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crypto/rsa, crypto/ecdsa: fail earlier on zero parameters
Change-Id: Ia6ed49d5ef3a256a55e6d4eaa1b4d9f0fc447013 Reviewed-on: https://go-review.googlesource.com/21560 Reviewed-by: Robert Griesemer <gri@golang.org>
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@ -23,6 +23,7 @@ import (
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"crypto/elliptic"
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"crypto/sha512"
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"encoding/asn1"
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"errors"
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"io"
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"math/big"
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)
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@ -140,6 +141,8 @@ func fermatInverse(k, N *big.Int) *big.Int {
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return new(big.Int).Exp(k, nMinus2, N)
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}
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var errZeroParam = errors.New("zero parameter")
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// Sign signs an arbitrary length hash (which should be the result of hashing a
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// larger message) using the private key, priv. It returns the signature as a
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// pair of integers. The security of the private key depends on the entropy of
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@ -180,7 +183,9 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
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// See [NSA] 3.4.1
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c := priv.PublicKey.Curve
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N := c.Params().N
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if N.Sign() == 0 {
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return nil, nil, errZeroParam
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}
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var k, kInv *big.Int
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for {
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for {
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@ -193,7 +198,7 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
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if in, ok := priv.Curve.(invertible); ok {
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kInv = in.Inverse(k)
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} else {
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kInv = fermatInverse(k, N)
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kInv = fermatInverse(k, N) // N != 0
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}
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r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
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@ -207,7 +212,7 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
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s = new(big.Int).Mul(priv.D, r)
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s.Add(s, e)
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s.Mul(s, kInv)
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s.Mod(s, N)
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s.Mod(s, N) // N != 0
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if s.Sign() != 0 {
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break
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}
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@ -465,6 +465,9 @@ func decrypt(random io.Reader, priv *PrivateKey, c *big.Int) (m *big.Int, err er
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err = ErrDecryption
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return
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}
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if priv.N.Sign() == 0 {
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return nil, ErrDecryption
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}
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var ir *big.Int
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if random != nil {
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@ -490,7 +493,7 @@ func decrypt(random io.Reader, priv *PrivateKey, c *big.Int) (m *big.Int, err er
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}
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}
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bigE := big.NewInt(int64(priv.E))
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rpowe := new(big.Int).Exp(r, bigE, priv.N)
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rpowe := new(big.Int).Exp(r, bigE, priv.N) // N != 0
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cCopy := new(big.Int).Set(c)
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cCopy.Mul(cCopy, rpowe)
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cCopy.Mod(cCopy, priv.N)
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