From f20f8b8b0a4236c7438c830261a5860cbd9efe80 Mon Sep 17 00:00:00 2001
From: Adam Langley <agl@golang.org>
Date: Mon, 25 Mar 2013 19:08:29 -0400
Subject: [PATCH] crypto/rsa: don't correct private exponent unless needed.
At some point in the past, I believe the GCD algorithm was setting d to
be negative. The RSA code has been correcting that ever since but, now,
it appears to have changed and the correction isn't needed.
Having d be too large is harmless, it's just a little odd and I
happened to notice.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7948044
---
src/pkg/crypto/rsa/rsa.go | 4 +++-
src/pkg/crypto/rsa/rsa_test.go | 3 +++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/src/pkg/crypto/rsa/rsa.go b/src/pkg/crypto/rsa/rsa.go
index 35a5f7c3c6..f56fb37ee5 100644
--- a/src/pkg/crypto/rsa/rsa.go
+++ b/src/pkg/crypto/rsa/rsa.go
@@ -203,7 +203,9 @@ NextSetOfPrimes:
g.GCD(priv.D, y, e, totient)
if g.Cmp(bigOne) == 0 {
- priv.D.Add(priv.D, totient)
+ if priv.D.Sign() < 0 {
+ priv.D.Add(priv.D, totient)
+ }
priv.Primes = primes
priv.N = n
diff --git a/src/pkg/crypto/rsa/rsa_test.go b/src/pkg/crypto/rsa/rsa_test.go
index f08cfe73c4..ffd96e62f6 100644
--- a/src/pkg/crypto/rsa/rsa_test.go
+++ b/src/pkg/crypto/rsa/rsa_test.go
@@ -93,6 +93,9 @@ func testKeyBasics(t *testing.T, priv *PrivateKey) {
if err := priv.Validate(); err != nil {
t.Errorf("Validate() failed: %s", err)
}
+ if priv.D.Cmp(priv.N) > 0 {
+ t.Errorf("private exponent too large")
+ }
pub := &priv.PublicKey
m := big.NewInt(42)
--
2.30.9