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0e52100400
Because the algorithm to use is decided already when creating an EVP_PKEY_CTX regardless of how it was created, it turns out that it's unnecessary to provide the SIGNATURE method explicitly, and rather always have it be fetched implicitly. This means fewer changes for applications that want to use new signature algorithms / implementations. Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/10303)
119 lines
3.7 KiB
Plaintext
119 lines
3.7 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover
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- recover signature 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_verify_recover_init(EVP_PKEY_CTX *ctx);
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int EVP_PKEY_verify_recover(EVP_PKEY_CTX *ctx,
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unsigned char *rout, size_t *routlen,
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const unsigned char *sig, size_t siglen);
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=head1 DESCRIPTION
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EVP_PKEY_verify_recover_init() initializes a public key algorithm context
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I<ctx> for signing using the algorithm given when the context was created
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using L<EVP_PKEY_CTX_new(3)> or variants thereof. The algorithm is used to
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fetch a B<EVP_SIGNATURE> method implicitly, see L<provider(7)/Implicit fetch>
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for more information about implict fetches.
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The EVP_PKEY_verify_recover() function recovers signed data
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using I<ctx>. The signature is specified using the I<sig> and
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I<siglen> parameters. If I<rout> is NULL then the maximum size of the output
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buffer is written to the I<routlen> parameter. If I<rout> is not NULL then
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before the call the I<routlen> parameter should contain the length of the
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I<rout> buffer, if the call is successful recovered data is written to
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I<rout> and the amount of data written to I<routlen>.
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=head1 NOTES
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Normally an application is only interested in whether a signature verification
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operation is successful in those cases the EVP_verify() function should be
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used.
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Sometimes however it is useful to obtain the data originally signed using a
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signing operation. Only certain public key algorithms can recover a signature
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in this way (for example RSA in PKCS padding mode).
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After the call to EVP_PKEY_verify_recover_init() algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation.
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The function EVP_PKEY_verify_recover() 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_verify_recover_init() and EVP_PKEY_verify_recover() return 1 for success
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and 0 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 EXAMPLES
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Recover digest originally signed using PKCS#1 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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unsigned char *rout, *sig;
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size_t routlen, siglen;
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EVP_PKEY *verify_key;
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/*
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* NB: assumes verify_key, sig and siglen are already set up
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* and that verify_key is an RSA public key
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*/
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ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */);
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if (!ctx)
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/* Error occurred */
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if (EVP_PKEY_verify_recover_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_verify_recover(ctx, NULL, &routlen, sig, siglen) <= 0)
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/* Error */
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rout = OPENSSL_malloc(routlen);
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if (!rout)
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/* malloc failure */
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if (EVP_PKEY_verify_recover(ctx, rout, &routlen, sig, siglen) <= 0)
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/* Error */
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/* Recovered data is routlen bytes written to buffer rout */
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_encrypt(3)>,
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L<EVP_PKEY_decrypt(3)>,
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L<EVP_PKEY_sign(3)>,
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L<EVP_PKEY_verify(3)>,
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L<EVP_PKEY_derive(3)>
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=head1 HISTORY
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These functions were added in OpenSSL 1.0.0.
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=head1 COPYRIGHT
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Copyright 2013-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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