ssh: add in-memory knownhosts utilities

pkg/ssh/knownhosts/knownhosts.go

@@ -0,0 +1,446 @@
+// Copyright 2017 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.
+
+// Copyright 2020 The FluxCD contributors. All rights reserved.
+// This package provides an in-memory known hosts database
+// derived from the golang.org/x/crypto/ssh/knownhosts
+// package.
+// It has been slightly modified and adapted to work with
+// in-memory host keys not related to any known_hosts files
+// on disk, and the database can be initialized with just a
+// known_hosts byte blob.
+// https://pkg.go.dev/golang.org/x/crypto/ssh/knownhosts
+
+package knownhosts
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/knownhosts"
+)
+
+// See the sshd manpage
+// (http://man.openbsd.org/sshd#SSH_KNOWN_HOSTS_FILE_FORMAT) for
+// background.
+
+type addr struct{ host, port string }
+
+func (a *addr) String() string {
+	h := a.host
+	if strings.Contains(h, ":") {
+		h = "[" + h + "]"
+	}
+	return h + ":" + a.port
+}
+
+type matcher interface {
+	match(addr) bool
+}
+
+type hostPattern struct {
+	negate bool
+	addr   addr
+}
+
+func (p *hostPattern) String() string {
+	n := ""
+	if p.negate {
+		n = "!"
+	}
+
+	return n + p.addr.String()
+}
+
+type hostPatterns []hostPattern
+
+func (ps hostPatterns) match(a addr) bool {
+	matched := false
+	for _, p := range ps {
+		if !p.match(a) {
+			continue
+		}
+		if p.negate {
+			return false
+		}
+		matched = true
+	}
+	return matched
+}
+
+// See
+// https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/addrmatch.c
+// The matching of * has no regard for separators, unlike filesystem globs
+func wildcardMatch(pat []byte, str []byte) bool {
+	for {
+		if len(pat) == 0 {
+			return len(str) == 0
+		}
+		if len(str) == 0 {
+			return false
+		}
+
+		if pat[0] == '*' {
+			if len(pat) == 1 {
+				return true
+			}
+
+			for j := range str {
+				if wildcardMatch(pat[1:], str[j:]) {
+					return true
+				}
+			}
+			return false
+		}
+
+		if pat[0] == '?' || pat[0] == str[0] {
+			pat = pat[1:]
+			str = str[1:]
+		} else {
+			return false
+		}
+	}
+}
+
+func (p *hostPattern) match(a addr) bool {
+	return wildcardMatch([]byte(p.addr.host), []byte(a.host)) && p.addr.port == a.port
+}
+
+type inMemoryHostKeyDB struct {
+	hostKeys []hostKey
+	revoked  map[string]*ssh.PublicKey
+}
+
+func newInMemoryHostKeyDB() *inMemoryHostKeyDB {
+	db := &inMemoryHostKeyDB{
+		revoked: make(map[string]*ssh.PublicKey),
+	}
+
+	return db
+}
+
+func keyEq(a, b ssh.PublicKey) bool {
+	return bytes.Equal(a.Marshal(), b.Marshal())
+}
+
+type hostKey struct {
+	matcher matcher
+	cert    bool
+	key     ssh.PublicKey
+}
+
+func (l *hostKey) match(a addr) bool {
+	return l.matcher.match(a)
+}
+
+// IsAuthorityForHost can be used as a callback in ssh.CertChecker
+func (db *inMemoryHostKeyDB) IsHostAuthority(remote ssh.PublicKey, address string) bool {
+	h, p, err := net.SplitHostPort(address)
+	if err != nil {
+		return false
+	}
+	a := addr{host: h, port: p}
+
+	for _, l := range db.hostKeys {
+		if l.cert && keyEq(l.key, remote) && l.match(a) {
+			return true
+		}
+	}
+	return false
+}
+
+// IsRevoked can be used as a callback in ssh.CertChecker
+func (db *inMemoryHostKeyDB) IsRevoked(key *ssh.Certificate) bool {
+	_, ok := db.revoked[string(key.Marshal())]
+	return ok
+}
+
+const markerCert = "@cert-authority"
+const markerRevoked = "@revoked"
+
+func nextWord(line []byte) (string, []byte) {
+	i := bytes.IndexAny(line, "\t ")
+	if i == -1 {
+		return string(line), nil
+	}
+
+	return string(line[:i]), bytes.TrimSpace(line[i:])
+}
+
+func parseLine(line []byte) (marker, host string, key ssh.PublicKey, err error) {
+	if w, next := nextWord(line); w == markerCert || w == markerRevoked {
+		marker = w
+		line = next
+	}
+
+	host, line = nextWord(line)
+	if len(line) == 0 {
+		return "", "", nil, errors.New("knownhosts: missing host pattern")
+	}
+
+	// ignore the keytype as it's in the key blob anyway.
+	_, line = nextWord(line)
+	if len(line) == 0 {
+		return "", "", nil, errors.New("knownhosts: missing key type pattern")
+	}
+
+	keyBlob, _ := nextWord(line)
+
+	keyBytes, err := base64.StdEncoding.DecodeString(keyBlob)
+	if err != nil {
+		return "", "", nil, err
+	}
+	key, err = ssh.ParsePublicKey(keyBytes)
+	if err != nil {
+		return "", "", nil, err
+	}
+
+	return marker, host, key, nil
+}
+
+func (db *inMemoryHostKeyDB) parseLine(line []byte) error {
+	marker, pattern, key, err := parseLine(line)
+	if err != nil {
+		return err
+	}
+
+	if marker == markerRevoked {
+		db.revoked[string(key.Marshal())] = &key
+		return nil
+	}
+
+	entry := hostKey{
+		key:  key,
+		cert: marker == markerCert,
+	}
+
+	if pattern[0] == '|' {
+		entry.matcher, err = newHashedHost(pattern)
+	} else {
+		entry.matcher, err = newHostnameMatcher(pattern)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	db.hostKeys = append(db.hostKeys, entry)
+	return nil
+}
+
+func newHostnameMatcher(pattern string) (matcher, error) {
+	var hps hostPatterns
+	for _, p := range strings.Split(pattern, ",") {
+		if len(p) == 0 {
+			continue
+		}
+
+		var a addr
+		var negate bool
+		if p[0] == '!' {
+			negate = true
+			p = p[1:]
+		}
+
+		if len(p) == 0 {
+			return nil, errors.New("knownhosts: negation without following hostname")
+		}
+
+		var err error
+		if p[0] == '[' {
+			a.host, a.port, err = net.SplitHostPort(p)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			a.host, a.port, err = net.SplitHostPort(p)
+			if err != nil {
+				a.host = p
+				a.port = "22"
+			}
+		}
+		hps = append(hps, hostPattern{
+			negate: negate,
+			addr:   a,
+		})
+	}
+	return hps, nil
+}
+
+// check checks a key against the host database. This should not be
+// used for verifying certificates.
+func (db *inMemoryHostKeyDB) check(address string, remote net.Addr, remoteKey ssh.PublicKey) error {
+	if revoked := db.revoked[string(remoteKey.Marshal())]; revoked != nil {
+		return &knownhosts.RevokedError{Revoked: knownhosts.KnownKey{Key: *revoked}}
+	}
+
+	host, port, err := net.SplitHostPort(remote.String())
+	if err != nil {
+		return fmt.Errorf("knownhosts: SplitHostPort(%s): %v", remote, err)
+	}
+
+	hostToCheck := addr{host, port}
+	if address != "" {
+		// Give preference to the hostname if available.
+		host, port, err := net.SplitHostPort(address)
+		if err != nil {
+			return fmt.Errorf("knownhosts: SplitHostPort(%s): %v", address, err)
+		}
+
+		hostToCheck = addr{host, port}
+	}
+
+	return db.checkAddr(hostToCheck, remoteKey)
+}
+
+// checkAddr checks if we can find the given public key for the
+// given address.  If we only find an entry for the IP address,
+// or only the hostname, then this still succeeds.
+func (db *inMemoryHostKeyDB) checkAddr(a addr, remoteKey ssh.PublicKey) error {
+	// TODO(hanwen): are these the right semantics? What if there
+	// is just a key for the IP address, but not for the
+	// hostname?
+
+	// Algorithm => key.
+	knownKeys := map[string]ssh.PublicKey{}
+	for _, l := range db.hostKeys {
+		if l.match(a) {
+			typ := l.key.Type()
+			if _, ok := knownKeys[typ]; !ok {
+				knownKeys[typ] = l.key
+			}
+		}
+	}
+
+	keyErr := &knownhosts.KeyError{}
+	for _, v := range knownKeys {
+		keyErr.Want = append(keyErr.Want, knownhosts.KnownKey{Key: v})
+	}
+
+	// Unknown remote host.
+	if len(knownKeys) == 0 {
+		return keyErr
+	}
+
+	// If the remote host starts using a different, unknown key type, we
+	// also interpret that as a mismatch.
+	if known, ok := knownKeys[remoteKey.Type()]; !ok || !keyEq(known, remoteKey) {
+		return keyErr
+	}
+
+	return nil
+}
+
+// The Read function parses file contents.
+func (db *inMemoryHostKeyDB) Read(r io.Reader) error {
+	scanner := bufio.NewScanner(r)
+
+	lineNum := 0
+	for scanner.Scan() {
+		lineNum++
+		line := scanner.Bytes()
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 || line[0] == '#' {
+			continue
+		}
+
+		if err := db.parseLine(line); err != nil {
+			return fmt.Errorf("knownhosts: %v", err)
+		}
+	}
+	return scanner.Err()
+}
+
+// New creates a host key callback from the given OpenSSH host key
+// file bytes. The returned callback is for use in
+// ssh.ClientConfig.HostKeyCallback. By preference, the key check
+// operates on the hostname if available, i.e. if a server changes its
+// IP address, the host key check will still succeed, even though a
+// record of the new IP address is not available.
+func New(b []byte) (ssh.HostKeyCallback, error) {
+	db := newInMemoryHostKeyDB()
+	r := bytes.NewReader(b)
+	if err := db.Read(r); err != nil {
+		return nil, err
+	}
+
+	var certChecker ssh.CertChecker
+	certChecker.IsHostAuthority = db.IsHostAuthority
+	certChecker.IsRevoked = db.IsRevoked
+	certChecker.HostKeyFallback = db.check
+
+	return certChecker.CheckHostKey, nil
+}
+
+func decodeHash(encoded string) (hashType string, salt, hash []byte, err error) {
+	if len(encoded) == 0 || encoded[0] != '|' {
+		err = errors.New("knownhosts: hashed host must start with '|'")
+		return
+	}
+	components := strings.Split(encoded, "|")
+	if len(components) != 4 {
+		err = fmt.Errorf("knownhosts: got %d components, want 3", len(components))
+		return
+	}
+
+	hashType = components[1]
+	if salt, err = base64.StdEncoding.DecodeString(components[2]); err != nil {
+		return
+	}
+	if hash, err = base64.StdEncoding.DecodeString(components[3]); err != nil {
+		return
+	}
+	return
+}
+
+func encodeHash(typ string, salt []byte, hash []byte) string {
+	return strings.Join([]string{"",
+		typ,
+		base64.StdEncoding.EncodeToString(salt),
+		base64.StdEncoding.EncodeToString(hash),
+	}, "|")
+}
+
+// See https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/hostfile.c#120
+func hashHost(hostname string, salt []byte) []byte {
+	mac := hmac.New(sha1.New, salt)
+	mac.Write([]byte(hostname))
+	return mac.Sum(nil)
+}
+
+type hashedHost struct {
+	salt []byte
+	hash []byte
+}
+
+const sha1HashType = "1"
+
+func newHashedHost(encoded string) (*hashedHost, error) {
+	typ, salt, hash, err := decodeHash(encoded)
+	if err != nil {
+		return nil, err
+	}
+
+	// The type field seems for future algorithm agility, but it's
+	// actually hardcoded in openssh currently, see
+	// https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/hostfile.c#120
+	if typ != sha1HashType {
+		return nil, fmt.Errorf("knownhosts: got hash type %s, must be '1'", typ)
+	}
+
+	return &hashedHost{salt: salt, hash: hash}, nil
+}
+
+func (h *hashedHost) match(a addr) bool {
+	return bytes.Equal(hashHost(knownhosts.Normalize(a.String()), h.salt), h.hash)
+}

pkg/ssh/knownhosts/knownhosts_test.go

@@ -0,0 +1,327 @@
+// Copyright 2017 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.
+
+// Copyright 2020 The FluxCD contributors. All rights reserved.
+// This package provides an in-memory known hosts database
+// derived from the golang.org/x/crypto/ssh/knownhosts
+// package.
+// It has been slightly modified and adapted to work with
+// in-memory host keys not related to any known_hosts files
+// on disk, and the database can be initialized with just a
+// known_hosts byte blob.
+// https://pkg.go.dev/golang.org/x/crypto/ssh/knownhosts
+
+package knownhosts
+
+import (
+	"bytes"
+	"fmt"
+	"net"
+	"reflect"
+	"testing"
+
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/knownhosts"
+)
+
+const edKeyStr = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGBAarftlLeoyf+v+nVchEZII/vna2PCV8FaX4vsF5BX"
+const alternateEdKeyStr = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIXffBYeYL+WVzVru8npl5JHt2cjlr4ornFTWzoij9sx"
+const ecKeyStr = "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBNLCu01+wpXe3xB5olXCN4SqU2rQu0qjSRKJO4Bg+JRCPU+ENcgdA5srTU8xYDz/GEa4dzK5ldPw4J/gZgSXCMs="
+
+var ecKey, alternateEdKey, edKey ssh.PublicKey
+var testAddr = &net.TCPAddr{
+	IP:   net.IP{198, 41, 30, 196},
+	Port: 22,
+}
+
+var testAddr6 = &net.TCPAddr{
+	IP: net.IP{198, 41, 30, 196,
+		1, 2, 3, 4,
+		1, 2, 3, 4,
+		1, 2, 3, 4,
+	},
+	Port: 22,
+}
+
+func init() {
+	var err error
+	ecKey, _, _, _, err = ssh.ParseAuthorizedKey([]byte(ecKeyStr))
+	if err != nil {
+		panic(err)
+	}
+	edKey, _, _, _, err = ssh.ParseAuthorizedKey([]byte(edKeyStr))
+	if err != nil {
+		panic(err)
+	}
+	alternateEdKey, _, _, _, err = ssh.ParseAuthorizedKey([]byte(alternateEdKeyStr))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func testDB(t *testing.T, s string) *inMemoryHostKeyDB {
+	db := newInMemoryHostKeyDB()
+	if err := db.Read(bytes.NewBufferString(s)); err != nil {
+		t.Fatalf("Read: %v", err)
+	}
+
+	return db
+}
+
+func TestRevoked(t *testing.T) {
+	db := testDB(t, "\n\n@revoked * "+edKeyStr+"\n")
+	want := &knownhosts.RevokedError{
+		Revoked: knownhosts.KnownKey{
+			Key: edKey,
+		},
+	}
+	if err := db.check("", &net.TCPAddr{
+		Port: 42,
+	}, edKey); err == nil {
+		t.Fatal("no error for revoked key")
+	} else if !reflect.DeepEqual(want, err) {
+		t.Fatalf("got %#v, want %#v", want, err)
+	}
+}
+
+func TestHostAuthority(t *testing.T) {
+	for _, m := range []struct {
+		authorityFor string
+		address      string
+
+		good bool
+	}{
+		{authorityFor: "localhost", address: "localhost:22", good: true},
+		{authorityFor: "localhost", address: "localhost", good: false},
+		{authorityFor: "localhost", address: "localhost:1234", good: false},
+		{authorityFor: "[localhost]:1234", address: "localhost:1234", good: true},
+		{authorityFor: "[localhost]:1234", address: "localhost:22", good: false},
+		{authorityFor: "[localhost]:1234", address: "localhost", good: false},
+	} {
+		db := testDB(t, `@cert-authority `+m.authorityFor+` `+edKeyStr)
+		if ok := db.IsHostAuthority(db.hostKeys[0].key, m.address); ok != m.good {
+			t.Errorf("IsHostAuthority: authority %s, address %s, wanted good = %v, got good = %v",
+				m.authorityFor, m.address, m.good, ok)
+		}
+	}
+}
+
+func TestBracket(t *testing.T) {
+	db := testDB(t, `[git.eclipse.org]:29418,[198.41.30.196]:29418 `+edKeyStr)
+
+	if err := db.check("git.eclipse.org:29418", &net.TCPAddr{
+		IP:   net.IP{198, 41, 30, 196},
+		Port: 29418,
+	}, edKey); err != nil {
+		t.Errorf("got error %v, want none", err)
+	}
+
+	if err := db.check("git.eclipse.org:29419", &net.TCPAddr{
+		Port: 42,
+	}, edKey); err == nil {
+		t.Fatalf("no error for unknown address")
+	} else if ke, ok := err.(*knownhosts.KeyError); !ok {
+		t.Fatalf("got type %T, want *KeyError", err)
+	} else if len(ke.Want) > 0 {
+		t.Fatalf("got Want %v, want []", ke.Want)
+	}
+}
+
+func TestNewKeyType(t *testing.T) {
+	str := fmt.Sprintf("%s %s", testAddr, edKeyStr)
+	db := testDB(t, str)
+	if err := db.check("", testAddr, ecKey); err == nil {
+		t.Fatalf("no error for unknown address")
+	} else if ke, ok := err.(*knownhosts.KeyError); !ok {
+		t.Fatalf("got type %T, want *KeyError", err)
+	} else if len(ke.Want) == 0 {
+		t.Fatalf("got empty KeyError.Want")
+	}
+}
+
+func TestSameKeyType(t *testing.T) {
+	str := fmt.Sprintf("%s %s", testAddr, edKeyStr)
+	db := testDB(t, str)
+	if err := db.check("", testAddr, alternateEdKey); err == nil {
+		t.Fatalf("no error for unknown address")
+	} else if ke, ok := err.(*knownhosts.KeyError); !ok {
+		t.Fatalf("got type %T, want *KeyError", err)
+	} else if len(ke.Want) == 0 {
+		t.Fatalf("got empty KeyError.Want")
+	} else if got, want := ke.Want[0].Key.Marshal(), edKey.Marshal(); !bytes.Equal(got, want) {
+		t.Fatalf("got key %q, want %q", got, want)
+	}
+}
+
+func TestIPAddress(t *testing.T) {
+	str := fmt.Sprintf("%s %s", testAddr, edKeyStr)
+	db := testDB(t, str)
+	if err := db.check("", testAddr, edKey); err != nil {
+		t.Errorf("got error %q, want none", err)
+	}
+}
+
+func TestIPv6Address(t *testing.T) {
+	str := fmt.Sprintf("%s %s", testAddr6, edKeyStr)
+	db := testDB(t, str)
+
+	if err := db.check("", testAddr6, edKey); err != nil {
+		t.Errorf("got error %q, want none", err)
+	}
+}
+
+func TestBasic(t *testing.T) {
+	str := fmt.Sprintf("#comment\n\nserver.org,%s %s\notherhost %s", testAddr, edKeyStr, ecKeyStr)
+	db := testDB(t, str)
+	if err := db.check("server.org:22", testAddr, edKey); err != nil {
+		t.Errorf("got error %v, want none", err)
+	}
+
+	want := knownhosts.KnownKey{
+		Key: edKey,
+	}
+	if err := db.check("server.org:22", testAddr, ecKey); err == nil {
+		t.Errorf("succeeded, want KeyError")
+	} else if ke, ok := err.(*knownhosts.KeyError); !ok {
+		t.Errorf("got %T, want *KeyError", err)
+	} else if len(ke.Want) != 1 {
+		t.Errorf("got %v, want 1 entry", ke)
+	} else if !reflect.DeepEqual(ke.Want[0], want) {
+		t.Errorf("got %v, want %v", ke.Want[0], want)
+	}
+}
+
+func TestHostNamePrecedence(t *testing.T) {
+	var evilAddr = &net.TCPAddr{
+		IP:   net.IP{66, 66, 66, 66},
+		Port: 22,
+	}
+
+	str := fmt.Sprintf("server.org,%s %s\nevil.org,%s %s", testAddr, edKeyStr, evilAddr, ecKeyStr)
+	db := testDB(t, str)
+
+	if err := db.check("server.org:22", evilAddr, ecKey); err == nil {
+		t.Errorf("check succeeded")
+	} else if _, ok := err.(*knownhosts.KeyError); !ok {
+		t.Errorf("got %T, want *KeyError", err)
+	}
+}
+
+func TestDBOrderingPrecedenceKeyType(t *testing.T) {
+	str := fmt.Sprintf("server.org,%s %s\nserver.org,%s %s", testAddr, edKeyStr, testAddr, alternateEdKeyStr)
+	db := testDB(t, str)
+
+	if err := db.check("server.org:22", testAddr, alternateEdKey); err == nil {
+		t.Errorf("check succeeded")
+	} else if _, ok := err.(*knownhosts.KeyError); !ok {
+		t.Errorf("got %T, want *KeyError", err)
+	}
+}
+
+func TestNegate(t *testing.T) {
+	str := fmt.Sprintf("%s,!server.org %s", testAddr, edKeyStr)
+	db := testDB(t, str)
+	if err := db.check("server.org:22", testAddr, ecKey); err == nil {
+		t.Errorf("succeeded")
+	} else if ke, ok := err.(*knownhosts.KeyError); !ok {
+		t.Errorf("got error type %T, want *KeyError", err)
+	} else if len(ke.Want) != 0 {
+		t.Errorf("got expected keys %d (first of type %s), want []", len(ke.Want), ke.Want[0].Key.Type())
+	}
+}
+
+func TestWildcard(t *testing.T) {
+	str := fmt.Sprintf("server*.domain %s", edKeyStr)
+	db := testDB(t, str)
+
+	want := &knownhosts.KeyError{
+		Want: []knownhosts.KnownKey{{
+			Key: edKey,
+		}},
+	}
+
+	got := db.check("server.domain:22", &net.TCPAddr{}, ecKey)
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %s, want %s", got, want)
+	}
+}
+
+func TestWildcardMatch(t *testing.T) {
+	for _, c := range []struct {
+		pat, str string
+		want     bool
+	}{
+		{"a?b", "abb", true},
+		{"ab", "abc", false},
+		{"abc", "ab", false},
+		{"a*b", "axxxb", true},
+		{"a*b", "axbxb", true},
+		{"a*b", "axbxbc", false},
+		{"a*?", "axbxc", true},
+		{"a*b*", "axxbxxxxxx", true},
+		{"a*b*c", "axxbxxxxxxc", true},
+		{"a*b*?", "axxbxxxxxxc", true},
+		{"a*b*z", "axxbxxbxxxz", true},
+		{"a*b*z", "axxbxxzxxxz", true},
+		{"a*b*z", "axxbxxzxxx", false},
+	} {
+		got := wildcardMatch([]byte(c.pat), []byte(c.str))
+		if got != c.want {
+			t.Errorf("wildcardMatch(%q, %q) = %v, want %v", c.pat, c.str, got, c.want)
+		}
+
+	}
+}
+
+// TODO(hanwen): test coverage for certificates.
+
+const testHostname = "hostname"
+
+// generated with keygen -H -f
+const encodedTestHostnameHash = "|1|IHXZvQMvTcZTUU29+2vXFgx8Frs=|UGccIWfRVDwilMBnA3WJoRAC75Y="
+
+func TestHostHash(t *testing.T) {
+	testHostHash(t, testHostname, encodedTestHostnameHash)
+}
+
+func TestHashList(t *testing.T) {
+	encoded := knownhosts.HashHostname(testHostname)
+	testHostHash(t, testHostname, encoded)
+}
+
+func testHostHash(t *testing.T, hostname, encoded string) {
+	typ, salt, hash, err := decodeHash(encoded)
+	if err != nil {
+		t.Fatalf("decodeHash: %v", err)
+	}
+
+	if got := encodeHash(typ, salt, hash); got != encoded {
+		t.Errorf("got encoding %s want %s", got, encoded)
+	}
+
+	if typ != sha1HashType {
+		t.Fatalf("got hash type %q, want %q", typ, sha1HashType)
+	}
+
+	got := hashHost(hostname, salt)
+	if !bytes.Equal(got, hash) {
+		t.Errorf("got hash %x want %x", got, hash)
+	}
+}
+
+func TestHashedHostkeyCheck(t *testing.T) {
+	str := fmt.Sprintf("%s %s", knownhosts.HashHostname(testHostname), edKeyStr)
+	db := testDB(t, str)
+	if err := db.check(testHostname+":22", testAddr, edKey); err != nil {
+		t.Errorf("check(%s): %v", testHostname, err)
+	}
+	want := &knownhosts.KeyError{
+		Want: []knownhosts.KnownKey{{
+			Key: edKey,
+		}},
+	}
+	if got := db.check(testHostname+":22", testAddr, alternateEdKey); !reflect.DeepEqual(got, want) {
+		t.Errorf("got error %v, want %v", got, want)
+	}
+}