bench-forgejo/models/gpg_key.go
zeripath fcb535c5c3
Sign merges, CRUD, Wiki and Repository initialisation with gpg key (#7631)
This PR fixes #7598 by providing a configurable way of signing commits across the Gitea instance. Per repository configurability and import/generation of trusted secure keys is not provided by this PR - from a security PoV that's probably impossible to do properly. Similarly web-signing, that is asking the user to sign something, is not implemented - this could be done at a later stage however.

## Features
- [x] If commit.gpgsign is set in .gitconfig sign commits and files created through repofiles. (merges should already have been signed.)
- [x] Verify commits signed with the default gpg as valid
- [x] Signer, Committer and Author can all be different
    - [x] Allow signer to be arbitrarily different - We still require the key to have an activated email on Gitea. A more complete implementation would be to use a keyserver and mark external-or-unactivated with an "unknown" trust level icon.
- [x] Add a signing-key.gpg endpoint to get the default gpg pub key if available
    - Rather than add a fake web-flow user I've added this as an endpoint on /api/v1/signing-key.gpg
    - [x] Try to match the default key with a user on gitea - this is done at verification time
- [x] Make things configurable?
    - app.ini configuration done
    - [x] when checking commits are signed need to check if they're actually verifiable too
- [x] Add documentation

I have decided that adjusting the docker to create a default gpg key is not the correct thing to do and therefore have not implemented this.
2019-10-16 14:42:42 +01:00

769 lines
22 KiB
Go

// Copyright 2017 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package models
import (
"bytes"
"container/list"
"crypto"
"encoding/base64"
"fmt"
"hash"
"io"
"strings"
"time"
"code.gitea.io/gitea/modules/git"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/timeutil"
"github.com/go-xorm/xorm"
"github.com/keybase/go-crypto/openpgp"
"github.com/keybase/go-crypto/openpgp/armor"
"github.com/keybase/go-crypto/openpgp/packet"
)
// GPGKey represents a GPG key.
type GPGKey struct {
ID int64 `xorm:"pk autoincr"`
OwnerID int64 `xorm:"INDEX NOT NULL"`
KeyID string `xorm:"INDEX CHAR(16) NOT NULL"`
PrimaryKeyID string `xorm:"CHAR(16)"`
Content string `xorm:"TEXT NOT NULL"`
CreatedUnix timeutil.TimeStamp `xorm:"created"`
ExpiredUnix timeutil.TimeStamp
AddedUnix timeutil.TimeStamp
SubsKey []*GPGKey `xorm:"-"`
Emails []*EmailAddress
CanSign bool
CanEncryptComms bool
CanEncryptStorage bool
CanCertify bool
}
//GPGKeyImport the original import of key
type GPGKeyImport struct {
KeyID string `xorm:"pk CHAR(16) NOT NULL"`
Content string `xorm:"TEXT NOT NULL"`
}
// BeforeInsert will be invoked by XORM before inserting a record
func (key *GPGKey) BeforeInsert() {
key.AddedUnix = timeutil.TimeStampNow()
}
// AfterLoad is invoked from XORM after setting the values of all fields of this object.
func (key *GPGKey) AfterLoad(session *xorm.Session) {
err := session.Where("primary_key_id=?", key.KeyID).Find(&key.SubsKey)
if err != nil {
log.Error("Find Sub GPGkeys[%s]: %v", key.KeyID, err)
}
}
// ListGPGKeys returns a list of public keys belongs to given user.
func ListGPGKeys(uid int64) ([]*GPGKey, error) {
keys := make([]*GPGKey, 0, 5)
return keys, x.Where("owner_id=? AND primary_key_id=''", uid).Find(&keys)
}
// GetGPGKeyByID returns public key by given ID.
func GetGPGKeyByID(keyID int64) (*GPGKey, error) {
key := new(GPGKey)
has, err := x.ID(keyID).Get(key)
if err != nil {
return nil, err
} else if !has {
return nil, ErrGPGKeyNotExist{keyID}
}
return key, nil
}
// GetGPGKeysByKeyID returns public key by given ID.
func GetGPGKeysByKeyID(keyID string) ([]*GPGKey, error) {
keys := make([]*GPGKey, 0, 1)
return keys, x.Where("key_id=?", keyID).Find(&keys)
}
// GetGPGImportByKeyID returns the import public armored key by given KeyID.
func GetGPGImportByKeyID(keyID string) (*GPGKeyImport, error) {
key := new(GPGKeyImport)
has, err := x.ID(keyID).Get(key)
if err != nil {
return nil, err
} else if !has {
return nil, ErrGPGKeyImportNotExist{keyID}
}
return key, nil
}
// checkArmoredGPGKeyString checks if the given key string is a valid GPG armored key.
// The function returns the actual public key on success
func checkArmoredGPGKeyString(content string) (*openpgp.Entity, error) {
list, err := openpgp.ReadArmoredKeyRing(strings.NewReader(content))
if err != nil {
return nil, ErrGPGKeyParsing{err}
}
return list[0], nil
}
//addGPGKey add key, import and subkeys to database
func addGPGKey(e Engine, key *GPGKey, content string) (err error) {
//Add GPGKeyImport
if _, err = e.Insert(GPGKeyImport{
KeyID: key.KeyID,
Content: content,
}); err != nil {
return err
}
// Save GPG primary key.
if _, err = e.Insert(key); err != nil {
return err
}
// Save GPG subs key.
for _, subkey := range key.SubsKey {
if err := addGPGSubKey(e, subkey); err != nil {
return err
}
}
return nil
}
//addGPGSubKey add subkeys to database
func addGPGSubKey(e Engine, key *GPGKey) (err error) {
// Save GPG primary key.
if _, err = e.Insert(key); err != nil {
return err
}
// Save GPG subs key.
for _, subkey := range key.SubsKey {
if err := addGPGSubKey(e, subkey); err != nil {
return err
}
}
return nil
}
// AddGPGKey adds new public key to database.
func AddGPGKey(ownerID int64, content string) (*GPGKey, error) {
ekey, err := checkArmoredGPGKeyString(content)
if err != nil {
return nil, err
}
// Key ID cannot be duplicated.
has, err := x.Where("key_id=?", ekey.PrimaryKey.KeyIdString()).
Get(new(GPGKey))
if err != nil {
return nil, err
} else if has {
return nil, ErrGPGKeyIDAlreadyUsed{ekey.PrimaryKey.KeyIdString()}
}
//Get DB session
sess := x.NewSession()
defer sess.Close()
if err = sess.Begin(); err != nil {
return nil, err
}
key, err := parseGPGKey(ownerID, ekey)
if err != nil {
return nil, err
}
if err = addGPGKey(sess, key, content); err != nil {
return nil, err
}
return key, sess.Commit()
}
//base64EncPubKey encode public key content to base 64
func base64EncPubKey(pubkey *packet.PublicKey) (string, error) {
var w bytes.Buffer
err := pubkey.Serialize(&w)
if err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(w.Bytes()), nil
}
//base64DecPubKey decode public key content from base 64
func base64DecPubKey(content string) (*packet.PublicKey, error) {
b, err := readerFromBase64(content)
if err != nil {
return nil, err
}
//Read key
p, err := packet.Read(b)
if err != nil {
return nil, err
}
//Check type
pkey, ok := p.(*packet.PublicKey)
if !ok {
return nil, fmt.Errorf("key is not a public key")
}
return pkey, nil
}
//GPGKeyToEntity retrieve the imported key and the traducted entity
func GPGKeyToEntity(k *GPGKey) (*openpgp.Entity, error) {
impKey, err := GetGPGImportByKeyID(k.KeyID)
if err != nil {
return nil, err
}
return checkArmoredGPGKeyString(impKey.Content)
}
//parseSubGPGKey parse a sub Key
func parseSubGPGKey(ownerID int64, primaryID string, pubkey *packet.PublicKey, expiry time.Time) (*GPGKey, error) {
content, err := base64EncPubKey(pubkey)
if err != nil {
return nil, err
}
return &GPGKey{
OwnerID: ownerID,
KeyID: pubkey.KeyIdString(),
PrimaryKeyID: primaryID,
Content: content,
CreatedUnix: timeutil.TimeStamp(pubkey.CreationTime.Unix()),
ExpiredUnix: timeutil.TimeStamp(expiry.Unix()),
CanSign: pubkey.CanSign(),
CanEncryptComms: pubkey.PubKeyAlgo.CanEncrypt(),
CanEncryptStorage: pubkey.PubKeyAlgo.CanEncrypt(),
CanCertify: pubkey.PubKeyAlgo.CanSign(),
}, nil
}
//getExpiryTime extract the expire time of primary key based on sig
func getExpiryTime(e *openpgp.Entity) time.Time {
expiry := time.Time{}
//Extract self-sign for expire date based on : https://github.com/golang/crypto/blob/master/openpgp/keys.go#L165
var selfSig *packet.Signature
for _, ident := range e.Identities {
if selfSig == nil {
selfSig = ident.SelfSignature
} else if ident.SelfSignature.IsPrimaryId != nil && *ident.SelfSignature.IsPrimaryId {
selfSig = ident.SelfSignature
break
}
}
if selfSig.KeyLifetimeSecs != nil {
expiry = e.PrimaryKey.CreationTime.Add(time.Duration(*selfSig.KeyLifetimeSecs) * time.Second)
}
return expiry
}
//parseGPGKey parse a PrimaryKey entity (primary key + subs keys + self-signature)
func parseGPGKey(ownerID int64, e *openpgp.Entity) (*GPGKey, error) {
pubkey := e.PrimaryKey
expiry := getExpiryTime(e)
//Parse Subkeys
subkeys := make([]*GPGKey, len(e.Subkeys))
for i, k := range e.Subkeys {
subs, err := parseSubGPGKey(ownerID, pubkey.KeyIdString(), k.PublicKey, expiry)
if err != nil {
return nil, err
}
subkeys[i] = subs
}
//Check emails
userEmails, err := GetEmailAddresses(ownerID)
if err != nil {
return nil, err
}
emails := make([]*EmailAddress, 0, len(e.Identities))
for _, ident := range e.Identities {
email := strings.ToLower(strings.TrimSpace(ident.UserId.Email))
for _, e := range userEmails {
if e.Email == email {
emails = append(emails, e)
break
}
}
}
//In the case no email as been found
if len(emails) == 0 {
failedEmails := make([]string, 0, len(e.Identities))
for _, ident := range e.Identities {
failedEmails = append(failedEmails, ident.UserId.Email)
}
return nil, ErrGPGNoEmailFound{failedEmails}
}
content, err := base64EncPubKey(pubkey)
if err != nil {
return nil, err
}
return &GPGKey{
OwnerID: ownerID,
KeyID: pubkey.KeyIdString(),
PrimaryKeyID: "",
Content: content,
CreatedUnix: timeutil.TimeStamp(pubkey.CreationTime.Unix()),
ExpiredUnix: timeutil.TimeStamp(expiry.Unix()),
Emails: emails,
SubsKey: subkeys,
CanSign: pubkey.CanSign(),
CanEncryptComms: pubkey.PubKeyAlgo.CanEncrypt(),
CanEncryptStorage: pubkey.PubKeyAlgo.CanEncrypt(),
CanCertify: pubkey.PubKeyAlgo.CanSign(),
}, nil
}
// deleteGPGKey does the actual key deletion
func deleteGPGKey(e *xorm.Session, keyID string) (int64, error) {
if keyID == "" {
return 0, fmt.Errorf("empty KeyId forbidden") //Should never happen but just to be sure
}
//Delete imported key
n, err := e.Where("key_id=?", keyID).Delete(new(GPGKeyImport))
if err != nil {
return n, err
}
return e.Where("key_id=?", keyID).Or("primary_key_id=?", keyID).Delete(new(GPGKey))
}
// DeleteGPGKey deletes GPG key information in database.
func DeleteGPGKey(doer *User, id int64) (err error) {
key, err := GetGPGKeyByID(id)
if err != nil {
if IsErrGPGKeyNotExist(err) {
return nil
}
return fmt.Errorf("GetPublicKeyByID: %v", err)
}
// Check if user has access to delete this key.
if !doer.IsAdmin && doer.ID != key.OwnerID {
return ErrGPGKeyAccessDenied{doer.ID, key.ID}
}
sess := x.NewSession()
defer sess.Close()
if err = sess.Begin(); err != nil {
return err
}
if _, err = deleteGPGKey(sess, key.KeyID); err != nil {
return err
}
return sess.Commit()
}
// CommitVerification represents a commit validation of signature
type CommitVerification struct {
Verified bool
Warning bool
Reason string
SigningUser *User
CommittingUser *User
SigningEmail string
SigningKey *GPGKey
}
// SignCommit represents a commit with validation of signature.
type SignCommit struct {
Verification *CommitVerification
*UserCommit
}
const (
// BadSignature is used as the reason when the signature has a KeyID that is in the db
// but no key that has that ID verifies the signature. This is a suspicious failure.
BadSignature = "gpg.error.probable_bad_signature"
// BadDefaultSignature is used as the reason when the signature has a KeyID that matches the
// default Key but is not verified by the default key. This is a suspicious failure.
BadDefaultSignature = "gpg.error.probable_bad_default_signature"
// NoKeyFound is used as the reason when no key can be found to verify the signature.
NoKeyFound = "gpg.error.no_gpg_keys_found"
)
func readerFromBase64(s string) (io.Reader, error) {
bs, err := base64.StdEncoding.DecodeString(s)
if err != nil {
return nil, err
}
return bytes.NewBuffer(bs), nil
}
func populateHash(hashFunc crypto.Hash, msg []byte) (hash.Hash, error) {
h := hashFunc.New()
if _, err := h.Write(msg); err != nil {
return nil, err
}
return h, nil
}
// readArmoredSign read an armored signature block with the given type. https://sourcegraph.com/github.com/golang/crypto/-/blob/openpgp/read.go#L24:6-24:17
func readArmoredSign(r io.Reader) (body io.Reader, err error) {
block, err := armor.Decode(r)
if err != nil {
return
}
if block.Type != openpgp.SignatureType {
return nil, fmt.Errorf("expected '" + openpgp.SignatureType + "', got: " + block.Type)
}
return block.Body, nil
}
func extractSignature(s string) (*packet.Signature, error) {
r, err := readArmoredSign(strings.NewReader(s))
if err != nil {
return nil, fmt.Errorf("Failed to read signature armor")
}
p, err := packet.Read(r)
if err != nil {
return nil, fmt.Errorf("Failed to read signature packet")
}
sig, ok := p.(*packet.Signature)
if !ok {
return nil, fmt.Errorf("Packet is not a signature")
}
return sig, nil
}
func verifySign(s *packet.Signature, h hash.Hash, k *GPGKey) error {
//Check if key can sign
if !k.CanSign {
return fmt.Errorf("key can not sign")
}
//Decode key
pkey, err := base64DecPubKey(k.Content)
if err != nil {
return err
}
return pkey.VerifySignature(h, s)
}
func hashAndVerify(sig *packet.Signature, payload string, k *GPGKey, committer, signer *User, email string) *CommitVerification {
//Generating hash of commit
hash, err := populateHash(sig.Hash, []byte(payload))
if err != nil { //Skipping failed to generate hash
log.Error("PopulateHash: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.generate_hash",
}
}
if err := verifySign(sig, hash, k); err == nil {
return &CommitVerification{ //Everything is ok
CommittingUser: committer,
Verified: true,
Reason: fmt.Sprintf("%s <%s> / %s", signer.Name, signer.Email, k.KeyID),
SigningUser: signer,
SigningKey: k,
SigningEmail: email,
}
}
return nil
}
func hashAndVerifyWithSubKeys(sig *packet.Signature, payload string, k *GPGKey, committer, signer *User, email string) *CommitVerification {
commitVerification := hashAndVerify(sig, payload, k, committer, signer, email)
if commitVerification != nil {
return commitVerification
}
//And test also SubsKey
for _, sk := range k.SubsKey {
commitVerification := hashAndVerify(sig, payload, sk, committer, signer, email)
if commitVerification != nil {
return commitVerification
}
}
return nil
}
func hashAndVerifyForKeyID(sig *packet.Signature, payload string, committer *User, keyID, name, email string) *CommitVerification {
if keyID == "" {
return nil
}
keys, err := GetGPGKeysByKeyID(keyID)
if err != nil {
log.Error("GetGPGKeysByKeyID: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.failed_retrieval_gpg_keys",
}
}
if len(keys) == 0 {
return nil
}
for _, key := range keys {
activated := false
if len(email) != 0 {
for _, e := range key.Emails {
if e.IsActivated && strings.EqualFold(e.Email, email) {
activated = true
email = e.Email
break
}
}
} else {
for _, e := range key.Emails {
if e.IsActivated {
activated = true
email = e.Email
break
}
}
}
if !activated {
continue
}
signer := &User{
Name: name,
Email: email,
}
if key.OwnerID != 0 {
owner, err := GetUserByID(key.OwnerID)
if err == nil {
signer = owner
} else if !IsErrUserNotExist(err) {
log.Error("Failed to GetUserByID: %d for key ID: %d (%s) %v", key.OwnerID, key.ID, key.KeyID, err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.no_committer_account",
}
}
}
commitVerification := hashAndVerifyWithSubKeys(sig, payload, key, committer, signer, email)
if commitVerification != nil {
return commitVerification
}
}
// This is a bad situation ... We have a key id that is in our database but the signature doesn't match.
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Warning: true,
Reason: BadSignature,
}
}
// ParseCommitWithSignature check if signature is good against keystore.
func ParseCommitWithSignature(c *git.Commit) *CommitVerification {
var committer *User
if c.Committer != nil {
var err error
//Find Committer account
committer, err = GetUserByEmail(c.Committer.Email) //This finds the user by primary email or activated email so commit will not be valid if email is not
if err != nil { //Skipping not user for commiter
committer = &User{
Name: c.Committer.Name,
Email: c.Committer.Email,
}
// We can expect this to often be an ErrUserNotExist. in the case
// it is not, however, it is important to log it.
if !IsErrUserNotExist(err) {
log.Error("GetUserByEmail: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.no_committer_account",
}
}
}
}
// If no signature just report the committer
if c.Signature == nil {
return &CommitVerification{
CommittingUser: committer,
Verified: false, //Default value
Reason: "gpg.error.not_signed_commit", //Default value
}
}
//Parsing signature
sig, err := extractSignature(c.Signature.Signature)
if err != nil { //Skipping failed to extract sign
log.Error("SignatureRead err: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.extract_sign",
}
}
keyID := ""
if sig.IssuerKeyId != nil && (*sig.IssuerKeyId) != 0 {
keyID = fmt.Sprintf("%X", *sig.IssuerKeyId)
}
if keyID == "" && sig.IssuerFingerprint != nil && len(sig.IssuerFingerprint) > 0 {
keyID = fmt.Sprintf("%X", sig.IssuerFingerprint[12:20])
}
defaultReason := NoKeyFound
// First check if the sig has a keyID and if so just look at that
if commitVerification := hashAndVerifyForKeyID(
sig,
c.Signature.Payload,
committer,
keyID,
setting.AppName,
""); commitVerification != nil {
if commitVerification.Reason == BadSignature {
defaultReason = BadSignature
} else {
return commitVerification
}
}
// Now try to associate the signature with the committer, if present
if committer.ID != 0 {
keys, err := ListGPGKeys(committer.ID)
if err != nil { //Skipping failed to get gpg keys of user
log.Error("ListGPGKeys: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.failed_retrieval_gpg_keys",
}
}
for _, k := range keys {
//Pre-check (& optimization) that emails attached to key can be attached to the commiter email and can validate
canValidate := false
email := ""
for _, e := range k.Emails {
if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) {
canValidate = true
email = e.Email
break
}
}
if !canValidate {
continue //Skip this key
}
commitVerification := hashAndVerifyWithSubKeys(sig, c.Signature.Payload, k, committer, committer, email)
if commitVerification != nil {
return commitVerification
}
}
}
if setting.Repository.Signing.SigningKey != "" && setting.Repository.Signing.SigningKey != "default" && setting.Repository.Signing.SigningKey != "none" {
// OK we should try the default key
gpgSettings := git.GPGSettings{
Sign: true,
KeyID: setting.Repository.Signing.SigningKey,
Name: setting.Repository.Signing.SigningName,
Email: setting.Repository.Signing.SigningEmail,
}
if err := gpgSettings.LoadPublicKeyContent(); err != nil {
log.Error("Error getting default signing key: %s %v", gpgSettings.KeyID, err)
} else if commitVerification := verifyWithGPGSettings(&gpgSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
if commitVerification.Reason == BadSignature {
defaultReason = BadSignature
} else {
return commitVerification
}
}
}
defaultGPGSettings, err := c.GetRepositoryDefaultPublicGPGKey(false)
if err != nil {
log.Error("Error getting default public gpg key: %v", err)
} else if defaultGPGSettings.Sign {
if commitVerification := verifyWithGPGSettings(defaultGPGSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
if commitVerification.Reason == BadSignature {
defaultReason = BadSignature
} else {
return commitVerification
}
}
}
return &CommitVerification{ //Default at this stage
CommittingUser: committer,
Verified: false,
Warning: defaultReason != NoKeyFound,
Reason: defaultReason,
SigningKey: &GPGKey{
KeyID: keyID,
},
}
}
func verifyWithGPGSettings(gpgSettings *git.GPGSettings, sig *packet.Signature, payload string, committer *User, keyID string) *CommitVerification {
// First try to find the key in the db
if commitVerification := hashAndVerifyForKeyID(sig, payload, committer, gpgSettings.KeyID, gpgSettings.Name, gpgSettings.Email); commitVerification != nil {
return commitVerification
}
// Otherwise we have to parse the key
ekey, err := checkArmoredGPGKeyString(gpgSettings.PublicKeyContent)
if err != nil {
log.Error("Unable to get default signing key: %v", err)
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.generate_hash",
}
}
pubkey := ekey.PrimaryKey
content, err := base64EncPubKey(pubkey)
if err != nil {
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.generate_hash",
}
}
k := &GPGKey{
Content: content,
CanSign: pubkey.CanSign(),
KeyID: pubkey.KeyIdString(),
}
if commitVerification := hashAndVerifyWithSubKeys(sig, payload, k, committer, &User{
Name: gpgSettings.Name,
Email: gpgSettings.Email,
}, gpgSettings.Email); commitVerification != nil {
return commitVerification
}
if keyID == k.KeyID {
// This is a bad situation ... We have a key id that matches our default key but the signature doesn't match.
return &CommitVerification{
CommittingUser: committer,
Verified: false,
Warning: true,
Reason: BadSignature,
}
}
return nil
}
// ParseCommitsWithSignature checks if signaute of commits are corresponding to users gpg keys.
func ParseCommitsWithSignature(oldCommits *list.List) *list.List {
var (
newCommits = list.New()
e = oldCommits.Front()
)
for e != nil {
c := e.Value.(UserCommit)
newCommits.PushBack(SignCommit{
UserCommit: &c,
Verification: ParseCommitWithSignature(c.Commit),
})
e = e.Next()
}
return newCommits
}