125 lines
5.8 KiB
HTML
125 lines
5.8 KiB
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<?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:" />
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</head>
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<body>
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<ul id="index">
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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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<h1 id="NAME">NAME</h1>
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<p>EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover_init_ex, EVP_PKEY_verify_recover - recover signature using a public key algorithm</p>
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<h1 id="SYNOPSIS">SYNOPSIS</h1>
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<pre><code> #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_init_ex(EVP_PKEY_CTX *ctx,
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const OSSL_PARAM params[]);
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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);</code></pre>
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<h1 id="DESCRIPTION">DESCRIPTION</h1>
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<p>EVP_PKEY_verify_recover_init() initializes a public key algorithm context <i>ctx</i> for signing using the algorithm given when the context was created using <a href="../man3/EVP_PKEY_CTX_new.html">EVP_PKEY_CTX_new(3)</a> or variants thereof. The algorithm is used to fetch a <b>EVP_SIGNATURE</b> method implicitly, see <a href="../man7/provider.html">"Implicit fetch" in provider(7)</a> for more information about implicit fetches.</p>
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<p>EVP_PKEY_verify_recover_init_ex() is the same as EVP_PKEY_verify_recover_init() but additionally sets the passed parameters <i>params</i> on the context before returning.</p>
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<p>The EVP_PKEY_verify_recover() function recovers signed data using <i>ctx</i>. The signature is specified using the <i>sig</i> and <i>siglen</i> parameters. If <i>rout</i> is NULL then the maximum size of the output buffer is written to the <i>routlen</i> parameter. If <i>rout</i> is not NULL then before the call the <i>routlen</i> parameter should contain the length of the <i>rout</i> buffer, if the call is successful recovered data is written to <i>rout</i> and the amount of data written to <i>routlen</i>.</p>
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<h1 id="NOTES">NOTES</h1>
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<p>Normally an application is only interested in whether a signature verification operation is successful in those cases the EVP_verify() function should be used.</p>
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<p>Sometimes however it is useful to obtain the data originally signed using a signing operation. Only certain public key algorithms can recover a signature in this way (for example RSA in PKCS padding mode).</p>
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<p>After the call to EVP_PKEY_verify_recover_init() algorithm specific control operations can be performed to set any appropriate parameters for the operation.</p>
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<p>The function EVP_PKEY_verify_recover() can be called more than once on the same context if several operations are performed using the same parameters.</p>
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<h1 id="RETURN-VALUES">RETURN VALUES</h1>
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<p>EVP_PKEY_verify_recover_init() and EVP_PKEY_verify_recover() 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.</p>
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<h1 id="EXAMPLES">EXAMPLES</h1>
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<p>Recover digest originally signed using PKCS#1 and SHA256 digest:</p>
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<pre><code> #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 */</code></pre>
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<h1 id="SEE-ALSO">SEE ALSO</h1>
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<p><a href="../man3/EVP_PKEY_CTX_new.html">EVP_PKEY_CTX_new(3)</a>, <a href="../man3/EVP_PKEY_encrypt.html">EVP_PKEY_encrypt(3)</a>, <a href="../man3/EVP_PKEY_decrypt.html">EVP_PKEY_decrypt(3)</a>, <a href="../man3/EVP_PKEY_sign.html">EVP_PKEY_sign(3)</a>, <a href="../man3/EVP_PKEY_verify.html">EVP_PKEY_verify(3)</a>, <a href="../man3/EVP_PKEY_derive.html">EVP_PKEY_derive(3)</a></p>
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<h1 id="HISTORY">HISTORY</h1>
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<p>The EVP_PKEY_verify_recover_init() and EVP_PKEY_verify_recover() functions were added in OpenSSL 1.0.0.</p>
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<p>The EVP_PKEY_verify_recover_init_ex() function was added in OpenSSL 3.0.</p>
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<h1 id="COPYRIGHT">COPYRIGHT</h1>
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<p>Copyright 2013-2021 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 this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <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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