NAME¶

SSL_CIPHER_get_name, SSL_CIPHER_standard_name, OPENSSL_cipher_name, SSL_CIPHER_get_bits, SSL_CIPHER_get_version, SSL_CIPHER_description, SSL_CIPHER_get_cipher_nid, SSL_CIPHER_get_digest_nid, SSL_CIPHER_get_handshake_digest, SSL_CIPHER_get_kx_nid, SSL_CIPHER_get_auth_nid, SSL_CIPHER_is_aead, SSL_CIPHER_find, SSL_CIPHER_get_id, SSL_CIPHER_get_protocol_id - get SSL_CIPHER properties

SYNOPSIS¶

 #include <openssl/ssl.h>
 const char *SSL_CIPHER_get_name(const SSL_CIPHER *cipher);
 const char *SSL_CIPHER_standard_name(const SSL_CIPHER *cipher);
 const char *OPENSSL_cipher_name(const char *stdname);
 int SSL_CIPHER_get_bits(const SSL_CIPHER *cipher, int *alg_bits);
 const char *SSL_CIPHER_get_version(const SSL_CIPHER *cipher);
 char *SSL_CIPHER_description(const SSL_CIPHER *cipher, char *buf, int size);
 int SSL_CIPHER_get_cipher_nid(const SSL_CIPHER *c);
 int SSL_CIPHER_get_digest_nid(const SSL_CIPHER *c);
 const EVP_MD *SSL_CIPHER_get_handshake_digest(const SSL_CIPHER *c);
 int SSL_CIPHER_get_kx_nid(const SSL_CIPHER *c);
 int SSL_CIPHER_get_auth_nid(const SSL_CIPHER *c);
 int SSL_CIPHER_is_aead(const SSL_CIPHER *c);
 const SSL_CIPHER *SSL_CIPHER_find(SSL *ssl, const unsigned char *ptr);
 uint32_t SSL_CIPHER_get_id(const SSL_CIPHER *c);
 uint32_t SSL_CIPHER_get_protocol_id(const SSL_CIPHER *c);

DESCRIPTION¶

SSL_CIPHER_get_name() returns a pointer to the name of cipher. If the cipher is NULL, it returns "(NONE)".

SSL_CIPHER_standard_name() returns a pointer to the standard RFC name of cipher. If the cipher is NULL, it returns "(NONE)". If the cipher has no standard name, it returns NULL. If cipher was defined in both SSLv3 and TLS, it returns the TLS name.

OPENSSL_cipher_name() returns a pointer to the OpenSSL name of stdname. If the stdname is NULL, or stdname has no corresponding OpenSSL name, it returns "(NONE)". Where both exist, stdname should be the TLS name rather than the SSLv3 name.

SSL_CIPHER_get_bits() returns the number of secret bits used for cipher. If cipher is NULL, 0 is returned.

SSL_CIPHER_get_version() returns string which indicates the SSL/TLS protocol version that first defined the cipher. It returns "(NONE)" if cipher is NULL.

SSL_CIPHER_get_cipher_nid() returns the cipher NID corresponding to c. If there is no cipher (e.g. for cipher suites with no encryption) then NID_undef is returned.

SSL_CIPHER_get_digest_nid() returns the digest NID corresponding to the MAC used by c during record encryption/decryption. If there is no digest (e.g. for AEAD cipher suites) then NID_undef is returned.

SSL_CIPHER_get_handshake_digest() returns an EVP_MD for the digest used during the SSL/TLS handshake when using the SSL_CIPHER c. Note that this may be different to the digest used to calculate the MAC for encrypted records.

SSL_CIPHER_get_kx_nid() returns the key exchange NID corresponding to the method used by c. If there is no key exchange, then NID_undef is returned. If any appropriate key exchange algorithm can be used (as in the case of TLS 1.3 cipher suites) NID_kx_any is returned. Examples (not comprehensive):

 NID_kx_rsa
 NID_kx_ecdhe
 NID_kx_dhe
 NID_kx_psk

SSL_CIPHER_get_auth_nid() returns the authentication NID corresponding to the method used by c. If there is no authentication, then NID_undef is returned. If any appropriate authentication algorithm can be used (as in the case of TLS 1.3 cipher suites) NID_auth_any is returned. Examples (not comprehensive):

 NID_auth_rsa
 NID_auth_ecdsa
 NID_auth_psk

SSL_CIPHER_is_aead() returns 1 if the cipher c is AEAD (e.g. GCM or ChaCha20/Poly1305), and 0 if it is not AEAD.

SSL_CIPHER_find() returns a SSL_CIPHER structure which has the cipher ID stored in ptr. The ptr parameter is a two element array of char, which stores the two-byte TLS cipher ID (as allocated by IANA) in network byte order. This parameter is usually retrieved from a TLS packet by using functions like SSL_client_hello_get0_ciphers(3). SSL_CIPHER_find() returns NULL if an error occurs or the indicated cipher is not found.

SSL_CIPHER_get_id() returns the OpenSSL-specific ID of the given cipher c. That ID is not the same as the IANA-specific ID.

SSL_CIPHER_get_protocol_id() returns the two-byte ID used in the TLS protocol of the given cipher c.

SSL_CIPHER_description() returns a textual description of the cipher used into the buffer buf of length len provided. If buf is provided, it must be at least 128 bytes, otherwise a buffer will be allocated using OPENSSL_malloc(). If the provided buffer is too small, or the allocation fails, NULL is returned.

The string returned by SSL_CIPHER_description() consists of several fields separated by whitespace:

<ciphername>

Textual representation of the cipher name.

<protocol version>

The minimum protocol version that the ciphersuite supports, such as TLSv1.2. Note that this is not always the same as the protocol version in which the ciphersuite was first defined because some ciphersuites are backwards compatible with earlier protocol versions.

Kx=<key exchange>

Key exchange method such as RSA, ECDHE, etc.

Au=<authentication>

Authentication method such as RSA, None, etc.. None is the representation of anonymous ciphers.

Enc=<symmetric encryption method>

Encryption method, with number of secret bits, such as AESGCM(128).

Mac=<message authentication code>

Message digest, such as SHA256.

Some examples for the output of SSL_CIPHER_description():

 ECDHE-RSA-AES256-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(256) Mac=AEAD
 RSA-PSK-AES256-CBC-SHA384 TLSv1.0 Kx=RSAPSK   Au=RSA  Enc=AES(256)  Mac=SHA384

RETURN VALUES¶

SSL_CIPHER_get_name(), SSL_CIPHER_standard_name(), OPENSSL_cipher_name(), SSL_CIPHER_get_version() and SSL_CIPHER_description() return the corresponding value in a NUL-terminated string for a specific cipher or "(NONE)" if the cipher is not found.

SSL_CIPHER_get_bits() returns a positive integer representing the number of secret bits or 0 if an error occurred.

SSL_CIPHER_get_cipher_nid(), SSL_CIPHER_get_digest_nid(), SSL_CIPHER_get_kx_nid() and SSL_CIPHER_get_auth_nid() return the NID value or NID_undef if an error occurred.

SSL_CIPHER_get_handshake_digest() returns a valid EVP_MD structure or NULL if an error occurred.

SSL_CIPHER_is_aead() returns 1 if the cipher is AEAD or 0 otherwise.

SSL_CIPHER_find() returns a valid SSL_CIPHER structure or NULL if an error occurred.

SSL_CIPHER_get_id() returns a 4-byte integer representing the OpenSSL-specific ID.

SSL_CIPHER_get_protocol_id() returns a 2-byte integer representing the TLS protocol-specific ID.

SEE ALSO¶

ssl(7), SSL_get_current_cipher(3), SSL_get_ciphers(3), openssl-ciphers(1)

HISTORY¶

The SSL_CIPHER_get_version() function was updated to always return the correct protocol string in OpenSSL 1.1.0.

The SSL_CIPHER_description() function was changed to return NULL on error, rather than a fixed string, in OpenSSL 1.1.0.

The SSL_CIPHER_get_handshake_digest() function was added in OpenSSL 1.1.1.

The SSL_CIPHER_standard_name() function was globally available in OpenSSL 1.1.1.
Before OpenSSL 1.1.1, tracing (enable-ssl-trace argument to Configure) was required to enable this function.

The OPENSSL_cipher_name() function was added in OpenSSL 1.1.1.

COPYRIGHT¶

Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.