4 files changed, 59 insertions, 9 deletions

diff --git a/openssl/crypto/bn/asm/x86_64-gcc.c b/openssl/crypto/bn/asm/x86_64-gcc.c
index acb0b4011..31476abeb 100644
--- a/openssl/crypto/bn/asm/x86_64-gcc.c
+++ b/openssl/crypto/bn/asm/x86_64-gcc.c
@@ -189,7 +189,7 @@ BN_ULONG bn_add_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
 
 	if (n <= 0) return 0;
 
-	asm (
+	asm volatile (
 	"	subq	%2,%2		\n"
 	".p2align 4			\n"
 	"1:	movq	(%4,%2,8),%0	\n"
@@ -200,7 +200,7 @@ BN_ULONG bn_add_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
 	"	sbbq	%0,%0		\n"
 		: "=&a"(ret),"+c"(n),"=&r"(i)
 		: "r"(rp),"r"(ap),"r"(bp)
-		: "cc"
+		: "cc", "memory"
 	);
 
   return ret&1;
@@ -212,7 +212,7 @@ BN_ULONG bn_sub_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
 
 	if (n <= 0) return 0;
 
-	asm (
+	asm volatile (
 	"	subq	%2,%2		\n"
 	".p2align 4			\n"
 	"1:	movq	(%4,%2,8),%0	\n"
@@ -223,7 +223,7 @@ BN_ULONG bn_sub_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
 	"	sbbq	%0,%0		\n"
 		: "=&a"(ret),"+c"(n),"=&r"(i)
 		: "r"(rp),"r"(ap),"r"(bp)
-		: "cc"
+		: "cc", "memory"
 	);
 
   return ret&1;
diff --git a/openssl/crypto/bn/bn_exp.c b/openssl/crypto/bn/bn_exp.c
index 5e7eb3373..611fa3262 100644
--- a/openssl/crypto/bn/bn_exp.c
+++ b/openssl/crypto/bn/bn_exp.c
@@ -874,7 +874,14 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
 	bits = BN_num_bits(p);
 	if (bits == 0)
 		{
-		ret = BN_one(rr);
+		/* x**0 mod 1 is still zero. */
+		if (BN_is_one(m))
+			{
+			ret = 1;
+			BN_zero(rr);
+			}
+		else
+			ret = BN_one(rr);
 		return ret;
 		}
 	if (a == 0)
diff --git a/openssl/crypto/bn/bn_nist.c b/openssl/crypto/bn/bn_nist.c
index e22968d4a..abb157085 100644
--- a/openssl/crypto/bn/bn_nist.c
+++ b/openssl/crypto/bn/bn_nist.c
@@ -1088,9 +1088,9 @@ int BN_nist_mod_521(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 	/* ... and right shift */
 	for (val=t_d[0],i=0; i<BN_NIST_521_TOP-1; i++)
 		{
-		tmp = val>>BN_NIST_521_RSHIFT;
-		val = t_d[i+1];
-		t_d[i] = (tmp | val<<BN_NIST_521_LSHIFT) & BN_MASK2;
+		t_d[i] = ( val>>BN_NIST_521_RSHIFT |
+			  (tmp=t_d[i+1])<<BN_NIST_521_LSHIFT ) & BN_MASK2;
+		val=tmp;
 		}
 	t_d[i] = val>>BN_NIST_521_RSHIFT;
 	/* lower 521 bits */
diff --git a/openssl/crypto/bn/exptest.c b/openssl/crypto/bn/exptest.c
index 074a8e882..5fa02a122 100644
--- a/openssl/crypto/bn/exptest.c
+++ b/openssl/crypto/bn/exptest.c
@@ -71,6 +71,43 @@
 
 static const char rnd_seed[] = "string to make the random number generator think it has entropy";
 
+/* test_exp_mod_zero tests that x**0 mod 1 == 0. It returns zero on success. */
+static int test_exp_mod_zero() {
+	BIGNUM a, p, m;
+	BIGNUM r;
+	BN_CTX *ctx = BN_CTX_new();
+	int ret = 1;
+
+	BN_init(&m);
+	BN_one(&m);
+
+	BN_init(&a);
+	BN_one(&a);
+
+	BN_init(&p);
+	BN_zero(&p);
+
+	BN_init(&r);
+	BN_mod_exp(&r, &a, &p, &m, ctx);
+	BN_CTX_free(ctx);
+
+	if (BN_is_zero(&r))
+		ret = 0;
+	else
+		{
+		printf("1**0 mod 1 = ");
+		BN_print_fp(stdout, &r);
+		printf(", should be 0\n");
+		}
+
+	BN_free(&r);
+	BN_free(&a);
+	BN_free(&p);
+	BN_free(&m);
+
+	return ret;
+}
+
 int main(int argc, char *argv[])
 	{
 	BN_CTX *ctx;
@@ -190,7 +227,13 @@ int main(int argc, char *argv[])
 	ERR_remove_thread_state(NULL);
 	CRYPTO_mem_leaks(out);
 	BIO_free(out);
-	printf(" done\n");
+	printf("\n");
+
+	if (test_exp_mod_zero() != 0)
+		goto err;
+
+	printf("done\n");
+
 	EXIT(0);
 err:
 	ERR_load_crypto_strings();