1=pod 2 3=head1 NAME 4 5EVP_PKEY_sign_init, EVP_PKEY_sign_init_ex, EVP_PKEY_sign 6- sign using a public key algorithm 7 8=head1 SYNOPSIS 9 10 #include <openssl/evp.h> 11 12 int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); 13 int EVP_PKEY_sign_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]); 14 int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, 15 unsigned char *sig, size_t *siglen, 16 const unsigned char *tbs, size_t tbslen); 17 18=head1 DESCRIPTION 19 20EVP_PKEY_sign_init() initializes a public key algorithm context I<ctx> for 21signing using the algorithm given when the context was created 22using L<EVP_PKEY_CTX_new(3)> or variants thereof. The algorithm is used to 23fetch a B<EVP_SIGNATURE> method implicitly, see L<provider(7)/Implicit fetch> 24for more information about implicit fetches. 25 26EVP_PKEY_sign_init_ex() is the same as EVP_PKEY_sign_init() but additionally 27sets the passed parameters I<params> on the context before returning. 28 29The EVP_PKEY_sign() function performs a public key signing operation 30using I<ctx>. The data to be signed is specified using the I<tbs> and 31I<tbslen> parameters. If I<sig> is NULL then the maximum size of the output 32buffer is written to the I<siglen> parameter. If I<sig> is not NULL then 33before the call the I<siglen> parameter should contain the length of the 34I<sig> buffer, if the call is successful the signature is written to 35I<sig> and the amount of data written to I<siglen>. 36 37=head1 NOTES 38 39EVP_PKEY_sign() does not hash the data to be signed, and therefore is 40normally used to sign digests. For signing arbitrary messages, see the 41L<EVP_DigestSignInit(3)> and 42L<EVP_SignInit(3)> signing interfaces instead. 43 44After the call to EVP_PKEY_sign_init() algorithm specific control 45operations can be performed to set any appropriate parameters for the 46operation (see L<EVP_PKEY_CTX_ctrl(3)>). 47 48The function EVP_PKEY_sign() can be called more than once on the same 49context if several operations are performed using the same parameters. 50 51=head1 RETURN VALUES 52 53EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 54or a negative value for failure. In particular a return value of -2 55indicates the operation is not supported by the public key algorithm. 56 57=head1 EXAMPLES 58 59Sign data using RSA with PKCS#1 padding and SHA256 digest: 60 61 #include <openssl/evp.h> 62 #include <openssl/rsa.h> 63 64 EVP_PKEY_CTX *ctx; 65 /* md is a SHA-256 digest in this example. */ 66 unsigned char *md, *sig; 67 size_t mdlen = 32, siglen; 68 EVP_PKEY *signing_key; 69 70 /* 71 * NB: assumes signing_key and md are set up before the next 72 * step. signing_key must be an RSA private key and md must 73 * point to the SHA-256 digest to be signed. 74 */ 75 ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */); 76 if (!ctx) 77 /* Error occurred */ 78 if (EVP_PKEY_sign_init(ctx) <= 0) 79 /* Error */ 80 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) 81 /* Error */ 82 if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) 83 /* Error */ 84 85 /* Determine buffer length */ 86 if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) 87 /* Error */ 88 89 sig = OPENSSL_malloc(siglen); 90 91 if (!sig) 92 /* malloc failure */ 93 94 if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) 95 /* Error */ 96 97 /* Signature is siglen bytes written to buffer sig */ 98 99 100=head1 SEE ALSO 101 102L<EVP_PKEY_CTX_new(3)>, 103L<EVP_PKEY_CTX_ctrl(3)>, 104L<EVP_PKEY_encrypt(3)>, 105L<EVP_PKEY_decrypt(3)>, 106L<EVP_PKEY_verify(3)>, 107L<EVP_PKEY_verify_recover(3)>, 108L<EVP_PKEY_derive(3)> 109 110=head1 HISTORY 111 112The EVP_PKEY_sign_init() and EVP_PKEY_sign() functions were added in 113OpenSSL 1.0.0. 114 115The EVP_PKEY_sign_init_ex() function was added in OpenSSL 3.0. 116 117=head1 COPYRIGHT 118 119Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved. 120 121Licensed under the Apache License 2.0 (the "License"). You may not use 122this file except in compliance with the License. You can obtain a copy 123in the file LICENSE in the source distribution or at 124L<https://www.openssl.org/source/license.html>. 125 126=cut 127