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Merged
merged 4 commits into from
Dec 15, 2020
Merged

Standardise logging of failed authentication attempts in internal SSH #13962

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156d2cb
Standardise failed authentication attempt logging
zeripath Dec 12, 2020
56ec015
english spelling
zeripath Dec 12, 2020
701fbbd
splellign
zeripath Dec 12, 2020
7cfa45b
Merge branch 'master' into report-permission-denied-in-ssh-2
6543 Dec 15, 2020
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20 changes: 19 additions & 1 deletion docs/content/doc/usage/fail2ban-setup.en-us.md
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Original file line number Diff line number Diff line change
Expand Up @@ -25,9 +25,27 @@ on a bad authentication from the web or CLI using SSH or HTTP respectively:
```log
2018/04/26 18:15:54 [I] Failed authentication attempt for user from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:05:09 modules/ssh/ssh.go:143:publicKeyHandler() [W] Failed authentication attempt from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:05:09 modules/ssh/ssh.go:155:publicKeyHandler() [W] Failed authentication attempt from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:05:09 modules/ssh/ssh.go:188:publicKeyHandler() [E] SearchPublicKeyByContent: public key does not exist [id: 0] Failed authentication attempt from xxx.xxx.xxx.xxx
2020/10/15 16:05:09 modules/ssh/ssh.go:198:publicKeyHandler() [W] Failed authentication attempt from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:05:09 modules/ssh/ssh.go:213:publicKeyHandler() [W] Failed authentication attempt from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:05:09 modules/ssh/ssh.go:227:publicKeyHandler() [W] Failed authentication attempt from xxx.xxx.xxx.xxx
```

```log
2020/10/15 16:08:44 ...s/context/context.go:204:HandleText() [E] invalid credentials from xxx.xxx.xxx.xxx
```
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50 changes: 43 additions & 7 deletions modules/ssh/ssh.go
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Original file line number Diff line number Diff line change
Expand Up @@ -134,14 +134,25 @@ func sessionHandler(session ssh.Session) {
}

func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
if log.IsDebug() { // <- FingerprintSHA256 is kinda expensive so only calculate it if necessary
log.Debug("Handle Public Key: Fingerprint: %s from %s", gossh.FingerprintSHA256(key), ctx.RemoteAddr())
}

if ctx.User() != setting.SSH.BuiltinServerUser {
log.Warn("Permission Denied: Invalid SSH username %s - must use %s for all git operations via ssh", ctx.User(), setting.SSH.BuiltinServerUser)
log.Warn("Invalid SSH username %s - must use %s for all git operations via ssh", ctx.User(), setting.SSH.BuiltinServerUser)
log.Warn("Failed authentication attempt from %s", ctx.RemoteAddr())
return false
}

// check if we have a certificate
if cert, ok := key.(*gossh.Certificate); ok {
if log.IsDebug() { // <- FingerprintSHA256 is kinda expensive so only calculate it if necessary
log.Debug("Handle Certificate: %s Fingerprint: %s is a certificate", ctx.RemoteAddr(), gossh.FingerprintSHA256(key))
}

if len(setting.SSH.TrustedUserCAKeys) == 0 {
log.Warn("Certificate Rejected: No trusted certificate authorities for this server")
log.Warn("Failed authentication attempt from %s", ctx.RemoteAddr())
return false
}

Expand All @@ -151,7 +162,7 @@ func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
pkey, err := models.SearchPublicKeyByContentExact(principal)
if err != nil {
if models.IsErrKeyNotExist(err) {
log.Debug("Principal Rejected: Unknown Principal: %s", principal)
log.Debug("Principal Rejected: %s Unknown Principal: %s", ctx.RemoteAddr(), principal)
continue principalLoop
}
log.Error("SearchPublicKeyByContentExact: %v", err)
Expand All @@ -172,33 +183,58 @@ func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {

// check the CA of the cert
if !c.IsUserAuthority(cert.SignatureKey) {
log.Debug("Principal Rejected: Untrusted Authority Signature Fingerprint %s for Principal: %s", gossh.FingerprintSHA256(cert.SignatureKey), principal)
if log.IsDebug() {
log.Debug("Principal Rejected: %s Untrusted Authority Signature Fingerprint %s for Principal: %s", ctx.RemoteAddr(), gossh.FingerprintSHA256(cert.SignatureKey), principal)
}
continue principalLoop
}

// validate the cert for this principal
if err := c.CheckCert(principal, cert); err != nil {
// User is presenting an invalid cerficate - STOP any further processing
log.Error("Permission Denied: Invalid Certificate KeyID %s with Signature Fingerprint %s presented for Principal: %s", cert.KeyId, gossh.FingerprintSHA256(cert.SignatureKey), principal)
// User is presenting an invalid certificate - STOP any further processing
if log.IsError() {
log.Error("Invalid Certificate KeyID %s with Signature Fingerprint %s presented for Principal: %s from %s", cert.KeyId, gossh.FingerprintSHA256(cert.SignatureKey), principal, ctx.RemoteAddr())
}
log.Warn("Failed authentication attempt from %s", ctx.RemoteAddr())

return false
}

if log.IsDebug() { // <- FingerprintSHA256 is kinda expensive so only calculate it if necessary
log.Debug("Successfully authenticated: %s Certificate Fingerprint: %s Principal: %s", ctx.RemoteAddr(), gossh.FingerprintSHA256(key), principal)
}
ctx.SetValue(giteaKeyID, pkey.ID)

return true
}

if log.IsWarn() {
log.Warn("From %s Fingerprint: %s is a certificate, but no valid principals found", ctx.RemoteAddr(), gossh.FingerprintSHA256(key))
log.Warn("Failed authentication attempt from %s", ctx.RemoteAddr())
}
return false
}

if log.IsDebug() { // <- FingerprintSHA256 is kinda expensive so only calculate it if necessary
log.Debug("Handle Public Key: %s Fingerprint: %s is not a certificate", ctx.RemoteAddr(), gossh.FingerprintSHA256(key))
}

pkey, err := models.SearchPublicKeyByContent(strings.TrimSpace(string(gossh.MarshalAuthorizedKey(key))))
if err != nil {
if models.IsErrKeyNotExist(err) {
log.Warn("Permission Denied: Unknown public key : %s", gossh.FingerprintSHA256(key))
if log.IsWarn() {
log.Warn("Unknown public key: %s from %s", gossh.FingerprintSHA256(key), ctx.RemoteAddr())
log.Warn("Failed authentication attempt from %s", ctx.RemoteAddr())
}
return false
}
log.Error("SearchPublicKeyByContent: %v Failed authentication attempt from %s", err, ctx.RemoteAddr())
log.Error("SearchPublicKeyByContent: %v", err)
return false
}

if log.IsDebug() { // <- FingerprintSHA256 is kinda expensive so only calculate it if necessary
log.Debug("Successfully authenticated: %s Public Key Fingerprint: %s", ctx.RemoteAddr(), gossh.FingerprintSHA256(key))
}
ctx.SetValue(giteaKeyID, pkey.ID)

return true
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