ref: 3bb0b9f4ea46431189b2cae2a6c2887f786d822a
parent: 844bbecadb3a4263a183ce03021849ac41cbd20f
author: cinap_lenrek <[email protected]>
date: Wed Aug 26 01:59:42 EDT 2015
libsec: add q parameter to dh_new() for subgroup support, sanitize dh parameters
--- a/sys/include/libsec.h
+++ b/sys/include/libsec.h
@@ -447,15 +447,16 @@
{mpint *g; /* base g */
mpint *p; /* large prime */
+ mpint *q; /* subgroup prime */
mpint *x; /* random secret */
- mpint *y; /* public key y = g ^ x % p */
+ mpint *y; /* public key y = g**x % p */
};
-/* generate new public key: y = g ^ x % p */
-mpint* dh_new(DHstate *dh, mpint *p, mpint *g);
+/* generate new public key: y = g**x % p */
+mpint* dh_new(DHstate *dh, mpint *p, mpint *q, mpint *g);
-/* calculate shared key: k = pub ^ x % p */
-mpint* dh_finish(DHstate *dh, mpint *pub);
+/* calculate shared key: k = y**x % p */
+mpint* dh_finish(DHstate *dh, mpint *y);
/* password-based key derivation function 2 (RFC 2898) */
void pbkdf2_hmac_sha1(uchar *p, ulong plen, uchar *s, ulong slen, ulong rounds, uchar *d, ulong dlen);
--- a/sys/src/libsec/port/dh.c
+++ b/sys/src/libsec/port/dh.c
@@ -3,38 +3,72 @@
#include <libsec.h>
mpint*
-dh_new(DHstate *dh, mpint *p, mpint *g)
+dh_new(DHstate *dh, mpint *p, mpint *q, mpint *g)
{+ mpint *pm1;
+ int n;
+
memset(dh, 0, sizeof(*dh));
- dh->g = mpcopy(g);
+ if(mpcmp(g, mpone) <= 0)
+ return nil;
+
+ n = mpsignif(p);
+ pm1 = mpnew(n);
+ mpsub(p, mpone, pm1);
dh->p = mpcopy(p);
- if(dh->g != nil && dh->p != nil){- dh->x = mprand(mpsignif(dh->p), genrandom, nil);
- dh->y = mpnew(0);
- if(dh->x != nil && dh->y != nil){- mpexp(dh->g, dh->x, dh->p, dh->y);
- return dh->y;
- }
+ dh->g = mpcopy(g);
+ dh->q = mpcopy(q != nil ? q : pm1);
+ dh->x = mpnew(mpsignif(dh->q));
+ dh->y = mpnew(n);
+ for(;;){+ mpnrand(dh->q, genrandom, dh->x);
+ mpexp(dh->g, dh->x, dh->p, dh->y);
+ if(mpcmp(dh->y, mpone) > 0 && mpcmp(dh->y, pm1) < 0)
+ break;
}
- dh_finish(dh, nil);
- return nil;
+ mpfree(pm1);
+
+ return dh->y;
}
mpint*
-dh_finish(DHstate *dh, mpint *pub)
+dh_finish(DHstate *dh, mpint *y)
{- mpint *k;
+ mpint *k = nil;
- k = nil;
- if(pub != nil && dh->x != nil && dh->p != nil){- if((k = mpnew(0)) != nil)
- mpexp(pub, dh->x, dh->p, k);
+ if(y == nil || dh->x == nil || dh->p == nil || dh->q == nil)
+ goto Out;
+
+ /* y > 1 */
+ if(mpcmp(y, mpone) <= 0)
+ goto Out;
+
+ k = mpnew(mpsignif(dh->p));
+
+ /* y < p-1 */
+ mpsub(dh->p, mpone, k);
+ if(mpcmp(y, k) >= 0){+Bad:
+ mpfree(k);
+ k = nil;
+ goto Out;
}
- mpfree(dh->g);
+
+ /* y**q % p == 1 if q < p-1 */
+ if(mpcmp(dh->q, k) < 0){+ mpexp(y, dh->q, dh->p, k);
+ if(mpcmp(k, mpone) != 0)
+ goto Bad;
+ }
+
+ mpexp(y, dh->x, dh->p, k);
+
+Out:
mpfree(dh->p);
+ mpfree(dh->q);
+ mpfree(dh->g);
mpfree(dh->x);
mpfree(dh->y);
memset(dh, 0, sizeof(*dh));
return k;
}
-
--- a/sys/src/libsec/port/tlshand.c
+++ b/sys/src/libsec/port/tlshand.c
@@ -797,7 +797,7 @@
Y = bytestomp(Ys);
K = nil;
- if(P == nil || G == nil || Y == nil || dh_new(&dh, P, G) == nil)
+ if(P == nil || G == nil || Y == nil || dh_new(&dh, P, nil, G) == nil)
goto Out;
epm = mptobytes(dh.y);
K = dh_finish(&dh, Y);