| /* Copyright (c) 2019, Google Inc. |
| * |
| * Permission to use, copy, modify, and/or distribute this software for any |
| * purpose with or without fee is hereby granted, provided that the above |
| * copyright notice and this permission notice appear in all copies. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION |
| * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
| * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ |
| |
| #include <openssl/bytestring.h> |
| #include <openssl/err.h> |
| #include <openssl/evp.h> |
| #include <openssl/mem.h> |
| #include <openssl/sha.h> |
| #include <openssl/trust_token.h> |
| |
| #include "internal.h" |
| |
| |
| // The Trust Token API is described in |
| // https://github.com/WICG/trust-token-api/blob/master/README.md and provides a |
| // protocol for issuing and redeeming tokens built on top of the PMBTokens |
| // construction. |
| |
| const TRUST_TOKEN_METHOD *TRUST_TOKEN_experiment_v1(void) { |
| static const TRUST_TOKEN_METHOD kMethod = { |
| pmbtoken_exp1_generate_key, |
| pmbtoken_exp1_client_key_from_bytes, |
| pmbtoken_exp1_issuer_key_from_bytes, |
| pmbtoken_exp1_blind, |
| pmbtoken_exp1_sign, |
| pmbtoken_exp1_unblind, |
| pmbtoken_exp1_read, |
| }; |
| return &kMethod; |
| } |
| |
| TRUST_TOKEN *TRUST_TOKEN_new(const uint8_t *data, size_t len) { |
| TRUST_TOKEN *ret = OPENSSL_malloc(sizeof(TRUST_TOKEN)); |
| if (ret == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| return NULL; |
| } |
| OPENSSL_memset(ret, 0, sizeof(TRUST_TOKEN)); |
| ret->data = OPENSSL_memdup(data, len); |
| if (len != 0 && ret->data == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| OPENSSL_free(ret); |
| return NULL; |
| } |
| ret->len = len; |
| return ret; |
| } |
| |
| void TRUST_TOKEN_free(TRUST_TOKEN *token) { |
| if (token == NULL) { |
| return; |
| } |
| OPENSSL_free(token->data); |
| OPENSSL_free(token); |
| } |
| |
| int TRUST_TOKEN_generate_key(const TRUST_TOKEN_METHOD *method, |
| uint8_t *out_priv_key, size_t *out_priv_key_len, |
| size_t max_priv_key_len, uint8_t *out_pub_key, |
| size_t *out_pub_key_len, size_t max_pub_key_len, |
| uint32_t id) { |
| // Prepend the key ID in front of the PMBTokens format. |
| int ret = 0; |
| CBB priv_cbb, pub_cbb; |
| CBB_zero(&priv_cbb); |
| CBB_zero(&pub_cbb); |
| if (!CBB_init_fixed(&priv_cbb, out_priv_key, max_priv_key_len) || |
| !CBB_init_fixed(&pub_cbb, out_pub_key, max_pub_key_len) || |
| !CBB_add_u32(&priv_cbb, id) || |
| !CBB_add_u32(&pub_cbb, id)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_BUFFER_TOO_SMALL); |
| goto err; |
| } |
| |
| if (!method->generate_key(&priv_cbb, &pub_cbb)) { |
| goto err; |
| } |
| |
| if (!CBB_finish(&priv_cbb, NULL, out_priv_key_len) || |
| !CBB_finish(&pub_cbb, NULL, out_pub_key_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_BUFFER_TOO_SMALL); |
| goto err; |
| } |
| |
| ret = 1; |
| |
| err: |
| CBB_cleanup(&priv_cbb); |
| CBB_cleanup(&pub_cbb); |
| return ret; |
| } |
| |
| TRUST_TOKEN_CLIENT *TRUST_TOKEN_CLIENT_new(const TRUST_TOKEN_METHOD *method, |
| size_t max_batchsize) { |
| if (max_batchsize > 0xffff) { |
| // The protocol supports only two-byte token counts. |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_OVERFLOW); |
| return NULL; |
| } |
| |
| TRUST_TOKEN_CLIENT *ret = OPENSSL_malloc(sizeof(TRUST_TOKEN_CLIENT)); |
| if (ret == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| return NULL; |
| } |
| OPENSSL_memset(ret, 0, sizeof(TRUST_TOKEN_CLIENT)); |
| ret->method = method; |
| ret->max_batchsize = (uint16_t)max_batchsize; |
| return ret; |
| } |
| |
| void TRUST_TOKEN_CLIENT_free(TRUST_TOKEN_CLIENT *ctx) { |
| if (ctx == NULL) { |
| return; |
| } |
| EVP_PKEY_free(ctx->srr_key); |
| sk_PMBTOKEN_PRETOKEN_pop_free(ctx->pretokens, PMBTOKEN_PRETOKEN_free); |
| OPENSSL_free(ctx); |
| } |
| |
| int TRUST_TOKEN_CLIENT_add_key(TRUST_TOKEN_CLIENT *ctx, size_t *out_key_index, |
| const uint8_t *key, size_t key_len) { |
| if (ctx->num_keys == OPENSSL_ARRAY_SIZE(ctx->keys)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_TOO_MANY_KEYS); |
| return 0; |
| } |
| |
| struct trust_token_client_key_st *key_s = &ctx->keys[ctx->num_keys]; |
| CBS cbs; |
| CBS_init(&cbs, key, key_len); |
| uint32_t key_id; |
| if (!CBS_get_u32(&cbs, &key_id) || |
| !ctx->method->client_key_from_bytes(&key_s->key, CBS_data(&cbs), |
| CBS_len(&cbs))) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| return 0; |
| } |
| key_s->id = key_id; |
| *out_key_index = ctx->num_keys; |
| ctx->num_keys += 1; |
| return 1; |
| } |
| |
| int TRUST_TOKEN_CLIENT_set_srr_key(TRUST_TOKEN_CLIENT *ctx, EVP_PKEY *key) { |
| EVP_PKEY_free(ctx->srr_key); |
| EVP_PKEY_up_ref(key); |
| ctx->srr_key = key; |
| return 1; |
| } |
| |
| int TRUST_TOKEN_CLIENT_begin_issuance(TRUST_TOKEN_CLIENT *ctx, uint8_t **out, |
| size_t *out_len, size_t count) { |
| if (count > ctx->max_batchsize) { |
| count = ctx->max_batchsize; |
| } |
| |
| int ret = 0; |
| CBB request; |
| STACK_OF(PMBTOKEN_PRETOKEN) *pretokens = NULL; |
| if (!CBB_init(&request, 0) || |
| !CBB_add_u16(&request, count)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| pretokens = ctx->method->blind(&request, count); |
| if (pretokens == NULL) { |
| goto err; |
| } |
| |
| if (!CBB_finish(&request, out, out_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| sk_PMBTOKEN_PRETOKEN_pop_free(ctx->pretokens, PMBTOKEN_PRETOKEN_free); |
| ctx->pretokens = pretokens; |
| pretokens = NULL; |
| ret = 1; |
| |
| err: |
| CBB_cleanup(&request); |
| sk_PMBTOKEN_PRETOKEN_pop_free(pretokens, PMBTOKEN_PRETOKEN_free); |
| return ret; |
| } |
| |
| STACK_OF(TRUST_TOKEN) * |
| TRUST_TOKEN_CLIENT_finish_issuance(TRUST_TOKEN_CLIENT *ctx, |
| size_t *out_key_index, |
| const uint8_t *response, |
| size_t response_len) { |
| CBS in; |
| CBS_init(&in, response, response_len); |
| uint16_t count; |
| uint32_t key_id; |
| if (!CBS_get_u16(&in, &count) || |
| !CBS_get_u32(&in, &key_id)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| return NULL; |
| } |
| |
| size_t key_index = 0; |
| const struct trust_token_client_key_st *key = NULL; |
| for (size_t i = 0; i < ctx->num_keys; i++) { |
| if (ctx->keys[i].id == key_id) { |
| key_index = i; |
| key = &ctx->keys[i]; |
| break; |
| } |
| } |
| |
| if (key == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_KEY_ID); |
| return NULL; |
| } |
| |
| if (count > sk_PMBTOKEN_PRETOKEN_num(ctx->pretokens)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| return NULL; |
| } |
| |
| STACK_OF(TRUST_TOKEN) *tokens = |
| ctx->method->unblind(&key->key, ctx->pretokens, &in, count, key_id); |
| if (tokens == NULL) { |
| return NULL; |
| } |
| |
| if (CBS_len(&in) != 0) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| sk_TRUST_TOKEN_pop_free(tokens, TRUST_TOKEN_free); |
| return NULL; |
| } |
| |
| sk_PMBTOKEN_PRETOKEN_pop_free(ctx->pretokens, PMBTOKEN_PRETOKEN_free); |
| ctx->pretokens = NULL; |
| |
| *out_key_index = key_index; |
| return tokens; |
| } |
| |
| int TRUST_TOKEN_CLIENT_begin_redemption(TRUST_TOKEN_CLIENT *ctx, uint8_t **out, |
| size_t *out_len, |
| const TRUST_TOKEN *token, |
| const uint8_t *data, size_t data_len, |
| uint64_t time) { |
| CBB request, token_inner, inner; |
| if (!CBB_init(&request, 0) || |
| !CBB_add_u16_length_prefixed(&request, &token_inner) || |
| !CBB_add_bytes(&token_inner, token->data, token->len) || |
| !CBB_add_u16_length_prefixed(&request, &inner) || |
| !CBB_add_bytes(&inner, data, data_len) || |
| !CBB_add_u64(&request, time) || |
| !CBB_finish(&request, out, out_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| CBB_cleanup(&request); |
| return 0; |
| } |
| return 1; |
| } |
| |
| int TRUST_TOKEN_CLIENT_finish_redemption(TRUST_TOKEN_CLIENT *ctx, |
| uint8_t **out_srr, size_t *out_srr_len, |
| uint8_t **out_sig, size_t *out_sig_len, |
| const uint8_t *response, |
| size_t response_len) { |
| if (ctx->srr_key == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_NO_SRR_KEY_CONFIGURED); |
| return 0; |
| } |
| |
| CBS in, srr, sig; |
| CBS_init(&in, response, response_len); |
| if (!CBS_get_u16_length_prefixed(&in, &srr) || |
| !CBS_get_u16_length_prefixed(&in, &sig)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_ERROR); |
| return 0; |
| } |
| |
| EVP_MD_CTX md_ctx; |
| EVP_MD_CTX_init(&md_ctx); |
| int sig_ok = EVP_DigestVerifyInit(&md_ctx, NULL, NULL, NULL, ctx->srr_key) && |
| EVP_DigestVerify(&md_ctx, CBS_data(&sig), CBS_len(&sig), |
| CBS_data(&srr), CBS_len(&srr)); |
| EVP_MD_CTX_cleanup(&md_ctx); |
| |
| if (!sig_ok) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_SRR_SIGNATURE_ERROR); |
| return 0; |
| } |
| |
| uint8_t *srr_buf = NULL, *sig_buf = NULL; |
| size_t srr_len, sig_len; |
| if (!CBS_stow(&srr, &srr_buf, &srr_len) || |
| !CBS_stow(&sig, &sig_buf, &sig_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| OPENSSL_free(srr_buf); |
| OPENSSL_free(sig_buf); |
| return 0; |
| } |
| |
| *out_srr = srr_buf; |
| *out_srr_len = srr_len; |
| *out_sig = sig_buf; |
| *out_sig_len = sig_len; |
| return 1; |
| } |
| |
| TRUST_TOKEN_ISSUER *TRUST_TOKEN_ISSUER_new(const TRUST_TOKEN_METHOD *method, |
| size_t max_batchsize) { |
| if (max_batchsize > 0xffff) { |
| // The protocol supports only two-byte token counts. |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_OVERFLOW); |
| return NULL; |
| } |
| |
| TRUST_TOKEN_ISSUER *ret = OPENSSL_malloc(sizeof(TRUST_TOKEN_ISSUER)); |
| if (ret == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| return NULL; |
| } |
| OPENSSL_memset(ret, 0, sizeof(TRUST_TOKEN_ISSUER)); |
| ret->method = method; |
| ret->max_batchsize = (uint16_t)max_batchsize; |
| return ret; |
| } |
| |
| void TRUST_TOKEN_ISSUER_free(TRUST_TOKEN_ISSUER *ctx) { |
| if (ctx == NULL) { |
| return; |
| } |
| EVP_PKEY_free(ctx->srr_key); |
| OPENSSL_free(ctx->metadata_key); |
| OPENSSL_free(ctx); |
| } |
| |
| int TRUST_TOKEN_ISSUER_add_key(TRUST_TOKEN_ISSUER *ctx, const uint8_t *key, |
| size_t key_len) { |
| if (ctx->num_keys == OPENSSL_ARRAY_SIZE(ctx->keys)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_TOO_MANY_KEYS); |
| return 0; |
| } |
| |
| struct trust_token_issuer_key_st *key_s = &ctx->keys[ctx->num_keys]; |
| CBS cbs; |
| CBS_init(&cbs, key, key_len); |
| uint32_t key_id; |
| if (!CBS_get_u32(&cbs, &key_id) || |
| !ctx->method->issuer_key_from_bytes(&key_s->key, CBS_data(&cbs), |
| CBS_len(&cbs))) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| return 0; |
| } |
| |
| key_s->id = key_id; |
| ctx->num_keys += 1; |
| return 1; |
| } |
| |
| int TRUST_TOKEN_ISSUER_set_srr_key(TRUST_TOKEN_ISSUER *ctx, EVP_PKEY *key) { |
| EVP_PKEY_free(ctx->srr_key); |
| EVP_PKEY_up_ref(key); |
| ctx->srr_key = key; |
| return 1; |
| } |
| |
| int TRUST_TOKEN_ISSUER_set_metadata_key(TRUST_TOKEN_ISSUER *ctx, |
| const uint8_t *key, size_t len) { |
| if (len < 32) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_METADATA_KEY); |
| } |
| OPENSSL_free(ctx->metadata_key); |
| ctx->metadata_key_len = 0; |
| ctx->metadata_key = OPENSSL_memdup(key, len); |
| if (ctx->metadata_key == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| return 0; |
| } |
| ctx->metadata_key_len = len; |
| return 1; |
| } |
| |
| static const struct trust_token_issuer_key_st *trust_token_issuer_get_key( |
| const TRUST_TOKEN_ISSUER *ctx, uint32_t key_id) { |
| for (size_t i = 0; i < ctx->num_keys; i++) { |
| if (ctx->keys[i].id == key_id) { |
| return &ctx->keys[i]; |
| } |
| } |
| return NULL; |
| } |
| |
| int TRUST_TOKEN_ISSUER_issue(const TRUST_TOKEN_ISSUER *ctx, uint8_t **out, |
| size_t *out_len, size_t *out_tokens_issued, |
| const uint8_t *request, size_t request_len, |
| uint32_t public_metadata, uint8_t private_metadata, |
| size_t max_issuance) { |
| if (max_issuance > ctx->max_batchsize) { |
| max_issuance = ctx->max_batchsize; |
| } |
| |
| const struct trust_token_issuer_key_st *key = |
| trust_token_issuer_get_key(ctx, public_metadata); |
| if (key == NULL || private_metadata > 1) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_METADATA); |
| return 0; |
| } |
| |
| CBS in; |
| uint16_t num_requested; |
| CBS_init(&in, request, request_len); |
| if (!CBS_get_u16(&in, &num_requested)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| return 0; |
| } |
| |
| size_t num_to_issue = num_requested; |
| if (num_to_issue > max_issuance) { |
| num_to_issue = max_issuance; |
| } |
| |
| int ret = 0; |
| CBB response; |
| if (!CBB_init(&response, 0) || |
| !CBB_add_u16(&response, num_to_issue) || |
| !CBB_add_u32(&response, public_metadata)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| if (!ctx->method->sign(&key->key, &response, &in, num_requested, num_to_issue, |
| private_metadata)) { |
| goto err; |
| } |
| |
| if (CBS_len(&in) != 0) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE); |
| goto err; |
| } |
| |
| if (!CBB_finish(&response, out, out_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| *out_tokens_issued = num_to_issue; |
| ret = 1; |
| |
| err: |
| CBB_cleanup(&response); |
| return ret; |
| } |
| |
| // https://tools.ietf.org/html/rfc7049#section-2.1 |
| static int add_cbor_int_with_type(CBB *cbb, uint8_t major_type, |
| uint64_t value) { |
| if (value <= 23) { |
| return CBB_add_u8(cbb, value | major_type); |
| } |
| if (value <= 0xff) { |
| return CBB_add_u8(cbb, 0x18 | major_type) && CBB_add_u8(cbb, value); |
| } |
| if (value <= 0xffff) { |
| return CBB_add_u8(cbb, 0x19 | major_type) && CBB_add_u16(cbb, value); |
| } |
| if (value <= 0xffffffff) { |
| return CBB_add_u8(cbb, 0x1a | major_type) && CBB_add_u32(cbb, value); |
| } |
| if (value <= 0xffffffffffffffff) { |
| return CBB_add_u8(cbb, 0x1b | major_type) && CBB_add_u64(cbb, value); |
| } |
| |
| return 0; |
| } |
| |
| // https://tools.ietf.org/html/rfc7049#section-2.1 |
| static int add_cbor_int(CBB *cbb, uint64_t value) { |
| return add_cbor_int_with_type(cbb, 0, value); |
| } |
| |
| // https://tools.ietf.org/html/rfc7049#section-2.1 |
| static int add_cbor_bytes(CBB *cbb, const uint8_t *data, size_t len) { |
| return add_cbor_int_with_type(cbb, 0x40, len) && |
| CBB_add_bytes(cbb, data, len); |
| } |
| |
| // https://tools.ietf.org/html/rfc7049#section-2.1 |
| static int add_cbor_text(CBB *cbb, const char *data, size_t len) { |
| return add_cbor_int_with_type(cbb, 0x60, len) && |
| CBB_add_bytes(cbb, (const uint8_t *)data, len); |
| } |
| |
| // https://tools.ietf.org/html/rfc7049#section-2.1 |
| static int add_cbor_map(CBB *cbb, uint8_t size) { |
| return add_cbor_int_with_type(cbb, 0xa0, size); |
| } |
| |
| static uint8_t get_metadata_obfuscator(const uint8_t *key, size_t key_len, |
| const uint8_t *client_data, |
| size_t client_data_len) { |
| uint8_t metadata_obfuscator[SHA256_DIGEST_LENGTH]; |
| SHA256_CTX sha_ctx; |
| SHA256_Init(&sha_ctx); |
| SHA256_Update(&sha_ctx, key, key_len); |
| SHA256_Update(&sha_ctx, client_data, client_data_len); |
| SHA256_Final(metadata_obfuscator, &sha_ctx); |
| return metadata_obfuscator[0] >> 7; |
| } |
| |
| int TRUST_TOKEN_ISSUER_redeem(const TRUST_TOKEN_ISSUER *ctx, uint8_t **out, |
| size_t *out_len, TRUST_TOKEN **out_token, |
| uint8_t **out_client_data, |
| size_t *out_client_data_len, |
| uint64_t *out_redemption_time, |
| const uint8_t *request, size_t request_len, |
| uint64_t lifetime) { |
| CBS request_cbs, token_cbs; |
| CBS_init(&request_cbs, request, request_len); |
| if (!CBS_get_u16_length_prefixed(&request_cbs, &token_cbs)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_ERROR); |
| return 0; |
| } |
| |
| uint32_t public_metadata = 0; |
| uint8_t private_metadata = 0; |
| |
| CBS token_copy = token_cbs; |
| |
| // Parse the token. If there is an error, treat it as an invalid token. |
| if (!CBS_get_u32(&token_cbs, &public_metadata)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_TOKEN); |
| return 0; |
| } |
| |
| const struct trust_token_issuer_key_st *key = |
| trust_token_issuer_get_key(ctx, public_metadata); |
| uint8_t nonce[PMBTOKEN_NONCE_SIZE]; |
| if (key == NULL || |
| !ctx->method->read(&key->key, nonce, &private_metadata, |
| CBS_data(&token_cbs), CBS_len(&token_cbs))) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_TOKEN); |
| return 0; |
| } |
| |
| int ok = 0; |
| CBB response, srr; |
| uint8_t *srr_buf = NULL, *sig_buf = NULL, *client_data_buf = NULL; |
| size_t srr_len = 0, sig_len = 0, client_data_len = 0; |
| EVP_MD_CTX md_ctx; |
| EVP_MD_CTX_init(&md_ctx); |
| CBB_zero(&srr); |
| if (!CBB_init(&response, 0)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| CBS client_data; |
| uint64_t redemption_time; |
| if (!CBS_get_u16_length_prefixed(&request_cbs, &client_data) || |
| !CBS_get_u64(&request_cbs, &redemption_time)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_ERROR); |
| goto err; |
| } |
| |
| const uint8_t kTokenHashDSTLabel[] = "TrustTokenV0 TokenHash"; |
| uint8_t token_hash[SHA256_DIGEST_LENGTH]; |
| SHA256_CTX sha_ctx; |
| SHA256_Init(&sha_ctx); |
| SHA256_Update(&sha_ctx, kTokenHashDSTLabel, sizeof(kTokenHashDSTLabel)); |
| SHA256_Update(&sha_ctx, CBS_data(&token_copy), CBS_len(&token_copy)); |
| SHA256_Final(token_hash, &sha_ctx); |
| |
| uint8_t metadata_obfuscator = get_metadata_obfuscator( |
| ctx->metadata_key, ctx->metadata_key_len, token_hash, sizeof(token_hash)); |
| |
| // The SRR is constructed as per the format described in |
| // https://docs.google.com/document/d/1TNnya6B8pyomDK2F1R9CL3dY10OAmqWlnCxsWyOBDVQ/edit#heading=h.7mkzvhpqb8l5 |
| |
| static const char kClientDataLabel[] = "client-data"; |
| static const char kExpiryTimestampLabel[] = "expiry-timestamp"; |
| static const char kMetadataLabel[] = "metadata"; |
| static const char kPrivateLabel[] = "private"; |
| static const char kPublicLabel[] = "public"; |
| static const char kTokenHashLabel[] = "token-hash"; |
| |
| // CBOR requires map keys to be sorted by length then sorted lexically. |
| // https://tools.ietf.org/html/rfc7049#section-3.9 |
| assert(strlen(kMetadataLabel) < strlen(kTokenHashLabel)); |
| assert(strlen(kTokenHashLabel) < strlen(kClientDataLabel)); |
| assert(strlen(kClientDataLabel) < strlen(kExpiryTimestampLabel)); |
| assert(strlen(kPublicLabel) < strlen(kPrivateLabel)); |
| |
| size_t map_entries = 4; |
| |
| if (!CBB_init(&srr, 0) || |
| !add_cbor_map(&srr, map_entries) || // SRR map |
| !add_cbor_text(&srr, kMetadataLabel, strlen(kMetadataLabel)) || |
| !add_cbor_map(&srr, 2) || // Metadata map |
| !add_cbor_text(&srr, kPublicLabel, strlen(kPublicLabel)) || |
| !add_cbor_int(&srr, public_metadata) || |
| !add_cbor_text(&srr, kPrivateLabel, strlen(kPrivateLabel)) || |
| !add_cbor_int(&srr, private_metadata ^ metadata_obfuscator) || |
| !add_cbor_text(&srr, kTokenHashLabel, strlen(kTokenHashLabel)) || |
| !add_cbor_bytes(&srr, token_hash, sizeof(token_hash)) || |
| !add_cbor_text(&srr, kClientDataLabel, strlen(kClientDataLabel)) || |
| !CBB_add_bytes(&srr, CBS_data(&client_data), CBS_len(&client_data)) || |
| !add_cbor_text(&srr, kExpiryTimestampLabel, |
| strlen(kExpiryTimestampLabel)) || |
| !add_cbor_int(&srr, redemption_time + lifetime) || |
| !CBB_finish(&srr, &srr_buf, &srr_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| if (!EVP_DigestSignInit(&md_ctx, NULL, NULL, NULL, ctx->srr_key) || |
| !EVP_DigestSign(&md_ctx, NULL, &sig_len, srr_buf, srr_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_SRR_SIGNATURE_ERROR); |
| goto err; |
| } |
| |
| CBB child; |
| uint8_t *ptr; |
| if (!CBB_add_u16_length_prefixed(&response, &child) || |
| !CBB_add_bytes(&child, srr_buf, srr_len) || |
| !CBB_add_u16_length_prefixed(&response, &child) || |
| !CBB_reserve(&child, &ptr, sig_len) || |
| !EVP_DigestSign(&md_ctx, ptr, &sig_len, srr_buf, srr_len) || |
| !CBB_did_write(&child, sig_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| if (!CBS_stow(&client_data, &client_data_buf, &client_data_len) || |
| !CBB_finish(&response, out, out_len)) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| |
| TRUST_TOKEN *token = TRUST_TOKEN_new(nonce, PMBTOKEN_NONCE_SIZE); |
| if (token == NULL) { |
| OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE); |
| goto err; |
| } |
| *out_token = token; |
| *out_client_data = client_data_buf; |
| *out_client_data_len = client_data_len; |
| *out_redemption_time = redemption_time; |
| |
| ok = 1; |
| |
| err: |
| CBB_cleanup(&response); |
| CBB_cleanup(&srr); |
| OPENSSL_free(srr_buf); |
| OPENSSL_free(sig_buf); |
| EVP_MD_CTX_cleanup(&md_ctx); |
| if (!ok) { |
| OPENSSL_free(client_data_buf); |
| } |
| return ok; |
| } |
| |
| int TRUST_TOKEN_decode_private_metadata(const TRUST_TOKEN_METHOD *method, |
| uint8_t *out_value, const uint8_t *key, |
| size_t key_len, const uint8_t *nonce, |
| size_t nonce_len, |
| uint8_t encrypted_bit) { |
| uint8_t metadata_obfuscator = |
| get_metadata_obfuscator(key, key_len, nonce, nonce_len); |
| *out_value = encrypted_bit ^ metadata_obfuscator; |
| return 1; |
| } |