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ssh: add support for hashing hostnames in known_hosts #274

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merged 1 commit into from
May 16, 2022
Merged

ssh: add support for hashing hostnames in known_hosts #274

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11 changes: 8 additions & 3 deletions ssh/host_key.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,8 +33,8 @@ import (
// clientHostKeyAlgos defines what HostKey algorithms to be
// used by the ssh client when using `ssh.Dial`. The default is
// empty, which defaults to Golang's preferred HostKey algorithms.
func ScanHostKey(host string, timeout time.Duration, clientHostKeyAlgos []string) ([]byte, error) {
col := &HostKeyCollector{}
func ScanHostKey(host string, timeout time.Duration, clientHostKeyAlgos []string, hashKeys bool) ([]byte, error) {
col := &HostKeyCollector{hashKeys: hashKeys}
config := &ssh.ClientConfig{
HostKeyCallback: col.StoreKey(),
Timeout: timeout,
Expand All @@ -54,6 +54,7 @@ func ScanHostKey(host string, timeout time.Duration, clientHostKeyAlgos []string
// HostKeyCallBack to collect public keys from an SSH server.
type HostKeyCollector struct {
knownKeys []byte
hashKeys bool
}

// StoreKey stores the public key in bytes as returned by the host.
Expand All @@ -62,9 +63,13 @@ type HostKeyCollector struct {
// the algorithm you want to collect.
func (c *HostKeyCollector) StoreKey() ssh.HostKeyCallback {
return func(hostname string, remote net.Addr, key ssh.PublicKey) error {
h := knownhosts.Normalize(hostname)
if c.hashKeys {
h = knownhosts.HashHostname(h)
}
c.knownKeys = append(
c.knownKeys,
fmt.Sprintf("%s %s %s\n", knownhosts.Normalize(hostname), key.Type(), base64.StdEncoding.EncodeToString(key.Marshal()))...,
fmt.Sprintf("%s %s %s\n", h, key.Type(), base64.StdEncoding.EncodeToString(key.Marshal()))...,
)
return nil
}
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2 changes: 1 addition & 1 deletion ssh/host_key_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,7 @@ func TestScanHost(t *testing.T) {

go startSSH(listener, sshConfig)

kh, err := ScanHostKey(serverAddr, 5*time.Second, []string{tt.sshKeyTypeName})
kh, err := ScanHostKey(serverAddr, 5*time.Second, []string{tt.sshKeyTypeName}, false)
if tt.wantErr == "" {
g.Expect(err).NotTo(HaveOccurred())
// Confirm the returned key is of expected type.
Expand Down