File openssl-rsakeygen-minimum-distance.patch of Package openssl.1633

Index: openssl-1.0.1i/crypto/rsa/rsa_gen.c
===================================================================
--- openssl-1.0.1i.orig/crypto/rsa/rsa_gen.c
+++ openssl-1.0.1i/crypto/rsa/rsa_gen.c
@@ -421,6 +421,15 @@ static int rsa_builtin_keygen(RSA *rsa,
 	bitsp=(bits+1)/2;
 	bitsq=bits-bitsp;
 
+	/* prepare a maximum for p and q */
+	/* 0xB504F334 is (sqrt(2)/2)*2^32 */
+	if (!BN_set_word(r0, 0xB504F334)) goto err;
+	if (!BN_lshift(r0, r0, bitsp - 32)) goto err;
+
+	/* prepare minimum p and q difference */
+	if (!BN_one(r3)) goto err;
+	if (!BN_lshift(r3, r3, bitsp - 100)) goto err;
+
 	/* We need the RSA components non-NULL */
 	if(!rsa->n && ((rsa->n=BN_new()) == NULL)) goto err;
 	if(!rsa->d && ((rsa->d=BN_new()) == NULL)) goto err;
@@ -438,6 +447,8 @@ static int rsa_builtin_keygen(RSA *rsa,
 		{
 		if(!BN_generate_prime_ex(rsa->p, bitsp, 0, NULL, NULL, cb))
 			goto err;
+                if (BN_cmp(rsa->p, r0) < 0)
+                        continue;
 		if (!BN_sub(r2,rsa->p,BN_value_one())) goto err;
 		if (!BN_gcd(r1,r2,rsa->e,ctx)) goto err;
 		if (BN_is_one(r1)) break;
@@ -448,21 +459,16 @@ static int rsa_builtin_keygen(RSA *rsa,
 		goto err;
 	for (;;)
 		{
-		/* When generating ridiculously small keys, we can get stuck
-		 * continually regenerating the same prime values. Check for
-		 * this and bail if it happens 3 times. */
-		unsigned int degenerate = 0;
-		do
-			{
-			if(!BN_generate_prime_ex(rsa->q, bitsq, 0, NULL, NULL, cb))
-				goto err;
-			} while((BN_cmp(rsa->p, rsa->q) == 0) && (++degenerate < 3));
-		if(degenerate == 3)
-			{
-			ok = 0; /* we set our own err */
-			RSAerr(RSA_F_RSA_BUILTIN_KEYGEN,RSA_R_KEY_SIZE_TOO_SMALL);
+		/* This function will take care of setting the topmost bit via BN_rand(..,1,1), so
+		 * the maximum distance between p and q is less than 2^bitsq */
+		if(!BN_generate_prime_ex(rsa->q, bitsq, 0, NULL, NULL, cb))
 			goto err;
-			}
+                if (BN_cmp(rsa->q, r0) < 0)
+                        continue;
+		/* check for minimum distance between p and q, 2^(bitsp-100) */
+		if (!BN_sub(r2, rsa->q, rsa->p)) goto err;
+		if (BN_ucmp(r2, r3) <= 0)
+			continue;
 		if (!BN_sub(r2,rsa->q,BN_value_one())) goto err;
 		if (!BN_gcd(r1,r2,rsa->e,ctx)) goto err;
 		if (BN_is_one(r1))