/* * 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_PLATFORM_C) #include "mbedtls/platform.h" #else #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C) #include #define mbedtls_printf printf #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */ #endif /* MBEDTLS_PLATFORM_C */ #if !defined(MBEDTLS_CCM_ALT) /* * Initialize context */ void mbedtls_ccm_init(mbedtls_ccm_context *ctx) { 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; cipher_info = mbedtls_cipher_info_from_values(cipher, keybits, MBEDTLS_MODE_ECB); if (cipher_info == NULL) { return MBEDTLS_ERR_CCM_BAD_INPUT; } if (mbedtls_cipher_info_get_block_size(cipher_info) != 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)); } #define CCM_STATE__CLEAR 0 #define CCM_STATE__STARTED (1 << 0) #define CCM_STATE__LENGTHS_SET (1 << 1) #define CCM_STATE__AUTH_DATA_STARTED (1 << 2) #define CCM_STATE__AUTH_DATA_FINISHED (1 << 3) #define CCM_STATE__ERROR (1 << 4) /* * Encrypt or decrypt a partial block with CTR */ static int mbedtls_ccm_crypt(mbedtls_ccm_context *ctx, size_t offset, size_t use_len, const unsigned char *input, unsigned char *output) { size_t olen = 0; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char tmp_buf[16] = { 0 }; if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctx->ctr, 16, tmp_buf, &olen)) != 0) { ctx->state |= CCM_STATE__ERROR; mbedtls_platform_zeroize(tmp_buf, sizeof(tmp_buf)); return ret; } mbedtls_xor(output, input, tmp_buf + offset, use_len); mbedtls_platform_zeroize(tmp_buf, sizeof(tmp_buf)); return ret; } static void mbedtls_ccm_clear_state(mbedtls_ccm_context *ctx) { ctx->state = CCM_STATE__CLEAR; memset(ctx->y, 0, 16); memset(ctx->ctr, 0, 16); } static int ccm_calculate_first_block_if_ready(mbedtls_ccm_context *ctx) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char i; size_t len_left, olen; /* length calculation can be done only after both * mbedtls_ccm_starts() and mbedtls_ccm_set_lengths() have been executed */ if (!(ctx->state & CCM_STATE__STARTED) || !(ctx->state & CCM_STATE__LENGTHS_SET)) { return 0; } /* CCM expects non-empty tag. * CCM* allows empty tag. For CCM* without tag, ignore plaintext length. */ if (ctx->tag_len == 0) { if (ctx->mode == MBEDTLS_CCM_STAR_ENCRYPT || ctx->mode == MBEDTLS_CCM_STAR_DECRYPT) { ctx->plaintext_len = 0; } else { return MBEDTLS_ERR_CCM_BAD_INPUT; } } /* * First block: * 0 .. 0 flags * 1 .. iv_len nonce (aka iv) - set by: mbedtls_ccm_starts() * iv_len+1 .. 15 length * * With flags as (bits): * 7 0 * 6 add present? * 5 .. 3 (t - 2) / 2 * 2 .. 0 q - 1 */ ctx->y[0] |= (ctx->add_len > 0) << 6; ctx->y[0] |= ((ctx->tag_len - 2) / 2) << 3; ctx->y[0] |= ctx->q - 1; for (i = 0, len_left = ctx->plaintext_len; i < ctx->q; i++, len_left >>= 8) { ctx->y[15-i] = MBEDTLS_BYTE_0(len_left); } if (len_left > 0) { ctx->state |= CCM_STATE__ERROR; return MBEDTLS_ERR_CCM_BAD_INPUT; } /* Start CBC-MAC with first block*/ if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen)) != 0) { ctx->state |= CCM_STATE__ERROR; return ret; } return 0; } int mbedtls_ccm_starts(mbedtls_ccm_context *ctx, int mode, const unsigned char *iv, size_t iv_len) { /* Also implies q is within bounds */ if (iv_len < 7 || iv_len > 13) { return MBEDTLS_ERR_CCM_BAD_INPUT; } ctx->mode = mode; ctx->q = 16 - 1 - (unsigned char) iv_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 */ memset(ctx->ctr, 0, 16); ctx->ctr[0] = ctx->q - 1; memcpy(ctx->ctr + 1, iv, iv_len); memset(ctx->ctr + 1 + iv_len, 0, ctx->q); ctx->ctr[15] = 1; /* * See ccm_calculate_first_block_if_ready() for block layout description */ memcpy(ctx->y + 1, iv, iv_len); ctx->state |= CCM_STATE__STARTED; return ccm_calculate_first_block_if_ready(ctx); } int mbedtls_ccm_set_lengths(mbedtls_ccm_context *ctx, size_t total_ad_len, size_t plaintext_len, size_t tag_len) { /* * 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; } if (total_ad_len >= 0xFF00) { return MBEDTLS_ERR_CCM_BAD_INPUT; } ctx->plaintext_len = plaintext_len; ctx->add_len = total_ad_len; ctx->tag_len = tag_len; ctx->processed = 0; ctx->state |= CCM_STATE__LENGTHS_SET; return ccm_calculate_first_block_if_ready(ctx); } int mbedtls_ccm_update_ad(mbedtls_ccm_context *ctx, const unsigned char *add, size_t add_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen, use_len, offset; if (ctx->state & CCM_STATE__ERROR) { return MBEDTLS_ERR_CCM_BAD_INPUT; } if (add_len > 0) { if (ctx->state & CCM_STATE__AUTH_DATA_FINISHED) { return MBEDTLS_ERR_CCM_BAD_INPUT; } if (!(ctx->state & CCM_STATE__AUTH_DATA_STARTED)) { if (add_len > ctx->add_len) { return MBEDTLS_ERR_CCM_BAD_INPUT; } ctx->y[0] ^= (unsigned char) ((ctx->add_len >> 8) & 0xFF); ctx->y[1] ^= (unsigned char) ((ctx->add_len) & 0xFF); ctx->state |= CCM_STATE__AUTH_DATA_STARTED; } else if (ctx->processed + add_len > ctx->add_len) { return MBEDTLS_ERR_CCM_BAD_INPUT; } while (add_len > 0) { offset = (ctx->processed + 2) % 16; /* account for y[0] and y[1] * holding total auth data length */ use_len = 16 - offset; if (use_len > add_len) { use_len = add_len; } mbedtls_xor(ctx->y + offset, ctx->y + offset, add, use_len); ctx->processed += use_len; add_len -= use_len; add += use_len; if (use_len + offset == 16 || ctx->processed == ctx->add_len) { if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen)) != 0) { ctx->state |= CCM_STATE__ERROR; return ret; } } } if (ctx->processed == ctx->add_len) { ctx->state |= CCM_STATE__AUTH_DATA_FINISHED; ctx->processed = 0; // prepare for mbedtls_ccm_update() } } return 0; } int mbedtls_ccm_update(mbedtls_ccm_context *ctx, const unsigned char *input, size_t input_len, unsigned char *output, size_t output_size, size_t *output_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char i; size_t use_len, offset, olen; unsigned char local_output[16]; if (ctx->state & CCM_STATE__ERROR) { return MBEDTLS_ERR_CCM_BAD_INPUT; } /* Check against plaintext length only if performing operation with * authentication */ if (ctx->tag_len != 0 && ctx->processed + input_len > ctx->plaintext_len) { return MBEDTLS_ERR_CCM_BAD_INPUT; } if (output_size < input_len) { return MBEDTLS_ERR_CCM_BAD_INPUT; } *output_len = input_len; ret = 0; while (input_len > 0) { offset = ctx->processed % 16; use_len = 16 - offset; if (use_len > input_len) { use_len = input_len; } ctx->processed += use_len; if (ctx->mode == MBEDTLS_CCM_ENCRYPT || \ ctx->mode == MBEDTLS_CCM_STAR_ENCRYPT) { mbedtls_xor(ctx->y + offset, ctx->y + offset, input, use_len); if (use_len + offset == 16 || ctx->processed == ctx->plaintext_len) { if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen)) != 0) { ctx->state |= CCM_STATE__ERROR; goto exit; } } ret = mbedtls_ccm_crypt(ctx, offset, use_len, input, output); if (ret != 0) { goto exit; } } if (ctx->mode == MBEDTLS_CCM_DECRYPT || \ ctx->mode == MBEDTLS_CCM_STAR_DECRYPT) { /* Since output may be in shared memory, we cannot be sure that * it will contain what we wrote to it. Therefore, we should avoid using * it as input to any operations. * Write decrypted data to local_output to avoid using output variable as * input in the XOR operation for Y. */ ret = mbedtls_ccm_crypt(ctx, offset, use_len, input, local_output); if (ret != 0) { goto exit; } mbedtls_xor(ctx->y + offset, ctx->y + offset, local_output, use_len); memcpy(output, local_output, use_len); if (use_len + offset == 16 || ctx->processed == ctx->plaintext_len) { if ((ret = mbedtls_cipher_update(&ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen)) != 0) { ctx->state |= CCM_STATE__ERROR; goto exit; } } } if (use_len + offset == 16 || ctx->processed == ctx->plaintext_len) { for (i = 0; i < ctx->q; i++) { if (++(ctx->ctr)[15-i] != 0) { break; } } } input_len -= use_len; input += use_len; output += use_len; } exit: mbedtls_platform_zeroize(local_output, 16); return ret; } int mbedtls_ccm_finish(mbedtls_ccm_context *ctx, unsigned char *tag, size_t tag_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char i; if (ctx->state & CCM_STATE__ERROR) { return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; } if (ctx->add_len > 0 && !(ctx->state & CCM_STATE__AUTH_DATA_FINISHED)) { return MBEDTLS_ERR_CCM_BAD_INPUT; } if (ctx->plaintext_len > 0 && ctx->processed != ctx->plaintext_len) { return MBEDTLS_ERR_CCM_BAD_INPUT; } /* * Authentication: reset counter and crypt/mask internal tag */ for (i = 0; i < ctx->q; i++) { ctx->ctr[15-i] = 0; } ret = mbedtls_ccm_crypt(ctx, 0, 16, ctx->y, ctx->y); if (ret != 0) { return ret; } if (tag != NULL) { memcpy(tag, ctx->y, tag_len); } mbedtls_ccm_clear_state(ctx); return 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; size_t olen; if ((ret = mbedtls_ccm_starts(ctx, mode, iv, iv_len)) != 0) { return ret; } if ((ret = mbedtls_ccm_set_lengths(ctx, add_len, length, tag_len)) != 0) { return ret; } if ((ret = mbedtls_ccm_update_ad(ctx, add, add_len)) != 0) { return ret; } if ((ret = mbedtls_ccm_update(ctx, input, length, output, length, &olen)) != 0) { return ret; } if ((ret = mbedtls_ccm_finish(ctx, tag, tag_len)) != 0) { return ret; } 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) { return ccm_auth_crypt(ctx, MBEDTLS_CCM_STAR_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) { return ccm_auth_crypt(ctx, MBEDTLS_CCM_ENCRYPT, length, iv, iv_len, add, add_len, input, output, tag, tag_len); } /* * Authenticated decryption */ static int mbedtls_ccm_compare_tags(const unsigned char *tag1, const unsigned char *tag2, size_t tag_len) { unsigned char i; int diff; /* Check tag in "constant-time" */ for (diff = 0, i = 0; i < tag_len; i++) { diff |= tag1[i] ^ tag2[i]; } if (diff != 0) { return MBEDTLS_ERR_CCM_AUTH_FAILED; } return 0; } static int ccm_auth_decrypt(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, const unsigned char *tag, size_t tag_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char check_tag[16]; if ((ret = ccm_auth_crypt(ctx, mode, length, iv, iv_len, add, add_len, input, output, check_tag, tag_len)) != 0) { return ret; } if ((ret = mbedtls_ccm_compare_tags(tag, check_tag, tag_len)) != 0) { mbedtls_platform_zeroize(output, length); return ret; } return 0; } 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) { return ccm_auth_decrypt(ctx, MBEDTLS_CCM_STAR_DECRYPT, length, iv, iv_len, add, add_len, input, output, tag, tag_len); } 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) { return ccm_auth_decrypt(ctx, MBEDTLS_CCM_DECRYPT, 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 */