ref: 4c2d87cd65fc769d434f23fb54e328811e52d43a
dir: /libsec/hkdf.c/
#include "os.h"
#include <libsec.h>
/* rfc5869 */
void
hkdf_x(salt, nsalt, info, ninfo, key, nkey, d, dlen, x, xlen)
uchar *salt, *info, *key, *d;
ulong nsalt, ninfo, nkey, dlen;
DigestState* (*x)(uchar*, ulong, uchar*, ulong, uchar*, DigestState*);
int xlen;
{
uchar prk[256], tmp[256], cnt;
DigestState *ds;
assert(xlen <= sizeof(tmp));
memset(tmp, 0, xlen);
if(nsalt == 0){
salt = tmp;
nsalt = xlen;
}
/* note that salt and key are swapped in this case */
(*x)(key, nkey, salt, nsalt, prk, nil);
ds = nil;
for(cnt=1;; cnt++) {
if(ninfo > 0)
ds = (*x)(info, ninfo, prk, xlen, nil, ds);
(*x)(&cnt, 1, prk, xlen, tmp, ds);
if(dlen <= xlen){
memmove(d, tmp, dlen);
break;
}
memmove(d, tmp, xlen);
dlen -= xlen;
d += xlen;
ds = (*x)(tmp, xlen, prk, xlen, nil, nil);
}
}