| /* Copyright 2016 The BoringSSL Authors |
| * |
| * 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/ssl.h> |
| |
| #include <assert.h> |
| #include <string.h> |
| |
| #include <algorithm> |
| #include <string_view> |
| #include <utility> |
| |
| #include <openssl/aead.h> |
| #include <openssl/aes.h> |
| #include <openssl/bytestring.h> |
| #include <openssl/chacha.h> |
| #include <openssl/digest.h> |
| #include <openssl/hkdf.h> |
| #include <openssl/hmac.h> |
| #include <openssl/mem.h> |
| |
| #include "../crypto/fipsmodule/tls/internal.h" |
| #include "../crypto/internal.h" |
| #include "internal.h" |
| |
| |
| BSSL_NAMESPACE_BEGIN |
| |
| static bool init_key_schedule(SSL_HANDSHAKE *hs, SSLTranscript *transcript, |
| uint16_t version, const SSL_CIPHER *cipher) { |
| if (!transcript->InitHash(version, cipher)) { |
| return false; |
| } |
| |
| // Initialize the secret to the zero key. |
| hs->secret.clear(); |
| hs->secret.Resize(transcript->DigestLen()); |
| return true; |
| } |
| |
| static bool hkdf_extract_to_secret(SSL_HANDSHAKE *hs, |
| const SSLTranscript &transcript, |
| Span<const uint8_t> in) { |
| size_t len; |
| if (!HKDF_extract(hs->secret.data(), &len, transcript.Digest(), in.data(), |
| in.size(), hs->secret.data(), hs->secret.size())) { |
| return false; |
| } |
| assert(len == hs->secret.size()); |
| return true; |
| } |
| |
| bool tls13_init_key_schedule(SSL_HANDSHAKE *hs, Span<const uint8_t> psk) { |
| if (!init_key_schedule(hs, &hs->transcript, ssl_protocol_version(hs->ssl), |
| hs->new_cipher)) { |
| return false; |
| } |
| |
| // Handback includes the whole handshake transcript, so we cannot free the |
| // transcript buffer in the handback case. |
| if (!hs->handback) { |
| hs->transcript.FreeBuffer(); |
| } |
| return hkdf_extract_to_secret(hs, hs->transcript, psk); |
| } |
| |
| bool tls13_init_early_key_schedule(SSL_HANDSHAKE *hs, |
| const SSL_SESSION *session) { |
| assert(!hs->ssl->server); |
| // When offering ECH, early data is associated with ClientHelloInner, not |
| // ClientHelloOuter. |
| SSLTranscript *transcript = |
| hs->selected_ech_config ? &hs->inner_transcript : &hs->transcript; |
| return init_key_schedule(hs, transcript, |
| ssl_session_protocol_version(session), |
| session->cipher) && |
| hkdf_extract_to_secret(hs, *transcript, session->secret); |
| } |
| |
| static bool hkdf_expand_label_with_prefix(Span<uint8_t> out, |
| const EVP_MD *digest, |
| Span<const uint8_t> secret, |
| std::string_view label_prefix, |
| std::string_view label, |
| Span<const uint8_t> hash) { |
| // This is a copy of CRYPTO_tls13_hkdf_expand_label, but modified to take an |
| // arbitrary prefix for the label instead of using the hardcoded "tls13 " |
| // prefix. |
| CBB cbb, child; |
| uint8_t *hkdf_label = NULL; |
| size_t hkdf_label_len; |
| CBB_zero(&cbb); |
| if (!CBB_init(&cbb, |
| 2 + 1 + label_prefix.size() + label.size() + 1 + hash.size()) || |
| !CBB_add_u16(&cbb, out.size()) || |
| !CBB_add_u8_length_prefixed(&cbb, &child) || |
| !CBB_add_bytes(&child, |
| reinterpret_cast<const uint8_t *>(label_prefix.data()), |
| label_prefix.size()) || |
| !CBB_add_bytes(&child, reinterpret_cast<const uint8_t *>(label.data()), |
| label.size()) || |
| !CBB_add_u8_length_prefixed(&cbb, &child) || |
| !CBB_add_bytes(&child, hash.data(), hash.size()) || |
| !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) { |
| CBB_cleanup(&cbb); |
| return false; |
| } |
| |
| const int ret = HKDF_expand(out.data(), out.size(), digest, secret.data(), |
| secret.size(), hkdf_label, hkdf_label_len); |
| OPENSSL_free(hkdf_label); |
| return ret == 1; |
| } |
| |
| static bool hkdf_expand_label(Span<uint8_t> out, const EVP_MD *digest, |
| Span<const uint8_t> secret, |
| std::string_view label, Span<const uint8_t> hash, |
| bool is_dtls) { |
| if (is_dtls) { |
| return hkdf_expand_label_with_prefix(out, digest, secret, "dtls13", label, |
| hash); |
| } |
| return CRYPTO_tls13_hkdf_expand_label( |
| out.data(), out.size(), digest, secret.data(), secret.size(), |
| reinterpret_cast<const uint8_t *>(label.data()), label.size(), |
| hash.data(), hash.size()) == 1; |
| } |
| |
| static const char kTLS13LabelDerived[] = "derived"; |
| |
| bool tls13_advance_key_schedule(SSL_HANDSHAKE *hs, Span<const uint8_t> in) { |
| uint8_t derive_context[EVP_MAX_MD_SIZE]; |
| unsigned derive_context_len; |
| return EVP_Digest(nullptr, 0, derive_context, &derive_context_len, |
| hs->transcript.Digest(), nullptr) && |
| hkdf_expand_label(Span(hs->secret), hs->transcript.Digest(), |
| hs->secret, kTLS13LabelDerived, |
| Span(derive_context, derive_context_len), |
| SSL_is_dtls(hs->ssl)) && |
| hkdf_extract_to_secret(hs, hs->transcript, in); |
| } |
| |
| // derive_secret_with_transcript derives a secret of length |
| // |transcript.DigestLen()| and writes the result in |out| with the given label, |
| // the current base secret, and the state of |transcript|. It returns true on |
| // success and false on error. |
| static bool derive_secret_with_transcript( |
| const SSL_HANDSHAKE *hs, InplaceVector<uint8_t, SSL_MAX_MD_SIZE> *out, |
| const SSLTranscript &transcript, std::string_view label) { |
| uint8_t context_hash[EVP_MAX_MD_SIZE]; |
| size_t context_hash_len; |
| if (!transcript.GetHash(context_hash, &context_hash_len)) { |
| return false; |
| } |
| |
| out->ResizeForOverwrite(transcript.DigestLen()); |
| return hkdf_expand_label(Span(*out), transcript.Digest(), hs->secret, label, |
| Span(context_hash, context_hash_len), |
| SSL_is_dtls(hs->ssl)); |
| } |
| |
| static bool derive_secret(SSL_HANDSHAKE *hs, |
| InplaceVector<uint8_t, SSL_MAX_MD_SIZE> *out, |
| std::string_view label) { |
| return derive_secret_with_transcript(hs, out, hs->transcript, label); |
| } |
| |
| bool tls13_set_traffic_key(SSL *ssl, enum ssl_encryption_level_t level, |
| enum evp_aead_direction_t direction, |
| const SSL_SESSION *session, |
| Span<const uint8_t> traffic_secret) { |
| uint16_t version = ssl_session_protocol_version(session); |
| const EVP_MD *digest = ssl_session_get_digest(session); |
| bool is_dtls = SSL_is_dtls(ssl); |
| UniquePtr<SSLAEADContext> traffic_aead; |
| if (SSL_is_quic(ssl)) { |
| // Install a placeholder SSLAEADContext so that SSL accessors work. The |
| // encryption itself will be handled by the SSL_QUIC_METHOD. |
| traffic_aead = SSLAEADContext::CreatePlaceholderForQUIC(session->cipher); |
| } else { |
| // Look up cipher suite properties. |
| const EVP_AEAD *aead; |
| size_t discard; |
| if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher, |
| version)) { |
| return false; |
| } |
| |
| // Derive the key and IV. |
| uint8_t key_buf[EVP_AEAD_MAX_KEY_LENGTH], iv_buf[EVP_AEAD_MAX_NONCE_LENGTH]; |
| auto key = Span(key_buf).first(EVP_AEAD_key_length(aead)); |
| auto iv = Span(iv_buf).first(EVP_AEAD_nonce_length(aead)); |
| if (!hkdf_expand_label(key, digest, traffic_secret, "key", {}, is_dtls) || |
| !hkdf_expand_label(iv, digest, traffic_secret, "iv", {}, is_dtls)) { |
| return false; |
| } |
| |
| traffic_aead = SSLAEADContext::Create(direction, session->ssl_version, |
| session->cipher, key, {}, iv); |
| } |
| |
| if (!traffic_aead) { |
| return false; |
| } |
| |
| if (direction == evp_aead_open) { |
| if (!ssl->method->set_read_state(ssl, level, std::move(traffic_aead), |
| traffic_secret)) { |
| return false; |
| } |
| ssl->s3->read_traffic_secret.CopyFrom(traffic_secret); |
| } else { |
| if (!ssl->method->set_write_state(ssl, level, std::move(traffic_aead), |
| traffic_secret)) { |
| return false; |
| } |
| ssl->s3->write_traffic_secret.CopyFrom(traffic_secret); |
| } |
| |
| return true; |
| } |
| |
| namespace { |
| |
| class AESRecordNumberEncrypter : public RecordNumberEncrypter { |
| public: |
| bool SetKey(Span<const uint8_t> key) override { |
| return AES_set_encrypt_key(key.data(), key.size() * 8, &key_) == 0; |
| } |
| |
| bool GenerateMask(Span<uint8_t> out, Span<const uint8_t> sample) override { |
| if (sample.size() < AES_BLOCK_SIZE || out.size() > AES_BLOCK_SIZE) { |
| return false; |
| } |
| uint8_t mask[AES_BLOCK_SIZE]; |
| AES_encrypt(sample.data(), mask, &key_); |
| OPENSSL_memcpy(out.data(), mask, out.size()); |
| return true; |
| } |
| |
| private: |
| AES_KEY key_; |
| }; |
| |
| class AES128RecordNumberEncrypter : public AESRecordNumberEncrypter { |
| public: |
| size_t KeySize() override { return 16; } |
| }; |
| |
| class AES256RecordNumberEncrypter : public AESRecordNumberEncrypter { |
| public: |
| size_t KeySize() override { return 32; } |
| }; |
| |
| class ChaChaRecordNumberEncrypter : public RecordNumberEncrypter { |
| public: |
| size_t KeySize() override { return kKeySize; } |
| |
| bool SetKey(Span<const uint8_t> key) override { |
| if (key.size() != kKeySize) { |
| return false; |
| } |
| OPENSSL_memcpy(key_, key.data(), key.size()); |
| return true; |
| } |
| |
| bool GenerateMask(Span<uint8_t> out, Span<const uint8_t> sample) override { |
| // RFC 9147 section 4.2.3 uses the first 4 bytes of the sample as the |
| // counter and the next 12 bytes as the nonce. If we have less than 4+12=16 |
| // bytes in the sample, then we'll read past the end of the |sample| buffer. |
| // The counter is interpreted as little-endian per RFC 8439. |
| if (sample.size() < 16) { |
| return false; |
| } |
| uint32_t counter = CRYPTO_load_u32_le(sample.data()); |
| Span<const uint8_t> nonce = sample.subspan(4); |
| OPENSSL_memset(out.data(), 0, out.size()); |
| CRYPTO_chacha_20(out.data(), out.data(), out.size(), key_, nonce.data(), |
| counter); |
| return true; |
| } |
| |
| private: |
| static constexpr size_t kKeySize = 32; |
| uint8_t key_[kKeySize]; |
| }; |
| |
| #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) |
| class NullRecordNumberEncrypter : public RecordNumberEncrypter { |
| public: |
| size_t KeySize() override { return 0; } |
| bool SetKey(Span<const uint8_t> key) override { return true; } |
| bool GenerateMask(Span<uint8_t> out, Span<const uint8_t> sample) override { |
| OPENSSL_memset(out.data(), 0, out.size()); |
| return true; |
| } |
| }; |
| #endif // BORINGSSL_UNSAFE_FUZZER_MODE |
| |
| } // namespace |
| |
| UniquePtr<RecordNumberEncrypter> RecordNumberEncrypter::Create( |
| const SSL_CIPHER *cipher, Span<const uint8_t> traffic_secret) { |
| const EVP_MD *digest = ssl_get_handshake_digest(TLS1_3_VERSION, cipher); |
| UniquePtr<RecordNumberEncrypter> ret; |
| #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) |
| ret = MakeUnique<NullRecordNumberEncrypter>(); |
| #else |
| if (cipher->algorithm_enc == SSL_AES128GCM) { |
| ret = MakeUnique<AES128RecordNumberEncrypter>(); |
| } else if (cipher->algorithm_enc == SSL_AES256GCM) { |
| ret = MakeUnique<AES256RecordNumberEncrypter>(); |
| } else if (cipher->algorithm_enc == SSL_CHACHA20POLY1305) { |
| ret = MakeUnique<ChaChaRecordNumberEncrypter>(); |
| } else { |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| } |
| #endif // BORINGSSL_UNSAFE_FUZZER_MODE |
| if (ret == nullptr) { |
| return nullptr; |
| } |
| |
| uint8_t rne_key_buf[RecordNumberEncrypter::kMaxKeySize]; |
| auto rne_key = Span(rne_key_buf).first(ret->KeySize()); |
| if (!hkdf_expand_label(rne_key, digest, traffic_secret, "sn", {}, |
| /*is_dtls=*/true) || |
| !ret->SetKey(rne_key)) { |
| return nullptr; |
| } |
| return ret; |
| } |
| |
| static const char kTLS13LabelExporter[] = "exp master"; |
| |
| static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic"; |
| static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic"; |
| static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic"; |
| static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic"; |
| static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic"; |
| |
| bool tls13_derive_early_secret(SSL_HANDSHAKE *hs) { |
| SSL *const ssl = hs->ssl; |
| // When offering ECH on the client, early data is associated with |
| // ClientHelloInner, not ClientHelloOuter. |
| const SSLTranscript &transcript = (!ssl->server && hs->selected_ech_config) |
| ? hs->inner_transcript |
| : hs->transcript; |
| if (!derive_secret_with_transcript(hs, &hs->early_traffic_secret, transcript, |
| kTLS13LabelClientEarlyTraffic) || |
| !ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET", |
| hs->early_traffic_secret)) { |
| return false; |
| } |
| return true; |
| } |
| |
| bool tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) { |
| SSL *const ssl = hs->ssl; |
| if (!derive_secret(hs, &hs->client_handshake_secret, |
| kTLS13LabelClientHandshakeTraffic) || |
| !ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET", |
| hs->client_handshake_secret) || |
| !derive_secret(hs, &hs->server_handshake_secret, |
| kTLS13LabelServerHandshakeTraffic) || |
| !ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET", |
| hs->server_handshake_secret)) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| bool tls13_derive_application_secrets(SSL_HANDSHAKE *hs) { |
| SSL *const ssl = hs->ssl; |
| if (!derive_secret(hs, &hs->client_traffic_secret_0, |
| kTLS13LabelClientApplicationTraffic) || |
| !ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0", |
| hs->client_traffic_secret_0) || |
| !derive_secret(hs, &hs->server_traffic_secret_0, |
| kTLS13LabelServerApplicationTraffic) || |
| !ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0", |
| hs->server_traffic_secret_0) || |
| !derive_secret(hs, &ssl->s3->exporter_secret, kTLS13LabelExporter) || |
| !ssl_log_secret(ssl, "EXPORTER_SECRET", ssl->s3->exporter_secret)) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static const char kTLS13LabelApplicationTraffic[] = "traffic upd"; |
| |
| bool tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { |
| Span<uint8_t> secret = direction == evp_aead_open |
| ? Span(ssl->s3->read_traffic_secret) |
| : Span(ssl->s3->write_traffic_secret); |
| |
| const SSL_SESSION *session = SSL_get_session(ssl); |
| const EVP_MD *digest = ssl_session_get_digest(session); |
| return hkdf_expand_label(secret, digest, secret, |
| kTLS13LabelApplicationTraffic, {}, |
| SSL_is_dtls(ssl)) && |
| tls13_set_traffic_key(ssl, ssl_encryption_application, direction, |
| session, secret); |
| } |
| |
| static const char kTLS13LabelResumption[] = "res master"; |
| |
| bool tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) { |
| return derive_secret(hs, &hs->new_session->secret, kTLS13LabelResumption); |
| } |
| |
| static const char kTLS13LabelFinished[] = "finished"; |
| |
| // tls13_verify_data sets |out| to be the HMAC of |context| using a derived |
| // Finished key for both Finished messages and the PSK binder. |out| must have |
| // space available for |EVP_MAX_MD_SIZE| bytes. |
| static bool tls13_verify_data(uint8_t *out, size_t *out_len, |
| const EVP_MD *digest, uint16_t version, |
| Span<const uint8_t> secret, |
| Span<const uint8_t> context, bool is_dtls) { |
| uint8_t key_buf[EVP_MAX_MD_SIZE]; |
| auto key = Span(key_buf, EVP_MD_size(digest)); |
| unsigned len; |
| if (!hkdf_expand_label(key, digest, secret, kTLS13LabelFinished, {}, |
| is_dtls) || |
| HMAC(digest, key.data(), key.size(), context.data(), context.size(), out, |
| &len) == nullptr) { |
| return false; |
| } |
| *out_len = len; |
| return true; |
| } |
| |
| bool tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, |
| bool is_server) { |
| Span<const uint8_t> traffic_secret = |
| is_server ? hs->server_handshake_secret : hs->client_handshake_secret; |
| |
| uint8_t context_hash[EVP_MAX_MD_SIZE]; |
| size_t context_hash_len; |
| if (!hs->transcript.GetHash(context_hash, &context_hash_len) || |
| !tls13_verify_data(out, out_len, hs->transcript.Digest(), |
| hs->ssl->s3->version, traffic_secret, |
| Span(context_hash, context_hash_len), |
| SSL_is_dtls(hs->ssl))) { |
| return false; |
| } |
| return true; |
| } |
| |
| static const char kTLS13LabelResumptionPSK[] = "resumption"; |
| |
| bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce, |
| bool is_dtls) { |
| const EVP_MD *digest = ssl_session_get_digest(session); |
| // The session initially stores the resumption_master_secret, which we |
| // override with the PSK. |
| assert(session->secret.size() == EVP_MD_size(digest)); |
| return hkdf_expand_label(Span(session->secret), digest, session->secret, |
| kTLS13LabelResumptionPSK, nonce, is_dtls); |
| } |
| |
| static const char kTLS13LabelExportKeying[] = "exporter"; |
| |
| bool tls13_export_keying_material(SSL *ssl, Span<uint8_t> out, |
| Span<const uint8_t> secret, |
| std::string_view label, |
| Span<const uint8_t> context) { |
| if (secret.empty()) { |
| assert(0); |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| return false; |
| } |
| |
| const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl)); |
| |
| uint8_t hash_buf[EVP_MAX_MD_SIZE]; |
| uint8_t export_context_buf[EVP_MAX_MD_SIZE]; |
| unsigned hash_len; |
| unsigned export_context_len; |
| if (!EVP_Digest(context.data(), context.size(), hash_buf, &hash_len, digest, |
| nullptr) || |
| !EVP_Digest(nullptr, 0, export_context_buf, &export_context_len, digest, |
| nullptr)) { |
| return false; |
| } |
| |
| auto hash = Span(hash_buf, hash_len); |
| auto export_context = Span(export_context_buf, export_context_len); |
| uint8_t derived_secret_buf[EVP_MAX_MD_SIZE]; |
| auto derived_secret = Span(derived_secret_buf, EVP_MD_size(digest)); |
| return hkdf_expand_label(derived_secret, digest, secret, label, |
| export_context, SSL_is_dtls(ssl)) && |
| hkdf_expand_label(out, digest, derived_secret, kTLS13LabelExportKeying, |
| hash, SSL_is_dtls(ssl)); |
| } |
| |
| static const char kTLS13LabelPSKBinder[] = "res binder"; |
| |
| static bool tls13_psk_binder(uint8_t *out, size_t *out_len, |
| const SSL_SESSION *session, |
| const SSLTranscript &transcript, |
| Span<const uint8_t> client_hello, |
| size_t binders_len, bool is_dtls) { |
| const EVP_MD *digest = ssl_session_get_digest(session); |
| |
| // Compute the binder key. |
| // |
| // TODO(davidben): Ideally we wouldn't recompute early secret and the binder |
| // key each time. |
| uint8_t binder_context[EVP_MAX_MD_SIZE]; |
| unsigned binder_context_len; |
| uint8_t early_secret[EVP_MAX_MD_SIZE] = {0}; |
| size_t early_secret_len; |
| uint8_t binder_key_buf[EVP_MAX_MD_SIZE] = {0}; |
| auto binder_key = Span(binder_key_buf, EVP_MD_size(digest)); |
| if (!EVP_Digest(nullptr, 0, binder_context, &binder_context_len, digest, |
| nullptr) || |
| !HKDF_extract(early_secret, &early_secret_len, digest, |
| session->secret.data(), session->secret.size(), nullptr, |
| 0) || |
| !hkdf_expand_label(binder_key, digest, |
| Span(early_secret, early_secret_len), |
| kTLS13LabelPSKBinder, |
| Span(binder_context, binder_context_len), is_dtls)) { |
| return false; |
| } |
| |
| // Hash the transcript and truncated ClientHello. |
| if (client_hello.size() < binders_len) { |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| return false; |
| } |
| auto truncated = client_hello.subspan(0, client_hello.size() - binders_len); |
| uint8_t context[EVP_MAX_MD_SIZE]; |
| unsigned context_len; |
| ScopedEVP_MD_CTX ctx; |
| if (!is_dtls) { |
| if (!transcript.CopyToHashContext(ctx.get(), digest) || |
| !EVP_DigestUpdate(ctx.get(), truncated.data(), truncated.size()) || |
| !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) { |
| return false; |
| } |
| } else { |
| // In DTLS 1.3, the transcript hash is computed over only the TLS 1.3 |
| // handshake messages (i.e. only type and length in the header), not the |
| // full DTLSHandshake messages that are in |truncated|. This code pulls |
| // the header and body out of the truncated ClientHello and writes those |
| // to the hash context so the correct binder value is computed. |
| if (truncated.size() < DTLS1_HM_HEADER_LENGTH) { |
| return false; |
| } |
| auto header = truncated.subspan(0, 4); |
| auto body = truncated.subspan(12); |
| if (!transcript.CopyToHashContext(ctx.get(), digest) || |
| !EVP_DigestUpdate(ctx.get(), header.data(), header.size()) || |
| !EVP_DigestUpdate(ctx.get(), body.data(), body.size()) || |
| !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) { |
| return false; |
| } |
| } |
| |
| if (!tls13_verify_data(out, out_len, digest, session->ssl_version, binder_key, |
| Span(context, context_len), is_dtls)) { |
| return false; |
| } |
| |
| assert(*out_len == EVP_MD_size(digest)); |
| return true; |
| } |
| |
| bool tls13_write_psk_binder(const SSL_HANDSHAKE *hs, |
| const SSLTranscript &transcript, Span<uint8_t> msg, |
| size_t *out_binder_len) { |
| const SSL *const ssl = hs->ssl; |
| const EVP_MD *digest = ssl_session_get_digest(ssl->session.get()); |
| const size_t hash_len = EVP_MD_size(digest); |
| // We only offer one PSK, so the binders are a u16 and u8 length |
| // prefix, followed by the binder. The caller is assumed to have constructed |
| // |msg| with placeholder binders. |
| const size_t binders_len = 3 + hash_len; |
| uint8_t verify_data[EVP_MAX_MD_SIZE]; |
| size_t verify_data_len; |
| if (!tls13_psk_binder(verify_data, &verify_data_len, ssl->session.get(), |
| transcript, msg, binders_len, SSL_is_dtls(hs->ssl)) || |
| verify_data_len != hash_len) { |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| return false; |
| } |
| |
| auto msg_binder = msg.last(verify_data_len); |
| OPENSSL_memcpy(msg_binder.data(), verify_data, verify_data_len); |
| if (out_binder_len != nullptr) { |
| *out_binder_len = verify_data_len; |
| } |
| return true; |
| } |
| |
| bool tls13_verify_psk_binder(const SSL_HANDSHAKE *hs, |
| const SSL_SESSION *session, const SSLMessage &msg, |
| CBS *binders) { |
| uint8_t verify_data[EVP_MAX_MD_SIZE]; |
| size_t verify_data_len; |
| CBS binder; |
| // The binders are computed over |msg| with |binders| and its u16 length |
| // prefix removed. The caller is assumed to have parsed |msg|, extracted |
| // |binders|, and verified the PSK extension is last. |
| if (!tls13_psk_binder(verify_data, &verify_data_len, session, hs->transcript, |
| msg.raw, 2 + CBS_len(binders), SSL_is_dtls(hs->ssl)) || |
| // We only consider the first PSK, so compare against the first binder. |
| !CBS_get_u8_length_prefixed(binders, &binder)) { |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| return false; |
| } |
| |
| bool binder_ok = |
| CBS_len(&binder) == verify_data_len && |
| CRYPTO_memcmp(CBS_data(&binder), verify_data, verify_data_len) == 0; |
| #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) |
| binder_ok = true; |
| #endif |
| if (!binder_ok) { |
| OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| size_t ssl_ech_confirmation_signal_hello_offset(const SSL *ssl) { |
| static_assert(ECH_CONFIRMATION_SIGNAL_LEN < SSL3_RANDOM_SIZE, |
| "the confirmation signal is a suffix of the random"); |
| const size_t header_len = |
| SSL_is_dtls(ssl) ? DTLS1_HM_HEADER_LENGTH : SSL3_HM_HEADER_LENGTH; |
| return header_len + 2 /* version */ + SSL3_RANDOM_SIZE - |
| ECH_CONFIRMATION_SIGNAL_LEN; |
| } |
| |
| bool ssl_ech_accept_confirmation(const SSL_HANDSHAKE *hs, Span<uint8_t> out, |
| Span<const uint8_t> client_random, |
| const SSLTranscript &transcript, bool is_hrr, |
| Span<const uint8_t> msg, size_t offset) { |
| // See draft-ietf-tls-esni-13, sections 7.2 and 7.2.1. |
| static const uint8_t kZeros[EVP_MAX_MD_SIZE] = {0}; |
| |
| // We hash |msg|, with bytes from |offset| zeroed. |
| if (msg.size() < offset + ECH_CONFIRMATION_SIGNAL_LEN) { |
| OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| return false; |
| } |
| |
| // We represent DTLS messages with the longer DTLS 1.2 header, but DTLS 1.3 |
| // removes the extra fields from the transcript. |
| auto header = msg.subspan(0, SSL3_HM_HEADER_LENGTH); |
| size_t full_header_len = |
| SSL_is_dtls(hs->ssl) ? DTLS1_HM_HEADER_LENGTH : SSL3_HM_HEADER_LENGTH; |
| auto before_zeros = msg.subspan(full_header_len, offset - full_header_len); |
| auto after_zeros = msg.subspan(offset + ECH_CONFIRMATION_SIGNAL_LEN); |
| |
| uint8_t context[EVP_MAX_MD_SIZE]; |
| unsigned context_len; |
| ScopedEVP_MD_CTX ctx; |
| if (!transcript.CopyToHashContext(ctx.get(), transcript.Digest()) || |
| !EVP_DigestUpdate(ctx.get(), header.data(), header.size()) || |
| !EVP_DigestUpdate(ctx.get(), before_zeros.data(), before_zeros.size()) || |
| !EVP_DigestUpdate(ctx.get(), kZeros, ECH_CONFIRMATION_SIGNAL_LEN) || |
| !EVP_DigestUpdate(ctx.get(), after_zeros.data(), after_zeros.size()) || |
| !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) { |
| return false; |
| } |
| |
| uint8_t secret[EVP_MAX_MD_SIZE]; |
| size_t secret_len; |
| if (!HKDF_extract(secret, &secret_len, transcript.Digest(), |
| client_random.data(), client_random.size(), kZeros, |
| transcript.DigestLen())) { |
| return false; |
| } |
| |
| assert(out.size() == ECH_CONFIRMATION_SIGNAL_LEN); |
| return hkdf_expand_label( |
| out, transcript.Digest(), Span(secret, secret_len), |
| is_hrr ? "hrr ech accept confirmation" : "ech accept confirmation", |
| Span(context, context_len), SSL_is_dtls(hs->ssl)); |
| } |
| |
| BSSL_NAMESPACE_END |
