Add option to provide signature for a token to verify key ownership (#14054)

* Add option to provide signed token to verify key ownership

Currently we will only allow a key to be matched to a user if it matches
an activated email address. This PR provides a different mechanism - if
the user provides a signature for automatically generated token (based
on the timestamp, user creation time, user ID, username and primary
email.

* Ensure verified keys can act for all active emails for the user

* Add code to mark keys as verified

* Slight UI adjustments

* Slight UI adjustments 2

* Simplify signature verification slightly

* fix postgres test

* add api routes

* handle swapped primary-keys

* Verify the no-reply address for verified keys

* Only add email addresses that are activated to keys

* Fix committer shortcut properly

* Restructure gpg_keys.go

* Use common Verification Token code

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/gpg_key_common.go

@@ -0,0 +1,137 @@
+// Copyright 2021 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"
+	"crypto"
+	"encoding/base64"
+	"fmt"
+	"hash"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/keybase/go-crypto/openpgp"
+	"github.com/keybase/go-crypto/openpgp/armor"
+	"github.com/keybase/go-crypto/openpgp/packet"
+)
+
+//   __________________  ________   ____  __.
+//  /  _____/\______   \/  _____/  |    |/ _|____ ___.__.
+// /   \  ___ |     ___/   \  ___  |      <_/ __ <   |  |
+// \    \_\  \|    |   \    \_\  \ |    |  \  ___/\___  |
+//  \______  /|____|    \______  / |____|__ \___  > ____|
+//         \/                  \/          \/   \/\/
+// _________
+// \_   ___ \  ____   _____   _____   ____   ____
+// /    \  \/ /  _ \ /     \ /     \ /  _ \ /    \
+// \     \___(  <_> )  Y Y  \  Y Y  (  <_> )   |  \
+//  \______  /\____/|__|_|  /__|_|  /\____/|___|  /
+//         \/             \/      \/            \/
+
+// This file provides common functions relating to GPG Keys
+
+// 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.EntityList, error) {
+	list, err := openpgp.ReadArmoredKeyRing(strings.NewReader(content))
+	if err != nil {
+		return nil, ErrGPGKeyParsing{err}
+	}
+	return list, nil
+}
+
+// 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
+}
+
+func readerFromBase64(s string) (io.Reader, error) {
+	bs, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewBuffer(bs), 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
+}
+
+// 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
+}
+
+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
+}