1 From 2cfbb875208f4acecfb0b72de5aebe37e8d03a35 Mon Sep 17 00:00:00 2001

     2 From: Robert Griesemer <[email protected]>

     3 Date: Tue, 5 Apr 2016 09:44:00 -0700

     4 Subject: [PATCH 74/79] crypto/dsa: eliminate invalid PublicKey early

     5 

     6 For PublicKey.P == 0, Verify will fail. Don't even try.

     7 

     8 Change-Id: I1009f2b3dead8d0041626c946633acb10086d8c8

     9 Reviewed-on: https://go-review.googlesource.com/21533

    10 Reviewed-by: Brad Fitzpatrick <[email protected]>

    11 Run-TryBot: Brad Fitzpatrick <[email protected]>

    12 TryBot-Result: Gobot Gobot <[email protected]>

    13 Reviewed-on: https://go-review.googlesource.com/21637

    14 ---

    15  src/crypto/dsa/dsa.go | 4 ++++

    16  1 file changed, 4 insertions(+)

    17 

    18 diff --git a/src/crypto/dsa/dsa.go b/src/crypto/dsa/dsa.go

    19 index b7565a6..0ecb24a 100644

    20 --- a/src/crypto/dsa/dsa.go

    21 +++ b/src/crypto/dsa/dsa.go

    22 @@ -249,6 +249,10 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err

    23  func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {

    24  	// FIPS 186-3, section 4.7

    25  

    26 +	if pub.P.Sign() == 0 {

    27 +		return false

    28 +	}

    29 +

    30  	if r.Sign() < 1 || r.Cmp(pub.Q) >= 0 {

    31  		return false

    32  	}

    33 -- 

    34 2.7.4

    35