diff options
| -rw-r--r-- | include/openssl/ssl.h | 2 | ||||
| -rw-r--r-- | ssl/d1_lib.c | 36 | ||||
| -rw-r--r-- | ssl/ssl_ciph.c | 52 | ||||
| -rw-r--r-- | ssl/ssl_locl.h | 3 | ||||
| -rw-r--r-- | util/libssl.num | 1 |
5 files changed, 94 insertions, 0 deletions
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h index f0aa306133..7b40b37db2 100644 --- a/include/openssl/ssl.h +++ b/include/openssl/ssl.h @@ -1630,6 +1630,8 @@ __owur const SSL_METHOD *DTLS_method(void); /* DTLS 1.0 and 1.2 */ __owur const SSL_METHOD *DTLS_server_method(void); /* DTLS 1.0 and 1.2 */ __owur const SSL_METHOD *DTLS_client_method(void); /* DTLS 1.0 and 1.2 */ +__owur size_t DTLS_get_data_mtu(const SSL *s); + __owur STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *s); __owur STACK_OF(SSL_CIPHER) *SSL_CTX_get_ciphers(const SSL_CTX *ctx); __owur STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *s); diff --git a/ssl/d1_lib.c b/ssl/d1_lib.c index 112c69904e..e7a6650aff 100644 --- a/ssl/d1_lib.c +++ b/ssl/d1_lib.c @@ -1088,3 +1088,39 @@ unsigned int dtls1_min_mtu(SSL *s) { return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s)); } + +size_t DTLS_get_data_mtu(const SSL *s) +{ + size_t mac_overhead, int_overhead, blocksize, ext_overhead; + const SSL_CIPHER *ciph = SSL_get_current_cipher(s); + size_t mtu = s->d1->mtu; + + if (ciph == NULL) + return 0; + + if (!ssl_cipher_get_overhead(ciph, &mac_overhead, &int_overhead, + &blocksize, &ext_overhead)) + return 0; + + if (SSL_USE_ETM(s)) + ext_overhead += mac_overhead; + else + int_overhead += mac_overhead; + + /* Subtract external overhead (e.g. IV/nonce, separate MAC) */ + if (ext_overhead + DTLS1_RT_HEADER_LENGTH >= mtu) + return 0; + mtu -= ext_overhead + DTLS1_RT_HEADER_LENGTH; + + /* Round encrypted payload down to cipher block size (for CBC etc.) + * No check for overflow since 'mtu % blocksize' cannot exceed mtu. */ + if (blocksize) + mtu -= (mtu % blocksize); + + /* Subtract internal overhead (e.g. CBC padding len byte) */ + if (int_overhead >= mtu) + return 0; + mtu -= int_overhead; + + return mtu; +} diff --git a/ssl/ssl_ciph.c b/ssl/ssl_ciph.c index adccbfc4d8..acc1840ee1 100644 --- a/ssl/ssl_ciph.c +++ b/ssl/ssl_ciph.c @@ -1947,3 +1947,55 @@ int SSL_CIPHER_is_aead(const SSL_CIPHER *c) { return (c->algorithm_mac & SSL_AEAD) ? 1 : 0; } + +int ssl_cipher_get_overhead(const SSL_CIPHER *c, size_t *mac_overhead, + size_t *int_overhead, size_t *blocksize, + size_t *ext_overhead) +{ + size_t mac = 0, in = 0, blk = 0, out = 0; + + /* Some hard-coded numbers for the CCM/Poly1305 MAC overhead + * because there are no handy #defines for those. */ + if (c->algorithm_enc & SSL_AESGCM) { + out = EVP_GCM_TLS_EXPLICIT_IV_LEN + EVP_GCM_TLS_TAG_LEN; + } else if (c->algorithm_enc & (SSL_AES128CCM | SSL_AES256CCM)) { + out = EVP_CCM_TLS_EXPLICIT_IV_LEN + 16; + } else if (c->algorithm_enc & (SSL_AES128CCM8 | SSL_AES256CCM8)) { + out = EVP_CCM_TLS_EXPLICIT_IV_LEN + 8; + } else if (c->algorithm_enc & SSL_CHACHA20POLY1305) { + out = 16; + } else if (c->algorithm_mac & SSL_AEAD) { + /* We're supposed to have handled all the AEAD modes above */ + return 0; + } else { + /* Non-AEAD modes. Calculate MAC/cipher overhead separately */ + int digest_nid = SSL_CIPHER_get_digest_nid(c); + const EVP_MD *e_md = EVP_get_digestbynid(digest_nid); + + if (e_md == NULL) + return 0; + + mac = EVP_MD_size(e_md); + if (c->algorithm_enc != SSL_eNULL) { + int cipher_nid = SSL_CIPHER_get_cipher_nid(c); + const EVP_CIPHER *e_ciph = EVP_get_cipherbynid(cipher_nid); + + /* If it wasn't AEAD or SSL_eNULL, we expect it to be a + known CBC cipher. */ + if (e_ciph == NULL || + EVP_CIPHER_mode(e_ciph) != EVP_CIPH_CBC_MODE) + return 0; + + in = 1; /* padding length byte */ + out = EVP_CIPHER_iv_length(e_ciph); + blk = EVP_CIPHER_block_size(e_ciph); + } + } + + *mac_overhead = mac; + *int_overhead = in; + *blocksize = blk; + *ext_overhead = out; + + return 1; +} diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h index d5a6fe236e..1cf27b95aa 100644 --- a/ssl/ssl_locl.h +++ b/ssl/ssl_locl.h @@ -1817,6 +1817,9 @@ __owur int ssl_cipher_get_evp(const SSL_SESSION *s, const EVP_CIPHER **enc, const EVP_MD **md, int *mac_pkey_type, int *mac_secret_size, SSL_COMP **comp, int use_etm); +__owur int ssl_cipher_get_overhead(const SSL_CIPHER *c, size_t *mac_overhead, + size_t *int_overhead, size_t *blocksize, + size_t *ext_overhead); __owur int ssl_cipher_get_cert_index(const SSL_CIPHER *c); __owur const SSL_CIPHER *ssl_get_cipher_by_char(SSL *ssl, const unsigned char *ptr); diff --git a/util/libssl.num b/util/libssl.num index 7e004796b6..9f44b38415 100644 --- a/util/libssl.num +++ b/util/libssl.num @@ -404,3 +404,4 @@ SSL_SESSION_get0_cipher 404 1_1_0 EXIST::FUNCTION: SSL_SESSION_get0_id_context 405 1_1_0 EXIST::FUNCTION: SSL_SESSION_set1_id 406 1_1_0 EXIST::FUNCTION: SSL_CTX_set1_cert_store 407 1_1_1 EXIST::FUNCTION: +DTLS_get_data_mtu 408 1_1_1 EXIST::FUNCTION: |