From 66e1081a1567d40bd50a5cea47d546eac292cbc2 Mon Sep 17 00:00:00 2001
From: Ben Laurie <ben@openssl.org>
Date: Thu, 20 Mar 2003 16:00:18 +0000
Subject: [PATCH] Blinding fix.

---
 CHANGES              |  6 ++++++
 crypto/rsa/rsa_eay.c | 27 +++++++++++++++++++++++----
 crypto/rsa/rsa_lib.c |  8 +++++++-
 3 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/CHANGES b/CHANGES
index 46916103b9..ab440fc46d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -10,6 +10,12 @@
      in ssl3_get_client_key_exchange (ssl/s3_srvr.c).
      [Bodo Moeller]
 
+  *) Turn on RSA blinding by default, to avoid a timing attack. Applications
+     that don't want it can call RSA_blinding_off(). They would be ill-advised
+     to do so in most cases. The automatic enabling can also be turned off
+     by defining OPENSSL_FORCE_NO_RSA_BLINDING at compile-time.
+     [Ben Laurie, Steve Henson, Geoff Thorpe]
+
  Changes between 0.9.6h and 0.9.6i  [19 Feb 2003]
 
   *) In ssl3_get_record (ssl/s3_pkt.c), minimize information leaked
diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c
index c49abe6e3e..444111fc39 100644
--- a/crypto/rsa/rsa_eay.c
+++ b/crypto/rsa/rsa_eay.c
@@ -190,6 +190,25 @@ err:
 	return(r);
 	}
 
+static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx)
+	{
+	int ret = 1;
+	CRYPTO_w_lock(CRYPTO_LOCK_RSA);
+	/* Check again inside the lock - the macro's check is racey */
+	if(rsa->blinding == NULL)
+		ret = RSA_blinding_on(rsa, ctx);
+	CRYPTO_w_unlock(CRYPTO_LOCK_RSA);
+	return ret;
+	}
+
+#define BLINDING_HELPER(rsa, ctx, err_instr) \
+	do { \
+		if(((rsa)->flags & RSA_FLAG_BLINDING) && \
+				((rsa)->blinding == NULL) && \
+				!rsa_eay_blinding(rsa, ctx)) \
+			err_instr \
+	} while(0)
+
 /* signing */
 static int RSA_eay_private_encrypt(int flen, unsigned char *from,
 	     unsigned char *to, RSA *rsa, int padding)
@@ -234,8 +253,8 @@ static int RSA_eay_private_encrypt(int flen, unsigned char *from,
 		goto err;
 		}
 
-	if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL))
-		RSA_blinding_on(rsa,ctx);
+	BLINDING_HELPER(rsa, ctx, goto err;);
+
 	if (rsa->flags & RSA_FLAG_BLINDING)
 		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
 
@@ -313,8 +332,8 @@ static int RSA_eay_private_decrypt(int flen, unsigned char *from,
 		goto err;
 		}
 
-	if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL))
-		RSA_blinding_on(rsa,ctx);
+	BLINDING_HELPER(rsa, ctx, goto err;);
+
 	if (rsa->flags & RSA_FLAG_BLINDING)
 		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
 
diff --git a/crypto/rsa/rsa_lib.c b/crypto/rsa/rsa_lib.c
index 422643e9f2..0aeefae7db 100644
--- a/crypto/rsa/rsa_lib.c
+++ b/crypto/rsa/rsa_lib.c
@@ -71,7 +71,13 @@ static STACK_OF(CRYPTO_EX_DATA_FUNCS) *rsa_meth=NULL;
 
 RSA *RSA_new(void)
 	{
-	return(RSA_new_method(NULL));
+	RSA *r=RSA_new_method(NULL);
+
+#ifndef OPENSSL_NO_FORCE_RSA_BLINDING
+	r->flags|=RSA_FLAG_BLINDING;
+#endif
+
+	return r;
 	}
 
 void RSA_set_default_method(RSA_METHOD *meth)
-- 
2.25.1