=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);
 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>

Protocol version, such as B<TLSv1.2>, when the cipher was first defined.

=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 null-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 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 SEE ALSO

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

=head1 COPYRIGHT

Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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
