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72 lines
2.1 KiB
Go
72 lines
2.1 KiB
Go
/*
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Copyright 2020 The Flux CD contributors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package ssh
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import (
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"encoding/base64"
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"fmt"
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"net"
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"time"
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"golang.org/x/crypto/ssh"
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"golang.org/x/crypto/ssh/knownhosts"
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)
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// ScanHostKey collects the given host's preferred public key for the
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// Any errors (e.g. authentication failures) are ignored, except if
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// no key could be collected from the host.
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func ScanHostKey(host string, timeout time.Duration) ([]byte, error) {
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col := &HostKeyCollector{}
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config := &ssh.ClientConfig{
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HostKeyCallback: col.StoreKey(),
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Timeout: timeout,
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}
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client, err := ssh.Dial("tcp", host, config)
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if err == nil {
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defer client.Close()
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}
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if len(col.knownKeys) > 0 {
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return col.knownKeys, nil
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}
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return col.knownKeys, err
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}
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// HostKeyCollector offers a StoreKey method which provides an
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// HostKeyCallBack to collect public keys from an SSH server.
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type HostKeyCollector struct {
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knownKeys []byte
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}
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// StoreKey stores the public key in bytes as returned by the host.
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// To collect multiple public key types from the host, multiple
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// SSH dials need with the ClientConfig HostKeyAlgorithms set to
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// the algorithm you want to collect.
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func (c *HostKeyCollector) StoreKey() ssh.HostKeyCallback {
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return func(hostname string, remote net.Addr, key ssh.PublicKey) error {
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c.knownKeys = append(
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c.knownKeys,
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fmt.Sprintf("%s %s %s\n", knownhosts.Normalize(hostname), key.Type(), base64.StdEncoding.EncodeToString(key.Marshal()))...,
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)
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return nil
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}
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}
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// GetKnownKeys returns the collected public keys in bytes.
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func (c *HostKeyCollector) GetKnownKeys() []byte {
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return c.knownKeys
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}
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