Subversion Repositories planix.SVN

#include "os.h"
#include <libsec.h>

static void
ccpolyotk(Chachastate *cs, DigestState *ds)
{
        uchar otk[ChachaBsize];

        memset(ds, 0, sizeof(*ds));
        memset(otk, 0, 32);
        chacha_setblock(cs, 0);
        chacha_encrypt(otk, ChachaBsize, cs);
        poly1305(nil, 0, otk, 32, nil, ds);
}

static void
ccpolypad(uchar *buf, ulong nbuf, DigestState *ds)
{
        static uchar zeros[16] = {0};
        ulong npad;

        if(nbuf == 0)
                return;
        poly1305(buf, nbuf, nil, 0, nil, ds);
        npad = nbuf % 16;
        if(npad == 0)
                return;
        poly1305(zeros, 16 - npad, nil, 0, nil, ds);
}

static void
ccpolylen(ulong n, uchar tag[16], DigestState *ds)
{
        uchar info[8];

        info[0] = n;
        info[1] = n>>8;
        info[2] = n>>16;
        info[3] = n>>24;
        info[4] = 0;
        info[5] = 0;
        info[6] = 0;
        info[7] = 0;
        poly1305(info, 8, nil, 0, tag, ds);
}

void
ccpoly_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs)
{
        DigestState ds;

        ccpolyotk(cs, &ds);
        if(cs->ivwords == 2){
                poly1305(aad, naad, nil, 0, nil, &ds);
                ccpolylen(naad, nil, &ds);
                chacha_encrypt(dat, ndat, cs);
                poly1305(dat, ndat, nil, 0, nil, &ds);
                ccpolylen(ndat, tag, &ds);
        } else {
                ccpolypad(aad, naad, &ds);
                chacha_encrypt(dat, ndat, cs);
                ccpolypad(dat, ndat, &ds);
                ccpolylen(naad, nil, &ds);
                ccpolylen(ndat, tag, &ds);
        }
}

int
ccpoly_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs)
{
        DigestState ds;
        uchar tmp[16];

        ccpolyotk(cs, &ds);
        if(cs->ivwords == 2){
                poly1305(aad, naad, nil, 0, nil, &ds);
                ccpolylen(naad, nil, &ds);
                poly1305(dat, ndat, nil, 0, nil, &ds);
                ccpolylen(ndat, tmp, &ds);
        } else {
                ccpolypad(aad, naad, &ds);
                ccpolypad(dat, ndat, &ds);
                ccpolylen(naad, nil, &ds);
                ccpolylen(ndat, tmp, &ds);
        }
        if(tsmemcmp(tag, tmp, 16) != 0)
                return -1;
        chacha_encrypt(dat, ndat, cs);
        return 0;
}