[release-branch.go1.7] crypto/elliptic: fix carry bug in x86-64 P-256 implementation.
Patch from Vlad Krasnov and confirmed to be under CLA.
Fixes #20040.
Change-Id: Ieb8436c4dcb6669a1620f1e0d257efd047b1b87c
Reviewed-on: https://go-review.googlesource.com/41070
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit 9294fa2749ffee7edbbb817a0ef9fe633136fa9c)
Reviewed-on: https://go-review.googlesource.com/43773
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
diff --git a/src/crypto/elliptic/elliptic_test.go b/src/crypto/elliptic/elliptic_test.go
index 7f3f1a2..b68cb59 100644
--- a/src/crypto/elliptic/elliptic_test.go
+++ b/src/crypto/elliptic/elliptic_test.go
@@ -300,6 +300,29 @@
},
}
+type scalarMultTest struct {
+ k string
+ xIn, yIn string
+ xOut, yOut string
+}
+
+var p256MultTests = []scalarMultTest{
+ {
+ "2a265f8bcbdcaf94d58519141e578124cb40d64a501fba9c11847b28965bc737",
+ "023819813ac969847059028ea88a1f30dfbcde03fc791d3a252c6b41211882ea",
+ "f93e4ae433cc12cf2a43fc0ef26400c0e125508224cdb649380f25479148a4ad",
+ "4d4de80f1534850d261075997e3049321a0864082d24a917863366c0724f5ae3",
+ "a22d2b7f7818a3563e0f7a76c9bf0921ac55e06e2e4d11795b233824b1db8cc0",
+ },
+ {
+ "313f72ff9fe811bf573176231b286a3bdb6f1b14e05c40146590727a71c3bccd",
+ "cc11887b2d66cbae8f4d306627192522932146b42f01d3c6f92bd5c8ba739b06",
+ "a2f08a029cd06b46183085bae9248b0ed15b70280c7ef13a457f5af382426031",
+ "831c3f6b5f762d2f461901577af41354ac5f228c2591f84f8a6e51e2e3f17991",
+ "93f90934cd0ef2c698cc471c60a93524e87ab31ca2412252337f364513e43684",
+ },
+}
+
func TestBaseMult(t *testing.T) {
p224 := P224()
for i, e := range p224BaseMultTests {
@@ -379,6 +402,19 @@
break
}
}
+
+ for i, e := range p256MultTests {
+ x, _ := new(big.Int).SetString(e.xIn, 16)
+ y, _ := new(big.Int).SetString(e.yIn, 16)
+ k, _ := new(big.Int).SetString(e.k, 16)
+ expectedX, _ := new(big.Int).SetString(e.xOut, 16)
+ expectedY, _ := new(big.Int).SetString(e.yOut, 16)
+
+ xx, yy := p256.ScalarMult(x, y, k.Bytes())
+ if xx.Cmp(expectedX) != 0 || yy.Cmp(expectedY) != 0 {
+ t.Errorf("#%d: got (%x, %x), want (%x, %x)", i, xx, yy, expectedX, expectedY)
+ }
+ }
}
func TestInfinity(t *testing.T) {
diff --git a/src/crypto/elliptic/p256_asm_amd64.s b/src/crypto/elliptic/p256_asm_amd64.s
index 6c7bde1..ea4a6fa 100644
--- a/src/crypto/elliptic/p256_asm_amd64.s
+++ b/src/crypto/elliptic/p256_asm_amd64.s
@@ -1314,12 +1314,12 @@
ADCQ p256const0<>(SB), acc5
ADCQ $0, acc6
ADCQ p256const1<>(SB), acc7
- ADCQ $0, mul0
+ ANDQ $1, mul0
- CMOVQNE acc0, acc4
- CMOVQNE acc1, acc5
- CMOVQNE acc2, acc6
- CMOVQNE acc3, acc7
+ CMOVQEQ acc0, acc4
+ CMOVQEQ acc1, acc5
+ CMOVQEQ acc2, acc6
+ CMOVQEQ acc3, acc7
RET
/* ---------------------------------------*/
