108e907645
Clarify the intended use of EVP_PKEY_sign. Make the code example compile.
Reviewed-by: Dr Stephen Henson <steve@openssl.org>
(cherry picked from commit d64c533a20)
106 lines
3.1 KiB
Text
106 lines
3.1 KiB
Text
=pod
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=head1 NAME
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EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx);
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int EVP_PKEY_sign(EVP_PKEY_CTX *ctx,
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unsigned char *sig, size_t *siglen,
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const unsigned char *tbs, size_t tbslen);
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=head1 DESCRIPTION
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The EVP_PKEY_sign_init() function initializes a public key algorithm
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context using key B<pkey> for a signing operation.
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The EVP_PKEY_sign() function performs a public key signing operation
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using B<ctx>. The data to be signed is specified using the B<tbs> and
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B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output
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buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then
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before the call the B<siglen> parameter should contain the length of the
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B<sig> buffer, if the call is successful the signature is written to
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B<sig> and the amount of data written to B<siglen>.
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=head1 NOTES
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EVP_PKEY_sign() does not hash the data to be signed, and therefore is
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normally used to sign digests. For signing arbitrary messages, see the
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L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)> and
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L<EVP_SignInit(3)|EVP_SignInit(3)> signing interfaces instead.
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After the call to EVP_PKEY_sign_init() algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation (see L<EVP_PKEY_CTX_ctrl(3)|EVP_PKEY_CTX_ctrl(3)>).
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The function EVP_PKEY_sign() can be called more than once on the same
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context if several operations are performed using the same parameters.
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=head1 RETURN VALUES
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EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0
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or a negative value for failure. In particular a return value of -2
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indicates the operation is not supported by the public key algorithm.
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=head1 EXAMPLE
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Sign data using RSA with PKCS#1 padding and SHA256 digest:
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#include <openssl/evp.h>
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#include <openssl/rsa.h>
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EVP_PKEY_CTX *ctx;
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/* md is a SHA-256 digest in this example. */
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unsigned char *md, *sig;
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size_t mdlen = 32, siglen;
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EVP_PKEY *signing_key;
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/*
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* NB: assumes signing_key and md are set up before the next
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* step. signing_key must be an RSA private key and md must
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* point to the SHA-256 digest to be signed.
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*/
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ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */);
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if (!ctx)
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/* Error occurred */
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if (EVP_PKEY_sign_init(ctx) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
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/* Error */
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/* Determine buffer length */
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if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0)
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/* Error */
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sig = OPENSSL_malloc(siglen);
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if (!sig)
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/* malloc failure */
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if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0)
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/* Error */
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/* Signature is siglen bytes written to buffer sig */
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_CTX_ctrl(3)|EVP_PKEY_CTX_ctrl(3)>,
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L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
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L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
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L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
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L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>,
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L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>
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=head1 HISTORY
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These functions were first added to OpenSSL 1.0.0.
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=cut
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