ref: 52d407f86f35b4a9f2be36c6d61032e2ecb9f754
dir: /sys/src/libsec/port/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); } }