--- /dev/null
+#include "jpake.h"
+
+#include <openssl/crypto.h>
+#include <openssl/sha.h>
+#include <openssl/err.h>
+#include <memory.h>
+
+/*
+ * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or
+ * Bob's (x3, x4, x1, x2). If you see what I mean.
+ */
+
+typedef struct
+ {
+ 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} */
+ } JPAKE_CTX_PUBLIC;
+
+struct JPAKE_CTX
+ {
+ JPAKE_CTX_PUBLIC p;
+ 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 */
+ };
+
+static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
+ {
+ zkp->gr = BN_new();
+ zkp->b = BN_new();
+ }
+
+static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
+ {
+ BN_free(zkp->b);
+ BN_free(zkp->gr);
+ }
+
+/* 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
+
+void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
+ {
+ p->gx = BN_new();
+ JPAKE_ZKP_init(&p->zkpx);
+ }
+
+void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
+ {
+ JPAKE_ZKP_release(&p->zkpx);
+ BN_free(p->gx);
+ }
+
+void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
+ {
+ JPAKE_STEP_PART_init(&s1->p1);
+ JPAKE_STEP_PART_init(&s1->p2);
+ }
+
+void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
+ {
+ JPAKE_STEP_PART_release(&s1->p2);
+ JPAKE_STEP_PART_release(&s1->p1);
+ }
+
+static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name,
+ const char *peer_name, const BIGNUM *p,
+ const BIGNUM *g, const BIGNUM *q,
+ const BIGNUM *secret)
+ {
+ ctx->p.name = OPENSSL_strdup(name);
+ ctx->p.peer_name = OPENSSL_strdup(peer_name);
+ ctx->p.p = BN_dup(p);
+ ctx->p.g = BN_dup(g);
+ ctx->p.q = BN_dup(q);
+ ctx->secret = BN_dup(secret);
+
+ ctx->p.gxc = BN_new();
+ ctx->p.gxd = BN_new();
+
+ ctx->xa = BN_new();
+ ctx->xb = BN_new();
+ ctx->key = BN_new();
+ ctx->ctx = BN_CTX_new();
+ }
+
+static void JPAKE_CTX_release(JPAKE_CTX *ctx)
+ {
+ BN_CTX_free(ctx->ctx);
+ BN_clear_free(ctx->key);
+ BN_clear_free(ctx->xb);
+ BN_clear_free(ctx->xa);
+
+ BN_free(ctx->p.gxd);
+ BN_free(ctx->p.gxc);
+
+ BN_clear_free(ctx->secret);
+ BN_free(ctx->p.q);
+ BN_free(ctx->p.g);
+ BN_free(ctx->p.p);
+ OPENSSL_free(ctx->p.peer_name);
+ OPENSSL_free(ctx->p.name);
+
+ memset(ctx, '\0', sizeof *ctx);
+ }
+
+JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name,
+ const BIGNUM *p, const BIGNUM *g, const BIGNUM *q,
+ const BIGNUM *secret)
+ {
+ JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
+
+ JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
+
+ return ctx;
+ }
+
+void JPAKE_CTX_free(JPAKE_CTX *ctx)
+ {
+ JPAKE_CTX_release(ctx);
+ OPENSSL_free(ctx);
+ }
+
+static void hashlength(SHA_CTX *sha, size_t l)
+ {
+ unsigned char b[2];
+
+ OPENSSL_assert(l <= 0xffff);
+ b[0] = l >> 8;
+ b[1] = l&0xff;
+ SHA1_Update(sha, b, 2);
+ }
+
+static void hashstring(SHA_CTX *sha, const char *string)
+ {
+ size_t l = strlen(string);
+
+ hashlength(sha, l);
+ SHA1_Update(sha, string, l);
+ }
+
+static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
+ {
+ size_t l = BN_num_bytes(bn);
+ 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) */
+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.
+ */
+ SHA1_Init(&sha);
+ hashbn(&sha, zkpg);
+ OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
+ hashbn(&sha, p->zkpx.gr);
+ hashbn(&sha, p->gx);
+ hashstring(&sha, proof_name);
+ SHA1_Final(md, &sha);
+ BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
+ }
+
+/*
+ * 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 *r = BN_new();
+ 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
+ */
+ BN_rand_range(r, ctx->p.q);
+ /* g^r */
+ BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
+
+ /* h=hash... */
+ zkp_hash(h, zkpg, p, ctx->p.name);
+
+ /* 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 */
+ BN_free(t);
+ BN_free(h);
+ BN_free(r);
+ }
+
+static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
+ JPAKE_CTX *ctx)
+ {
+ BIGNUM *h = BN_new();
+ BIGNUM *t1 = BN_new();
+ BIGNUM *t2 = BN_new();
+ BIGNUM *t3 = BN_new();
+ int ret = 0;
+
+ zkp_hash(h, zkpg, p, ctx->p.peer_name);
+
+ /* t1 = g^b */
+ BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
+ /* 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) */
+ BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
+
+ /* 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 */
+ BN_free(t3);
+ BN_free(t2);
+ BN_free(t1);
+ BN_free(h);
+
+ return ret;
+ }
+
+static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
+ const BIGNUM *g, JPAKE_CTX *ctx)
+ {
+ BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
+ generate_zkp(p, x, g, ctx);
+ }
+
+/* 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) */
+ BN_rand_range(ctx->xa, ctx->p.q);
+
+ /* q-1 */
+ qm1 = BN_new();
+ BN_copy(qm1, ctx->p.q);
+ BN_sub_word(qm1, 1);
+
+ /* ... and xb in [0, q-1) */
+ BN_rand_range(ctx->xb, qm1);
+ /* [1, q) */
+ BN_add_word(ctx->xb, 1);
+
+ /* cleanup */
+ BN_free(qm1);
+ }
+
+int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
+ {
+ genrand(ctx);
+ generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
+ generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
+
+ 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)
+ {
+ 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) */
+ 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 */
+ 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 */
+ BN_copy(ctx->p.gxc, received->p1.gx);
+ BN_copy(ctx->p.gxd, received->p2.gx);
+
+ return 1;
+ }
+
+
+int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
+ {
+ BIGNUM *t1 = BN_new();
+ BIGNUM *t2 = BN_new();
+
+ /*
+ * 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} */
+ BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
+ /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
+ BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
+ /* 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}
+ */
+ generate_step_part(send, t2, t1, ctx);
+
+ /* cleanup */
+ BN_free(t1);
+ BN_free(t2);
+
+ return 1;
+ }
+
+/* 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]
+ */
+
+ /* 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 */
+ BN_sub(t2, ctx->p.q, ctx->secret);
+ /* 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} */
+ BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
+ /* K = t1^{xb} */
+ BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
+
+ /* cleanup */
+ BN_free(t3);
+ BN_free(t2);
+ BN_free(t1);
+
+ return 1;
+ }
+
+int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
+ {
+ BIGNUM *t1 = BN_new();
+ BIGNUM *t2 = BN_new();
+ int ret = 0;
+
+ /*
+ * 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} */
+ BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
+ /* 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))
+ ret = 1;
+ else
+ JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
+
+ compute_key(ctx, received->gx);
+
+ /* cleanup */
+ BN_free(t2);
+ BN_free(t1);
+
+ return ret;
+ }
+
+static void quickhashbn(unsigned char *md, const BIGNUM *bn)
+ {
+ SHA_CTX sha;
+
+ SHA1_Init(&sha);
+ hashbn(&sha, bn);
+ SHA1_Final(md, &sha);
+ }
+
+void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
+ {}
+
+int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
+ {
+ quickhashbn(send->hhk, ctx->key);
+ SHA1(send->hhk, sizeof send->hhk, send->hhk);
+
+ return 1;
+ }
+
+int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
+ {
+ unsigned char hhk[SHA_DIGEST_LENGTH];
+
+ quickhashbn(hhk, ctx->key);
+ SHA1(hhk, sizeof hhk, hhk);
+ if(memcmp(hhk, received->hhk, sizeof hhk))
+ {
+ JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
+ return 0;
+ }
+ return 1;
+ }
+
+void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
+ {}
+
+void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
+ {}
+
+int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
+ {
+ quickhashbn(send->hk, ctx->key);
+
+ return 1;
+ }
+
+int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
+ {
+ unsigned char hk[SHA_DIGEST_LENGTH];
+
+ quickhashbn(hk, ctx->key);
+ if(memcmp(hk, received->hk, sizeof hk))
+ {
+ JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
+ return 0;
+ }
+ return 1;
+ }
+
+void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
+ {}
+
+const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)
+ {
+ return ctx->key;
+ }
+
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