/* * aes_icm.c * * AES Integer Counter Mode * * David A. McGrew * Cisco Systems, Inc. */ /* * * Copyright (c) 2001-2017 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 #define ALIGN_32 0 #include "aes_icm.h" #include "alloc.h" #include "cipher_types.h" srtp_debug_module_t srtp_mod_aes_icm = { 0, /* debugging is off by default */ "aes icm" /* printable module name */ }; /* * integer counter mode works as follows: * * 16 bits * <-----> * +------+------+------+------+------+------+------+------+ * | nonce | pakcet 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) * */ static srtp_err_status_t srtp_aes_icm_alloc(srtp_cipher_t **c, int key_len, int tlen) { srtp_aes_icm_ctx_t *icm; debug_print(srtp_mod_aes_icm, "allocating cipher with key length %d", key_len); /* * The check for key_len = 30/46 does not apply. Our usage * of aes functions with key_len = values other than 30 * has not broken anything. Don't know what would be the * effect of skipping this check for srtp in general. */ if (key_len != SRTP_AES_ICM_128_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; } /* set pointers */ (*c)->state = icm; switch (key_len) { case SRTP_AES_ICM_256_KEY_LEN_WSALT: (*c)->algorithm = SRTP_AES_ICM_256; (*c)->type = &srtp_aes_icm_256; break; default: (*c)->algorithm = SRTP_AES_ICM_128; (*c)->type = &srtp_aes_icm_128; break; } /* set key size */ icm->key_size = key_len; (*c)->key_len = key_len; return srtp_err_status_ok; } static srtp_err_status_t srtp_aes_icm_dealloc(srtp_cipher_t *c) { srtp_aes_icm_ctx_t *ctx; if (c == NULL) { return srtp_err_status_bad_param; } ctx = (srtp_aes_icm_ctx_t *)c->state; if (ctx) { /* zeroize the key material */ octet_string_set_to_zero(ctx, sizeof(srtp_aes_icm_ctx_t)); srtp_crypto_free(ctx); } /* free the cipher context */ srtp_crypto_free(c); return srtp_err_status_ok; } /* * aes_icm_context_init(...) initializes the aes_icm_context * using the value in key[]. * * the key is the secret key * * the salt is unpredictable (but not necessarily secret) data which * randomizes the starting point in the keystream */ static srtp_err_status_t srtp_aes_icm_context_init(void *cv, const uint8_t *key) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; srtp_err_status_t status; int base_key_len, copy_len; if (c->key_size == SRTP_AES_ICM_128_KEY_LEN_WSALT || c->key_size == SRTP_AES_ICM_256_KEY_LEN_WSALT) { base_key_len = c->key_size - SRTP_SALT_LEN; } else { return srtp_err_status_bad_param; } /* * 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); copy_len = c->key_size - base_key_len; /* force last two octets of the offset to be left zero (for srtp * compatibility) */ if (copy_len > SRTP_SALT_LEN) { copy_len = SRTP_SALT_LEN; } memcpy(&c->counter, key + base_key_len, copy_len); memcpy(&c->offset, key + base_key_len, copy_len); debug_print(srtp_mod_aes_icm, "key: %s", srtp_octet_string_hex_string(key, base_key_len)); debug_print(srtp_mod_aes_icm, "offset: %s", v128_hex_string(&c->offset)); /* expand key */ status = srtp_aes_expand_encryption_key(key, base_key_len, &c->expanded_key); if (status) { v128_set_to_zero(&c->counter); v128_set_to_zero(&c->offset); return status; } /* indicate that the keystream_buffer is empty */ c->bytes_in_buffer = 0; 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_set_iv(void *cv, uint8_t *iv, srtp_cipher_direction_t direction) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; v128_t nonce; /* 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)); /* indicate that the keystream_buffer is empty */ c->bytes_in_buffer = 0; return srtp_err_status_ok; } /* * aes_icm_advance(...) refills the keystream_buffer and * advances the block index of the sicm_context forward by one * * this is an internal, hopefully inlined function */ static void srtp_aes_icm_advance(srtp_aes_icm_ctx_t *c) { /* fill buffer with new keystream */ v128_copy(&c->keystream_buffer, &c->counter); srtp_aes_encrypt(&c->keystream_buffer, &c->expanded_key); c->bytes_in_buffer = sizeof(v128_t); debug_print(srtp_mod_aes_icm, "counter: %s", v128_hex_string(&c->counter)); debug_print(srtp_mod_aes_icm, "ciphertext: %s", v128_hex_string(&c->keystream_buffer)); /* clock counter forward */ if (!++(c->counter.v8[15])) { ++(c->counter.v8[14]); } } /* * icm_encrypt deals with the following cases: * * bytes_to_encr < bytes_in_buffer * - add keystream into data * * bytes_to_encr > bytes_in_buffer * - add keystream into data until keystream_buffer is depleted * - loop over blocks, filling keystream_buffer and then * adding keystream into data * - fill buffer then add in remaining (< 16) bytes of keystream */ static srtp_err_status_t srtp_aes_icm_encrypt(void *cv, unsigned char *buf, unsigned int *enc_len) { srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv; unsigned int bytes_to_encr = *enc_len; unsigned int i; uint32_t *b; /* check that there's enough segment left*/ if ((bytes_to_encr + htons(c->counter.v16[7])) > 0xffff) { return srtp_err_status_terminus; } debug_print(srtp_mod_aes_icm, "block index: %d", htons(c->counter.v16[7])); if (bytes_to_encr <= (unsigned int)c->bytes_in_buffer) { /* deal with odd case of small bytes_to_encr */ for (i = (sizeof(v128_t) - c->bytes_in_buffer); i < (sizeof(v128_t) - c->bytes_in_buffer + bytes_to_encr); i++) { *buf++ ^= c->keystream_buffer.v8[i]; } c->bytes_in_buffer -= bytes_to_encr; /* return now to avoid the main loop */ return srtp_err_status_ok; } else { /* encrypt bytes until the remaining data is 16-byte aligned */ for (i = (sizeof(v128_t) - c->bytes_in_buffer); i < sizeof(v128_t); i++) { *buf++ ^= c->keystream_buffer.v8[i]; } bytes_to_encr -= c->bytes_in_buffer; c->bytes_in_buffer = 0; } /* now loop over entire 16-byte blocks of keystream */ for (i = 0; i < (bytes_to_encr / sizeof(v128_t)); i++) { /* fill buffer with new keystream */ srtp_aes_icm_advance(c); /* * add keystream into the data buffer (this would be a lot faster * if we could assume 32-bit alignment!) */ #if ALIGN_32 b = (uint32_t *)buf; *b++ ^= c->keystream_buffer.v32[0]; *b++ ^= c->keystream_buffer.v32[1]; *b++ ^= c->keystream_buffer.v32[2]; *b++ ^= c->keystream_buffer.v32[3]; buf = (uint8_t *)b; #else if ((((uintptr_t)buf) & 0x03) != 0) { *buf++ ^= c->keystream_buffer.v8[0]; *buf++ ^= c->keystream_buffer.v8[1]; *buf++ ^= c->keystream_buffer.v8[2]; *buf++ ^= c->keystream_buffer.v8[3]; *buf++ ^= c->keystream_buffer.v8[4]; *buf++ ^= c->keystream_buffer.v8[5]; *buf++ ^= c->keystream_buffer.v8[6]; *buf++ ^= c->keystream_buffer.v8[7]; *buf++ ^= c->keystream_buffer.v8[8]; *buf++ ^= c->keystream_buffer.v8[9]; *buf++ ^= c->keystream_buffer.v8[10]; *buf++ ^= c->keystream_buffer.v8[11]; *buf++ ^= c->keystream_buffer.v8[12]; *buf++ ^= c->keystream_buffer.v8[13]; *buf++ ^= c->keystream_buffer.v8[14]; *buf++ ^= c->keystream_buffer.v8[15]; } else { b = (uint32_t *)buf; *b++ ^= c->keystream_buffer.v32[0]; *b++ ^= c->keystream_buffer.v32[1]; *b++ ^= c->keystream_buffer.v32[2]; *b++ ^= c->keystream_buffer.v32[3]; buf = (uint8_t *)b; } #endif /* #if ALIGN_32 */ } /* if there is a tail end of the data, process it */ if ((bytes_to_encr & 0xf) != 0) { /* fill buffer with new keystream */ srtp_aes_icm_advance(c); for (i = 0; i < (bytes_to_encr & 0xf); i++) { *buf++ ^= c->keystream_buffer.v8[i]; } /* reset the keystream buffer size to right value */ c->bytes_in_buffer = sizeof(v128_t) - i; } else { /* no tail, so just reset the keystream buffer size to zero */ c->bytes_in_buffer = 0; } return srtp_err_status_ok; } static const char srtp_aes_icm_128_description[] = "AES-128 integer counter mode"; static const char srtp_aes_icm_256_description[] = "AES-256 integer counter mode"; /* clang-format off */ static const uint8_t srtp_aes_icm_128_test_case_0_key[SRTP_AES_ICM_128_KEY_LEN_WSALT] = { 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c, 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd }; /* clang-format on */ /* clang-format off */ static uint8_t srtp_aes_icm_128_test_case_0_nonce[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; /* clang-format on */ /* clang-format off */ static const uint8_t srtp_aes_icm_128_test_case_0_plaintext[32] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, }; /* clang-format on */ /* clang-format off */ static const uint8_t srtp_aes_icm_128_test_case_0_ciphertext[32] = { 0xe0, 0x3e, 0xad, 0x09, 0x35, 0xc9, 0x5e, 0x80, 0xe1, 0x66, 0xb1, 0x6d, 0xd9, 0x2b, 0x4e, 0xb4, 0xd2, 0x35, 0x13, 0x16, 0x2b, 0x02, 0xd0, 0xf7, 0x2a, 0x43, 0xa2, 0xfe, 0x4a, 0x5f, 0x97, 0xab }; /* clang-format on */ static const srtp_cipher_test_case_t srtp_aes_icm_128_test_case_0 = { SRTP_AES_ICM_128_KEY_LEN_WSALT, /* octets in key */ srtp_aes_icm_128_test_case_0_key, /* key */ srtp_aes_icm_128_test_case_0_nonce, /* packet index */ 32, /* octets in plaintext */ srtp_aes_icm_128_test_case_0_plaintext, /* plaintext */ 32, /* octets in ciphertext */ srtp_aes_icm_128_test_case_0_ciphertext, /* ciphertext */ 0, /* */ NULL, /* */ 0, /* */ NULL /* pointer to next testcase */ }; /* clang-format off */ static const uint8_t srtp_aes_icm_256_test_case_0_key[SRTP_AES_ICM_256_KEY_LEN_WSALT] = { 0x57, 0xf8, 0x2f, 0xe3, 0x61, 0x3f, 0xd1, 0x70, 0xa8, 0x5e, 0xc9, 0x3c, 0x40, 0xb1, 0xf0, 0x92, 0x2e, 0xc4, 0xcb, 0x0d, 0xc0, 0x25, 0xb5, 0x82, 0x72, 0x14, 0x7c, 0xc4, 0x38, 0x94, 0x4a, 0x98, 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd }; /* clang-format on */ /* clang-format off */ static uint8_t srtp_aes_icm_256_test_case_0_nonce[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; /* clang-format on */ /* clang-format off */ static const uint8_t srtp_aes_icm_256_test_case_0_plaintext[32] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, }; /* clang-format on */ /* clang-format off */ static const uint8_t srtp_aes_icm_256_test_case_0_ciphertext[32] = { 0x92, 0xbd, 0xd2, 0x8a, 0x93, 0xc3, 0xf5, 0x25, 0x11, 0xc6, 0x77, 0xd0, 0x8b, 0x55, 0x15, 0xa4, 0x9d, 0xa7, 0x1b, 0x23, 0x78, 0xa8, 0x54, 0xf6, 0x70, 0x50, 0x75, 0x6d, 0xed, 0x16, 0x5b, 0xac }; /* clang-format on */ static const srtp_cipher_test_case_t srtp_aes_icm_256_test_case_0 = { SRTP_AES_ICM_256_KEY_LEN_WSALT, /* octets in key */ srtp_aes_icm_256_test_case_0_key, /* key */ srtp_aes_icm_256_test_case_0_nonce, /* packet index */ 32, /* octets in plaintext */ srtp_aes_icm_256_test_case_0_plaintext, /* plaintext */ 32, /* octets in ciphertext */ srtp_aes_icm_256_test_case_0_ciphertext, /* ciphertext */ 0, /* */ NULL, /* */ 0, /* */ NULL, /* pointer to next testcase */ }; /* * note: the encrypt function is identical to the decrypt function */ const srtp_cipher_type_t srtp_aes_icm_128 = { srtp_aes_icm_alloc, /* */ srtp_aes_icm_dealloc, /* */ srtp_aes_icm_context_init, /* */ 0, /* set_aad */ srtp_aes_icm_encrypt, /* */ srtp_aes_icm_encrypt, /* */ srtp_aes_icm_set_iv, /* */ 0, /* get_tag */ srtp_aes_icm_128_description, /* */ &srtp_aes_icm_128_test_case_0, /* */ SRTP_AES_ICM_128 /* */ }; const srtp_cipher_type_t srtp_aes_icm_256 = { srtp_aes_icm_alloc, /* */ srtp_aes_icm_dealloc, /* */ srtp_aes_icm_context_init, /* */ 0, /* set_aad */ srtp_aes_icm_encrypt, /* */ srtp_aes_icm_encrypt, /* */ srtp_aes_icm_set_iv, /* */ 0, /* get_tag */ srtp_aes_icm_256_description, /* */ &srtp_aes_icm_256_test_case_0, /* */ SRTP_AES_ICM_256 /* */ };