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<a href="/plan9/">Plan 9 from Bell Labs</a>’s /usr/web/sources/contrib/maht/hmac.c


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Copyright © 2009 Alcatel-Lucent. 
Distributed under the
<a href="/plan9/license.html">Lucent Public License version 1.02</a>.
 
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#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>

/*
This does hmac encoding of plain data with a key.
It prints each encoding with it's plain.
The reason it was written was to generate and verify tokens for given days without the need for a shared key i.e. :
generate : hmac -t sha1 -k KEY 'Wed Jun 18 hh:mm:ss EDT 2008'
verify : hmac -t sha1 -k KEY 'Wed Jun 18 hh:mm:ss EDT 2008' 'Thu Jun 19 hh:mm:ss EDT 2008' | grep -s '^1EF503BF7317D955A8957E5FA4E170B0757FB9CD' && echo verified || echo not found

it also signs stdin

-q supresses printing the plain
-n supresses printing the \n as well
BUGS
aes has a TODO in libsec and prints BEBAFECABEBAFECA0000000000000000

why does nl = "" work ?
*/

void
usage(void) {
fprint(2, "hmac [-q] [-t sha1(default) | md5 | aes] -k key plain0 plain1 ... plainn\n");
exits("usage");
}

#define BUFSIZE 1024

int
main(int argc, char **argv) {
char *key = nil;
char *nl = "\n";
int i = 0;
int fromstdin;
int quiet = 0;
uchar *digest;

DigestState* (*hmac)( uchar *data, ulong dlen, uchar *key, ulong klen, uchar *digest, DigestState *state) = hmac_sha1;
int dlen = SHA1dlen;

char *t;

ARGBEGIN {
case 'k' :
key = ARGF();
break;
case 'q' :
quiet = 1;
break;
case 'n' :
quiet = 1;
nl = "";
break;
case 't' :
t = ARGF();
if(strcmp(t, "sha1") == 0) {
hmac = hmac_sha1;
dlen = SHA1dlen;
} else if (strcmp(t, "md5") == 0) {
hmac = hmac_md5;
dlen = MD5dlen;
} else if (strcmp(t, "aes") == 0) {
hmac = hmac_aes;
dlen = AESdlen;
} else
usage();
break;
}ARGEND;

if(!key)
usage();

fmtinstall('H', encodefmt);
digest = (uchar*)malloc(dlen);
for(i = 0; i < argc; i++) {
hmac((uchar*)argv[i], strlen(argv[i]), (uchar*)key, strlen(key), digest, nil);
if(quiet)
print("%.*H%s", dlen, digest, nl);
else
print("%.*H\t%s\n", dlen, digest, argv[i]);
}

uchar buf[BUFSIZE];
DigestState *s = nil;
while((i = read(0, buf, BUFSIZE)) > 0) {
fromstdin = 1;
s = hmac(buf, i, (uchar*)key, strlen(key), nil, s);
}
hmac(nil, 0, (uchar*)key, strlen(key), digest, s);

if(fromstdin) {
if(quiet)
print("%.*H%s", dlen, digest, nl);
else
print("%.*H\t<stdin>\n", dlen, digest);
}
free(digest);
exits(nil);
}

# 8c hmac.c && 8l hmac.8 && 8.out -k key2 < /tmp/512

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