=pod

=head1 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

=head1 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);

=head1 DESCRIPTION

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

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

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

SSL_CIPHER_get_bits() returns the number of secret bits used for B<cipher>.
If B<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 B<cipher> is NULL.

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

SSL_CIPHER_get_digest_nid() returns the digest NID corresponding to the MAC
used by B<c> during record encryption/decryption. If there is no digest (e.g.
for AEAD cipher suites) then B<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 B<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 B<c>. If there is no key exchange, then B<NID_undef> is returned.
If any appropriate key exchange algorithm can be used (as in the case of TLS 1.3
cipher suites) B<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 B<c>. If there is no authentication, then B<NID_undef> is returned.
If any appropriate authentication algorithm can be used (as in the case of
TLS 1.3 cipher suites) B<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 B<c> is AEAD (e.g. GCM or
ChaCha20/Poly1305), and 0 if it is not AEAD.

SSL_CIPHER_find() returns a B<SSL_CIPHER> structure which has the cipher ID stored
in B<ptr>. The B<ptr> parameter is a two element array of B<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
L<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 B<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 B<c>.

SSL_CIPHER_description() returns a textual description of the cipher used
into the buffer B<buf> of length B<len> provided.  If B<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,
B<NULL> is returned.

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

=over 4

=item <ciphername>

Textual representation of the cipher name.

=item <protocol version>

The minimum protocol version that the ciphersuite supports, such as B<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.

=item Kx=<key exchange>

Key exchange method such as B<RSA>, B<ECDHE>, etc.

=item Au=<authentication>

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

=item Enc=<symmetric encryption method>

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

=item Mac=<message authentication code>

Message digest, such as B<SHA256>.

=back

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

=head1 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
B<NID_undef> if an error occurred.

SSL_CIPHER_get_handshake_digest() returns a valid B<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 B<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.

=head1 SEE ALSO

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

=head1 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 B<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 (B<enable-ssl-trace> argument to Configure) was
required to enable this function.

The OPENSSL_cipher_name() function was added in OpenSSL 1.1.1.

=head1 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
L<https://www.openssl.org/source/license.html>.

=cut
