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Check EC point is on curve at Verifier instantiation #116

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merged 2 commits into from
Dec 12, 2022
Merged

Check EC point is on curve at Verifier instantiation #116

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064ff82
Check EC point is on curve at Verifier instantiation
thomas-fossati Nov 18, 2022
dd75bac
remove go 1.17 from the support matrix
thomas-fossati Dec 6, 2022
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8 changes: 4 additions & 4 deletions testdata/sign1-sign-0000.json
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,9 @@
"key": {
"kty": "EC",
"crv": "P-256",
"x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
"y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
"d": "V8kgd2ZBRuh2dgyVINBUqpPDr7BOMGcF22CQMIUHtNM"
"x": "f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",
"y": "x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0",
"d": "jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI"
},
"alg": "ES256",
"sign1::sign": {
Expand All @@ -32,4 +32,4 @@
},
"fixedOutputLength": 32
}
}
}
3 changes: 3 additions & 0 deletions verifier.go
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,9 @@ func NewVerifier(alg Algorithm, key crypto.PublicKey) (Verifier, error) {
if !ok {
return nil, fmt.Errorf("%v: %w", alg, ErrAlgorithmMismatch)
}
if !vk.Curve.IsOnCurve(vk.X, vk.Y) {
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return nil, errors.New("public key point is not on curve")
}
return &ecdsaVerifier{
alg: alg,
key: vk,
Expand Down
29 changes: 29 additions & 0 deletions verifier_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,32 @@ package cose
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"encoding/base64"
"math/big"
"reflect"
"testing"
)

func mustBase64ToBigInt(s string) *big.Int {
val, err := base64.RawURLEncoding.DecodeString(s)
if err != nil {
panic(err)
}
return new(big.Int).SetBytes(val)
}

func generateBogusECKey() *ecdsa.PublicKey {
return &ecdsa.PublicKey{
Curve: elliptic.P256(),
// x-coord is not on curve p-256
X: mustBase64ToBigInt("MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqx7D4"),
Y: mustBase64ToBigInt("4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM"),
}
}

func TestNewVerifier(t *testing.T) {
// generate ecdsa key
ecdsaKey := generateTestECDSAKey(t).Public().(*ecdsa.PublicKey)
Expand All @@ -25,6 +45,9 @@ func TestNewVerifier(t *testing.T) {
rsaKeyLowEntropy = &key.PublicKey
}

// craft an EC public key with the x-coord not on curve
ecdsaKeyPointNotOnCurve := generateBogusECKey()

// run tests
tests := []struct {
name string
Expand Down Expand Up @@ -88,6 +111,12 @@ func TestNewVerifier(t *testing.T) {
alg: 0,
wantErr: true,
},
{
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name: "bogus ecdsa public key (point not on curve)",
alg: AlgorithmES256,
key: ecdsaKeyPointNotOnCurve,
wantErr: true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down