10564b1175
groff 1.23.0 added .MR to its -man macro package. The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020." From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.
Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.
Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized. groff's .MR does not. This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.
152 lines
3.0 KiB
Groff
152 lines
3.0 KiB
Groff
.TH SECHASH 3
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.SH NAME
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md4, md5, sha1, hmac_md5, hmac_sha1, md5pickle, md5unpickle, sha1pickle, sha1unpickle \- cryptographically secure hashes
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <mp.h>
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.br
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.B #include <libsec.h>
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.PP
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.B
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DigestState* md4(uchar *data, ulong dlen, uchar *digest,
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.B
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DigestState *state)
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.PP
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.B
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DigestState* md5(uchar *data, ulong dlen, uchar *digest,
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.B
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DigestState *state)
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.PP
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.B
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char* md5pickle(MD5state *state)
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.PP
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.B
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MD5state* md5unpickle(char *p);
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.PP
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.B
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DigestState* sha1(uchar *data, ulong dlen, uchar *digest,
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.B
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DigestState *state)
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.PP
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.B
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char* sha1pickle(MD5state *state)
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.PP
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.B
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MD5state* sha1unpickle(char *p);
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.PP
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.B
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DigestState* hmac_md5(uchar *data, ulong dlen,
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.br
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.B
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uchar *key, ulong klen,
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.br
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.B
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uchar *digest, DigestState *state)
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.PP
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.B
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DigestState* hmac_sha1(uchar *data, ulong dlen,
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.br
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.B
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uchar *key, ulong klen,
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.br
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.B
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uchar *digest, DigestState *state)
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.SH DESCRIPTION
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.PP
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These functions implement
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the cryptographic hash functions MD4, MD5, and SHA1. The output of the
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hash is called a
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.IR digest .
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A hash is secure if, given the hashed data and the digest,
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it is difficult to predict the change to the digest resulting
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from some change to the data without rehashing
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the whole data. Therefore, if a secret is part of the hashed
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data, the digest can be used as an integrity check of the data by anyone
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possessing the secret.
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.PP
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The routines
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.IR md4 ,
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.IR md5 ,
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.IR sha1 ,
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.IR hmac_md5 ,
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and
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.I hmac_sha1
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differ only in the length of the resulting digest
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and in the security of the hash. Usage for each is the same.
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The first call to the routine should have
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.B nil
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as the
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.I state
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parameter. This call returns a state which can be used to chain
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subsequent calls.
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The last call should have digest non-\fBnil\fR.
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.I Digest
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must point to a buffer of at least the size of the digest produced.
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This last call will free the state and copy the result into
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.IR digest .
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For example, to hash a single buffer using
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.IR md5 :
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.EX
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uchar digest[MD5dlen];
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md5(data, len, digest, nil);
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.EE
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.PP
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To chain a number of buffers together,
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bounded on each end by some secret:
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.EX
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char buf[256];
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uchar digest[MD5dlen];
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DigestState *s;
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s = md5("my password", 11, nil, nil);
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while((n = read(fd, buf, 256)) > 0)
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md5(buf, n, nil, s);
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md5("drowssap ym", 11, digest, s);
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.EE
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.PP
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The constants
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.IR MD4dlen ,
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.IR MD5dlen ,
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and
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.I SHA1dlen
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define the lengths of the digests.
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.PP
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.I Hmac_md5
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and
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.I hmac_sha1
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are used slightly differently. These hash algorithms are keyed and require
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a key to be specified on every call.
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The digest lengths for these hashes are
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.I MD5dlen
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and
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.I SHA1dlen
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respectively.
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.PP
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The functions
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.I md5pickle
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and
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.I sha1pickle
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marshal the state of a digest for transmission.
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.I Md5unpickle
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and
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.I sha1unpickle
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unmarshal a pickled digest.
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All four routines return a pointer to a newly
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.MR malloc 3 'd
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object.
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.SH SOURCE
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.B \*9/src/libsec
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.SH SEE ALSO
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.MR aes 3 ,
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.MR blowfish 3 ,
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.MR des 3 ,
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.MR elgamal 3 ,
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.MR rc4 3 ,
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.MR rsa 3
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