/* * NIST SP800-38C compliant CCM implementation * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* * Definition of CCM: * http://csrc.nist.gov/publications/nistpubs/800-38C/SP800-38C_updated-July20_2007.pdf * RFC 3610 "Counter with CBC-MAC (CCM)" * * Related: * RFC 5116 "An Interface and Algorithms for Authenticated Encryption" */ #include "common.h" #if defined(MBEDTLS_CCM_C) #include "mbedtls/ccm.h" #include "mbedtls/platform_util.h" #include "mbedtls/error.h" #include #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C) #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define mbedtls_printf printf #endif /* MBEDTLS_PLATFORM_C */ #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */ #if !defined(MBEDTLS_CCM_ALT) #define CCM_VALIDATE_RET(cond) \ MBEDTLS_INTERNAL_VALIDATE_RET(cond, MBEDTLS_ERR_CCM_BAD_INPUT) #define CCM_VALIDATE(cond) \ MBEDTLS_INTERNAL_VALIDATE(cond) #define CCM_ENCRYPT 0 #define CCM_DECRYPT 1 /* * Initialize context */ void mbedtls_ccm_init(mbedtls_ccm_context *ctx) { CCM_VALIDATE(ctx != NULL); memset(ctx, 0, sizeof(mbedtls_ccm_context)); } int mbedtls_ccm_setkey(mbedtls_ccm_context *ctx, mbedtls_cipher_id_t cipher, const unsigned char *key, unsigned int keybits) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const mbedtls_cipher_info_t *cipher_info; CCM_VALIDATE_RET(ctx != NULL); CCM_VALIDATE_RET(key != NULL); cipher_info = mbedtls_cipher_info_from_values(cipher, keybits, MBEDTLS_MODE_ECB); if (cipher_info == NULL) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } if (cipher_info->block_size != 16) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } mbedtls_cipher_free(&ctx->cipher_ctx); if ((ret = mbedtls_cipher_setup(&ctx->cipher_ctx, cipher_info)) != 0) { return (ret); } if ((ret = mbedtls_cipher_setkey(&ctx->cipher_ctx, key, keybits, MBEDTLS_ENCRYPT)) != 0) { return (ret); } return (0); } /* * Free context */ void mbedtls_ccm_free(mbedtls_ccm_context *ctx) { if (ctx == NULL) { return; } mbedtls_cipher_free(&ctx->cipher_ctx); mbedtls_platform_zeroize(ctx, sizeof(mbedtls_ccm_context)); } /* * Macros for common operations. * Results in smaller compiled code than static inline functions. */ /* * Update the CBC-MAC state in y using a block in b * (Always using b as the source helps the compiler optimise a bit better.) */ #define UPDATE_CBC_MAC \ for (i = 0; i < 16; i++) \ y[i] ^= b[i]; \ \ if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, y, 16, y, &olen)) != 0) \ return (ret); /* * Encrypt or decrypt a partial block with CTR * Warning: using b for temporary storage! src and dst must not be b! * This avoids allocating one more 16 bytes buffer while allowing src == dst. */ #define CTR_CRYPT(dst, src, len) \ do { \ if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctr, \ 16, b, &olen)) != 0) { \ return (ret); \ } \ \ for (i = 0; i < (len); i++) \ (dst)[i] = (src)[i] ^ b[i]; \ } while (0) /* * Authenticated encryption or decryption */ static int ccm_auth_crypt(mbedtls_ccm_context *ctx, int mode, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, unsigned char *tag, size_t tag_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char i; unsigned char q; size_t len_left, olen; unsigned char b[16]; unsigned char y[16]; unsigned char ctr[16]; const unsigned char *src; unsigned char *dst; /* * Check length requirements: SP800-38C A.1 * Additional requirement: a < 2^16 - 2^8 to simplify the code. * 'length' checked later (when writing it to the first block) * * Also, loosen the requirements to enable support for CCM* (IEEE 802.15.4). */ if (tag_len == 2 || tag_len > 16 || tag_len % 2 != 0) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } /* Also implies q is within bounds */ if (iv_len < 7 || iv_len > 13) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } if (add_len >= 0xFF00) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } q = 16 - 1 - (unsigned char)iv_len; /* * First block B_0: * 0 .. 0 flags * 1 .. iv_len nonce (aka iv) * iv_len+1 .. 15 length * * With flags as (bits): * 7 0 * 6 add present? * 5 .. 3 (t - 2) / 2 * 2 .. 0 q - 1 */ b[0] = 0; b[0] |= (add_len > 0) << 6; b[0] |= ((tag_len - 2) / 2) << 3; b[0] |= q - 1; memcpy(b + 1, iv, iv_len); for (i = 0, len_left = length; i < q; i++, len_left >>= 8) { b[15 - i] = (unsigned char)(len_left & 0xFF); } if (len_left > 0) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } /* Start CBC-MAC with first block */ memset(y, 0, 16); UPDATE_CBC_MAC; /* * If there is additional data, update CBC-MAC with * add_len, add, 0 (padding to a block boundary) */ if (add_len > 0) { size_t use_len; len_left = add_len; src = add; memset(b, 0, 16); b[0] = (unsigned char)((add_len >> 8) & 0xFF); b[1] = (unsigned char)((add_len)&0xFF); use_len = len_left < 16 - 2 ? len_left : 16 - 2; memcpy(b + 2, src, use_len); len_left -= use_len; src += use_len; UPDATE_CBC_MAC; while (len_left > 0) { use_len = len_left > 16 ? 16 : len_left; memset(b, 0, 16); memcpy(b, src, use_len); UPDATE_CBC_MAC; len_left -= use_len; src += use_len; } } /* * Prepare counter block for encryption: * 0 .. 0 flags * 1 .. iv_len nonce (aka iv) * iv_len+1 .. 15 counter (initially 1) * * With flags as (bits): * 7 .. 3 0 * 2 .. 0 q - 1 */ ctr[0] = q - 1; memcpy(ctr + 1, iv, iv_len); memset(ctr + 1 + iv_len, 0, q); ctr[15] = 1; /* * Authenticate and {en,de}crypt the message. * * The only difference between encryption and decryption is * the respective order of authentication and {en,de}cryption. */ len_left = length; src = input; dst = output; while (len_left > 0) { size_t use_len = len_left > 16 ? 16 : len_left; if (mode == CCM_ENCRYPT) { memset(b, 0, 16); memcpy(b, src, use_len); UPDATE_CBC_MAC; } CTR_CRYPT(dst, src, use_len); if (mode == CCM_DECRYPT) { memset(b, 0, 16); memcpy(b, dst, use_len); UPDATE_CBC_MAC; } dst += use_len; src += use_len; len_left -= use_len; /* * Increment counter. * No need to check for overflow thanks to the length check above. */ for (i = 0; i < q; i++) if (++ctr[15 - i] != 0) { break; } } /* * Authentication: reset counter and crypt/mask internal tag */ for (i = 0; i < q; i++) { ctr[15 - i] = 0; } CTR_CRYPT(y, y, 16); memcpy(tag, y, tag_len); return (0); } /* * Authenticated encryption */ int mbedtls_ccm_star_encrypt_and_tag(mbedtls_ccm_context *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, unsigned char *tag, size_t tag_len) { CCM_VALIDATE_RET(ctx != NULL); CCM_VALIDATE_RET(iv != NULL); CCM_VALIDATE_RET(add_len == 0 || add != NULL); CCM_VALIDATE_RET(length == 0 || input != NULL); CCM_VALIDATE_RET(length == 0 || output != NULL); CCM_VALIDATE_RET(tag_len == 0 || tag != NULL); return (ccm_auth_crypt(ctx, CCM_ENCRYPT, length, iv, iv_len, add, add_len, input, output, tag, tag_len)); } int mbedtls_ccm_encrypt_and_tag(mbedtls_ccm_context *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, unsigned char *tag, size_t tag_len) { CCM_VALIDATE_RET(ctx != NULL); CCM_VALIDATE_RET(iv != NULL); CCM_VALIDATE_RET(add_len == 0 || add != NULL); CCM_VALIDATE_RET(length == 0 || input != NULL); CCM_VALIDATE_RET(length == 0 || output != NULL); CCM_VALIDATE_RET(tag_len == 0 || tag != NULL); if (tag_len == 0) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } return (mbedtls_ccm_star_encrypt_and_tag(ctx, length, iv, iv_len, add, add_len, input, output, tag, tag_len)); } /* * Authenticated decryption */ int mbedtls_ccm_star_auth_decrypt(mbedtls_ccm_context *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, const unsigned char *tag, size_t tag_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char check_tag[16]; unsigned char i; int diff; CCM_VALIDATE_RET(ctx != NULL); CCM_VALIDATE_RET(iv != NULL); CCM_VALIDATE_RET(add_len == 0 || add != NULL); CCM_VALIDATE_RET(length == 0 || input != NULL); CCM_VALIDATE_RET(length == 0 || output != NULL); CCM_VALIDATE_RET(tag_len == 0 || tag != NULL); if ((ret = ccm_auth_crypt(ctx, CCM_DECRYPT, length, iv, iv_len, add, add_len, input, output, check_tag, tag_len)) != 0) { return (ret); } /* Check tag in "constant-time" */ for (diff = 0, i = 0; i < tag_len; i++) { diff |= tag[i] ^ check_tag[i]; } if (diff != 0) { mbedtls_platform_zeroize(output, length); return (MBEDTLS_ERR_CCM_AUTH_FAILED); } return (0); } int mbedtls_ccm_auth_decrypt(mbedtls_ccm_context *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, const unsigned char *tag, size_t tag_len) { CCM_VALIDATE_RET(ctx != NULL); CCM_VALIDATE_RET(iv != NULL); CCM_VALIDATE_RET(add_len == 0 || add != NULL); CCM_VALIDATE_RET(length == 0 || input != NULL); CCM_VALIDATE_RET(length == 0 || output != NULL); CCM_VALIDATE_RET(tag_len == 0 || tag != NULL); if (tag_len == 0) { return (MBEDTLS_ERR_CCM_BAD_INPUT); } return (mbedtls_ccm_star_auth_decrypt(ctx, length, iv, iv_len, add, add_len, input, output, tag, tag_len)); } #endif /* !MBEDTLS_CCM_ALT */ #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C) /* * Examples 1 to 3 from SP800-38C Appendix C */ #define NB_TESTS 3 #define CCM_SELFTEST_PT_MAX_LEN 24 #define CCM_SELFTEST_CT_MAX_LEN 32 /* * The data is the same for all tests, only the used length changes */ static const unsigned char key_test_data[] = { 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f }; static const unsigned char iv_test_data[] = { 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b }; static const unsigned char ad_test_data[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13 }; static const unsigned char msg_test_data[CCM_SELFTEST_PT_MAX_LEN] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, }; static const size_t iv_len_test_data[NB_TESTS] = { 7, 8, 12 }; static const size_t add_len_test_data[NB_TESTS] = { 8, 16, 20 }; static const size_t msg_len_test_data[NB_TESTS] = { 4, 16, 24 }; static const size_t tag_len_test_data[NB_TESTS] = { 4, 6, 8 }; static const unsigned char res_test_data[NB_TESTS][CCM_SELFTEST_CT_MAX_LEN] = { { 0x71, 0x62, 0x01, 0x5b, 0x4d, 0xac, 0x25, 0x5d }, { 0xd2, 0xa1, 0xf0, 0xe0, 0x51, 0xea, 0x5f, 0x62, 0x08, 0x1a, 0x77, 0x92, 0x07, 0x3d, 0x59, 0x3d, 0x1f, 0xc6, 0x4f, 0xbf, 0xac, 0xcd }, { 0xe3, 0xb2, 0x01, 0xa9, 0xf5, 0xb7, 0x1a, 0x7a, 0x9b, 0x1c, 0xea, 0xec, 0xcd, 0x97, 0xe7, 0x0b, 0x61, 0x76, 0xaa, 0xd9, 0xa4, 0x42, 0x8a, 0xa5, 0x48, 0x43, 0x92, 0xfb, 0xc1, 0xb0, 0x99, 0x51 } }; int mbedtls_ccm_self_test(int verbose) { mbedtls_ccm_context ctx; /* * Some hardware accelerators require the input and output buffers * would be in RAM, because the flash is not accessible. * Use buffers on the stack to hold the test vectors data. */ unsigned char plaintext[CCM_SELFTEST_PT_MAX_LEN]; unsigned char ciphertext[CCM_SELFTEST_CT_MAX_LEN]; size_t i; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_ccm_init(&ctx); if (mbedtls_ccm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, key_test_data, 8 * sizeof key_test_data) != 0) { if (verbose != 0) { mbedtls_printf(" CCM: setup failed"); } return (1); } for (i = 0; i < NB_TESTS; i++) { if (verbose != 0) { mbedtls_printf(" CCM-AES #%u: ", (unsigned int)i + 1); } memset(plaintext, 0, CCM_SELFTEST_PT_MAX_LEN); memset(ciphertext, 0, CCM_SELFTEST_CT_MAX_LEN); memcpy(plaintext, msg_test_data, msg_len_test_data[i]); ret = mbedtls_ccm_encrypt_and_tag(&ctx, msg_len_test_data[i], iv_test_data, iv_len_test_data[i], ad_test_data, add_len_test_data[i], plaintext, ciphertext, ciphertext + msg_len_test_data[i], tag_len_test_data[i]); if (ret != 0 || memcmp(ciphertext, res_test_data[i], msg_len_test_data[i] + tag_len_test_data[i]) != 0) { if (verbose != 0) { mbedtls_printf("failed\n"); } return (1); } memset(plaintext, 0, CCM_SELFTEST_PT_MAX_LEN); ret = mbedtls_ccm_auth_decrypt(&ctx, msg_len_test_data[i], iv_test_data, iv_len_test_data[i], ad_test_data, add_len_test_data[i], ciphertext, plaintext, ciphertext + msg_len_test_data[i], tag_len_test_data[i]); if (ret != 0 || memcmp(plaintext, msg_test_data, msg_len_test_data[i]) != 0) { if (verbose != 0) { mbedtls_printf("failed\n"); } return (1); } if (verbose != 0) { mbedtls_printf("passed\n"); } } mbedtls_ccm_free(&ctx); if (verbose != 0) { mbedtls_printf("\n"); } return (0); } #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */ #endif /* MBEDTLS_CCM_C */