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crypto/rsa, crypto/ecdsa: fail earlier on zero parameters

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Change-Id: Ia6ed49d5ef3a256a55e6d4eaa1b4d9f0fc447013
Reviewed-on: https://go-review.googlesource.com/21560
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Brad Fitzpatrick 2016-04-05 20:40:40 +00:00
parent 7e0d66020c
commit d7c699d993
2 changed files with 12 additions and 4 deletions
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11
src/crypto/ecdsa/ecdsa.go
View file

@ -23,6 +23,7 @@ import (
"crypto/elliptic"
"crypto/sha512"
"encoding/asn1"
"errors"
"io"
"math/big"
)
@ -140,6 +141,8 @@ func fermatInverse(k, N *big.Int) *big.Int {
return new(big.Int).Exp(k, nMinus2, N)
}
var errZeroParam = errors.New("zero parameter")
// Sign signs an arbitrary length hash (which should be the result of hashing a
// larger message) using the private key, priv. It returns the signature as a
// pair of integers. The security of the private key depends on the entropy of
@ -180,7 +183,9 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
// See [NSA] 3.4.1
c := priv.PublicKey.Curve
N := c.Params().N
if N.Sign() == 0 {
return nil, nil, errZeroParam
}
var k, kInv *big.Int
for {
for {
@ -193,7 +198,7 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
if in, ok := priv.Curve.(invertible); ok {
kInv = in.Inverse(k)
} else {
kInv = fermatInverse(k, N)
kInv = fermatInverse(k, N) // N != 0
}
r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
@ -207,7 +212,7 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
s = new(big.Int).Mul(priv.D, r)
s.Add(s, e)
s.Mul(s, kInv)
s.Mod(s, N)
s.Mod(s, N) // N != 0
if s.Sign() != 0 {
break
}

5
src/crypto/rsa/rsa.go
View file

@ -465,6 +465,9 @@ func decrypt(random io.Reader, priv *PrivateKey, c *big.Int) (m *big.Int, err er
err = ErrDecryption
return
}
if priv.N.Sign() == 0 {
return nil, ErrDecryption
}
var ir *big.Int
if random != nil {
@ -490,7 +493,7 @@ func decrypt(random io.Reader, priv *PrivateKey, c *big.Int) (m *big.Int, err er
}
}
bigE := big.NewInt(int64(priv.E))
rpowe := new(big.Int).Exp(r, bigE, priv.N)
rpowe := new(big.Int).Exp(r, bigE, priv.N) // N != 0
cCopy := new(big.Int).Set(c)
cCopy.Mul(cCopy, rpowe)
cCopy.Mod(cCopy, priv.N)