forked from Psiphon-Labs/psiphon-tunnel-core
/
authPackage.go
151 lines (130 loc) · 4.28 KB
/
authPackage.go
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/*
* Copyright (c) 2016, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package common
import (
"bytes"
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"crypto/x509"
"encoding/base64"
"encoding/json"
"errors"
)
// AuthenticatedDataPackage is a JSON record containing some Psiphon data
// payload, such as list of Psiphon server entries. As it may be downloaded
// from various sources, it is digitally signed so that the data may be
// authenticated.
type AuthenticatedDataPackage struct {
Data string `json:"data"`
SigningPublicKeyDigest []byte `json:"signingPublicKeyDigest"`
Signature []byte `json:"signature"`
}
// GenerateAuthenticatedDataPackageKeys generates a key pair
// be used to sign and verify AuthenticatedDataPackages.
func GenerateAuthenticatedDataPackageKeys() (string, string, error) {
rsaKey, err := rsa.GenerateKey(rand.Reader, 4096)
if err != nil {
return "", "", ContextError(err)
}
publicKeyBytes, err := x509.MarshalPKIXPublicKey(rsaKey.Public())
if err != nil {
return "", "", ContextError(err)
}
privateKeyBytes := x509.MarshalPKCS1PrivateKey(rsaKey)
return base64.StdEncoding.EncodeToString(publicKeyBytes),
base64.StdEncoding.EncodeToString(privateKeyBytes),
nil
}
func sha256sum(data string) []byte {
hash := sha256.New()
hash.Write([]byte(data))
return hash.Sum(nil)
}
// WriteAuthenticatedDataPackage creates an AuthenticatedDataPackage
// containing the specified data and signed by the given key. The output
// conforms with the legacy format here:
// https://bitbucket.org/psiphon/psiphon-circumvention-system/src/c25d080f6827b141fe637050ce0d5bd0ae2e9db5/Automation/psi_ops_crypto_tools.py
func WriteAuthenticatedDataPackage(
data string, signingPublicKey, signingPrivateKey string) ([]byte, error) {
derEncodedPrivateKey, err := base64.StdEncoding.DecodeString(signingPrivateKey)
if err != nil {
return nil, ContextError(err)
}
rsaPrivateKey, err := x509.ParsePKCS1PrivateKey(derEncodedPrivateKey)
if err != nil {
return nil, ContextError(err)
}
signature, err := rsa.SignPKCS1v15(
rand.Reader,
rsaPrivateKey,
crypto.SHA256,
sha256sum(data))
if err != nil {
return nil, ContextError(err)
}
packageJSON, err := json.Marshal(
&AuthenticatedDataPackage{
Data: data,
SigningPublicKeyDigest: sha256sum(signingPublicKey),
Signature: signature,
})
if err != nil {
return nil, ContextError(err)
}
return packageJSON, nil
}
// ReadAuthenticatedDataPackage extracts and verifies authenticated
// data from an AuthenticatedDataPackage. The package must have been
// signed with the given key.
func ReadAuthenticatedDataPackage(
packageJSON []byte, signingPublicKey string) (string, error) {
var authenticatedDataPackage *AuthenticatedDataPackage
err := json.Unmarshal(packageJSON, &authenticatedDataPackage)
if err != nil {
return "", ContextError(err)
}
derEncodedPublicKey, err := base64.StdEncoding.DecodeString(signingPublicKey)
if err != nil {
return "", ContextError(err)
}
publicKey, err := x509.ParsePKIXPublicKey(derEncodedPublicKey)
if err != nil {
return "", ContextError(err)
}
rsaPublicKey, ok := publicKey.(*rsa.PublicKey)
if !ok {
return "", ContextError(errors.New("unexpected signing public key type"))
}
if 0 != bytes.Compare(
authenticatedDataPackage.SigningPublicKeyDigest,
sha256sum(signingPublicKey)) {
return "", ContextError(errors.New("unexpected signing public key digest"))
}
err = rsa.VerifyPKCS1v15(
rsaPublicKey,
crypto.SHA256,
sha256sum(authenticatedDataPackage.Data),
authenticatedDataPackage.Signature)
if err != nil {
return "", ContextError(err)
}
return authenticatedDataPackage.Data, nil
}