err_status_t srtp_aes_icm_mbedtls_context_init(void *cv, const uint8_t *key) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; uint32_t key_size_in_bits = (c->key_size << 3); int errcode = 0; /* * set counter and initial values to 'offset' value, being careful not to * go past the end of the key buffer */ v128_set_to_zero(&c->counter); v128_set_to_zero(&c->offset); memcpy(&c->counter, key + c->key_size, SRTP_SALT_LEN); memcpy(&c->offset, key + c->key_size, SRTP_SALT_LEN); /* force last two octets of the offset to zero (for srtp compatibility) */ c->offset.v8[SRTP_SALT_LEN] = c->offset.v8[SRTP_SALT_LEN + 1] = 0; c->counter.v8[SRTP_SALT_LEN] = c->counter.v8[SRTP_SALT_LEN + 1] = 0; debug_print(srtp_mod_aes_icm, "key: %s", srtp_octet_string_hex_string(key, c->key_size)); debug_print(srtp_mod_aes_icm, "offset: %s", v128_hex_string(&c->offset)); switch (c->key_size) { case SRTP_AES_256_KEY_LEN: case SRTP_AES_192_KEY_LEN: case SRTP_AES_128_KEY_LEN: break; default: return srtp_err_status_bad_param; break; } errcode = mbedtls_aes_setkey_enc(c->ctx, key, key_size_in_bits); if (errcode != 0) { debug_print(srtp_mod_aes_icm, "errCode: %d", errcode); } return srtp_err_status_ok; } /* * aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with * the offset */ static srtp_err_status_t srtp_aes_icm_mbedtls_set_iv( void *cv, uint8_t *iv, srtp_cipher_direction_t dir) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; v128_t nonce; (void)dir; c->nc_off = 0; /* set nonce (for alignment) */ v128_copy_octet_string(&nonce, iv); debug_print(srtp_mod_aes_icm, "setting iv: %s", v128_hex_string(&nonce)); v128_xor(&c->counter, &c->offset, &nonce); debug_print(srtp_mod_aes_icm, "set_counter: %s", v128_hex_string(&c->counter)); return srtp_err_status_ok; } /* * This function encrypts a buffer using AES CTR mode * * Parameters: * c Crypto context * buf data to encrypt * enc_len length of encrypt buffer */ static srtp_err_status_t srtp_aes_icm_mbedtls_encrypt(void *cv, unsigned char *buf, unsigned int *enc_len) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; int errCode = 0; debug_print(srtp_mod_aes_icm, "rs0: %s", v128_hex_string(&c->counter)); errCode = mbedtls_aes_crypt_ctr(c->ctx, *enc_len, &(c->nc_off), c->counter.v8, c->stream_block.v8, buf, buf); if (errCode != 0) { debug_print(srtp_mod_aes_icm, "encrypt error: %d", errCode); return srtp_err_status_cipher_fail; } return srtp_err_status_ok; } /* * Name of this crypto engine */ static const char srtp_aes_icm_128_mbedtls_description[] = "AES-128 counter mode using mbedtls"; static const char srtp_aes_icm_192_mbedtls_description[] = "AES-192 counter mode using mbedtls"; static const char srtp_aes_icm_256_mbedtls_description[] = "AES-256 counter mode using mbedtls"; /* * This is the function table for this crypto engine. * note: the encrypt function is identical to the decrypt function */ const srtp_cipher_type_t srtp_aes_icm_128 = { srtp_aes_icm_mbedtls_alloc, /* */ srtp_aes_icm_mbedtls_dealloc, /* */ srtp_aes_icm_mbedtls_context_init, /* */ 0, /* set_aad */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_set_iv, /* */ 0, /* get_tag */ srtp_aes_icm_128_mbedtls_description, /* */ &srtp_aes_icm_128_test_case_0, /* */ SRTP_AES_ICM_128 /* */ }; /* * This is the function table for this crypto engine. * note: the encrypt function is identical to the decrypt function */ const srtp_cipher_type_t srtp_aes_icm_192 = { srtp_aes_icm_mbedtls_alloc, /* */ srtp_aes_icm_mbedtls_dealloc, /* */ srtp_aes_icm_mbedtls_context_init, /* */ 0, /* set_aad */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_set_iv, /* */ 0, /* get_tag */ srtp_aes_icm_192_mbedtls_description, /* */ &srtp_aes_icm_192_test_case_0, /* */ SRTP_AES_ICM_192 /* */ }; /* * This is the function table for this crypto engine. * note: the encrypt function is identical to the decrypt function */ const srtp_cipher_type_t srtp_aes_icm_256 = { srtp_aes_icm_mbedtls_alloc, /* */ srtp_aes_icm_mbedtls_dealloc, /* */ srtp_aes_icm_mbedtls_context_init, /* */ 0, /* set_aad */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_encrypt, /* */ srtp_aes_icm_mbedtls_set_iv, /* */ 0, /* get_tag */ srtp_aes_icm_256_mbedtls_description, /* */ &srtp_aes_icm_256_test_case_0, /* */ SRTP_AES_ICM_256 /* */ };