From efed63d7839cf5bf6113efcd296ebeabc1cbcbe4 Mon Sep 17 00:00:00 2001
From: Ben Laurie <ben@openssl.org>
Date: Fri, 26 Nov 2010 16:03:23 +0000
Subject: [PATCH] Backport J-PAKE fix.

---
 CHANGES                  |  5 ++++-
 crypto/jpake/jpake.c     | 36 +++++++++++++++++++++++++++++++++---
 crypto/jpake/jpake.h     |  2 ++
 crypto/jpake/jpake_err.c |  4 +++-
 4 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/CHANGES b/CHANGES
index 4f98cec905..2b096100bc 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,7 +4,10 @@
 
  Changes between 0.9.8p and 0.9.8q [xx XXX xxxx]
 
-  *)
+  *) Fixed J-PAKE implementation error, originally discovered by
+     Sebastien Martini, further info and confirmation from Stefan
+     Arentz and Feng Hao. Note that this fix is a security fix.
+     [Ben Laurie]
 
  Changes between 0.9.8o and 0.9.8p [16 Nov 2010]
 
diff --git a/crypto/jpake/jpake.c b/crypto/jpake/jpake.c
index 577b7ef375..9736f89854 100644
--- a/crypto/jpake/jpake.c
+++ b/crypto/jpake/jpake.c
@@ -283,23 +283,53 @@ int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *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)
     {
-   /* 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);
diff --git a/crypto/jpake/jpake.h b/crypto/jpake/jpake.h
index 693ea188cb..fd143b4d9b 100644
--- a/crypto/jpake/jpake.h
+++ b/crypto/jpake/jpake.h
@@ -115,6 +115,8 @@ void ERR_load_JPAKE_strings(void);
 #define JPAKE_F_VERIFY_ZKP				 100
 
 /* Reason codes. */
+#define JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL		 108
+#define JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL		 109
 #define JPAKE_R_G_TO_THE_X4_IS_ONE			 105
 #define JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH		 106
 #define JPAKE_R_HASH_OF_KEY_MISMATCH			 107
diff --git a/crypto/jpake/jpake_err.c b/crypto/jpake/jpake_err.c
index 1b95067967..a9a9dee75c 100644
--- a/crypto/jpake/jpake_err.c
+++ b/crypto/jpake/jpake_err.c
@@ -1,6 +1,6 @@
 /* crypto/jpake/jpake_err.c */
 /* ====================================================================
- * Copyright (c) 1999-2008 The OpenSSL Project.  All rights reserved.
+ * Copyright (c) 1999-2010 The OpenSSL Project.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -80,6 +80,8 @@ static ERR_STRING_DATA JPAKE_str_functs[]=
 
 static ERR_STRING_DATA JPAKE_str_reasons[]=
 	{
+{ERR_REASON(JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL),"g to the x3 is not legal"},
+{ERR_REASON(JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL),"g to the x4 is not legal"},
 {ERR_REASON(JPAKE_R_G_TO_THE_X4_IS_ONE)  ,"g to the x4 is one"},
 {ERR_REASON(JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH),"hash of hash of key mismatch"},
 {ERR_REASON(JPAKE_R_HASH_OF_KEY_MISMATCH),"hash of key mismatch"},
-- 
2.25.1