crypto: signing builds with signify/minisign (#21798)

* internal/build: implement signify's signing func
* Add signify to the ci utility
* fix output file format
* Add unit test for signify
* holiman's + travis' feedback
* internal/build: verify signify's output
* crypto: move signify to common dir
* use go-minisign to verify binaries
* more holiman feedback
* crypto, ci: support minisign output
* only accept one-line trusted comments
* configurable untrusted comments
* code cleanup in tests
* revert to use ed25519 from the stdlib
* bug: fix for empty untrusted comments
* write timestamp as comment if trusted comment isn't present
* rename line checker to commentHasManyLines
* crypto: added signify fuzzer (#6)
* crypto: added signify fuzzer
* stuff
* crypto: updated signify fuzzer to fuzz comments
* crypto: repro signify crashes
* rebased fuzzer on build-signify branch
* hide fuzzer behind gofuzz build flag
* extract key data inside a single function
* don't treat \r as a newline
* travis: fix signing command line
* do not use an external binary in tests
* crypto: move signify to crypto/signify
* travis: fix formatting issue
* ci: fix linter build after package move

Co-authored-by: Marius van der Wijden <m.vanderwijden@live.de>

crypto/signify/signify.go

@@ -0,0 +1,118 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// signFile reads the contents of an input file and signs it (in armored format)
+// with the key provided, placing the signature into the output file.
+
+package signify
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+	"time"
+
+	"crypto/ed25519"
+)
+
+var (
+	errInvalidKeyHeader = errors.New("Incorrect key header")
+	errInvalidKeyLength = errors.New("invalid, key length != 104")
+)
+
+func parsePrivateKey(key string) (ed25519.PrivateKey, []byte, []byte, error) {
+	keydata, err := base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	if len(keydata) != 104 {
+		return nil, nil, nil, errInvalidKeyLength
+	}
+
+	if string(keydata[:2]) != "Ed" {
+		return nil, nil, nil, errInvalidKeyHeader
+	}
+
+	return ed25519.PrivateKey(keydata[40:]), keydata[:2], keydata[32:40], nil
+}
+
+func commentHasManyLines(comment string) bool {
+	firstLFIndex := strings.IndexByte(comment, 10)
+	return (firstLFIndex >= 0 && firstLFIndex < len(comment)-1)
+}
+
+// SignifySignFile creates a signature of the input file.
+func SignifySignFile(input string, output string, key string, unTrustedComment string, trustedComment string) error {
+	in, err := os.Open(input)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out, err := os.Create(output)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	skey, header, keyNum, err := parsePrivateKey(key)
+	if err != nil {
+		return err
+	}
+
+	filedata, err := ioutil.ReadAll(in)
+	if err != nil {
+		return err
+	}
+
+	rawSig := ed25519.Sign(skey, filedata)
+
+	var sigdata []byte
+	sigdata = append(sigdata, header...)
+	sigdata = append(sigdata, keyNum...)
+	sigdata = append(sigdata, rawSig...)
+
+	// Check that the trusted comment fits in one line
+	if commentHasManyLines(unTrustedComment) {
+		return errors.New("untrusted comment must fit on a single line")
+	}
+
+	if unTrustedComment == "" {
+		unTrustedComment = "verify with " + input + ".pub"
+	}
+	out.WriteString(fmt.Sprintf("untrusted comment: %s\n%s\n", unTrustedComment, base64.StdEncoding.EncodeToString(sigdata)))
+
+	// Add the trusted comment if unavailable
+	if trustedComment == "" {
+		trustedComment = fmt.Sprintf("timestamp:%d", time.Now().Unix())
+	}
+
+	// Check that the trusted comment fits in one line
+	if commentHasManyLines(trustedComment) {
+		return errors.New("trusted comment must fit on a single line")
+	}
+
+	var sigAndComment []byte
+	sigAndComment = append(sigAndComment, rawSig...)
+	sigAndComment = append(sigAndComment, []byte(trustedComment)...)
+	out.WriteString(fmt.Sprintf("trusted comment: %s\n%s\n", trustedComment, base64.StdEncoding.EncodeToString(ed25519.Sign(skey, sigAndComment))))
+
+	return nil
+}