From fc2e05c2d5c078d1fdf0ee56fc118ea471000a3a Mon Sep 17 00:00:00 2001
From: =?utf8?q?Bodo=20M=C3=B6ller?= <bodo@openssl.org>
Date: Thu, 30 Nov 2000 22:34:57 +0000
Subject: [PATCH] Fix BN_rshift, which caused lots of trouble.

---
 CHANGES              |  3 +++
 crypto/bn/bn_mul.c   |  2 +-
 crypto/bn/bn_shift.c |  5 +++++
 crypto/bn/bntest.c   | 20 ++------------------
 4 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/CHANGES b/CHANGES
index eb3e87ba72..71582c3e06 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3,6 +3,9 @@
 
  Changes between 0.9.6 and 0.9.7  [xx XXX 2000]
 
+  *) BN_rshift bugfix for n == 0.
+     [Bodo Moeller]
+
   *) Reformat the FAQ so the different questions and answers can be divided
      i sections depending on the subject.
      [Richard Levitte]
diff --git a/crypto/bn/bn_mul.c b/crypto/bn/bn_mul.c
index b6608c47de..ff351af10f 100644
--- a/crypto/bn/bn_mul.c
+++ b/crypto/bn/bn_mul.c
@@ -928,7 +928,7 @@ void bn_mul_high(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, BN_ULONG *l, int n2,
 	}
 #endif /* BN_RECURSION */
 
-int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
+int BN_mul(BIGNUM *r, /* almost const */ const BIGNUM *a, /* almost const */ const BIGNUM *b, BN_CTX *ctx)
 	{
 	int top,al,bl;
 	BIGNUM *rr;
diff --git a/crypto/bn/bn_shift.c b/crypto/bn/bn_shift.c
index 37c6988da3..70f785ea18 100644
--- a/crypto/bn/bn_shift.c
+++ b/crypto/bn/bn_shift.c
@@ -172,6 +172,11 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
 		r->neg=a->neg;
 		if (bn_wexpand(r,a->top-nw+1) == NULL) return(0);
 		}
+	else
+		{
+		if (n == 0)
+			return 1; /* or the copying loop will go berserk */
+		}
 
 	f= &(a->d[nw]);
 	t=r->d;
diff --git a/crypto/bn/bntest.c b/crypto/bn/bntest.c
index 3c0c95feb6..2df0d29b1a 100644
--- a/crypto/bn/bntest.c
+++ b/crypto/bn/bntest.c
@@ -165,7 +165,6 @@ int main(int argc, char *argv[])
 	if (!results)
 		BIO_puts(out,"obase=16\nibase=16\n");
 
-#if 0
 	message(out,"BN_add");
 	if (!test_add(out)) goto err;
 	BIO_flush(out);
@@ -230,7 +229,6 @@ int main(int argc, char *argv[])
 	message(out,"BN_exp");
 	if (!test_exp(out,ctx)) goto err;
 	BIO_flush(out);
-#endif
 
 	message(out,"BN_kronecker");
 	if (!test_kron(out,ctx)) goto err;
@@ -946,34 +944,20 @@ int test_kron(BIO *bp, BN_CTX *ctx)
 	 * don't want to test whether  b  is prime but whether BN_kronecker
 	 * works.) */
 
-#if 0
 	if (!BN_generate_prime(b, 512, 0, NULL, NULL, genprime_cb, NULL)) goto err;
-#else
-	if (!BN_set_word(b,65537)) goto err;
-#endif
 	putc('\n', stderr);
 
 	for (i = 0; i < num0; i++)
 		{
-#if 0
 		if (!BN_rand(a, 512, 0, 0)) goto err;
 		a->neg = rand_neg();
-#else
-		if (!BN_bin2bn("\x01\xff\xff\xff\xff", 5, a)) goto err;
-#endif
 
 		/* t := (b-1)/2  (note that b is odd) */
 		if (!BN_copy(t, b)) goto err;
 		if (!BN_sub_word(t, 1)) goto err;
 		if (!BN_rshift1(t, t)) goto err;
 		/* r := a^t mod b */
-#if 0
 		if (!BN_mod_exp(r, a, t, b, ctx)) goto err;
-#elif 0
-		if (!BN_mod_exp_recp(r, a, t, b, ctx)) goto err;
-#else
-		if (!BN_mod_exp_simple(r, a, t, b, ctx)) goto err;
-#endif
 
 		if (BN_is_word(r, 1))
 			legendre = 1;
@@ -989,7 +973,7 @@ int test_kron(BIO *bp, BN_CTX *ctx)
 				}
 			legendre = -1;
 			}
-
+		
 		kronecker = BN_kronecker(a, b, ctx);
 		if (kronecker < -1) goto err;
 		
@@ -997,7 +981,7 @@ int test_kron(BIO *bp, BN_CTX *ctx)
 			{
 			fprintf(stderr, "legendre != kronecker; a = ");
 			BN_print_fp(stderr, a);
-			fprintf(stderr, ", a = ");
+			fprintf(stderr, ", b = ");
 			BN_print_fp(stderr, b);
 			fprintf(stderr, "\n");
 			goto err;
-- 
2.25.1