196 lines
8.2 KiB
HTML
196 lines
8.2 KiB
HTML
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<head>
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<title>sechash(3) - Plan 9 from User Space</title>
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<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
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</head>
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<body bgcolor=#ffffff>
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<table border=0 cellpadding=0 cellspacing=0 width=100%>
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<tr height=10><td>
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<tr><td width=20><td>
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<tr><td width=20><td><b>SECHASH(3)</b><td align=right><b>SECHASH(3)</b>
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<tr><td width=20><td colspan=2>
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<br>
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<p><font size=+1><b>NAME </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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md4, md5, sha1, hmac_md5, hmac_sha1, md5pickle, md5unpickle, sha1pickle,
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sha1unpickle – cryptographically secure hashes<br>
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</table>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>#include <u.h><br>
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#include <libc.h><br>
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#include <mp.h><br>
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#include <libsec.h>
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>DigestState* md4(uchar *data, ulong dlen, uchar *digest, DigestState
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*state)
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</font></tt>
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<tt><font size=+1>DigestState* md5(uchar *data, ulong dlen, uchar *digest, DigestState
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*state)
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</font></tt>
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<tt><font size=+1>char* md5pickle(MD5state *state)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>MD5state* md5unpickle(char *p);
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>DigestState* sha1(uchar *data, ulong dlen, uchar *digest, DigestState
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*state)
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</font></tt>
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<tt><font size=+1>char* sha1pickle(MD5state *state)
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</font></tt>
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<tt><font size=+1>MD5state* sha1unpickle(char *p);
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>DigestState* hmac_md5(uchar *data, ulong dlen,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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uchar *key, ulong klen,<br>
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uchar *digest, DigestState *state)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</table>
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</table>
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</font></tt>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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</table>
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</table>
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<tt><font size=+1>DigestState* hmac_sha1(uchar *data, ulong dlen,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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uchar *key, ulong klen,<br>
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uchar *digest, DigestState *state)<br>
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</table>
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</table>
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</font></tt>
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</table>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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These functions implement the cryptographic hash functions MD4,
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MD5, and SHA1. The output of the hash is called a <i>digest</i>. A hash
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is secure if, given the hashed data and the digest, it is difficult
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to predict the change to the digest resulting from some change
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to the data without rehashing the whole data. Therefore, if
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a secret is part of the hashed data, the digest can be used as
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an integrity check of the data by anyone possessing the secret.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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The routines <i>md4</i>, <i>md5</i>, <i>sha1</i>, <i>hmac_md5</i>, and <i>hmac_sha1</i> differ only
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in the length of the resulting digest and in the security of the
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hash. Usage for each is the same. The first call to the routine
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should have <tt><font size=+1>nil</font></tt> as the <i>state</i> parameter. This call returns a state
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which can be used to chain subsequent calls. The last call
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should have digest non-nil. <i>Digest</i> must point to a buffer of at
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least the size of the digest produced. This last call will free
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the state and copy the result into <i>digest</i>. For example, to hash
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a single buffer using <i>md5</i>:<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>uchar digest[MD5dlen];<br>
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md5(data, len, digest, nil);<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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</table>
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To chain a number of buffers together, bounded on each end by
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some secret:<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>char buf[256];<br>
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uchar digest[MD5dlen];<br>
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DigestState *s;<br>
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s = md5("my password", 11, nil, nil);<br>
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while((n = read(fd, buf, 256)) > 0)<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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md5(buf, n, nil, s);<br>
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</table>
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md5("drowssap ym", 11, digest, s);<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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</table>
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The constants <i>MD4dlen</i>, <i>MD5dlen</i>, and <i>SHA1dlen</i> define the lengths
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of the digests.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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<i>Hmac_md5</i> and <i>hmac_sha1</i> are used slightly differently. These hash
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algorithms are keyed and require a key to be specified on every
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call. The digest lengths for these hashes are <i>MD5dlen</i> and <i>SHA1dlen</i>
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respectively.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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The functions <i>md5pickle</i> and <i>sha1pickle</i> marshal the state of a
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digest for transmission. <i>Md5unpickle</i> and <i>sha1unpickle</i> unmarshal
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a pickled digest. All four routines return a pointer to a newly
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<a href="../man3/malloc.html"><i>malloc</i>(3)</a>’d object.<br>
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</table>
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<p><font size=+1><b>SOURCE </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>/usr/local/plan9/src/libsec<br>
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</font></tt>
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</table>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<a href="../man3/aes.html"><i>aes</i>(3)</a>, <a href="../man3/blowfish.html"><i>blowfish</i>(3)</a>, <a href="../man3/des.html"><i>des</i>(3)</a>, <a href="../man3/elgamal.html"><i>elgamal</i>(3)</a>, <a href="../man3/rc4.html"><i>rc4</i>(3)</a>, <a href="../man3/rsa.html"><i>rsa</i>(3)</a><br>
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</table>
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<td width=20>
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<tr height=20><td>
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</table>
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<!-- TRAILER -->
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<table border=0 cellpadding=0 cellspacing=0 width=100%>
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<tr height=15><td width=10><td><td width=10>
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<tr><td><td>
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<center>
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<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>
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</center>
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</table>
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<!-- TRAILER -->
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</body></html>
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