The Tor Browser: security/nss/lib/freebl/dh.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/dh.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/dh.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * Diffie-Hellman parameter generation, key generation, and secret derivation.
  * KEA secret generation and verification.
  */
 #ifdef FREEBL_NO_DEPEND
 #include "stubs.h"
 #endif
 #include "prerr.h"
 #include "secerr.h"
 #include "blapi.h"
 #include "secitem.h"
 #include "mpi.h"
 #include "mpprime.h"
 #include "secmpi.h"
 #define KEA_DERIVED_SECRET_LEN 128
 /* Lengths are in bytes. */
 static unsigned int
 dh_GetSecretKeyLen(unsigned int primeLen)
 {
     /* Based on Table 2 in NIST SP 800-57. */
     if (primeLen >= 1920) { /* 15360 bits */
         return 64;  /* 512 bits */
     }
     if (primeLen >= 960) { /* 7680 bits */
         return 48;  /* 384 bits */
     }
     if (primeLen >= 384) { /* 3072 bits */
         return 32;  /* 256 bits */
     }
     if (primeLen >= 256) { /* 2048 bits */
         return 28;  /* 224 bits */
     }
     return 20;  /* 160 bits */
 }
 SECStatus
 DH_GenParam(int primeLen, DHParams **params)
 {
     PLArenaPool *arena;
     DHParams *dhparams;
     unsigned char *pb = NULL;
     unsigned char *ab = NULL;
     unsigned long counter = 0;
     mp_int p, q, a, h, psub1, test;
     mp_err err = MP_OKAY;
     SECStatus rv = SECSuccess;
     if (!params || primeLen < 0) {
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
     }
     arena = PORT_NewArena(NSS_FREEBL_DEFAULT_CHUNKSIZE);
     if (!arena) {
 	PORT_SetError(SEC_ERROR_NO_MEMORY);
 	return SECFailure;
     }
     dhparams = (DHParams *)PORT_ArenaZAlloc(arena, sizeof(DHParams));
     if (!dhparams) {
 	PORT_SetError(SEC_ERROR_NO_MEMORY);
 	PORT_FreeArena(arena, PR_TRUE);
 	return SECFailure;
     }
     dhparams->arena = arena;
     MP_DIGITS(&p) = 0;
     MP_DIGITS(&q) = 0;
     MP_DIGITS(&a) = 0;
     MP_DIGITS(&h) = 0;
     MP_DIGITS(&psub1) = 0;
     MP_DIGITS(&test) = 0;
     CHECK_MPI_OK( mp_init(&p) );
     CHECK_MPI_OK( mp_init(&q) );
     CHECK_MPI_OK( mp_init(&a) );
     CHECK_MPI_OK( mp_init(&h) );
     CHECK_MPI_OK( mp_init(&psub1) );
     CHECK_MPI_OK( mp_init(&test) );
     /* generate prime with MPI, uses Miller-Rabin to generate strong prime. */
     pb = PORT_Alloc(primeLen);
     CHECK_SEC_OK( RNG_GenerateGlobalRandomBytes(pb, primeLen) );
     pb[0]          |= 0x80; /* set high-order bit */
     pb[primeLen-1] |= 0x01; /* set low-order bit  */
     CHECK_MPI_OK( mp_read_unsigned_octets(&p, pb, primeLen) );
     CHECK_MPI_OK( mpp_make_prime(&p, primeLen * 8, PR_TRUE, &counter) );
     /* construct Sophie-Germain prime q = (p-1)/2. */
     CHECK_MPI_OK( mp_sub_d(&p, 1, &psub1) );
     CHECK_MPI_OK( mp_div_2(&psub1, &q)    );
     /* construct a generator from the prime. */
     ab = PORT_Alloc(primeLen);
     /* generate a candidate number a in p's field */
     CHECK_SEC_OK( RNG_GenerateGlobalRandomBytes(ab, primeLen) );
     CHECK_MPI_OK( mp_read_unsigned_octets(&a, ab, primeLen) );
     /* force a < p (note that quot(a/p) <= 1) */
     if ( mp_cmp(&a, &p) > 0 )
 	CHECK_MPI_OK( mp_sub(&a, &p, &a) );
     do {
 	/* check that a is in the range [2..p-1] */
 	if ( mp_cmp_d(&a, 2) < 0 || mp_cmp(&a, &psub1) >= 0) {
 	    /* a is outside of the allowed range.  Set a=3 and keep going. */
             mp_set(&a, 3);
 	}
 	/* if a**q mod p != 1 then a is a generator */
 	CHECK_MPI_OK( mp_exptmod(&a, &q, &p, &test) );
 	if ( mp_cmp_d(&test, 1) != 0 )
 	    break;
 	/* increment the candidate and try again. */
 	CHECK_MPI_OK( mp_add_d(&a, 1, &a) );
     } while (PR_TRUE);
     MPINT_TO_SECITEM(&p, &dhparams->prime, arena);
     MPINT_TO_SECITEM(&a, &dhparams->base, arena);
     *params = dhparams;
 cleanup:
     mp_clear(&p);
     mp_clear(&q);
     mp_clear(&a);
     mp_clear(&h);
     mp_clear(&psub1);
     mp_clear(&test);
     if (pb) PORT_ZFree(pb, primeLen);
     if (ab) PORT_ZFree(ab, primeLen);
     if (err) {
 	MP_TO_SEC_ERROR(err);
 	rv = SECFailure;
     }
     if (rv)
 	PORT_FreeArena(arena, PR_TRUE);
     return rv;
 }
 SECStatus
 DH_NewKey(DHParams *params, DHPrivateKey **privKey)
 {
     PLArenaPool *arena;
     DHPrivateKey *key;
     mp_int g, xa, p, Ya;
     mp_err   err = MP_OKAY;
     SECStatus rv = SECSuccess;
     if (!params || !privKey) {
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
     }
     arena = PORT_NewArena(NSS_FREEBL_DEFAULT_CHUNKSIZE);
     if (!arena) {
 	PORT_SetError(SEC_ERROR_NO_MEMORY);
 	return SECFailure;
     }
     key = (DHPrivateKey *)PORT_ArenaZAlloc(arena, sizeof(DHPrivateKey));
     if (!key) {
 	PORT_SetError(SEC_ERROR_NO_MEMORY);
 	PORT_FreeArena(arena, PR_TRUE);
 	return SECFailure;
     }
     key->arena = arena;
     MP_DIGITS(&g)  = 0;
     MP_DIGITS(&xa) = 0;
     MP_DIGITS(&p)  = 0;
     MP_DIGITS(&Ya) = 0;
     CHECK_MPI_OK( mp_init(&g)  );
     CHECK_MPI_OK( mp_init(&xa) );
     CHECK_MPI_OK( mp_init(&p)  );
     CHECK_MPI_OK( mp_init(&Ya) );
     /* Set private key's p */
     CHECK_SEC_OK( SECITEM_CopyItem(arena, &key->prime, &params->prime) );
     SECITEM_TO_MPINT(key->prime, &p);
     /* Set private key's g */
     CHECK_SEC_OK( SECITEM_CopyItem(arena, &key->base, &params->base) );
     SECITEM_TO_MPINT(key->base, &g);
     /* Generate private key xa */
     SECITEM_AllocItem(arena, &key->privateValue,
                       dh_GetSecretKeyLen(params->prime.len));
     RNG_GenerateGlobalRandomBytes(key->privateValue.data,
                                   key->privateValue.len);
     SECITEM_TO_MPINT( key->privateValue, &xa );
     /* xa < p */
     CHECK_MPI_OK( mp_mod(&xa, &p, &xa) );
     /* Compute public key Ya = g ** xa mod p */
     CHECK_MPI_OK( mp_exptmod(&g, &xa, &p, &Ya) );
     MPINT_TO_SECITEM(&Ya, &key->publicValue, key->arena);
     *privKey = key;
 cleanup:
     mp_clear(&g);
     mp_clear(&xa);
     mp_clear(&p);
     mp_clear(&Ya);
     if (err) {
 	MP_TO_SEC_ERROR(err);
 	rv = SECFailure;
     }
     if (rv)
 	PORT_FreeArena(arena, PR_TRUE);
     return rv;
 }
 SECStatus
 DH_Derive(SECItem *publicValue,
           SECItem *prime,
           SECItem *privateValue,
           SECItem *derivedSecret,
           unsigned int outBytes)
 {
     mp_int p, Xa, Yb, ZZ, psub1;
     mp_err err = MP_OKAY;
     int len = 0;
     unsigned int nb;
     unsigned char *secret = NULL;
     if (!publicValue || !prime || !privateValue || !derivedSecret) {
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
     }
     memset(derivedSecret, 0, sizeof *derivedSecret);
     MP_DIGITS(&p)  = 0;
     MP_DIGITS(&Xa) = 0;
     MP_DIGITS(&Yb) = 0;
     MP_DIGITS(&ZZ) = 0;
     MP_DIGITS(&psub1) = 0;
     CHECK_MPI_OK( mp_init(&p)  );
     CHECK_MPI_OK( mp_init(&Xa) );
     CHECK_MPI_OK( mp_init(&Yb) );
     CHECK_MPI_OK( mp_init(&ZZ) );
     CHECK_MPI_OK( mp_init(&psub1) );
     SECITEM_TO_MPINT(*publicValue,  &Yb);
     SECITEM_TO_MPINT(*privateValue, &Xa);
     SECITEM_TO_MPINT(*prime,        &p);
     CHECK_MPI_OK( mp_sub_d(&p, 1, &psub1) );
     /* We assume that the modulus, p, is a safe prime. That is, p = 2q+1 where
      * q is also a prime. Thus the orders of the subgroups are factors of 2q:
      * namely 1, 2, q and 2q.
      *
      * We check that the peer's public value isn't zero (which isn't in the
      * group), one (subgroup of order one) or p-1 (subgroup of order 2). We
      * also check that the public value is less than p, to avoid being fooled
      * by values like p+1 or 2*p-1.
      *
      * Thus we must be operating in the subgroup of size q or 2q. */
     if (mp_cmp_d(&Yb, 1) <= 0 ||
 	mp_cmp(&Yb, &psub1) >= 0) {
 	err = MP_BADARG;
 	goto cleanup;
     }
     /* ZZ = (Yb)**Xa mod p */
     CHECK_MPI_OK( mp_exptmod(&Yb, &Xa, &p, &ZZ) );
     /* number of bytes in the derived secret */
     len = mp_unsigned_octet_size(&ZZ);
     if (len <= 0) {
         err = MP_BADARG;
         goto cleanup;
     }
     /* allocate a buffer which can hold the entire derived secret. */
     secret = PORT_Alloc(len);
     /* grab the derived secret */
     err = mp_to_unsigned_octets(&ZZ, secret, len);
     if (err >= 0) err = MP_OKAY;
     /*
     ** if outBytes is 0 take all of the bytes from the derived secret.
     ** if outBytes is not 0 take exactly outBytes from the derived secret, zero
     ** pad at the beginning if necessary, and truncate beginning bytes
     ** if necessary.
     */
     if (outBytes > 0)
 	nb = outBytes;
     else
 	nb = len;
     SECITEM_AllocItem(NULL, derivedSecret, nb);
     if (len < nb) {
 	unsigned int offset = nb - len;
 	memset(derivedSecret->data, 0, offset);
 	memcpy(derivedSecret->data + offset, secret, len);
     } else {
 	memcpy(derivedSecret->data, secret + len - nb, nb);
     }
 cleanup:
     mp_clear(&p);
     mp_clear(&Xa);
     mp_clear(&Yb);
     mp_clear(&ZZ);
     mp_clear(&psub1);
     if (secret) {
 	/* free the buffer allocated for the full secret. */
 	PORT_ZFree(secret, len);
     }
     if (err) {
 	MP_TO_SEC_ERROR(err);
 	if (derivedSecret->data)
 	    PORT_ZFree(derivedSecret->data, derivedSecret->len);
 	return SECFailure;
     }
     return SECSuccess;
 }
 SECStatus
 KEA_Derive(SECItem *prime,
            SECItem *public1,
            SECItem *public2,
            SECItem *private1,
            SECItem *private2,
            SECItem *derivedSecret)
 {
     mp_int p, Y, R, r, x, t, u, w;
     mp_err err;
     unsigned char *secret = NULL;
     unsigned int len = 0, offset;
     if (!prime || !public1 || !public2 || !private1 || !private2 ||
         !derivedSecret) {
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
     }
     memset(derivedSecret, 0, sizeof *derivedSecret);
     MP_DIGITS(&p) = 0;
     MP_DIGITS(&Y) = 0;
     MP_DIGITS(&R) = 0;
     MP_DIGITS(&r) = 0;
     MP_DIGITS(&x) = 0;
     MP_DIGITS(&t) = 0;
     MP_DIGITS(&u) = 0;
     MP_DIGITS(&w) = 0;
     CHECK_MPI_OK( mp_init(&p) );
     CHECK_MPI_OK( mp_init(&Y) );
     CHECK_MPI_OK( mp_init(&R) );
     CHECK_MPI_OK( mp_init(&r) );
     CHECK_MPI_OK( mp_init(&x) );
     CHECK_MPI_OK( mp_init(&t) );
     CHECK_MPI_OK( mp_init(&u) );
     CHECK_MPI_OK( mp_init(&w) );
     SECITEM_TO_MPINT(*prime,    &p);
     SECITEM_TO_MPINT(*public1,  &Y);
     SECITEM_TO_MPINT(*public2,  &R);
     SECITEM_TO_MPINT(*private1, &r);
     SECITEM_TO_MPINT(*private2, &x);
     /* t = DH(Y, r, p) = Y ** r mod p */
     CHECK_MPI_OK( mp_exptmod(&Y, &r, &p, &t) );
     /* u = DH(R, x, p) = R ** x mod p */
     CHECK_MPI_OK( mp_exptmod(&R, &x, &p, &u) );
     /* w = (t + u) mod p */
     CHECK_MPI_OK( mp_addmod(&t, &u, &p, &w) );
     /* allocate a buffer for the full derived secret */
     len = mp_unsigned_octet_size(&w);
     secret = PORT_Alloc(len);
     /* grab the secret */
     err = mp_to_unsigned_octets(&w, secret, len);
     if (err > 0) err = MP_OKAY;
     /* allocate output buffer */
     SECITEM_AllocItem(NULL, derivedSecret, KEA_DERIVED_SECRET_LEN);
     memset(derivedSecret->data, 0, derivedSecret->len);
     /* copy in the 128 lsb of the secret */
     if (len >= KEA_DERIVED_SECRET_LEN) {
 	memcpy(derivedSecret->data, secret + (len - KEA_DERIVED_SECRET_LEN),
 	       KEA_DERIVED_SECRET_LEN);
     } else {
 	offset = KEA_DERIVED_SECRET_LEN - len;
 	memcpy(derivedSecret->data + offset, secret, len);
     }
 cleanup:
     mp_clear(&p);
     mp_clear(&Y);
     mp_clear(&R);
     mp_clear(&r);
     mp_clear(&x);
     mp_clear(&t);
     mp_clear(&u);
     mp_clear(&w);
     if (secret)
 	PORT_ZFree(secret, len);
     if (err) {
 	MP_TO_SEC_ERROR(err);
 	return SECFailure;
     }
     return SECSuccess;
 }
 PRBool
 KEA_Verify(SECItem *Y, SECItem *prime, SECItem *subPrime)
 {
     mp_int p, q, y, r;
     mp_err err;
     int cmp = 1;  /* default is false */
     if (!Y || !prime || !subPrime) {
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
     }
     MP_DIGITS(&p) = 0;
     MP_DIGITS(&q) = 0;
     MP_DIGITS(&y) = 0;
     MP_DIGITS(&r) = 0;
     CHECK_MPI_OK( mp_init(&p) );
     CHECK_MPI_OK( mp_init(&q) );
     CHECK_MPI_OK( mp_init(&y) );
     CHECK_MPI_OK( mp_init(&r) );
     SECITEM_TO_MPINT(*prime,    &p);
     SECITEM_TO_MPINT(*subPrime, &q);
     SECITEM_TO_MPINT(*Y,        &y);
     /* compute r = y**q mod p */
     CHECK_MPI_OK( mp_exptmod(&y, &q, &p, &r) );
     /* compare to 1 */
     cmp = mp_cmp_d(&r, 1);
 cleanup:
     mp_clear(&p);
     mp_clear(&q);
     mp_clear(&y);
     mp_clear(&r);
     if (err) {
 	MP_TO_SEC_ERROR(err);
 	return PR_FALSE;
     }
     return (cmp == 0) ? PR_TRUE : PR_FALSE;
 }

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security/nss/lib/freebl/dh.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/dh.c