notary/internal/note: signed note formats, keys, and operations
This is part of a design sketch for a Go module notary.
Eventually the code will live outside golang.org/x/exp.
Everything here is subject to change! Don't depend on it!
This CL implements a simple text format for the notary's
signed tree hashes.
Change-Id: I0d08e0943b3e2b83eace7baa059d4a05c5a330a5
Reviewed-on: https://go-review.googlesource.com/c/exp/+/156324
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
diff --git a/notary/go.mod b/notary/go.mod
new file mode 100644
index 0000000..4b4d966
--- /dev/null
+++ b/notary/go.mod
@@ -0,0 +1,5 @@
+module golang.org/x/exp/notary
+
+go 1.13
+
+require golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a
diff --git a/notary/go.sum b/notary/go.sum
new file mode 100644
index 0000000..6dea69e
--- /dev/null
+++ b/notary/go.sum
@@ -0,0 +1,3 @@
+golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a h1:YX8ljsm6wXlHZO+aRz9Exqr0evNhKRNe5K/gi+zKh4U=
+golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
diff --git a/notary/internal/note/example_test.go b/notary/internal/note/example_test.go
new file mode 100644
index 0000000..d715ea4
--- /dev/null
+++ b/notary/internal/note/example_test.go
@@ -0,0 +1,128 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package note_test
+
+import (
+ "fmt"
+ "io"
+ "os"
+
+ "golang.org/x/exp/notary/internal/note"
+)
+
+func ExampleSign() {
+ skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+ text := "If you think cryptography is the answer to your problem,\n" +
+ "then you don't know what your problem is.\n"
+
+ signer, err := note.NewSigner(skey)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+
+ msg, err := note.Sign(¬e.Note{Text: text}, signer)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ os.Stdout.Write(msg)
+
+ // Output:
+ // If you think cryptography is the answer to your problem,
+ // then you don't know what your problem is.
+ //
+ // — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+}
+
+func ExampleOpen() {
+ vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ msg := []byte("If you think cryptography is the answer to your problem,\n" +
+ "then you don't know what your problem is.\n" +
+ "\n" +
+ "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+ verifier, err := note.NewVerifier(vkey)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ notaries := note.NotaryList(verifier)
+
+ n, err := note.Open(msg, notaries)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ fmt.Printf("%s (%08x):\n%s", n.Sigs[0].Name, n.Sigs[0].Hash, n.Text)
+
+ // Output:
+ // PeterNeumann (c74f20a3):
+ // If you think cryptography is the answer to your problem,
+ // then you don't know what your problem is.
+}
+
+var rand = struct {
+ Reader io.Reader
+}{
+ zeroReader{},
+}
+
+type zeroReader struct{}
+
+func (zeroReader) Read(buf []byte) (int, error) {
+ for i := range buf {
+ buf[i] = 0
+ }
+ return len(buf), nil
+}
+
+func ExampleSign_add_signatures() {
+ vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ msg := []byte("If you think cryptography is the answer to your problem,\n" +
+ "then you don't know what your problem is.\n" +
+ "\n" +
+ "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+ verifier, err := note.NewVerifier(vkey)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ notaries := note.NotaryList(verifier)
+
+ n, err := note.Open([]byte(msg), notaries)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+
+ skey, vkey, err := note.GenerateKey(rand.Reader, "EnochRoot")
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ _ = vkey // give to verifiers
+
+ me, err := note.NewSigner(skey)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+
+ msg, err = note.Sign(n, me)
+ if err != nil {
+ fmt.Println(err)
+ return
+ }
+ os.Stdout.Write(msg)
+
+ // Output:
+ // If you think cryptography is the answer to your problem,
+ // then you don't know what your problem is.
+ //
+ // — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+ // — EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=
+}
diff --git a/notary/internal/note/note.go b/notary/internal/note/note.go
new file mode 100644
index 0000000..d4b14cf
--- /dev/null
+++ b/notary/internal/note/note.go
@@ -0,0 +1,664 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package note defines the notes signed by the Go module notary.
+//
+// This package is part of a DRAFT of what the Go module notary will look like.
+// Do not assume the details here are final!
+//
+// A note is text signed by one or more notary keys.
+// The text should be ignored unless the note is signed by
+// a trusted notary key and the signature has been verified.
+//
+// A notary key is identified by a name, typically the "host[/path]"
+// giving the base URL of the notary's transparency log.
+// The syntactic restrictions on a name are that it be non-empty,
+// well-formed UTF-8 containing neither Unicode spaces nor plus (U+002B).
+//
+// A notary signs texts using public key cryptography.
+// A given notary may have multiple public keys, each
+// identified by the first 32 bits of the SHA-256 hash of
+// the concatenation of the notary name, a newline, and
+// the encoded public key.
+//
+// Verifying Notes
+//
+// A Verifier allows verification of signatures by one notary public key.
+// It can report the name of the notary and the uint32 hash of the key,
+// and it can verify a purported signature by that key.
+//
+// The standard implementation of a Verifier is constructed
+// by NewVerifier starting from a verifier key, which is a
+// plain text string of the form "<name>+<hash>+<keydata>".
+//
+// A Notaries allows looking up a Verifier by the combination
+// of notary name and key hash.
+//
+// The standard implementation of a Notaries is constructed
+// by NotaryList from a list of known verifiers.
+//
+// A Note represents a text with one or more signatures.
+// An implementation can reject a note with too many signatures
+// (for example, more than 100 signatures).
+//
+// A Signature represents a signature on a note, verified or not.
+//
+// The Open function takes as input a signed message
+// and a set of known notaries. It decodes and verifies
+// the message signatures and returns a Note structure
+// containing the message text and (verified or unverified) signatures.
+//
+// Signing Notes
+//
+// A Signer allows signing a text with a given key.
+// It can report the name of the notary and the hash of the key
+// and can sign a raw text using that key.
+//
+// The standard implementation of a Signer is constructed
+// by NewSigner starting from an encoded signer key, which is a
+// plain text string of the form "PRIVATE+KEY+<name>+<hash>+<keydata>".
+// Anyone with an encoded signer key can sign messages using that key,
+// so it must be kept secret. The encoding begins with the literal text
+// "PRIVATE+KEY" to avoid confusion with the public verifier key.
+//
+// The Sign function takes as input a Note and a list of Signers
+// and returns an encoded, signed message.
+//
+// Signed Note Format
+//
+// A signed note consists of a text ending in newline (U+000A),
+// followed by a blank line (only a newline),
+// followed by one or more signature lines of this form:
+// em dash (U+2014), space (U+0020),
+// notary name, space, base64-encoded signature, newline.
+//
+// Signed notes must be valid UTF-8 and must not contain any
+// ASCII control characters (those below U+0020) other than newline.
+//
+// A signature is a base64 encoding of 4+n bytes.
+//
+// The first four bytes in the signature are the uint32 key hash
+// stored in big-endian order, which is to say they are the first
+// four bytes of the truncated SHA-256 used to derive the key hash
+// in the first place.
+//
+// The remaining n bytes are the result of using the specified key
+// to sign the note text (including the final newline but not the
+// separating blank line).
+//
+// Generating Keys
+//
+// There is only one key type, Ed25519 with algorithm identifier 1.
+// New key types may be introduced in the future as needed,
+// although doing so will require deploying the new algorithms to all clients
+// before starting to depend on them for signatures.
+//
+// The GenerateKey function generates and returns a new signer
+// and corresponding verifier.
+//
+// Example
+//
+// Here is a well-formed signed note:
+//
+// If you think cryptography is the answer to your problem,
+// then you don't know what your problem is.
+//
+// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+//
+// It can be constructed and displayed using:
+//
+// skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+// text := "If you think cryptography is the answer to your problem,\n" +
+// "then you don't know what your problem is.\n"
+//
+// signer, err := note.NewSigner(skey)
+// if err != nil {
+// log.Fatal(err)
+// }
+//
+// msg, err := note.Sign(¬e.Note{Text: text}, signer)
+// if err != nil {
+// log.Fatal(err)
+// }
+// os.Stdout.Write(msg)
+//
+// The note's text is two lines, including the final newline,
+// and the text is purportedly signed by a notary named
+// "PeterNeumann". (Although notary names are canonically
+// base URLs, the only syntactic requirement is that they
+// not contain spaces or newlines).
+//
+// If Open is given access to a Notaries including the
+// Verifier for this key, then it will succeed at verifiying
+// the encoded message and returning the parsed Note:
+//
+// vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+// msg := []byte("If you think cryptography is the answer to your problem,\n" +
+// "then you don't know what your problem is.\n" +
+// "\n" +
+// "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+//
+// verifier, err := note.NewVerifier(vkey)
+// if err != nil {
+// log.Fatal(err)
+// }
+// notaries := note.NotaryList(verifier)
+//
+// n, err := note.Open([]byte(msg), notaries)
+// if err != nil {
+// log.Fatal(err)
+// }
+// fmt.Printf("%s (%08x):\n%s", n.Sigs[0].Name, n.Sigs[0].Hash, n.Text)
+//
+// You can add your own signature to this message by re-signing the note:
+//
+// skey, vkey, err := note.GenerateKey(rand.Reader, "EnochRoot")
+// if err != nil {
+// log.Fatal(err)
+// }
+// _ = vkey // give to verifiers
+//
+// me, err := note.NewSigner(skey)
+// if err != nil {
+// log.Fatal(err)
+// }
+//
+// msg, err := note.Sign(n, me)
+// if err != nil {
+// log.Fatal(err)
+// }
+// os.Stdout.Write(msg)
+//
+// This will print a doubly-signed message, like:
+//
+// If you think cryptography is the answer to your problem,
+// then you don't know what your problem is.
+//
+// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+// — EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=
+//
+package note
+
+import (
+ "bytes"
+ "crypto/sha256"
+ "encoding/base64"
+ "encoding/binary"
+ "errors"
+ "fmt"
+ "io"
+ "strconv"
+ "strings"
+ "unicode"
+ "unicode/utf8"
+
+ "golang.org/x/crypto/ed25519"
+)
+
+// A Verifier verifies messages signed with a specific notary key.
+type Verifier interface {
+ // Name returns the name of the notary.
+ Name() string
+
+ // KeyHash returns the notary key hash.
+ KeyHash() uint32
+
+ // Verify reports whether sig is a valid signature of msg.
+ Verify(msg, sig []byte) bool
+}
+
+// A Signer signs messages using a specific notary key.
+type Signer interface {
+ // Name returns the name of the notary.
+ Name() string
+
+ // KeyHash returns the notary key hash.
+ KeyHash() uint32
+
+ // Sign returns a signature for the given message.
+ Sign(msg []byte) ([]byte, error)
+}
+
+// keyHash computes the key hash for the given notary name and encoded public key.
+func keyHash(name string, key []byte) uint32 {
+ h := sha256.New()
+ h.Write([]byte(name))
+ h.Write([]byte("\n"))
+ h.Write(key)
+ sum := h.Sum(nil)
+ return binary.BigEndian.Uint32(sum)
+}
+
+var (
+ errVerifierID = errors.New("malformed verifier id")
+ errVerifierAlg = errors.New("unknown verifier algorithm")
+ errVerifierHash = errors.New("invalid verifier hash")
+)
+
+const (
+ algEd25519 = 1
+)
+
+// isValidName reports whether name is valid.
+// It must be non-empty and not have any Unicode spaces or pluses.
+func isValidName(name string) bool {
+ return name != "" && utf8.ValidString(name) && strings.IndexFunc(name, unicode.IsSpace) < 0 && !strings.Contains(name, "+")
+}
+
+// NewVerifier construct a new Verifier from an encoded verifier key.
+func NewVerifier(vkey string) (Verifier, error) {
+ name, vkey := chop(vkey, "+")
+ hash16, key64 := chop(vkey, "+")
+ hash, err1 := strconv.ParseUint(hash16, 16, 32)
+ key, err2 := base64.StdEncoding.DecodeString(key64)
+ if len(hash16) != 8 || err1 != nil || err2 != nil || !isValidName(name) || len(key) == 0 {
+ return nil, errVerifierID
+ }
+ if uint32(hash) != keyHash(name, key) {
+ return nil, errVerifierHash
+ }
+
+ v := &verifier{
+ name: name,
+ hash: uint32(hash),
+ }
+
+ alg, key := key[0], key[1:]
+ switch alg {
+ default:
+ return nil, errVerifierAlg
+
+ case algEd25519:
+ if len(key) != 32 {
+ return nil, errVerifierID
+ }
+ v.verify = func(msg, sig []byte) bool {
+ return ed25519.Verify(key, msg, sig)
+ }
+ }
+
+ return v, nil
+}
+
+// chop chops s at the first instance of sep, if any,
+// and returns the text before and after sep.
+// If sep is not present, chop returns before is s and after is empty.
+func chop(s, sep string) (before, after string) {
+ i := strings.Index(s, sep)
+ if i < 0 {
+ return s, ""
+ }
+ return s[:i], s[i+len(sep):]
+}
+
+// verifier is a trivial Verifier implementation.
+type verifier struct {
+ name string
+ hash uint32
+ verify func([]byte, []byte) bool
+}
+
+func (v *verifier) Name() string { return v.name }
+func (v *verifier) KeyHash() uint32 { return v.hash }
+func (v *verifier) Verify(msg, sig []byte) bool { return v.verify(msg, sig) }
+
+// NewSigner constructs a new Signer from an encoded signer key.
+func NewSigner(skey string) (Signer, error) {
+ priv1, skey := chop(skey, "+")
+ priv2, skey := chop(skey, "+")
+ name, skey := chop(skey, "+")
+ hash16, key64 := chop(skey, "+")
+ hash, err1 := strconv.ParseUint(hash16, 16, 32)
+ key, err2 := base64.StdEncoding.DecodeString(key64)
+ if priv1 != "PRIVATE" || priv2 != "KEY" || len(hash16) != 8 || err1 != nil || err2 != nil || !isValidName(name) || len(key) == 0 {
+ return nil, errSignerID
+ }
+
+ // Note: hash is the hash of the public key and we have the private key.
+ // Must verify hash after deriving public key.
+
+ s := &signer{
+ name: name,
+ hash: uint32(hash),
+ }
+
+ var pubkey []byte
+
+ alg, key := key[0], key[1:]
+ switch alg {
+ default:
+ return nil, errSignerAlg
+
+ case algEd25519:
+ if len(key) != 32 {
+ return nil, errSignerID
+ }
+ key = ed25519.NewKeyFromSeed(key)
+ pubkey = append([]byte{algEd25519}, key[32:]...)
+ s.sign = func(msg []byte) ([]byte, error) {
+ return ed25519.Sign(key, msg), nil
+ }
+ }
+
+ if uint32(hash) != keyHash(name, pubkey) {
+ return nil, errSignerHash
+ }
+
+ return s, nil
+}
+
+var (
+ errSignerID = errors.New("malformed verifier id")
+ errSignerAlg = errors.New("unknown verifier algorithm")
+ errSignerHash = errors.New("invalid verifier hash")
+)
+
+// signer is a trivial Signer implementation.
+type signer struct {
+ name string
+ hash uint32
+ sign func([]byte) ([]byte, error)
+}
+
+func (s *signer) Name() string { return s.name }
+func (s *signer) KeyHash() uint32 { return s.hash }
+func (s *signer) Sign(msg []byte) ([]byte, error) { return s.sign(msg) }
+
+// GenerateKey generates a signer and verifier key pair for a named notary.
+// The signer key skey is private and must be kept secret.
+func GenerateKey(rand io.Reader, name string) (skey, vkey string, err error) {
+ pub, priv, err := ed25519.GenerateKey(rand)
+ if err != nil {
+ return "", "", err
+ }
+ pubkey := append([]byte{algEd25519}, pub...)
+ privkey := append([]byte{algEd25519}, priv.Seed()...)
+ h := keyHash(name, pubkey)
+
+ skey = fmt.Sprintf("PRIVATE+KEY+%s+%08x+%s", name, h, base64.StdEncoding.EncodeToString(privkey))
+ vkey = fmt.Sprintf("%s+%08x+%s", name, h, base64.StdEncoding.EncodeToString(pubkey))
+ return skey, vkey, nil
+}
+
+// A Notaries is a collection of known notary keys.
+type Notaries interface {
+ // Verifier returns the Verifier associated with the notary key
+ // identified by the name and hash.
+ // If the name, hash pair is unknown, Verifier should return
+ // an UnknownNotaryError.
+ Verifier(name string, hash uint32) (Verifier, error)
+}
+
+// An UnknownNotaryError indicates that the given notary key is not known.
+// The Open function records signatures for unknown notaries as
+// unverified signatures.
+type UnknownNotaryError struct {
+ Name string
+ KeyHash uint32
+}
+
+func (e *UnknownNotaryError) Error() string {
+ return fmt.Sprintf("unknown notary key %s+%08x", e.Name, e.KeyHash)
+}
+
+// An ambiguousNotaryError indicates that the given name and hash
+// match multiple notary keys passed to NotaryList.
+// (If this happens, some malicious actor has taken control of the
+// verifier list, at which point we may as well give up entirely,
+// but we diagnose the problem instead.)
+type ambiguousNotaryError struct {
+ name string
+ hash uint32
+}
+
+func (e *ambiguousNotaryError) Error() string {
+ return fmt.Sprintf("ambiguous notary key %s+%08x", e.name, e.hash)
+}
+
+// NotaryList returns a Notaries implementation that uses the given list of verifiers.
+func NotaryList(list ...Verifier) Notaries {
+ m := make(notaryMap)
+ for _, v := range list {
+ k := nameHash{v.Name(), v.KeyHash()}
+ m[k] = append(m[k], v)
+ }
+ return m
+}
+
+type nameHash struct {
+ name string
+ hash uint32
+}
+
+type notaryMap map[nameHash][]Verifier
+
+func (m notaryMap) Verifier(name string, hash uint32) (Verifier, error) {
+ v, ok := m[nameHash{name, hash}]
+ if !ok {
+ return nil, &UnknownNotaryError{name, hash}
+ }
+ if len(v) > 1 {
+ return nil, &ambiguousNotaryError{name, hash}
+ }
+ return v[0], nil
+}
+
+// A Note is a text and signatures.
+type Note struct {
+ Text string // text of note
+ Sigs []Signature // verified signatures
+ UnverifiedSigs []Signature // unverified signatures
+}
+
+// A Signature is a single signature found in a note.
+type Signature struct {
+ // Name and Hash give the name and key hash
+ // for the notary key that generated the signature.
+ Name string
+ Hash uint32
+
+ // Base64 records the base64-encoded signature bytes.
+ Base64 string
+}
+
+// An UnverifiedNoteError indicates that the note
+// successfully parsed but had no verifiable signatures.
+type UnverifiedNoteError struct {
+ Note *Note
+}
+
+func (e *UnverifiedNoteError) Error() string {
+ return "note has no verifiable signatures"
+}
+
+// An InvalidSignatureError indicates that the given notary key was known
+// and the associated Verifier rejected the signature.
+type InvalidSignatureError struct {
+ Name string
+ Hash uint32
+}
+
+func (e *InvalidSignatureError) Error() string {
+ return fmt.Sprintf("invalid signature for notary key %s+%08x", e.Name, e.Hash)
+}
+
+var (
+ errMalformedNote = errors.New("malformed note")
+ errInvalidSigner = errors.New("invalid signer")
+
+ sigSplit = []byte("\n\n")
+ sigPrefix = []byte("— ")
+)
+
+// Open opens and parses the message msg, checking signatures of the known notaries.
+//
+// For each signature in the message, Open calls known.Verifier to find a verifier.
+// If known.Verifier returns a verifier and the verifier accepts the signature,
+// Open records the signature in the returned note's Sigs field.
+// If known.Verifier returns a verifier but the verifier rejects the signature,
+// Open returns an InvalidSignatureError.
+// If known.Verifier returns an UnknownNotaryError,
+// Open records the signature in the returned note's UnverifiedSigs field.
+// If known.Verifier returns any other error, Open returns that error.
+//
+// If no known verifier has signed an otherwise valid note,
+// Open returns an UnverifiedNoteError.
+// In this case, the unverified note can be fetched from inside the error.
+func Open(msg []byte, known Notaries) (*Note, error) {
+ // Must have valid UTF-8 with no non-newline ASCII control characters.
+ for i := 0; i < len(msg); {
+ r, size := utf8.DecodeRune(msg[i:])
+ if r < 0x20 && r != '\n' || r == utf8.RuneError && size == 1 {
+ return nil, errMalformedNote
+ }
+ i += size
+ }
+
+ // Must end with signature block preceded by blank line.
+ split := bytes.LastIndex(msg, sigSplit)
+ if split < 0 {
+ return nil, errMalformedNote
+ }
+ text, sigs := msg[:split+1], msg[split+2:]
+ if len(sigs) == 0 || sigs[len(sigs)-1] != '\n' {
+ return nil, errMalformedNote
+ }
+
+ n := &Note{
+ Text: string(text),
+ }
+
+ var buf bytes.Buffer
+ buf.Write(text)
+
+ // Parse and verify signatures.
+ // Ignore duplicate signatures.
+ seen := make(map[nameHash]bool)
+ seenUnverified := make(map[string]bool)
+ numSig := 0
+ for len(sigs) > 0 {
+ // Pull out next signature line.
+ // We know sigs[len(sigs)-1] == '\n', so IndexByte always finds one.
+ i := bytes.IndexByte(sigs, '\n')
+ line := sigs[:i]
+ sigs = sigs[i+1:]
+
+ if !bytes.HasPrefix(line, sigPrefix) {
+ return nil, errMalformedNote
+ }
+ line = line[len(sigPrefix):]
+ name, b64 := chop(string(line), " ")
+ sig, err := base64.StdEncoding.DecodeString(b64)
+ if err != nil || !isValidName(name) || b64 == "" || len(sig) < 5 {
+ return nil, errMalformedNote
+ }
+ hash := binary.BigEndian.Uint32(sig[0:4])
+ sig = sig[4:]
+
+ if numSig++; numSig > 100 {
+ // Avoid spending forever parsing a note with many signatures.
+ return nil, errMalformedNote
+ }
+
+ v, err := known.Verifier(name, hash)
+ if _, ok := err.(*UnknownNotaryError); ok {
+ // Drop repeated identical unverified signatures.
+ if seenUnverified[string(line)] {
+ continue
+ }
+ seenUnverified[string(line)] = true
+ n.UnverifiedSigs = append(n.UnverifiedSigs, Signature{Name: name, Hash: hash, Base64: b64})
+ continue
+ }
+ if err != nil {
+ return nil, err
+ }
+
+ // Drop repeated signatures by a single verifier.
+ if seen[nameHash{name, hash}] {
+ continue
+ }
+ seen[nameHash{name, hash}] = true
+
+ ok := v.Verify(text, sig)
+ if !ok {
+ return nil, &InvalidSignatureError{name, hash}
+ }
+
+ n.Sigs = append(n.Sigs, Signature{Name: name, Hash: hash, Base64: b64})
+ }
+
+ // Parsed and verified all the signatures.
+ if len(n.Sigs) == 0 {
+ return nil, &UnverifiedNoteError{n}
+ }
+ return n, nil
+}
+
+// Sign signs the note with the given signers and returns the encoded message.
+// The new signatures from signers are listed in the encoded message after
+// the existing signatures already present in n.Sigs.
+// If any signer uses the same notary key as an existing signature,
+// the existing signature is elided from the output.
+func Sign(n *Note, signers ...Signer) ([]byte, error) {
+ var buf bytes.Buffer
+ if !strings.HasSuffix(n.Text, "\n") {
+ return nil, errMalformedNote
+ }
+ buf.WriteString(n.Text)
+
+ // Prepare signatures.
+ var sigs bytes.Buffer
+ have := make(map[nameHash]bool)
+ for _, s := range signers {
+ name := s.Name()
+ hash := s.KeyHash()
+ have[nameHash{name, hash}] = true
+ if !isValidName(name) {
+ return nil, errInvalidSigner
+ }
+
+ sig, err := s.Sign(buf.Bytes()) // buf holds n.Text
+ if err != nil {
+ return nil, err
+ }
+
+ var hbuf [4]byte
+ binary.BigEndian.PutUint32(hbuf[:], hash)
+ b64 := base64.StdEncoding.EncodeToString(append(hbuf[:], sig...))
+ sigs.WriteString("— ")
+ sigs.WriteString(name)
+ sigs.WriteString(" ")
+ sigs.WriteString(b64)
+ sigs.WriteString("\n")
+ }
+
+ buf.WriteString("\n")
+
+ // Emit existing signatures not replaced by new ones.
+ for _, list := range [][]Signature{n.Sigs, n.UnverifiedSigs} {
+ for _, sig := range list {
+ name, hash := sig.Name, sig.Hash
+ if !isValidName(name) {
+ return nil, errMalformedNote
+ }
+ if have[nameHash{name, hash}] {
+ continue
+ }
+ // Double-check hash against base64.
+ raw, err := base64.StdEncoding.DecodeString(sig.Base64)
+ if err != nil || len(raw) < 4 || binary.BigEndian.Uint32(raw) != hash {
+ return nil, errMalformedNote
+ }
+ buf.WriteString("— ")
+ buf.WriteString(sig.Name)
+ buf.WriteString(" ")
+ buf.WriteString(sig.Base64)
+ buf.WriteString("\n")
+ }
+ }
+ buf.Write(sigs.Bytes())
+
+ return buf.Bytes(), nil
+}
diff --git a/notary/internal/note/note_test.go b/notary/internal/note/note_test.go
new file mode 100644
index 0000000..3c46ca6
--- /dev/null
+++ b/notary/internal/note/note_test.go
@@ -0,0 +1,415 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package note
+
+import (
+ "crypto/rand"
+ "errors"
+ "fmt"
+ "strings"
+ "testing"
+ "testing/iotest"
+)
+
+func TestNewVerifier(t *testing.T) {
+ vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ _, err := NewVerifier(vkey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // Check various manglings are not accepted.
+ badKey := func(k string) {
+ _, err := NewVerifier(k)
+ if err == nil {
+ t.Errorf("NewVerifier(%q) succeeded, should have failed", k)
+ }
+ }
+
+ b := []byte(vkey)
+ for i := 0; i <= len(b); i++ {
+ for j := i + 1; j <= len(b); j++ {
+ if i != 0 || j != len(b) {
+ badKey(string(b[i:j]))
+ }
+ }
+ }
+ for i := 0; i < len(b); i++ {
+ b[i]++
+ badKey(string(b))
+ b[i]--
+ }
+
+ badKey("PeterNeumann+cc469956+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TWBADKEY==") // wrong length key, with adjusted key hash
+ badKey("PeterNeumann+173116ae+ZRpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW") // unknown algorithm, with adjusted key hash
+}
+
+func TestNewSigner(t *testing.T) {
+ skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+ _, err := NewSigner(skey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // Check various manglings are not accepted.
+ b := []byte(skey)
+ for i := 0; i <= len(b); i++ {
+ for j := i + 1; j <= len(b); j++ {
+ if i == 0 && j == len(b) {
+ continue
+ }
+ _, err := NewSigner(string(b[i:j]))
+ if err == nil {
+ t.Errorf("NewSigner(%q) succeeded, should have failed", b[i:j])
+ }
+ }
+ }
+ for i := 0; i < len(b); i++ {
+ b[i]++
+ _, err := NewSigner(string(b))
+ if err == nil {
+ t.Errorf("NewSigner(%q) succeeded, should have failed", b)
+ }
+ b[i]--
+ }
+}
+
+func TestGenerateKey(t *testing.T) {
+ // Generate key pair, make sure it is all self-consistent.
+ const Name = "EnochRoot"
+ skey, vkey, err := GenerateKey(rand.Reader, Name)
+ if err != nil {
+ t.Fatalf("GenerateKey: %v", err)
+ }
+ signer, err := NewSigner(skey)
+ if err != nil {
+ t.Fatalf("NewSigner: %v", err)
+ }
+ verifier, err := NewVerifier(vkey)
+ if err != nil {
+ t.Fatalf("NewVerifier: %v", err)
+ }
+
+ if name := signer.Name(); name != Name {
+ t.Errorf("signer.Name() = %q, want %q", name, Name)
+ }
+ if name := verifier.Name(); name != Name {
+ t.Errorf("verifier.Name() = %q, want %q", name, Name)
+ }
+ shash := signer.KeyHash()
+ vhash := verifier.KeyHash()
+ if shash != vhash {
+ t.Errorf("signer.KeyHash() = %#08x != verifier.KeyHash() = %#08x", shash, vhash)
+ }
+
+ msg := []byte("hi")
+ sig, err := signer.Sign(msg)
+ if err != nil {
+ t.Fatalf("signer.Sign: %v", err)
+ }
+ if !verifier.Verify(msg, sig) {
+ t.Fatalf("verifier.Verify failed on signature returned by signer.Sign")
+ }
+ sig[0]++
+ if verifier.Verify(msg, sig) {
+ t.Fatalf("verifier.Verify succceeded on corrupt signature")
+ }
+
+ // Check that GenerateKey returns error from rand reader.
+ _, _, err = GenerateKey(iotest.TimeoutReader(iotest.OneByteReader(rand.Reader)), Name)
+ if err == nil {
+ t.Fatalf("GenerateKey succeeded with error-returning rand reader")
+ }
+}
+
+func TestSign(t *testing.T) {
+ skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+ text := "If you think cryptography is the answer to your problem,\n" +
+ "then you don't know what your problem is.\n"
+
+ signer, err := NewSigner(skey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ msg, err := Sign(&Note{Text: text}, signer)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ want := `If you think cryptography is the answer to your problem,
+then you don't know what your problem is.
+
+— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+`
+ if string(msg) != want {
+ t.Errorf("Sign: wrong output\nhave:\n%s\nwant:\n%s", msg, want)
+ }
+
+ // Check that existing signature is replaced by new one.
+ msg, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "PeterNeumann", Hash: 0xc74f20a3, Base64: "BADSIGN="}}}, signer)
+ if err != nil {
+ t.Fatal(err)
+ }
+ if string(msg) != want {
+ t.Errorf("Sign replacing signature: wrong output\nhave:\n%s\nwant:\n%s", msg, want)
+ }
+
+ // Check various bad inputs.
+ _, err = Sign(&Note{Text: "abc"}, signer)
+ if err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Sign with short text: %v, want malformed note error", err)
+ }
+
+ _, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "a+b", Base64: "ABCD"}}})
+ if err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Sign with bad name: %v, want malformed note error", err)
+ }
+
+ _, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "PeterNeumann", Hash: 0xc74f20a3, Base64: "BADHASH="}}})
+ if err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Sign with bad pre-filled signature: %v, want malformed note error", err)
+ }
+
+ _, err = Sign(&Note{Text: text}, &badSigner{signer})
+ if err == nil || err.Error() != "invalid signer" {
+ t.Fatalf("Sign with bad signer: %v, want invalid signer error", err)
+ }
+
+ _, err = Sign(&Note{Text: text}, &errSigner{signer})
+ if err != errSurprise {
+ t.Fatalf("Sign with failing signer: %v, want errSurprise", err)
+ }
+}
+
+func TestNotaryList(t *testing.T) {
+ peterKey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ peterVerifier, err := NewVerifier(peterKey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ enochKey := "EnochRoot+af0cfe78+ATtqJ7zOtqQtYqOo0CpvDXNlMhV3HeJDpjrASKGLWdop"
+ enochVerifier, err := NewVerifier(enochKey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ list := NotaryList(peterVerifier, enochVerifier, enochVerifier)
+ v, err := list.Verifier("PeterNeumann", 0xc74f20a3)
+ if v != peterVerifier || err != nil {
+ t.Fatalf("list.Verifier(peter) = %v, %v, want %v, nil", v, err, peterVerifier)
+ }
+ v, err = list.Verifier("PeterNeumann", 0xc74f20a4)
+ if v != nil || err == nil || err.Error() != "unknown notary key PeterNeumann+c74f20a4" {
+ t.Fatalf("list.Verifier(peter bad hash) = %v, %v, want nil, unknown notary key error", v, err)
+ }
+
+ v, err = list.Verifier("PeterNeuman", 0xc74f20a3)
+ if v != nil || err == nil || err.Error() != "unknown notary key PeterNeuman+c74f20a3" {
+ t.Fatalf("list.Verifier(peter bad name) = %v, %v, want nil, unknown notary key error", v, err)
+ }
+ v, err = list.Verifier("EnochRoot", 0xaf0cfe78)
+ if v != nil || err == nil || err.Error() != "ambiguous notary key EnochRoot+af0cfe78" {
+ t.Fatalf("list.Verifier(enoch) = %v, %v, want nil, ambiguous notary key error", v, err)
+ }
+}
+
+type badSigner struct {
+ Signer
+}
+
+func (b *badSigner) Name() string {
+ return "bad name"
+}
+
+var errSurprise = errors.New("surprise!")
+
+type errSigner struct {
+ Signer
+}
+
+func (e *errSigner) Sign([]byte) ([]byte, error) {
+ return nil, errSurprise
+}
+
+func fmtSig(s Signature) string {
+ return fmt.Sprintf("{%q %#08x %s}", s.Name, s.Hash, s.Base64)
+}
+
+func TestOpen(t *testing.T) {
+ peterKey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ peterVerifier, err := NewVerifier(peterKey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ enochKey := "EnochRoot+af0cfe78+ATtqJ7zOtqQtYqOo0CpvDXNlMhV3HeJDpjrASKGLWdop"
+ enochVerifier, err := NewVerifier(enochKey)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ text := `If you think cryptography is the answer to your problem,
+then you don't know what your problem is.
+`
+ peterSig := "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n"
+ enochSig := "— EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=\n"
+
+ peter := Signature{"PeterNeumann", 0xc74f20a3, "x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM="}
+ enoch := Signature{"EnochRoot", 0xaf0cfe78, "rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ="}
+
+ // Check one signature verified, one not.
+ n, err := Open([]byte(text+"\n"+peterSig+enochSig), NotaryList(peterVerifier))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if n.Text != text {
+ t.Errorf("n.Text = %q, want %q", n.Text, text)
+ }
+ if len(n.Sigs) != 1 || n.Sigs[0] != peter {
+ t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+ }
+ if len(n.UnverifiedSigs) != 1 || n.UnverifiedSigs[0] != enoch {
+ t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+ }
+
+ // Check both verified.
+ n, err = Open([]byte(text+"\n"+peterSig+enochSig), NotaryList(peterVerifier, enochVerifier))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if len(n.Sigs) != 2 || n.Sigs[0] != peter || n.Sigs[1] != enoch {
+ t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter, enoch})
+ }
+ if len(n.UnverifiedSigs) != 0 {
+ t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{})
+ }
+
+ // Check both unverified.
+ n, err = Open([]byte(text+"\n"+peterSig+enochSig), NotaryList())
+ if n != nil || err == nil {
+ t.Fatalf("Open unverified = %v, %v, want nil, error", n, err)
+ }
+ e, ok := err.(*UnverifiedNoteError)
+ if !ok {
+ t.Fatalf("Open unverified: err is %T, want *UnverifiedNoteError", err)
+ }
+ if err.Error() != "note has no verifiable signatures" {
+ t.Fatalf("Open unverified: err.Error() = %q, want %q", err.Error(), "note has no verifiable signatures")
+ }
+
+ n = e.Note
+ if n == nil {
+ t.Fatalf("Open unverified: missing note in UnverifiedNoteError")
+ }
+ if len(n.Sigs) != 0 {
+ t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{})
+ }
+ if len(n.UnverifiedSigs) != 2 || n.UnverifiedSigs[0] != peter || n.UnverifiedSigs[1] != enoch {
+ t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter, enoch})
+ }
+
+ // Check duplicated verifier.
+ _, err = Open([]byte(text+"\n"+enochSig), NotaryList(enochVerifier, peterVerifier, enochVerifier))
+ if err == nil || err.Error() != "ambiguous notary key EnochRoot+af0cfe78" {
+ t.Fatalf("Open with duplicated verifier: err=%v, want ambiguous notary key", err)
+ }
+
+ // Check unused duplicated verifier.
+ _, err = Open([]byte(text+"\n"+peterSig), NotaryList(enochVerifier, peterVerifier, enochVerifier))
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // Check too many signatures.
+ n, err = Open([]byte(text+"\n"+strings.Repeat(peterSig, 101)), NotaryList(peterVerifier))
+ if n != nil || err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Open too many verified signatures = %v, %v, want nil, malformed note error", n, err)
+ }
+ n, err = Open([]byte(text+"\n"+strings.Repeat(peterSig, 101)), NotaryList())
+ if n != nil || err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Open too many verified signatures = %v, %v, want nil, malformed note error", n, err)
+ }
+
+ // Invalid signature.
+ n, err = Open([]byte(text+"\n"+peterSig[:60]+"ABCD"+peterSig[60:]), NotaryList(peterVerifier))
+ if n != nil || err == nil || err.Error() != "invalid signature for notary key PeterNeumann+c74f20a3" {
+ t.Fatalf("Open too many verified signatures = %v, %v, want nil, invalid signature error", n, err)
+ }
+
+ // Duplicated verified and unverified signatures.
+ enochABCD := Signature{"EnochRoot", 0xaf0cfe78, "rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n" + "ABCD" + "2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ="}
+ n, err = Open([]byte(text+"\n"+peterSig+peterSig+enochSig+enochSig+enochSig[:60]+"ABCD"+enochSig[60:]), NotaryList(peterVerifier))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if len(n.Sigs) != 1 || n.Sigs[0] != peter {
+ t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+ }
+ if len(n.UnverifiedSigs) != 2 || n.UnverifiedSigs[0] != enoch || n.UnverifiedSigs[1] != enochABCD {
+ t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.UnverifiedSigs, []Signature{enoch, enochABCD})
+ }
+
+ // Invalid encoded message syntax.
+ badMsgs := []string{
+ text,
+ text + "\n",
+ text + "\n" + peterSig[:len(peterSig)-1],
+ "\x01" + text + "\n" + peterSig,
+ "\xff" + text + "\n" + peterSig,
+ text + "\n" + "— Bad Name x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=",
+ text + "\n" + peterSig + "Unexpected line.\n",
+ }
+ for _, msg := range badMsgs {
+ n, err := Open([]byte(msg), NotaryList(peterVerifier))
+ if n != nil || err == nil || err.Error() != "malformed note" {
+ t.Fatalf("Open bad msg = %v, %v, want nil, malformed note error\nmsg:\n%s", n, err, msg)
+ }
+ }
+}
+
+func BenchmarkOpen(b *testing.B) {
+ vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+ msg := []byte("If you think cryptography is the answer to your problem,\n" +
+ "then you don't know what your problem is.\n" +
+ "\n" +
+ "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+ verifier, err := NewVerifier(vkey)
+ if err != nil {
+ b.Fatal(err)
+ }
+ notaries := NotaryList(verifier)
+ notaries0 := NotaryList()
+
+ // Try with 0 signatures and 1 signature so we can tell how much each signature adds.
+
+ b.Run("Sig0", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ _, err := Open(msg, notaries0)
+ e, ok := err.(*UnverifiedNoteError)
+ if !ok {
+ b.Fatal("expected UnverifiedNoteError")
+ }
+ n := e.Note
+ if len(n.Sigs) != 0 || len(n.UnverifiedSigs) != 1 {
+ b.Fatal("wrong signature count")
+ }
+ }
+ })
+
+ b.Run("Sig1", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ n, err := Open(msg, notaries)
+ if err != nil {
+ b.Fatal(err)
+ }
+ if len(n.Sigs) != 1 || len(n.UnverifiedSigs) != 0 {
+ b.Fatal("wrong signature count")
+ }
+ }
+ })
+}