145 lines
5.3 KiB
HTML
145 lines
5.3 KiB
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<html xmlns="http://www.w3.org/1999/xhtml">
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<title>EVP_PKEY_CTX_set_tls1_prf_md</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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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="#string_ctrls">STRING CTRLS</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="#copyright">COPYRIGHT</a></li>
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</p>
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<h1><a name="name">NAME</a></h1>
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<p>EVP_PKEY_CTX_set_tls1_prf_md,
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EVP_PKEY_CTX_set1_tls1_prf_secret, EVP_PKEY_CTX_add1_tls1_prf_seed -
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TLS PRF key derivation 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/kdf.h></pre>
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<pre>
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int EVP_PKEY_CTX_set_tls1_prf_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
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int EVP_PKEY_CTX_set1_tls1_prf_secret(EVP_PKEY_CTX *pctx,
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unsigned char *sec, int seclen);
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int EVP_PKEY_CTX_add1_tls1_prf_seed(EVP_PKEY_CTX *pctx,
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unsigned char *seed, int seedlen);</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>The <strong>EVP_PKEY_TLS1_PRF</strong> algorithm implements the PRF key derivation function for
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TLS. It has no associated private key and only implements key derivation
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using <em>EVP_PKEY_derive(3)</em>.</p>
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<p>EVP_PKEY_set_tls1_prf_md() sets the message digest associated with the
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TLS PRF. EVP_md5_sha1() is treated as a special case which uses the PRF
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algorithm using both <strong>MD5</strong> and <strong>SHA1</strong> as used in TLS 1.0 and 1.1.</p>
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<p>EVP_PKEY_CTX_set_tls1_prf_secret() sets the secret value of the TLS PRF
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to <strong>seclen</strong> bytes of the buffer <strong>sec</strong>. Any existing secret value is replaced
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and any seed is reset.</p>
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<p>EVP_PKEY_CTX_add1_tls1_prf_seed() sets the seed to <strong>seedlen</strong> bytes of <strong>seed</strong>.
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If a seed is already set it is appended to the existing value.</p>
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<p>
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</p>
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<hr />
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<h1><a name="string_ctrls">STRING CTRLS</a></h1>
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<p>The TLS PRF also supports string based control operations using
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<em>EVP_PKEY_CTX_ctrl_str(3)</em>.
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The <strong>type</strong> parameter "md" uses the supplied <strong>value</strong> as the name of the digest
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algorithm to use.
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The <strong>type</strong> parameters "secret" and "seed" use the supplied <strong>value</strong> parameter
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as a secret or seed value.
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The names "hexsecret" and "hexseed" are similar except they take a hex string
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which is converted to binary.</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>All these functions are implemented as macros.</p>
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<p>A context for the TLS PRF can be obtained by calling:</p>
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<pre>
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EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);</pre>
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<p>The digest, secret value and seed must be set before a key is derived or an
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error occurs.</p>
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<p>The total length of all seeds cannot exceed 1024 bytes in length: this should
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be more than enough for any normal use of the TLS PRF.</p>
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<p>The output length of the PRF is specified by the length parameter in the
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<code>EVP_PKEY_derive()</code> function. Since the output length is variable, setting
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the buffer to <strong>NULL</strong> is not meaningful for the TLS PRF.</p>
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<p>Optimised versions of the TLS PRF can be implemented in an ENGINE.</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>All these functions return 1 for success and 0 or a negative value for failure.
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In particular a return value of -2 indicates the operation is not supported by
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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>This example derives 10 bytes using SHA-256 with the secret key "secret"
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and seed value "seed":</p>
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<pre>
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EVP_PKEY_CTX *pctx;
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unsigned char out[10];
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size_t outlen = sizeof(out);</pre>
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<pre>
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pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);
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if (EVP_PKEY_derive_init(pctx) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_tls1_prf_md(pctx, EVP_sha256()) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set1_tls1_prf_secret(pctx, "secret", 6) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_add1_tls1_prf_seed(pctx, "seed", 4) <= 0)
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/* Error */
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if (EVP_PKEY_derive(pctx, out, &outlen) <= 0)
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/* Error */</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_CTX_ctrl_str(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="copyright">COPYRIGHT</a></h1>
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<p>Copyright 2016 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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