232 lines
8.8 KiB
C
232 lines
8.8 KiB
C
/*
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* This file is part of the Pico FIDO distribution (https://github.com/polhenarejos/pico-fido).
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* Copyright (c) 2022 Pol Henarejos.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "common.h"
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#include "mbedtls/chachapoly.h"
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#include "mbedtls/sha256.h"
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#include "credential.h"
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#include "bsp/board.h"
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#include "fido.h"
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#include "ctap.h"
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#include "random.h"
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#include "files.h"
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#include "file.h"
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#include "hsm.h"
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int credential_verify(uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash) {
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if (cred_id_len < 4+12+16)
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return -1;
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uint8_t key[32], *iv = cred_id + 4, *cipher = cred_id + 4 + 12, *tag = cred_id + cred_id_len - 16;
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memset(key, 0, sizeof(key));
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mbedtls_chachapoly_context chatx;
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mbedtls_chachapoly_init(&chatx);
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mbedtls_chachapoly_setkey(&chatx, key);
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return mbedtls_chachapoly_auth_decrypt(&chatx, cred_id_len - (4 + 12 + 16), iv, rp_id_hash, 32, tag, cipher, cipher);
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}
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int credential_create(CborCharString *rpId, CborByteString *userId, CborCharString *userName, CborCharString *userDisplayName, CredExtensions *extensions, bool use_sign_count, int alg, int curve, uint8_t *cred_id, size_t *cred_id_len) {
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CborEncoder encoder, mapEncoder, mapEncoder2;
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CborError error = CborNoError;
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uint8_t rp_id_hash[32];
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mbedtls_sha256((uint8_t *)rpId->data, rpId->len, rp_id_hash, 0);
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cbor_encoder_init(&encoder, cred_id+4+12, MAX_CRED_ID_LENGTH-(4+12+16), 0);
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CBOR_CHECK(cbor_encoder_create_map(&encoder, &mapEncoder, CborIndefiniteLength));
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CBOR_APPEND_KEY_UINT_VAL_STRING(mapEncoder, 0x01, *rpId);
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CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x02));
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CBOR_CHECK(cbor_encode_byte_string(&mapEncoder, rp_id_hash, 32));
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CBOR_APPEND_KEY_UINT_VAL_BYTES(mapEncoder, 0x03, *userId);
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CBOR_APPEND_KEY_UINT_VAL_STRING(mapEncoder, 0x04, *userName);
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CBOR_APPEND_KEY_UINT_VAL_STRING(mapEncoder, 0x05, *userDisplayName);
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CBOR_APPEND_KEY_UINT_VAL_UINT(mapEncoder, 0x06, board_millis());
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if (extensions->present == true) {
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CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x07));
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CBOR_CHECK(cbor_encoder_create_map(&mapEncoder, &mapEncoder2, CborIndefiniteLength));
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if (extensions->credProtect != 0) {
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CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder2, "credProtect"));
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CBOR_CHECK(cbor_encode_uint(&mapEncoder2, extensions->credProtect));
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}
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if (extensions->hmac_secret != NULL) {
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CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder2, "hmac-secret"));
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CBOR_CHECK(cbor_encode_boolean(&mapEncoder, *extensions->hmac_secret));
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}
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CBOR_CHECK(cbor_encoder_close_container(&mapEncoder, &mapEncoder2));
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}
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CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x08));
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CBOR_CHECK(cbor_encode_boolean(&mapEncoder, use_sign_count));
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if (alg != FIDO2_ALG_ES256 || curve != FIDO2_CURVE_P256) {
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CBOR_APPEND_KEY_UINT_VAL_INT(mapEncoder, 0x09, alg);
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CBOR_APPEND_KEY_UINT_VAL_INT(mapEncoder, 0x0A, curve);
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}
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CBOR_CHECK(cbor_encoder_close_container(&encoder, &mapEncoder));
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size_t rs = cbor_encoder_get_buffer_size(&encoder, cred_id);
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*cred_id_len = 4 + 12 + rs + 16;
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uint8_t key[32];
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memset(key, 0, sizeof(key));
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uint8_t iv[12];
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random_gen(NULL, iv, sizeof(12));
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mbedtls_chachapoly_context chatx;
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mbedtls_chachapoly_init(&chatx);
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mbedtls_chachapoly_setkey(&chatx, key);
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int ret = mbedtls_chachapoly_encrypt_and_tag(&chatx, rs, iv, rp_id_hash, 32, cred_id + 4 + 12, cred_id + 4 + 12, cred_id + 4 + 12 + rs);
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mbedtls_chachapoly_free(&chatx);
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if (ret != 0) {
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CBOR_ERROR(CTAP1_ERR_OTHER);
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}
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memcpy(cred_id, "\xf1\xd0\x02\x00", 4);
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memcpy(cred_id + 4, iv, 12);
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err:
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if (error != CborNoError) {
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if (error == CborErrorImproperValue)
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return CTAP2_ERR_CBOR_UNEXPECTED_TYPE;
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return error;
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}
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return 0;
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}
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int credential_load(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash, Credential *cred) {
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int ret = 0;
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uint8_t *copy_cred_id = (uint8_t *)calloc(1, cred_id_len);
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memcpy(copy_cred_id, cred_id, cred_id_len);
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ret = credential_verify(copy_cred_id, cred_id_len, rp_id_hash);
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if (ret != 0)
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return ret;
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CborParser parser;
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CborValue map;
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CborError error;
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memset(cred, 0, sizeof(Credential));
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cred->curve = FIDO2_CURVE_P256;
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cred->alg = FIDO2_ALG_ES256;
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CBOR_CHECK(cbor_parser_init(copy_cred_id + 4 + 12, cred_id_len - (4 + 12 + 16), 0, &parser, &map));
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CBOR_PARSE_MAP_START(map, 1) {
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uint64_t val_u = 0;
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CBOR_FIELD_GET_UINT(val_u, 1);
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if (val_u == 0x01) {
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CBOR_FIELD_GET_TEXT(cred->rpId, 1);
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}
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else if (val_u == 0x03) {
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CBOR_FIELD_GET_BYTES(cred->userId, 1);
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}
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else if (val_u == 0x06) {
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CBOR_FIELD_GET_UINT(cred->creation, 1);
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}
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else if (val_u == 0x07) {
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cred->extensions.present = true;
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CBOR_PARSE_MAP_START(_f1, 2)
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{
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CBOR_FIELD_GET_KEY_TEXT(2);
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CBOR_FIELD_KEY_TEXT_VAL_BOOL(2, "hmac-secret", cred->extensions.hmac_secret);
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CBOR_FIELD_KEY_TEXT_VAL_UINT(2, "credProtect", cred->extensions.credProtect);
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CBOR_ADVANCE(2);
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}
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CBOR_PARSE_MAP_END(_f1, 2);
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}
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else if (val_u == 0x08) {
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CBOR_FIELD_GET_BOOL(cred->use_sign_count, 1);
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}
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else if (val_u == 0x09) {
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CBOR_FIELD_GET_INT(cred->alg, 1);
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}
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else if (val_u == 0x0A) {
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CBOR_FIELD_GET_INT(cred->curve, 1);
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}
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else {
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CBOR_ADVANCE(1);
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}
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}
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cred->id.present = true;
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cred->id.data = (uint8_t *)calloc(1, cred_id_len);
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memcpy(cred->id.data, cred_id, cred_id_len);
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cred->id.len = cred_id_len;
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cred->present = true;
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err:
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free(copy_cred_id);
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if (error != CborNoError) {
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if (error == CborErrorImproperValue)
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return CTAP2_ERR_CBOR_UNEXPECTED_TYPE;
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return error;
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}
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return 0;
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}
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void credential_free(Credential *cred) {
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CBOR_FREE_BYTE_STRING(cred->rpId);
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CBOR_FREE_BYTE_STRING(cred->userId);
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CBOR_FREE_BYTE_STRING(cred->userName);
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CBOR_FREE_BYTE_STRING(cred->userDisplayName);
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CBOR_FREE_BYTE_STRING(cred->id);
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cred->present = false;
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cred->extensions.present = false;
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}
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int credential_store(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash) {
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int sloti = -1;
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Credential cred = {0};
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int ret = 0;
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ret = credential_load(cred_id, cred_id_len, rp_id_hash, &cred);
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if (ret != 0) {
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credential_free(&cred);
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return ret;
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}
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for (int i = 0; i < MAX_RESIDENT_CREDENTIALS; i++) {
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file_t *ef = search_dynamic_file(EF_CRED + i);
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Credential rcred = {0};
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if (!file_has_data(ef)) {
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if (sloti == -1)
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sloti = i;
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continue;
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}
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if (memcmp(file_get_data(ef), rp_id_hash, 32) != 0)
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continue;
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ret = credential_load(file_get_data(ef) + 32, file_get_size(ef)-32, rp_id_hash, &rcred);
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if (ret != 0) {
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credential_free(&rcred);
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continue;
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}
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if (memcmp(rcred.userId.data, cred.userId.data, MIN(rcred.userId.len, cred.userId.len)) == 0) {
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sloti = i;
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credential_free(&rcred);
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break;
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}
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credential_free(&rcred);
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}
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if (sloti == -1)
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return -1;
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credential_free(&cred);
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uint8_t *data = (uint8_t *)calloc(1, cred_id_len+32);
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memcpy(data, rp_id_hash, 32);
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memcpy(data + 32, cred_id, cred_id_len);
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file_t *ef = file_new(EF_CRED+sloti);
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flash_write_data_to_file(ef, data, cred_id_len + 32);
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low_flash_available();
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return 0;
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}
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int credential_derive_hmac_key(const uint8_t *cred_id, size_t cred_id_len, uint8_t *outk) {
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memset(outk, 0, 64);
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int r = 0;
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if ((r = load_keydev(outk)) != 0)
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return r;
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const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA512);
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mbedtls_md_hmac(md_info, outk, 32, (uint8_t *)"SLIP-0022", 9, outk);
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mbedtls_md_hmac(md_info, outk, 32, (uint8_t *)"\xf1\xd0\x02\x00", 4, outk);
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mbedtls_md_hmac(md_info, outk, 32, (uint8_t *)"hmac-secret", 11, outk);
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mbedtls_md_hmac(md_info, outk, 32, cred_id, cred_id_len, outk);
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return 0;
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}
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