| =pod |
| |
| =head1 NAME |
| |
| EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/evp.h> |
| |
| int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); |
| int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, |
| unsigned char *sig, size_t *siglen, |
| const unsigned char *tbs, size_t tbslen); |
| |
| =head1 DESCRIPTION |
| |
| The EVP_PKEY_sign_init() function initializes a public key algorithm |
| context using key B<pkey> for a signing operation. |
| |
| The EVP_PKEY_sign() function performs a public key signing operation |
| using B<ctx>. The data to be signed is specified using the B<tbs> and |
| B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output |
| buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then |
| before the call the B<siglen> parameter should contain the length of the |
| B<sig> buffer, if the call is successful the signature is written to |
| B<sig> and the amount of data written to B<siglen>. |
| |
| =head1 NOTES |
| |
| After the call to EVP_PKEY_sign_init() algorithm specific control |
| operations can be performed to set any appropriate parameters for the |
| operation. |
| |
| The function EVP_PKEY_sign() can be called more than once on the same |
| context if several operations are performed using the same parameters. |
| |
| =head1 RETURN VALUES |
| |
| EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 |
| or a negative value for failure. In particular a return value of -2 |
| indicates the operation is not supported by the public key algorithm. |
| |
| =head1 EXAMPLE |
| |
| Sign data using RSA with PKCS#1 padding and SHA256 digest: |
| |
| #include <openssl/evp.h> |
| #include <openssl/rsa.h> |
| |
| EVP_PKEY_CTX *ctx; |
| unsigned char *md, *sig; |
| size_t mdlen, siglen; |
| EVP_PKEY *signing_key; |
| /* NB: assumes signing_key, md and mdlen are already set up |
| * and that signing_key is an RSA private key |
| */ |
| ctx = EVP_PKEY_CTX_new(signing_key); |
| if (!ctx) |
| /* Error occurred */ |
| if (EVP_PKEY_sign_init(ctx) <= 0) |
| /* Error */ |
| if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
| /* Error */ |
| if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
| /* Error */ |
| |
| /* Determine buffer length */ |
| if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) |
| /* Error */ |
| |
| sig = OPENSSL_malloc(siglen); |
| |
| if (!sig) |
| /* malloc failure */ |
| |
| if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) |
| /* Error */ |
| |
| /* Signature is siglen bytes written to buffer sig */ |
| |
| |
| =head1 SEE ALSO |
| |
| L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>, |
| L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, |
| L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>, |
| L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, |
| L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>, |
| L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> |
| |
| =head1 HISTORY |
| |
| These functions were first added to OpenSSL 1.0.0. |
| |
| =cut |