| /* |
| * TLS 1.3 key schedule |
| * |
| * Copyright The Mbed TLS Contributors |
| * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later |
| */ |
| #if !defined(MBEDTLS_SSL_TLS1_3_KEYS_H) |
| #define MBEDTLS_SSL_TLS1_3_KEYS_H |
| |
| /* This requires MBEDTLS_SSL_TLS1_3_LABEL( idx, name, string ) to be defined at |
| * the point of use. See e.g. the definition of mbedtls_ssl_tls1_3_labels_union |
| * below. */ |
| #define MBEDTLS_SSL_TLS1_3_LABEL_LIST \ |
| MBEDTLS_SSL_TLS1_3_LABEL(finished, "finished") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(resumption, "resumption") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(traffic_upd, "traffic upd") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(exporter, "exporter") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(key, "key") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(iv, "iv") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(c_hs_traffic, "c hs traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(c_ap_traffic, "c ap traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(c_e_traffic, "c e traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(s_hs_traffic, "s hs traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(s_ap_traffic, "s ap traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(s_e_traffic, "s e traffic") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(e_exp_master, "e exp master") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(res_master, "res master") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(exp_master, "exp master") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(ext_binder, "ext binder") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(res_binder, "res binder") \ |
| MBEDTLS_SSL_TLS1_3_LABEL(derived, "derived") |
| |
| #define MBEDTLS_SSL_TLS1_3_LABEL(name, string) \ |
| const unsigned char name [sizeof(string) - 1]; |
| |
| union mbedtls_ssl_tls1_3_labels_union { |
| MBEDTLS_SSL_TLS1_3_LABEL_LIST |
| }; |
| struct mbedtls_ssl_tls1_3_labels_struct { |
| MBEDTLS_SSL_TLS1_3_LABEL_LIST |
| }; |
| #undef MBEDTLS_SSL_TLS1_3_LABEL |
| |
| extern const struct mbedtls_ssl_tls1_3_labels_struct mbedtls_ssl_tls1_3_labels; |
| |
| #define MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN(LABEL) \ |
| mbedtls_ssl_tls1_3_labels.LABEL, \ |
| sizeof(mbedtls_ssl_tls1_3_labels.LABEL) |
| |
| #define MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN \ |
| sizeof(union mbedtls_ssl_tls1_3_labels_union) |
| |
| /* The maximum length of HKDF contexts used in the TLS 1.3 standard. |
| * Since contexts are always hashes of message transcripts, this can |
| * be approximated from above by the maximum hash size. */ |
| #define MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN \ |
| MBEDTLS_MD_MAX_SIZE |
| |
| /* Maximum desired length for expanded key material generated |
| * by HKDF-Expand-Label. |
| * |
| * Warning: If this ever needs to be increased, the implementation |
| * ssl_tls1_3_hkdf_encode_label() in ssl_tls13_keys.c needs to be |
| * adjusted since it currently assumes that HKDF key expansion |
| * is never used with more than 255 Bytes of output. */ |
| #define MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN 255 |
| |
| /** |
| * \brief The \c HKDF-Expand-Label function from |
| * the TLS 1.3 standard RFC 8446. |
| * |
| * <tt> |
| * HKDF-Expand-Label( Secret, Label, Context, Length ) = |
| * HKDF-Expand( Secret, HkdfLabel, Length ) |
| * </tt> |
| * |
| * \param hash_alg The identifier for the hash algorithm to use. |
| * \param secret The \c Secret argument to \c HKDF-Expand-Label. |
| * This must be a readable buffer of length \p slen Bytes. |
| * \param slen The length of \p secret in Bytes. |
| * \param label The \c Label argument to \c HKDF-Expand-Label. |
| * This must be a readable buffer of length \p llen Bytes. |
| * \param llen The length of \p label in Bytes. |
| * \param ctx The \c Context argument to \c HKDF-Expand-Label. |
| * This must be a readable buffer of length \p clen Bytes. |
| * \param clen The length of \p context in Bytes. |
| * \param buf The destination buffer to hold the expanded secret. |
| * This must be a writable buffer of length \p blen Bytes. |
| * \param blen The desired size of the expanded secret in Bytes. |
| * |
| * \returns \c 0 on success. |
| * \return A negative error code on failure. |
| */ |
| |
| int mbedtls_ssl_tls1_3_hkdf_expand_label( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret, size_t slen, |
| const unsigned char *label, size_t llen, |
| const unsigned char *ctx, size_t clen, |
| unsigned char *buf, size_t blen); |
| |
| /** |
| * \brief This function is part of the TLS 1.3 key schedule. |
| * It extracts key and IV for the actual client/server traffic |
| * from the client/server traffic secrets. |
| * |
| * From RFC 8446: |
| * |
| * <tt> |
| * [sender]_write_key = HKDF-Expand-Label(Secret, "key", "", key_length) |
| * [sender]_write_iv = HKDF-Expand-Label(Secret, "iv", "", iv_length)* |
| * </tt> |
| * |
| * \param hash_alg The identifier for the hash algorithm to be used |
| * for the HKDF-based expansion of the secret. |
| * \param client_secret The client traffic secret. |
| * This must be a readable buffer of size \p slen Bytes |
| * \param server_secret The server traffic secret. |
| * This must be a readable buffer of size \p slen Bytes |
| * \param slen Length of the secrets \p client_secret and |
| * \p server_secret in Bytes. |
| * \param key_len The desired length of the key to be extracted in Bytes. |
| * \param iv_len The desired length of the IV to be extracted in Bytes. |
| * \param keys The address of the structure holding the generated |
| * keys and IVs. |
| * |
| * \returns \c 0 on success. |
| * \returns A negative error code on failure. |
| */ |
| |
| int mbedtls_ssl_tls1_3_make_traffic_keys( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *client_secret, |
| const unsigned char *server_secret, |
| size_t slen, size_t key_len, size_t iv_len, |
| mbedtls_ssl_key_set *keys); |
| |
| |
| #define MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED 0 |
| #define MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED 1 |
| |
| /** |
| * \brief The \c Derive-Secret function from the TLS 1.3 standard RFC 8446. |
| * |
| * <tt> |
| * Derive-Secret( Secret, Label, Messages ) = |
| * HKDF-Expand-Label( Secret, Label, |
| * Hash( Messages ), |
| * Hash.Length ) ) |
| * </tt> |
| * |
| * \param hash_alg The identifier for the hash function used for the |
| * applications of HKDF. |
| * \param secret The \c Secret argument to the \c Derive-Secret function. |
| * This must be a readable buffer of length \p slen Bytes. |
| * \param slen The length of \p secret in Bytes. |
| * \param label The \c Label argument to the \c Derive-Secret function. |
| * This must be a readable buffer of length \p llen Bytes. |
| * \param llen The length of \p label in Bytes. |
| * \param ctx The hash of the \c Messages argument to the |
| * \c Derive-Secret function, or the \c Messages argument |
| * itself, depending on \p context_already_hashed. |
| * \param clen The length of \p hash. |
| * \param ctx_hashed This indicates whether the \p ctx contains the hash of |
| * the \c Messages argument in the application of the |
| * \c Derive-Secret function |
| * (value MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED), or whether |
| * it is the content of \c Messages itself, in which case |
| * the function takes care of the hashing |
| * (value MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED). |
| * \param dstbuf The target buffer to write the output of |
| * \c Derive-Secret to. This must be a writable buffer of |
| * size \p buflen Bytes. |
| * \param buflen The length of \p dstbuf in Bytes. |
| * |
| * \returns \c 0 on success. |
| * \returns A negative error code on failure. |
| */ |
| int mbedtls_ssl_tls1_3_derive_secret( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret, size_t slen, |
| const unsigned char *label, size_t llen, |
| const unsigned char *ctx, size_t clen, |
| int ctx_hashed, |
| unsigned char *dstbuf, size_t buflen); |
| |
| /** |
| * \brief Compute the next secret in the TLS 1.3 key schedule |
| * |
| * The TLS 1.3 key schedule proceeds as follows to compute |
| * the three main secrets during the handshake: The early |
| * secret for early data, the handshake secret for all |
| * other encrypted handshake messages, and the master |
| * secret for all application traffic. |
| * |
| * <tt> |
| * 0 |
| * | |
| * v |
| * PSK -> HKDF-Extract = Early Secret |
| * | |
| * v |
| * Derive-Secret( ., "derived", "" ) |
| * | |
| * v |
| * (EC)DHE -> HKDF-Extract = Handshake Secret |
| * | |
| * v |
| * Derive-Secret( ., "derived", "" ) |
| * | |
| * v |
| * 0 -> HKDF-Extract = Master Secret |
| * </tt> |
| * |
| * Each of the three secrets in turn is the basis for further |
| * key derivations, such as the derivation of traffic keys and IVs; |
| * see e.g. mbedtls_ssl_tls1_3_make_traffic_keys(). |
| * |
| * This function implements one step in this evolution of secrets: |
| * |
| * <tt> |
| * old_secret |
| * | |
| * v |
| * Derive-Secret( ., "derived", "" ) |
| * | |
| * v |
| * input -> HKDF-Extract = new_secret |
| * </tt> |
| * |
| * \param hash_alg The identifier for the hash function used for the |
| * applications of HKDF. |
| * \param secret_old The address of the buffer holding the old secret |
| * on function entry. If not \c NULL, this must be a |
| * readable buffer whose size matches the output size |
| * of the hash function represented by \p hash_alg. |
| * If \c NULL, an all \c 0 array will be used instead. |
| * \param input The address of the buffer holding the additional |
| * input for the key derivation (e.g., the PSK or the |
| * ephemeral (EC)DH secret). If not \c NULL, this must be |
| * a readable buffer whose size \p input_len Bytes. |
| * If \c NULL, an all \c 0 array will be used instead. |
| * \param input_len The length of \p input in Bytes. |
| * \param secret_new The address of the buffer holding the new secret |
| * on function exit. This must be a writable buffer |
| * whose size matches the output size of the hash |
| * function represented by \p hash_alg. |
| * This may be the same as \p secret_old. |
| * |
| * \returns \c 0 on success. |
| * \returns A negative error code on failure. |
| */ |
| |
| int mbedtls_ssl_tls1_3_evolve_secret( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret_old, |
| const unsigned char *input, size_t input_len, |
| unsigned char *secret_new); |
| |
| #endif /* MBEDTLS_SSL_TLS1_3_KEYS_H */ |