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package proton_api_bridge
import (
"crypto/sha256"
"encoding/base64"
"io"
"github.com/ProtonMail/gopenpgp/v2/crypto"
"github.com/ProtonMail/gopenpgp/v2/helper"
)
func generatePassphrase() (string, error) {
token, err := crypto.RandomToken(32)
if err != nil {
return "", err
}
tokenBase64 := base64.StdEncoding.EncodeToString(token)
return tokenBase64, nil
}
func generateCryptoKey() (string, string, error) {
passphrase, err := generatePassphrase()
if err != nil {
return "", "", err
}
// all hardcoded values from iOS drive
key, err := helper.GenerateKey("Drive key", "noreply@protonmail.com", []byte(passphrase), "x25519", 0)
if err != nil {
return "", "", err
}
return passphrase, key, nil
}
// taken from Proton Go API Backend
func encryptWithSignature(kr, addrKR *crypto.KeyRing, b []byte) (string, string, error) {
enc, err := kr.Encrypt(crypto.NewPlainMessage(b), nil)
if err != nil {
return "", "", err
}
encArm, err := enc.GetArmored()
if err != nil {
return "", "", err
}
sig, err := addrKR.SignDetached(crypto.NewPlainMessage(b))
if err != nil {
return "", "", err
}
sigArm, err := sig.GetArmored()
if err != nil {
return "", "", err
}
return encArm, sigArm, nil
}
func generateNodeKeys(kr, addrKR *crypto.KeyRing) (string, string, string, error) {
nodePassphrase, nodeKey, err := generateCryptoKey()
if err != nil {
return "", "", "", err
}
nodePassphraseEnc, nodePassphraseSignature, err := encryptWithSignature(kr, addrKR, []byte(nodePassphrase))
if err != nil {
return "", "", "", err
}
return nodeKey, nodePassphraseEnc, nodePassphraseSignature, nil
}
func reencryptKeyPacket(srcKR, dstKR, addrKR *crypto.KeyRing, passphrase string) (string, error) {
oldSplitMessage, err := crypto.NewPGPSplitMessageFromArmored(passphrase)
if err != nil {
return "", err
}
sessionKey, err := srcKR.DecryptSessionKey(oldSplitMessage.KeyPacket)
if err != nil {
return "", err
}
newKeyPacket, err := dstKR.EncryptSessionKey(sessionKey)
if err != nil {
return "", err
}
newSplitMessage := crypto.NewPGPSplitMessage(newKeyPacket, oldSplitMessage.DataPacket)
return newSplitMessage.GetArmored()
}
func getKeyRing(kr, addrKR *crypto.KeyRing, key, passphrase, passphraseSignature string) (*crypto.KeyRing, error) {
enc, err := crypto.NewPGPMessageFromArmored(passphrase)
if err != nil {
return nil, err
}
dec, err := kr.Decrypt(enc, nil, crypto.GetUnixTime())
if err != nil {
return nil, err
}
sig, err := crypto.NewPGPSignatureFromArmored(passphraseSignature)
if err != nil {
return nil, err
}
if err := addrKR.VerifyDetached(dec, sig, crypto.GetUnixTime()); err != nil {
return nil, err
}
lockedKey, err := crypto.NewKeyFromArmored(key)
if err != nil {
return nil, err
}
unlockedKey, err := lockedKey.Unlock(dec.GetBinary())
if err != nil {
return nil, err
}
return crypto.NewKeyRing(unlockedKey)
}
func decryptBlockIntoBuffer(sessionKey *crypto.SessionKey, addrKR, nodeKR *crypto.KeyRing, originalHash, encSignature string, buffer io.ReaderFrom, block io.ReadCloser) error {
data, err := io.ReadAll(block)
if err != nil {
return err
}
plainMessage, err := sessionKey.Decrypt(data)
if err != nil {
return err
}
encSignatureArm, err := crypto.NewPGPMessageFromArmored(encSignature)
if err != nil {
return err
}
err = addrKR.VerifyDetachedEncrypted(plainMessage, encSignatureArm, nodeKR, crypto.GetUnixTime())
if err != nil {
return err
}
_, err = buffer.ReadFrom(plainMessage.NewReader())
if err != nil {
return err
}
h := sha256.New()
h.Write(data)
hash := h.Sum(nil)
base64Hash := base64.StdEncoding.EncodeToString(hash)
if err != nil {
return err
}
if base64Hash != originalHash {
return ErrDownloadedBlockHashVerificationFailed
}
return nil
}
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