#include <openssl/sha.h>
#include <openssl/err.h>
#include <memory.h>
-#include <assert.h>
+#include <string.h>
/*
* In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or
typedef struct
{
- char *name; // Must be unique
+ char *name; /* Must be unique */
char *peer_name;
BIGNUM *p;
BIGNUM *g;
BIGNUM *q;
- BIGNUM *gxc; // Alice's g^{x3} or Bob's g^{x1}
- BIGNUM *gxd; // Alice's g^{x4} or Bob's g^{x2}
+ BIGNUM *gxc; /* Alice's g^{x3} or Bob's g^{x1} */
+ BIGNUM *gxd; /* Alice's g^{x4} or Bob's g^{x2} */
} JPAKE_CTX_PUBLIC;
struct JPAKE_CTX
{
JPAKE_CTX_PUBLIC p;
- BIGNUM *secret; // The shared secret
+ BIGNUM *secret; /* The shared secret */
BN_CTX *ctx;
- BIGNUM *xa; // Alice's x1 or Bob's x3
- BIGNUM *xb; // Alice's x2 or Bob's x4
- BIGNUM *key; // The calculated (shared) key
+ BIGNUM *xa; /* Alice's x1 or Bob's x3 */
+ BIGNUM *xb; /* Alice's x2 or Bob's x4 */
+ BIGNUM *key; /* The calculated (shared) key */
};
static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
BN_free(zkp->gr);
}
-// Two birds with one stone - make the global name as expected
+/* Two birds with one stone - make the global name as expected */
#define JPAKE_STEP_PART_init JPAKE_STEP2_init
#define JPAKE_STEP_PART_release JPAKE_STEP2_release
{
unsigned char b[2];
- assert(l <= 0xffff);
+ OPENSSL_assert(l <= 0xffff);
b[0] = l >> 8;
b[1] = l&0xff;
SHA1_Update(sha, b, 2);
static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
{
size_t l = BN_num_bytes(bn);
- unsigned char *bin = alloca(l);
+ unsigned char *bin = OPENSSL_malloc(l);
hashlength(sha, l);
BN_bn2bin(bn, bin);
SHA1_Update(sha, bin, l);
+ OPENSSL_free(bin);
}
-// h=hash(g, g^r, g^x, name)
+/* h=hash(g, g^r, g^x, name) */
static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
const char *proof_name)
{
unsigned char md[SHA_DIGEST_LENGTH];
SHA_CTX sha;
- // XXX: hash should not allow moving of the boundaries - Java code
- // is flawed in this respect. Length encoding seems simplest.
+ /*
+ * XXX: hash should not allow moving of the boundaries - Java code
+ * is flawed in this respect. Length encoding seems simplest.
+ */
SHA1_Init(&sha);
hashbn(&sha, zkpg);
- assert(!BN_is_zero(p->zkpx.gr));
+ OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
hashbn(&sha, p->zkpx.gr);
hashbn(&sha, p->gx);
hashstring(&sha, proof_name);
BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
}
-// Prove knowledge of x
-// Note that p->gx has already been calculated
+/*
+ * Prove knowledge of x
+ * Note that p->gx has already been calculated
+ */
static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
const BIGNUM *zkpg, JPAKE_CTX *ctx)
{
BIGNUM *h = BN_new();
BIGNUM *t = BN_new();
- // r in [0,q)
- // XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
+ /*-
+ * r in [0,q)
+ * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
+ */
BN_rand_range(r, ctx->p.q);
- // g^r
+ /* g^r */
BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
- // h=hash...
+ /* h=hash... */
zkp_hash(h, zkpg, p, ctx->p.name);
- // b = r - x*h
+ /* b = r - x*h */
BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
- // cleanup
+ /* cleanup */
BN_free(t);
BN_free(h);
BN_free(r);
zkp_hash(h, zkpg, p, ctx->p.peer_name);
- // t1 = g^b
+ /* t1 = g^b */
BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
- // t2 = (g^x)^h = g^{hx}
+ /* t2 = (g^x)^h = g^{hx} */
BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
- // t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly)
+ /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
- // verify t3 == g^r
+ /* verify t3 == g^r */
if(BN_cmp(t3, p->zkpx.gr) == 0)
ret = 1;
else
JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
- // cleanup
+ /* cleanup */
BN_free(t3);
BN_free(t2);
BN_free(t1);
generate_zkp(p, x, g, ctx);
}
-// Generate each party's random numbers. xa is in [0, q), xb is in [1, q).
+/* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
static void genrand(JPAKE_CTX *ctx)
{
BIGNUM *qm1;
- // xa in [0, q)
+ /* xa in [0, q) */
BN_rand_range(ctx->xa, ctx->p.q);
- // q-1
+ /* q-1 */
qm1 = BN_new();
BN_copy(qm1, ctx->p.q);
BN_sub_word(qm1, 1);
- // ... and xb in [0, q-1)
+ /* ... and xb in [0, q-1) */
BN_rand_range(ctx->xb, qm1);
- // [1, q)
+ /* [1, q) */
BN_add_word(ctx->xb, 1);
- // cleanup
+ /* cleanup */
BN_free(qm1);
}
return 1;
}
+/* g^x is a legal value */
+static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
+ {
+ BIGNUM *t;
+ int res;
+
+ if(BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
+ return 0;
+
+ t = BN_new();
+ BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
+ res = BN_is_one(t);
+ BN_free(t);
+
+ return res;
+ }
+
int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
{
- // verify their ZKP(xc)
+ if(!is_legal(received->p1.gx, ctx))
+ {
+ JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
+ return 0;
+ }
+
+ if(!is_legal(received->p2.gx, ctx))
+ {
+ JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
+ return 0;
+ }
+
+ /* verify their ZKP(xc) */
if(!verify_zkp(&received->p1, ctx->p.g, ctx))
{
JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
return 0;
}
- // verify their ZKP(xd)
+ /* verify their ZKP(xd) */
if(!verify_zkp(&received->p2, ctx->p.g, ctx))
{
JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
return 0;
}
- // g^xd != 1
+ /* g^xd != 1 */
if(BN_is_one(received->p2.gx))
{
JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
return 0;
}
- // Save the bits we need for later
+ /* Save the bits we need for later */
BN_copy(ctx->p.gxc, received->p1.gx);
BN_copy(ctx->p.gxd, received->p2.gx);
BIGNUM *t1 = BN_new();
BIGNUM *t2 = BN_new();
- // X = g^{(xa + xc + xd) * xb * s}
- // t1 = g^xa
+ /*-
+ * X = g^{(xa + xc + xd) * xb * s}
+ * t1 = g^xa
+ */
BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
- // t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc}
+ /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
- // t1 = t2 * g^{xd} = g^{xa + xc + xd}
+ /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
- // t2 = xb * s
+ /* t2 = xb * s */
BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
- // ZKP(xb * s)
- // XXX: this is kinda funky, because we're using
- //
- // g' = g^{xa + xc + xd}
- //
- // as the generator, which means X is g'^{xb * s}
- // X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
+ /*-
+ * ZKP(xb * s)
+ * XXX: this is kinda funky, because we're using
+ *
+ * g' = g^{xa + xc + xd}
+ *
+ * as the generator, which means X is g'^{xb * s}
+ * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
+ */
generate_step_part(send, t2, t1, ctx);
- // cleanup
+ /* cleanup */
BN_free(t1);
BN_free(t2);
return 1;
}
-// gx = g^{xc + xa + xb} * xd * s
+/* gx = g^{xc + xa + xb} * xd * s */
static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
{
BIGNUM *t1 = BN_new();
BIGNUM *t2 = BN_new();
BIGNUM *t3 = BN_new();
- // K = (gx/g^{xb * xd * s})^{xb}
- // = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
- // = (g^{(xa + xc) * xd * s})^{xb}
- // = g^{(xa + xc) * xb * xd * s}
- // [which is the same regardless of who calculates it]
+ /*-
+ * K = (gx/g^{xb * xd * s})^{xb}
+ * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
+ * = (g^{(xa + xc) * xd * s})^{xb}
+ * = g^{(xa + xc) * xb * xd * s}
+ * [which is the same regardless of who calculates it]
+ */
- // t1 = (g^{xd})^{xb} = g^{xb * xd}
+ /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
- // t2 = -s = q-s
+ /* t2 = -s = q-s */
BN_sub(t2, ctx->p.q, ctx->secret);
- // t3 = t1^t2 = g^{-xb * xd * s}
+ /* t3 = t1^t2 = g^{-xb * xd * s} */
BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
- // t1 = gx * t3 = X/g^{xb * xd * s}
+ /* t1 = gx * t3 = X/g^{xb * xd * s} */
BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
- // K = t1^{xb}
+ /* K = t1^{xb} */
BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
- // cleanup
+ /* cleanup */
BN_free(t3);
BN_free(t2);
BN_free(t1);
BIGNUM *t2 = BN_new();
int ret = 0;
- // g' = g^{xc + xa + xb} [from our POV]
- // t1 = xa + xb
+ /*-
+ * g' = g^{xc + xa + xb} [from our POV]
+ * t1 = xa + xb
+ */
BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
- // t2 = g^{t1} = g^{xa+xb}
+ /* t2 = g^{t1} = g^{xa+xb} */
BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
- // t1 = g^{xc} * t2 = g^{xc + xa + xb}
+ /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
if(verify_zkp(received, t1, ctx))
compute_key(ctx, received->gx);
- // cleanup
+ /* cleanup */
BN_free(t2);
BN_free(t1);
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