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#include "os.h"
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#include <libsec.h>
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/* rfc2104 */
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DigestState*
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hmac_x(uchar *p, ulong len, uchar *key, ulong klen, uchar *digest, DigestState *s,
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	DigestState*(*x)(uchar*, ulong, uchar*, DigestState*), int xlen)
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{
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	int i;
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	uchar pad[Hmacblksz+1], innerdigest[256];
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	if(xlen > sizeof(innerdigest))
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		return nil;
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	if(klen > Hmacblksz){
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		if(xlen > Hmacblksz)
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			return nil;
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		(*x)(key, klen, innerdigest, nil);
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		key = innerdigest;
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		klen = xlen;
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	}
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	/* first time through */
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	if(s == nil || s->seeded == 0){
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		memset(pad, 0x36, Hmacblksz);
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		pad[Hmacblksz] = 0;
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		for(i = 0; i < klen; i++)
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			pad[i] ^= key[i];
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		s = (*x)(pad, Hmacblksz, nil, s);
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		if(s == nil)
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			return nil;
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	}
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	s = (*x)(p, len, nil, s);
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	if(digest == nil)
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		return s;
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	/* last time through */
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	memset(pad, 0x5c, Hmacblksz);
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	pad[Hmacblksz] = 0;
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	for(i = 0; i < klen; i++)
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		pad[i] ^= key[i];
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	(*x)(nil, 0, innerdigest, s);
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	s = (*x)(pad, Hmacblksz, nil, nil);
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	(*x)(innerdigest, xlen, digest, s);
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	return nil;
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}