#include <openssl/ssl.h> int SSL_get_shared_sigalgs(SSL *s, int idx, int *psign, int *phash, int *psignhash, unsigned char *rsig, unsigned char *rhash); int SSL_get_sigalgs(SSL *s, int idx, int *psign, int *phash, int *psignhash, unsigned char *rsig, unsigned char *rhash);
SSL_get_sigalgs() is similar to SSL_get_shared_sigalgs() except it returns information about all signature algorithms supported by s in the order they were sent by the peer.
If an application is only interested in the highest preference shared signature algorithm it can just set idx to zero.
Any or all of the parameters psign, phash, psignhash, rsig or rhash can be set to NULL if the value is not required. By setting them all to NULL and setting idx to zero the total number of signature algorithms can be determined: which can be zero.
These functions must be called after the peer has sent a list of supported signature algorithms: after a client hello (for servers) or a certificate request (for clients). They can (for example) be called in the certificate callback.
Only TLS 1.2, TLS 1.3 and DTLS 1.2 currently support signature algorithms. If these functions are called on an earlier version of TLS or DTLS zero is returned.
The shared signature algorithms returned by SSL_get_shared_sigalgs() are ordered according to configuration and peer preferences.
The raw values correspond to the on the wire form as defined by RFC5246 et al. The NIDs are OpenSSL equivalents. For example if the peer sent sha256(4) and rsa(1) then *rhash would be 4, *rsign 1, *phash NID_sha256, *psig NID_rsaEncryption and *psighash NID_sha256WithRSAEncryption.
If a signature algorithm is not recognised the corresponding NIDs will be set to NID_undef. This may be because the value is not supported, is not an appropriate combination (for example MD5 and DSA) or the signature algorithm does not use a hash (for example Ed25519).
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 https://www.openssl.org/source/license.html.