158 lines
5.4 KiB
HTML
Executable File
158 lines
5.4 KiB
HTML
Executable File
<?xml version="1.0" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>EVP_PKEY_verify_recover</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<link rev="made" href="mailto:root@localhost" />
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</head>
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<body style="background-color: white">
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<!-- INDEX BEGIN -->
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<div name="index">
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<p><a name="__index__"></a></p>
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<ul>
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<li><a href="#name">NAME</a></li>
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<li><a href="#synopsis">SYNOPSIS</a></li>
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<li><a href="#description">DESCRIPTION</a></li>
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<li><a href="#notes">NOTES</a></li>
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<li><a href="#return_values">RETURN VALUES</a></li>
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<li><a href="#examples">EXAMPLES</a></li>
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<li><a href="#see_also">SEE ALSO</a></li>
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<li><a href="#history">HISTORY</a></li>
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<li><a href="#copyright">COPYRIGHT</a></li>
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</ul>
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<hr name="index" />
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</div>
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<!-- INDEX END -->
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<p>
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</p>
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<hr />
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<h1><a name="name">NAME</a></h1>
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<p>EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover
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- recover signature using a public key algorithm</p>
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<p>
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</p>
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<hr />
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<h1><a name="synopsis">SYNOPSIS</a></h1>
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<pre>
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#include <openssl/evp.h></pre>
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<pre>
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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);</pre>
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<p>
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</p>
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<hr />
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<h1><a name="description">DESCRIPTION</a></h1>
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<p><code>EVP_PKEY_verify_recover_init()</code> initializes a public key algorithm context
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<em>ctx</em> for signing using the algorithm given when the context was created
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using <em>EVP_PKEY_CTX_new(3)</em> or variants thereof. The algorithm is used to
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fetch a <strong>EVP_SIGNATURE</strong> method implicitly, see <em>provider(7)/Implicit fetch</em>
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for more information about implict fetches.</p>
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<p>The <code>EVP_PKEY_verify_recover()</code> function recovers signed data
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using <em>ctx</em>. The signature is specified using the <em>sig</em> and
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<em>siglen</em> parameters. If <em>rout</em> is NULL then the maximum size of the output
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buffer is written to the <em>routlen</em> parameter. If <em>rout</em> is not NULL then
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before the call the <em>routlen</em> parameter should contain the length of the
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<em>rout</em> buffer, if the call is successful recovered data is written to
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<em>rout</em> and the amount of data written to <em>routlen</em>.</p>
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<p>
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</p>
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<hr />
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<h1><a name="notes">NOTES</a></h1>
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<p>Normally an application is only interested in whether a signature verification
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operation is successful in those cases the <code>EVP_verify()</code> function should be
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used.</p>
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<p>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).</p>
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<p>After the call to <code>EVP_PKEY_verify_recover_init()</code> algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation.</p>
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<p>The function <code>EVP_PKEY_verify_recover()</code> can be called more than once on the same
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context if several operations are performed using the same parameters.</p>
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<p>
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</p>
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<hr />
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<h1><a name="return_values">RETURN VALUES</a></h1>
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<p><code>EVP_PKEY_verify_recover_init()</code> and <code>EVP_PKEY_verify_recover()</code> 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.</p>
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<p>
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</p>
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<hr />
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<h1><a name="examples">EXAMPLES</a></h1>
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<p>Recover digest originally signed using PKCS#1 and SHA256 digest:</p>
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<pre>
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#include <openssl/evp.h>
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#include <openssl/rsa.h></pre>
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<pre>
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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;</pre>
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<pre>
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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 */</pre>
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<pre>
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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 */</pre>
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<pre>
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rout = OPENSSL_malloc(routlen);</pre>
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<pre>
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if (!rout)
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/* malloc failure */</pre>
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<pre>
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if (EVP_PKEY_verify_recover(ctx, rout, &routlen, sig, siglen) <= 0)
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/* Error */</pre>
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<pre>
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/* Recovered data is routlen bytes written to buffer rout */</pre>
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<p>
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</p>
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<hr />
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<h1><a name="see_also">SEE ALSO</a></h1>
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<p><em>EVP_PKEY_CTX_new(3)</em>,
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<em>EVP_PKEY_encrypt(3)</em>,
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<em>EVP_PKEY_decrypt(3)</em>,
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<em>EVP_PKEY_sign(3)</em>,
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<em>EVP_PKEY_verify(3)</em>,
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<em>EVP_PKEY_derive(3)</em></p>
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<p>
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</p>
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<hr />
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<h1><a name="history">HISTORY</a></h1>
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<p>These functions were added in OpenSSL 1.0.0.</p>
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<p>
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</p>
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<hr />
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<h1><a name="copyright">COPYRIGHT</a></h1>
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<p>Copyright 2013-2018 The OpenSSL Project Authors. All Rights Reserved.</p>
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<p>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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<a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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</body>
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</html>
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