apply J-PKAKE fix to HEAD (original by Ben)

CHANGES

@@ -123,7 +123,7 @@
      whose return value is often ignored. 
      [Steve Henson]
   
- Changes between 1.0.0b and 1.0.1  [xx XXX xxxx]
+ Changes between 1.0.0c and 1.0.1  [xx XXX xxxx]
 
   *) Add functions to copy EVP_PKEY_METHOD and retrieve flags and id.
      [Steve Henson]
@@ -162,7 +162,14 @@
        Add command line options to s_client/s_server.
      [Steve Henson]
 
- Changes between 1.0.0a and 1.0.0b  [xx XXX xxxx]
+ Changes between 1.0.0b and 1.0.0c  [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. CVE-2010-4252
+     [Ben Laurie]
+
+ Changes between 1.0.0a and 1.0.0b  [16 Nov 2010]
 
   *) Fix extension code to avoid race conditions which can result in a buffer
      overrun vulnerability: resumed sessions must not be modified as they can

crypto/jpake/jpake.c

@@ -282,8 +282,37 @@ 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)
     {
+    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))
 	{

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

crypto/jpake/jpake_err.c

 /* 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"},