/* * GCM block cipher, ESP DMA hardware accelerated version * Based on mbedTLS FIPS-197 compliant version. * * SPDX-FileCopyrightText: The Mbed TLS Contributors * * SPDX-License-Identifier: Apache-2.0 * * SPDX-FileContributor: 2016-2022 Espressif Systems (Shanghai) CO LTD */ /* * The AES block cipher was designed by Vincent Rijmen and Joan Daemen. * * http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf * http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf */ #include "soc/soc_caps.h" #if SOC_AES_SUPPORT_GCM #include "aes/esp_aes.h" #include "aes/esp_aes_gcm.h" #include "aes/esp_aes_internal.h" #include "hal/aes_hal.h" #include "esp_log.h" #include "mbedtls/aes.h" #include "esp_heap_caps.h" #include "soc/soc_memory_layout.h" #include #define ESP_PUT_BE64(a, val) \ do { \ *(uint64_t*)(a) = __builtin_bswap64( (uint64_t)(val) ); \ } while (0) /* For simplicity limit the maxium amount of aad bytes to a single DMA descriptor This should cover all normal, e.g. mbedtls, use cases */ #define ESP_AES_GCM_AAD_MAX_BYTES 4080 static const char *TAG = "esp-aes-gcm"; static void esp_gcm_ghash(esp_gcm_context *ctx, const unsigned char *x, size_t x_len, uint8_t *z); /* * Calculates the Initial Counter Block, J0 * and copies to to the esp_gcm_context */ static void esp_gcm_derive_J0(esp_gcm_context *ctx) { uint8_t len_buf[16]; memset(ctx->J0, 0, AES_BLOCK_BYTES); memset(len_buf, 0, AES_BLOCK_BYTES); /* If IV is 96 bits J0 = ( IV || 0^31 || 1 ) */ if (ctx->iv_len == 12) { memcpy(ctx->J0, ctx->iv, ctx->iv_len); ctx->J0[AES_BLOCK_BYTES - 1] |= 1; } else { /* For IV != 96 bit, J0 = GHASH(IV || 0[s+64] || [len(IV)]64) */ /* First calculate GHASH on IV */ esp_gcm_ghash(ctx, ctx->iv, ctx->iv_len, ctx->J0); /* Next create 128 bit block which is equal to 64 bit 0 + iv length truncated to 64 bits */ ESP_PUT_BE64(len_buf + 8, ctx->iv_len * 8); /* Calculate GHASH on last block */ esp_gcm_ghash(ctx, len_buf, 16, ctx->J0); } } /* * Increment J0 as per GCM spec, by applying the Standard Incrementing Function INC_32 to it. * j is the counter which needs to be incremented which is * copied to ctx->J0 after incrementing */ static void increment32_j0(esp_gcm_context *ctx, uint8_t *j) { uint8_t j_len = AES_BLOCK_BYTES; memcpy(j, ctx->J0, AES_BLOCK_BYTES); if (j) { for (uint32_t i = j_len; i > (j_len - 4); i--) { if (++j[i - 1] != 0) { break; } } memcpy(ctx->J0, j, AES_BLOCK_BYTES); } } /* Function to xor two data blocks */ static void xor_data(uint8_t *d, const uint8_t *s) { for (int i = 0; i < AES_BLOCK_BYTES; i++) { d[i] ^= s[i]; } } /* * 32-bit integer manipulation macros (big endian) */ #ifndef GET_UINT32_BE #define GET_UINT32_BE(n,b,i) \ { \ (n) = ( (uint32_t) (b)[(i) ] << 24 ) \ | ( (uint32_t) (b)[(i) + 1] << 16 ) \ | ( (uint32_t) (b)[(i) + 2] << 8 ) \ | ( (uint32_t) (b)[(i) + 3] ); \ } #endif #ifndef PUT_UINT32_BE #define PUT_UINT32_BE(n,b,i) \ { \ (b)[(i) ] = (unsigned char) ( (n) >> 24 ); \ (b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \ (b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \ (b)[(i) + 3] = (unsigned char) ( (n) ); \ } #endif /* Based on MbedTLS's implemenation * * Precompute small multiples of H, that is set * HH[i] || HL[i] = H times i, * where i is seen as a field element as in [MGV], ie high-order bits * correspond to low powers of P. The result is stored in the same way, that * is the high-order bit of HH corresponds to P^0 and the low-order bit of HL * corresponds to P^127. */ static int gcm_gen_table( esp_gcm_context *ctx ) { int i, j; uint64_t hi, lo; uint64_t vl, vh; unsigned char *h; h = ctx->H; /* pack h as two 64-bits ints, big-endian */ GET_UINT32_BE( hi, h, 0 ); GET_UINT32_BE( lo, h, 4 ); vh = (uint64_t) hi << 32 | lo; GET_UINT32_BE( hi, h, 8 ); GET_UINT32_BE( lo, h, 12 ); vl = (uint64_t) hi << 32 | lo; /* 8 = 1000 corresponds to 1 in GF(2^128) */ ctx->HL[8] = vl; ctx->HH[8] = vh; /* 0 corresponds to 0 in GF(2^128) */ ctx->HH[0] = 0; ctx->HL[0] = 0; for ( i = 4; i > 0; i >>= 1 ) { uint32_t T = ( vl & 1 ) * 0xe1000000U; vl = ( vh << 63 ) | ( vl >> 1 ); vh = ( vh >> 1 ) ^ ( (uint64_t) T << 32); ctx->HL[i] = vl; ctx->HH[i] = vh; } for ( i = 2; i <= 8; i *= 2 ) { uint64_t *HiL = ctx->HL + i, *HiH = ctx->HH + i; vh = *HiH; vl = *HiL; for ( j = 1; j < i; j++ ) { HiH[j] = vh ^ ctx->HH[j]; HiL[j] = vl ^ ctx->HL[j]; } } return ( 0 ); } /* * Shoup's method for multiplication use this table with * last4[x] = x times P^128 * where x and last4[x] are seen as elements of GF(2^128) as in [MGV] */ static const uint64_t last4[16] = { 0x0000, 0x1c20, 0x3840, 0x2460, 0x7080, 0x6ca0, 0x48c0, 0x54e0, 0xe100, 0xfd20, 0xd940, 0xc560, 0x9180, 0x8da0, 0xa9c0, 0xb5e0 }; /* Based on MbedTLS's implemenation * * Sets output to x times H using the precomputed tables. * x and output are seen as elements of GF(2^128) as in [MGV]. */ static void gcm_mult( esp_gcm_context *ctx, const unsigned char x[16], unsigned char output[16] ) { int i = 0; unsigned char lo, hi, rem; uint64_t zh, zl; lo = x[15] & 0xf; zh = ctx->HH[lo]; zl = ctx->HL[lo]; for ( i = 15; i >= 0; i-- ) { lo = x[i] & 0xf; hi = x[i] >> 4; if ( i != 15 ) { rem = (unsigned char) zl & 0xf; zl = ( zh << 60 ) | ( zl >> 4 ); zh = ( zh >> 4 ); zh ^= (uint64_t) last4[rem] << 48; zh ^= ctx->HH[lo]; zl ^= ctx->HL[lo]; } rem = (unsigned char) zl & 0xf; zl = ( zh << 60 ) | ( zl >> 4 ); zh = ( zh >> 4 ); zh ^= (uint64_t) last4[rem] << 48; zh ^= ctx->HH[hi]; zl ^= ctx->HL[hi]; } PUT_UINT32_BE( zh >> 32, output, 0 ); PUT_UINT32_BE( zh, output, 4 ); PUT_UINT32_BE( zl >> 32, output, 8 ); PUT_UINT32_BE( zl, output, 12 ); } /* Update the key value in gcm context */ int esp_aes_gcm_setkey( esp_gcm_context *ctx, mbedtls_cipher_id_t cipher, const unsigned char *key, unsigned int keybits ) { if (keybits != 128 && keybits != 192 && keybits != 256) { return MBEDTLS_ERR_AES_INVALID_KEY_LENGTH; } ctx->aes_ctx.key_bytes = keybits / 8; memcpy(ctx->aes_ctx.key, key, ctx->aes_ctx.key_bytes); return ( 0 ); } /* AES-GCM GHASH calculation z = GHASH(x) using h0 hash key */ static void esp_gcm_ghash(esp_gcm_context *ctx, const unsigned char *x, size_t x_len, uint8_t *z) { uint8_t tmp[AES_BLOCK_BYTES]; memset(tmp, 0, AES_BLOCK_BYTES); /* GHASH(X) is calculated on input string which is multiple of 128 bits * If input string bit length is not multiple of 128 bits it needs to * be padded by 0 * * Steps: * 1. Let X1, X2, ... , Xm-1, Xm denote the unique sequence of blocks such * that X = X1 || X2 || ... || Xm-1 || Xm. * 2. Let Y0 be the “zero block,” 0128. * 3. Fori=1,...,m,letYi =(Yi-1 ^ Xi)•H. * 4. Return Ym */ /* If input bit string is >= 128 bits, process full 128 bit blocks */ while (x_len >= AES_BLOCK_BYTES) { xor_data(z, x); gcm_mult(ctx, z, z); x += AES_BLOCK_BYTES; x_len -= AES_BLOCK_BYTES; } /* If input bit string is not multiple of 128 create last 128 bit * block by padding necessary 0s */ if (x_len) { memcpy(tmp, x, x_len); xor_data(z, tmp); gcm_mult(ctx, z, z); } } /* Function to init AES GCM context to zero */ void esp_aes_gcm_init( esp_gcm_context *ctx) { if (ctx == NULL) { return; } bzero(ctx, sizeof(esp_gcm_context)); ctx->gcm_state = ESP_AES_GCM_STATE_INIT; } /* Function to clear AES-GCM context */ void esp_aes_gcm_free( esp_gcm_context *ctx) { if (ctx == NULL) { return; } bzero(ctx, sizeof(esp_gcm_context)); } /* Setup AES-GCM */ int esp_aes_gcm_starts( esp_gcm_context *ctx, int mode, const unsigned char *iv, size_t iv_len ) { /* IV is limited to 2^32 bits, so 2^29 bytes */ /* IV is not allowed to be zero length */ if ( iv_len == 0 || ( (uint32_t) iv_len ) >> 29 != 0 ) { return ( MBEDTLS_ERR_GCM_BAD_INPUT ); } if (!ctx) { ESP_LOGE(TAG, "No AES context supplied"); return -1; } if (!iv) { ESP_LOGE(TAG, "No IV supplied"); return -1; } /* Initialize AES-GCM context */ memset(ctx->ghash, 0, sizeof(ctx->ghash)); ctx->data_len = 0; ctx->iv = iv; ctx->iv_len = iv_len; ctx->mode = mode; /* H and the lookup table are only generated once per ctx */ if (ctx->gcm_state == ESP_AES_GCM_STATE_INIT) { /* Lock the AES engine to calculate ghash key H in hardware */ esp_aes_acquire_hardware(); ctx->aes_ctx.key_in_hardware = aes_hal_setkey(ctx->aes_ctx.key, ctx->aes_ctx.key_bytes, mode); aes_hal_mode_init(ESP_AES_BLOCK_MODE_GCM); aes_hal_gcm_calc_hash(ctx->H); esp_aes_release_hardware(); gcm_gen_table(ctx); } ctx->gcm_state = ESP_AES_GCM_STATE_START; return ( 0 ); } int esp_aes_gcm_update_ad( esp_gcm_context *ctx, const unsigned char *aad, size_t aad_len ) { /* AD are limited to 2^32 bits, so 2^29 bytes */ if ( ( (uint32_t) aad_len ) >> 29 != 0 ) { return ( MBEDTLS_ERR_GCM_BAD_INPUT ); } if (!ctx) { ESP_LOGE(TAG, "No AES context supplied"); return -1; } if ( (aad_len > 0) && !aad) { ESP_LOGE(TAG, "No aad supplied"); return -1; } /* Initialize AES-GCM context */ memset(ctx->ghash, 0, sizeof(ctx->ghash)); ctx->data_len = 0; ctx->aad = aad; ctx->aad_len = aad_len; if (ctx->gcm_state != ESP_AES_GCM_STATE_START) { ESP_LOGE(TAG, "AES context in invalid state!"); return -1; } /* Once H is obtained we need to derive J0 (Initial Counter Block) */ esp_gcm_derive_J0(ctx); /* The initial counter block keeps updating during the esp_gcm_update call * however to calculate final authentication tag T we need original J0 * so we make a copy here */ memcpy(ctx->ori_j0, ctx->J0, 16); esp_gcm_ghash(ctx, ctx->aad, ctx->aad_len, ctx->ghash); return ( 0 ); } /* Perform AES-GCM operation */ int esp_aes_gcm_update( esp_gcm_context *ctx, const unsigned char *input, size_t input_length, unsigned char *output, size_t output_size, size_t *output_length ) { size_t nc_off = 0; uint8_t nonce_counter[AES_BLOCK_BYTES] = {0}; uint8_t stream[AES_BLOCK_BYTES] = {0}; if (!output_length) { ESP_LOGE(TAG, "No output length supplied"); return -1; } *output_length = input_length; if (!ctx) { ESP_LOGE(TAG, "No GCM context supplied"); return -1; } if (!input) { ESP_LOGE(TAG, "No input supplied"); return -1; } if (!output) { ESP_LOGE(TAG, "No output supplied"); return -1; } if ( output > input && (size_t) ( output - input ) < input_length ) { return ( MBEDTLS_ERR_GCM_BAD_INPUT ); } /* If this is the first time esp_gcm_update is getting called * calculate GHASH on aad and preincrement the ICB */ if (ctx->gcm_state == ESP_AES_GCM_STATE_START) { /* Jo needs to be incremented first time, later the CTR * operation will auto update it */ increment32_j0(ctx, nonce_counter); ctx->gcm_state = ESP_AES_GCM_STATE_UPDATE; } else if (ctx->gcm_state == ESP_AES_GCM_STATE_UPDATE) { memcpy(nonce_counter, ctx->J0, AES_BLOCK_BYTES); } /* Perform intermediate GHASH on "encrypted" data during decryption */ if (ctx->mode == ESP_AES_DECRYPT) { esp_gcm_ghash(ctx, input, input_length, ctx->ghash); } /* Output = GCTR(J0, Input): Encrypt/Decrypt the input */ esp_aes_crypt_ctr(&ctx->aes_ctx, input_length, &nc_off, nonce_counter, stream, input, output); /* ICB gets auto incremented after GCTR operation here so update the context */ memcpy(ctx->J0, nonce_counter, AES_BLOCK_BYTES); /* Keep updating the length counter for final tag calculation */ ctx->data_len += input_length; /* Perform intermediate GHASH on "encrypted" data during encryption*/ if (ctx->mode == ESP_AES_ENCRYPT) { esp_gcm_ghash(ctx, output, input_length, ctx->ghash); } return 0; } /* Function to read the tag value */ int esp_aes_gcm_finish( esp_gcm_context *ctx, unsigned char *output, size_t output_size, size_t *output_length, unsigned char *tag, size_t tag_len ) { size_t nc_off = 0; uint8_t len_block[AES_BLOCK_BYTES] = {0}; if ( tag_len > 16 || tag_len < 4 ) { return ( MBEDTLS_ERR_GCM_BAD_INPUT ); } /* Calculate final GHASH on aad_len, data length */ ESP_PUT_BE64(len_block, ctx->aad_len * 8); ESP_PUT_BE64(len_block + 8, ctx->data_len * 8); esp_gcm_ghash(ctx, len_block, AES_BLOCK_BYTES, ctx->ghash); /* Tag T = GCTR(J0, ) where T is truncated to tag_len */ esp_aes_crypt_ctr(&ctx->aes_ctx, tag_len, &nc_off, ctx->ori_j0, 0, ctx->ghash, tag); return 0; } /* Due to restrictions in the hardware (e.g. need to do the whole conversion in one go), some combinations of inputs are not supported */ static bool esp_aes_gcm_input_support_hw_accel(size_t length, const unsigned char *aad, size_t aad_len, const unsigned char *input, unsigned char *output, uint8_t *stream_in) { bool support_hw_accel = true; if (aad_len > ESP_AES_GCM_AAD_MAX_BYTES) { support_hw_accel = false; } else if (!esp_ptr_dma_capable(aad) && aad_len > 0) { /* aad in non internal DMA memory */ support_hw_accel = false; } else if (!esp_ptr_dma_capable(input) && length > 0) { /* input in non internal DMA memory */ support_hw_accel = false; } else if (!esp_ptr_dma_capable(output) && length > 0) { /* output in non internal DMA memory */ support_hw_accel = false; } else if (!esp_ptr_dma_capable(stream_in)) { /* Stream in (and therefor other descriptors and buffers that come from the stack) in non internal DMA memory */ support_hw_accel = false; } else if (length == 0) { support_hw_accel = false; } return support_hw_accel; } static int esp_aes_gcm_crypt_and_tag_partial_hw( esp_gcm_context *ctx, int mode, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *aad, size_t aad_len, const unsigned char *input, unsigned char *output, size_t tag_len, unsigned char *tag ) { int ret = 0; size_t olen; if ( ( ret = esp_aes_gcm_starts( ctx, mode, iv, iv_len ) ) != 0 ) { return ( ret ); } if ( ( ret = esp_aes_gcm_update_ad( ctx, aad, aad_len ) ) != 0 ) { return ( ret ); } if ( ( ret = esp_aes_gcm_update( ctx, input, length, output, 0, &olen ) ) != 0 ) { return ( ret ); } if ( ( ret = esp_aes_gcm_finish( ctx, output, 0, &olen, tag, tag_len ) ) != 0 ) { return ( ret ); } return ret; } int esp_aes_gcm_crypt_and_tag( esp_gcm_context *ctx, int mode, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *aad, size_t aad_len, const unsigned char *input, unsigned char *output, size_t tag_len, unsigned char *tag ) { int ret; lldesc_t aad_desc[2] = {}; lldesc_t *aad_head_desc = NULL; size_t remainder_bit; uint8_t stream_in[AES_BLOCK_BYTES] = {}; unsigned stream_bytes = aad_len % AES_BLOCK_BYTES; // bytes which aren't in a full block unsigned block_bytes = aad_len - stream_bytes; // bytes which are in a full block /* Due to hardware limition only certain cases are fully supported in HW */ if (!esp_aes_gcm_input_support_hw_accel(length, aad, aad_len, input, output, stream_in)) { return esp_aes_gcm_crypt_and_tag_partial_hw(ctx, mode, length, iv, iv_len, aad, aad_len, input, output, tag_len, tag); } /* Limit aad len to a single DMA descriptor to simplify DMA handling In practice, e.g. with mbedtls the length of aad will always be short */ if (aad_len > LLDESC_MAX_NUM_PER_DESC) { return -1; } /* IV and AD are limited to 2^32 bits, so 2^29 bytes */ /* IV is not allowed to be zero length */ if ( iv_len == 0 || ( (uint32_t) iv_len ) >> 29 != 0 || ( (uint32_t) aad_len ) >> 29 != 0 ) { return ( MBEDTLS_ERR_GCM_BAD_INPUT ); } if (!ctx) { ESP_LOGE(TAG, "No AES context supplied"); return -1; } if (!iv) { ESP_LOGE(TAG, "No IV supplied"); return -1; } if ( (aad_len > 0) && !aad) { ESP_LOGE(TAG, "No aad supplied"); return -1; } /* Initialize AES-GCM context */ memset(ctx->ghash, 0, sizeof(ctx->ghash)); ctx->data_len = 0; ctx->iv = iv; ctx->iv_len = iv_len; ctx->aad = aad; ctx->aad_len = aad_len; ctx->mode = mode; esp_aes_acquire_hardware(); ctx->aes_ctx.key_in_hardware = 0; ctx->aes_ctx.key_in_hardware = aes_hal_setkey(ctx->aes_ctx.key, ctx->aes_ctx.key_bytes, mode); if (block_bytes > 0) { aad_desc[0].length = block_bytes; aad_desc[0].size = block_bytes; aad_desc[0].owner = 1; aad_desc[0].buf = aad; } if (stream_bytes > 0) { memcpy(stream_in, aad + block_bytes, stream_bytes); aad_desc[0].empty = (uint32_t)&aad_desc[1]; aad_desc[1].length = AES_BLOCK_BYTES; aad_desc[1].size = AES_BLOCK_BYTES; aad_desc[1].owner = 1; aad_desc[1].buf = stream_in; } if (block_bytes > 0) { aad_head_desc = &aad_desc[0]; } else if (stream_bytes > 0) { aad_head_desc = &aad_desc[1]; } aes_hal_mode_init(ESP_AES_BLOCK_MODE_GCM); /* See TRM GCM chapter for description of this calculation */ remainder_bit = (8 * length) % 128; aes_hal_gcm_init( (aad_len + AES_BLOCK_BYTES - 1) / AES_BLOCK_BYTES, remainder_bit); aes_hal_gcm_calc_hash(ctx->H); gcm_gen_table(ctx); esp_gcm_derive_J0(ctx); aes_hal_gcm_set_j0(ctx->J0); ret = esp_aes_process_dma_gcm(&ctx->aes_ctx, input, output, length, aad_head_desc, aad_len); aes_hal_gcm_read_tag(tag, tag_len); esp_aes_release_hardware(); return ( ret ); } int esp_aes_gcm_auth_decrypt( esp_gcm_context *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *aad, size_t aad_len, const unsigned char *tag, size_t tag_len, const unsigned char *input, unsigned char *output ) { int ret; unsigned char check_tag[16]; size_t i; int diff; if ( ( ret = esp_aes_gcm_crypt_and_tag( ctx, ESP_AES_DECRYPT, length, iv, iv_len, aad, aad_len, input, output, tag_len, check_tag ) ) != 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 ) { bzero( output, length ); return ( MBEDTLS_ERR_GCM_AUTH_FAILED ); } return ( 0 ); } #endif //SOC_AES_SUPPORT_GCM