Fix side channel in ecp_nistz256-armv4.pl

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9239)

1 files changed, 33 insertions, 46 deletions

diff --git a/crypto/ec/asm/ecp_nistz256-armv4.pl b/crypto/ec/asm/ecp_nistz256-armv4.pl
index 4e6bfef4b5..4809360ac4 100755
--- a/crypto/ec/asm/ecp_nistz256-armv4.pl
+++ b/crypto/ec/asm/ecp_nistz256-armv4.pl
@@ -1398,7 +1398,7 @@ my ($Z1sqr, $Z2sqr) = ($Hsqr, $Rsqr);
 # 256-bit vectors on top. Then note that we push
 # starting from r0, which means that we have copy of
 # input arguments just below these temporary vectors.
-# We use three of them for !in1infty, !in2intfy and
+# We use three of them for ~in1infty, ~in2infty and
 # result of check for zero.
 
 $code.=<<___;
@@ -1428,7 +1428,7 @@ ecp_nistz256_point_add:
 #endif
 	movne	r12,#-1
 	stmia	r3,{r4-r11}
-	str	r12,[sp,#32*18+8]	@ !in2infty
+	str	r12,[sp,#32*18+8]	@ ~in2infty
 
 	ldmia	$a_ptr!,{r4-r11}	@ copy in1_x
 	add	r3,sp,#$in1_x
@@ -1449,7 +1449,7 @@ ecp_nistz256_point_add:
 #endif
 	movne	r12,#-1
 	stmia	r3,{r4-r11}
-	str	r12,[sp,#32*18+4]	@ !in1infty
+	str	r12,[sp,#32*18+4]	@ ~in1infty
 
 	add	$a_ptr,sp,#$in2_z
 	add	$b_ptr,sp,#$in2_z
@@ -1514,33 +1514,20 @@ ecp_nistz256_point_add:
 	orr	$a0,$a0,$a2
 	orr	$a4,$a4,$a6
 	orr	$a0,$a0,$a7
-	orrs	$a0,$a0,$a4
+	orr	$a0,$a0,$a4		@ ~is_equal(U1,U2)
 
-	bne	.Ladd_proceed		@ is_equal(U1,U2)?
+	ldr	$t0,[sp,#32*18+4]	@ ~in1infty
+	ldr	$t1,[sp,#32*18+8]	@ ~in2infty
+	ldr	$t2,[sp,#32*18+12]	@ ~is_equal(S1,S2)
+	mvn	$t0,$t0			@ -1/0 -> 0/-1
+	mvn	$t1,$t1			@ -1/0 -> 0/-1
+	orr	$a0,$t0
+	orr	$a0,$t1
+	orrs	$a0,$t2			@ set flags
 
-	ldr	$t0,[sp,#32*18+4]
-	ldr	$t1,[sp,#32*18+8]
-	ldr	$t2,[sp,#32*18+12]
-	tst	$t0,$t1
-	beq	.Ladd_proceed		@ (in1infty || in2infty)?
-	tst	$t2,$t2
-	beq	.Ladd_double		@ is_equal(S1,S2)?
+	@ if(~is_equal(U1,U2) | in1infty | in2infty | ~is_equal(S1,S2))
+	bne	.Ladd_proceed
 
-	ldr	$r_ptr,[sp,#32*18+16]
-	eor	r4,r4,r4
-	eor	r5,r5,r5
-	eor	r6,r6,r6
-	eor	r7,r7,r7
-	eor	r8,r8,r8
-	eor	r9,r9,r9
-	eor	r10,r10,r10
-	eor	r11,r11,r11
-	stmia	$r_ptr!,{r4-r11}
-	stmia	$r_ptr!,{r4-r11}
-	stmia	$r_ptr!,{r4-r11}
-	b	.Ladd_done
-
-.align	4
 .Ladd_double:
 	ldr	$a_ptr,[sp,#32*18+20]
 	add	sp,sp,#32*(18-5)+16	@ difference in frame sizes
@@ -1605,15 +1592,15 @@ ecp_nistz256_point_add:
 	add	$b_ptr,sp,#$S2
 	bl	__ecp_nistz256_sub_from	@ p256_sub(res_y, res_y, S2);
 
-	ldr	r11,[sp,#32*18+4]	@ !in1intfy
-	ldr	r12,[sp,#32*18+8]	@ !in2intfy
+	ldr	r11,[sp,#32*18+4]	@ ~in1infty
+	ldr	r12,[sp,#32*18+8]	@ ~in2infty
 	add	r1,sp,#$res_x
 	add	r2,sp,#$in2_x
-	and	r10,r11,r12
+	and	r10,r11,r12		@ ~in1infty & ~in2infty
 	mvn	r11,r11
 	add	r3,sp,#$in1_x
-	and	r11,r11,r12
-	mvn	r12,r12
+	and	r11,r11,r12		@ in1infty & ~in2infty
+	mvn	r12,r12			@ in2infty
 	ldr	$r_ptr,[sp,#32*18+16]
 ___
 for($i=0;$i<96;$i+=8) {			# conditional moves
@@ -1621,11 +1608,11 @@ $code.=<<___;
 	ldmia	r1!,{r4-r5}		@ res_x
 	ldmia	r2!,{r6-r7}		@ in2_x
 	ldmia	r3!,{r8-r9}		@ in1_x
-	and	r4,r4,r10
+	and	r4,r4,r10		@ ~in1infty & ~in2infty
 	and	r5,r5,r10
-	and	r6,r6,r11
+	and	r6,r6,r11		@ in1infty & ~in2infty
 	and	r7,r7,r11
-	and	r8,r8,r12
+	and	r8,r8,r12		@ in2infty
 	and	r9,r9,r12
 	orr	r4,r4,r6
 	orr	r5,r5,r7
@@ -1660,7 +1647,7 @@ my $Z1sqr = $S2;
 # 256-bit vectors on top. Then note that we push
 # starting from r0, which means that we have copy of
 # input arguments just below these temporary vectors.
-# We use two of them for !in1infty, !in2intfy.
+# We use two of them for ~in1infty, ~in2infty.
 
 my @ONE_mont=(1,0,0,-1,-1,-1,-2,0);
 
@@ -1691,7 +1678,7 @@ ecp_nistz256_point_add_affine:
 #endif
 	movne	r12,#-1
 	stmia	r3,{r4-r11}
-	str	r12,[sp,#32*15+4]	@ !in1infty
+	str	r12,[sp,#32*15+4]	@ ~in1infty
 
 	ldmia	$b_ptr!,{r4-r11}	@ copy in2_x
 	add	r3,sp,#$in2_x
@@ -1718,7 +1705,7 @@ ecp_nistz256_point_add_affine:
 	it	ne
 #endif
 	movne	r12,#-1
-	str	r12,[sp,#32*15+8]	@ !in2infty
+	str	r12,[sp,#32*15+8]	@ ~in2infty
 
 	add	$a_ptr,sp,#$in1_z
 	add	$b_ptr,sp,#$in1_z
@@ -1800,15 +1787,15 @@ ecp_nistz256_point_add_affine:
 	add	$b_ptr,sp,#$S2
 	bl	__ecp_nistz256_sub_from	@ p256_sub(res_y, res_y, S2);
 
-	ldr	r11,[sp,#32*15+4]	@ !in1intfy
-	ldr	r12,[sp,#32*15+8]	@ !in2intfy
+	ldr	r11,[sp,#32*15+4]	@ ~in1infty
+	ldr	r12,[sp,#32*15+8]	@ ~in2infty
 	add	r1,sp,#$res_x
 	add	r2,sp,#$in2_x
-	and	r10,r11,r12
+	and	r10,r11,r12		@ ~in1infty & ~in2infty
 	mvn	r11,r11
 	add	r3,sp,#$in1_x
-	and	r11,r11,r12
-	mvn	r12,r12
+	and	r11,r11,r12		@ in1infty & ~in2infty
+	mvn	r12,r12			@ in2infty
 	ldr	$r_ptr,[sp,#32*15]
 ___
 for($i=0;$i<64;$i+=8) {			# conditional moves
@@ -1816,11 +1803,11 @@ $code.=<<___;
 	ldmia	r1!,{r4-r5}		@ res_x
 	ldmia	r2!,{r6-r7}		@ in2_x
 	ldmia	r3!,{r8-r9}		@ in1_x
-	and	r4,r4,r10
+	and	r4,r4,r10		@ ~in1infty & ~in2infty
 	and	r5,r5,r10
-	and	r6,r6,r11
+	and	r6,r6,r11		@ in1infty & ~in2infty
 	and	r7,r7,r11
-	and	r8,r8,r12
+	and	r8,r8,r12		@ in2infty
 	and	r9,r9,r12
 	orr	r4,r4,r6
 	orr	r5,r5,r7