=pod

=head1 NAME

SSL_get0_peer_signature_name, SSL_get_peer_signature_nid,
SSL_get_peer_signature_type_nid, SSL_get0_signature_name,
SSL_get_signature_nid, SSL_get_signature_type_nid -
get TLS message signing types

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_get0_peer_signature_name(const SSL *ssl, const char **sigalg);
 int SSL_get_peer_signature_nid(SSL *ssl, int *psig_nid);
 int SSL_get_peer_signature_type_nid(const SSL *ssl, int *psigtype_nid);
 int SSL_get0_signature_name(SSL *ssl, const char **sigalg);
 int SSL_get_signature_nid(SSL *ssl, int *psig_nid);
 int SSL_get_signature_type_nid(const SSL *ssl, int *psigtype_nid);

=head1 DESCRIPTION

SSL_get0_peer_signature_name() sets I<*sigalg> to the IANA name of the
L<signature scheme|https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-signaturescheme>
used by the peer to sign the TLS handshake.
The caller must not free the returned pointer.
The returned string should be copied if it is to be retained beyond the
lifetime of the SSL connection.

SSL_get_peer_signature_nid() sets B<*psig_nid> to the NID of the digest used
by the peer to sign TLS messages. It is implemented as a macro.

SSL_get_peer_signature_type_nid() sets B<*psigtype_nid> to the signature
type used by the peer to sign TLS messages. Currently the signature type
is the NID of the public key type used for signing except for PSS signing
where it is B<EVP_PKEY_RSA_PSS>. To differentiate between
B<rsa_pss_rsae_*> and B<rsa_pss_pss_*> signatures, it's necessary to check
the type of public key in the peer's certificate.

SSL_get0_signature_name(), SSL_get_signature_nid() and
SSL_get_signature_type_nid() return the equivalent information for the local
end of the connection.

=head1 RETURN VALUES

These functions return 1 for success and 0 for failure. There are several
possible reasons for failure: the peer or local end is a client and did not
sign the handshake (did not use a client certificate), the cipher suite has no
signature (e.g. it uses RSA key exchange or is anonymous), the TLS version is
below 1.2 or the functions were called too early, e.g. before the peer signed a
message.

=head1 SEE ALSO

L<ssl(7)>, L<SSL_get_peer_certificate(3)>,

=head1 HISTORY

The SSL_get0_peer_signature_name() and SSL_get0_signature_name() functions were
added in OpenSSL 3.5.

SSL_get_signature_nid() was added in OpenSSL 1.1.1a.

=head1 COPYRIGHT

Copyright 2017-2025 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
