1=pod 2 3=head1 NAME 4 5SSL_CTX_set1_sigalgs, SSL_set1_sigalgs, SSL_CTX_set1_sigalgs_list, 6SSL_set1_sigalgs_list, SSL_CTX_set1_client_sigalgs, 7SSL_set1_client_sigalgs, SSL_CTX_set1_client_sigalgs_list, 8SSL_set1_client_sigalgs_list - set supported signature algorithms 9 10=head1 SYNOPSIS 11 12 #include <openssl/ssl.h> 13 14 long SSL_CTX_set1_sigalgs(SSL_CTX *ctx, const int *slist, long slistlen); 15 long SSL_set1_sigalgs(SSL *ssl, const int *slist, long slistlen); 16 long SSL_CTX_set1_sigalgs_list(SSL_CTX *ctx, const char *str); 17 long SSL_set1_sigalgs_list(SSL *ssl, const char *str); 18 19 long SSL_CTX_set1_client_sigalgs(SSL_CTX *ctx, const int *slist, long slistlen); 20 long SSL_set1_client_sigalgs(SSL *ssl, const int *slist, long slistlen); 21 long SSL_CTX_set1_client_sigalgs_list(SSL_CTX *ctx, const char *str); 22 long SSL_set1_client_sigalgs_list(SSL *ssl, const char *str); 23 24=head1 DESCRIPTION 25 26SSL_CTX_set1_sigalgs() and SSL_set1_sigalgs() set the supported signature 27algorithms for B<ctx> or B<ssl>. The array B<slist> of length B<slistlen> 28must consist of pairs of NIDs corresponding to digest and public key 29algorithms. 30 31SSL_CTX_set1_sigalgs_list() and SSL_set1_sigalgs_list() set the supported 32signature algorithms for B<ctx> or B<ssl>. The B<str> parameter 33must be a null terminated string consisting of a colon separated list of 34elements, where each element is either a combination of a public key 35algorithm and a digest separated by B<+>, or a TLS 1.3-style named 36SignatureScheme such as rsa_pss_pss_sha256. 37Signature scheme names and public key algorithm names (but not the digest 38names) in the B<algorithm+hash> form are case-insensitive. 39If a list entry is preceded with the C<?> character, it will be ignored if an 40implementation is missing. 41 42 43SSL_CTX_set1_client_sigalgs(), SSL_set1_client_sigalgs(), 44SSL_CTX_set1_client_sigalgs_list() and SSL_set1_client_sigalgs_list() set 45signature algorithms related to client authentication, otherwise they are 46identical to SSL_CTX_set1_sigalgs(), SSL_set1_sigalgs(), 47SSL_CTX_set1_sigalgs_list() and SSL_set1_sigalgs_list(). 48 49All these functions are implemented as macros. The signature algorithm 50parameter (integer array or string) is not freed: the application should 51free it, if necessary. 52 53=head1 NOTES 54 55If an application wishes to allow the setting of signature algorithms 56as one of many user configurable options it should consider using the more 57flexible SSL_CONF API instead. 58 59The signature algorithms set by a client are used directly in the supported 60signature algorithm in the client hello message. 61 62The supported signature algorithms set by a server are not sent to the 63client but are used to determine the set of shared signature algorithms 64and (if server preferences are set with SSL_OP_CIPHER_SERVER_PREFERENCE) 65their order. 66 67The client authentication signature algorithms set by a server are sent 68in a certificate request message if client authentication is enabled, 69otherwise they are unused. 70 71Similarly client authentication signature algorithms set by a client are 72used to determined the set of client authentication shared signature 73algorithms. 74 75Signature algorithms will neither be advertised nor used if the security level 76prohibits them (for example SHA1 if the security level is 4 or more). 77 78Currently the NID_md5, NID_sha1, NID_sha224, NID_sha256, NID_sha384 and 79NID_sha512 digest NIDs are supported and the public key algorithm NIDs 80EVP_PKEY_RSA, EVP_PKEY_RSA_PSS, EVP_PKEY_DSA and EVP_PKEY_EC. 81 82The short or long name values for digests can be used in a string (for 83example "MD5", "SHA1", "SHA224", "SHA256", "SHA384", "SHA512") and 84the public key algorithm strings "RSA", "RSA-PSS", "DSA" or "ECDSA". 85 86The TLS 1.3 signature scheme names (such as "rsa_pss_pss_sha256") can also 87be used with the B<_list> forms of the API. 88 89The use of MD5 as a digest is strongly discouraged due to security weaknesses. 90 91=head1 RETURN VALUES 92 93All these functions return 1 for success and 0 for failure. 94 95=head1 EXAMPLES 96 97Set supported signature algorithms to SHA256 with ECDSA and SHA256 with RSA 98using an array: 99 100 const int slist[] = {NID_sha256, EVP_PKEY_EC, NID_sha256, EVP_PKEY_RSA}; 101 102 SSL_CTX_set1_sigalgs(ctx, slist, 4); 103 104Set supported signature algorithms to SHA256 with ECDSA and SHA256 with RSA 105using a string: 106 107 SSL_CTX_set1_sigalgs_list(ctx, "ECDSA+SHA256:RSA+SHA256"); 108 109=head1 SEE ALSO 110 111L<ssl(7)>, L<SSL_get_shared_sigalgs(3)>, 112L<SSL_CONF_CTX_new(3)> 113 114=head1 HISTORY 115 116Support for ignoring unknown signature algorithms in 117SSL_CTX_set1_sigalgs_list(), SSL_set1_sigalgs_list(), 118SSL_CTX_set1_client_sigalgs_list() and SSL_set1_client_sigalgs_list() 119was added in OpenSSL 3.3. 120 121=head1 COPYRIGHT 122 123Copyright 2015-2025 The OpenSSL Project Authors. All Rights Reserved. 124 125Licensed under the Apache License 2.0 (the "License"). You may not use 126this file except in compliance with the License. You can obtain a copy 127in the file LICENSE in the source distribution or at 128L<https://www.openssl.org/source/license.html>. 129 130=cut 131