Add remote_port in the audit logs when it is available

The `request.remote_port` field is now present in the audit log when it
is available:

```
{
  "time": "2021-10-10T13:53:51.760039Z",
  "type": "response",
  "auth": {
    "client_token": "hmac-sha256:1304aab0ac65747684e1b58248cc16715fa8f558f8d27e90fcbcb213220c0edf",
    "accessor": "hmac-sha256:f8cf0601dadd19aac84f205ded44c62898e3746a42108a51105a92ccc39baa43",
    "display_name": "root",
    "policies": [
      "root"
    ],
    "token_policies": [
      "root"
    ],
    "token_type": "service",
    "token_issue_time": "2021-10-10T15:53:44+02:00"
  },
  "request": {
    "id": "829c04a1-0352-2d9d-9bc9-00b928d33df5",
    "operation": "update",
    "mount_type": "system",
    "client_token": "hmac-sha256:1304aab0ac65747684e1b58248cc16715fa8f558f8d27e90fcbcb213220c0edf",
    "client_token_accessor": "hmac-sha256:f8cf0601dadd19aac84f205ded44c62898e3746a42108a51105a92ccc39baa43",
    "namespace": {
      "id": "root"
    },
    "path": "sys/audit/file",
    "data": {
      "description": "hmac-sha256:321a1d105f8c6fd62be4f34c4da4f0e6d1cdee9eb2ff4af0b59e1410950fe86b",
      "local": false,
      "options": {
        "file_path": "hmac-sha256:2421b5bf8dab1f9775b2e6e66e58d7bca99ab729f3f311782fda50717eee55b3"
      },
      "type": "hmac-sha256:30dff9607b4087e3ae6808b4a3aa395b1fc064e467748c55c25ddf0e9b150fcc"
    },
    "remote_address": "127.0.0.1",
    "remote_port": 54798
  },
  "response": {
    "mount_type": "system"
  }
}
```

Closes hashicorp#7716

audit/format.go

@@ -122,6 +122,7 @@ func (f *AuditFormatter) FormatRequest(ctx context.Context, w io.Writer, config
 			Data:                          req.Data,
 			PolicyOverride:                req.PolicyOverride,
 			RemoteAddr:                    getRemoteAddr(req),
+			RemotePort:                    getRemotePort(req),
 			ReplicationCluster:            req.ReplicationCluster,
 			Headers:                       req.Headers,
 			ClientCertificateSerialNumber: getClientCertificateSerialNumber(connState),
@@ -284,6 +285,7 @@ func (f *AuditFormatter) FormatResponse(ctx context.Context, w io.Writer, config
 			Data:                          req.Data,
 			PolicyOverride:                req.PolicyOverride,
 			RemoteAddr:                    getRemoteAddr(req),
+			RemotePort:                    getRemotePort(req),
 			ClientCertificateSerialNumber: getClientCertificateSerialNumber(connState),
 			ReplicationCluster:            req.ReplicationCluster,
 			Headers:                       req.Headers,
@@ -346,6 +348,7 @@ type AuditRequest struct {
 	Data                          map[string]interface{} `json:"data,omitempty"`
 	PolicyOverride                bool                   `json:"policy_override,omitempty"`
 	RemoteAddr                    string                 `json:"remote_address,omitempty"`
+	RemotePort                    int                    `json:"remote_port,omitempty"`
 	WrapTTL                       int                    `json:"wrap_ttl,omitempty"`
 	Headers                       map[string][]string    `json:"headers,omitempty"`
 	ClientCertificateSerialNumber string                 `json:"client_certificate_serial_number,omitempty"`
@@ -406,6 +409,14 @@ func getRemoteAddr(req *logical.Request) string {
 	return ""
 }
 
+// getRemotePort safely gets the remote port avoiding a nil pointer
+func getRemotePort(req *logical.Request) int {
+	if req != nil && req.Connection != nil {
+		return req.Connection.RemotePort
+	}
+	return 0
+}
+
 func getClientCertificateSerialNumber(connState *tls.ConnectionState) string {
 	if connState == nil || len(connState.VerifiedChains) == 0 || len(connState.VerifiedChains[0]) == 0 {
 		return ""

http/logical.go

@@ -491,14 +491,18 @@ WRITE_RESPONSE:
 // attaching to a logical request
 func getConnection(r *http.Request) (connection *logical.Connection) {
 	var remoteAddr string
+	var remotePort int
 
-	remoteAddr, _, err := net.SplitHostPort(r.RemoteAddr)
+	remoteAddr, port, err := net.SplitHostPort(r.RemoteAddr)
 	if err != nil {
 		remoteAddr = ""
+	} else {
+		remotePort, _ = strconv.Atoi(port)
 	}
 
 	connection = &logical.Connection{
 		RemoteAddr: remoteAddr,
+		RemotePort: remotePort,
 		ConnState:  r.TLS,
 	}
 	return

sdk/logical/connection.go

@@ -10,6 +10,9 @@ type Connection struct {
 	// RemoteAddr is the network address that sent the request.
 	RemoteAddr string `json:"remote_addr"`
 
+	// RemotePort is the network port that sent the request.
+	RemotePort int `json:"remote_port"`
+
 	// ConnState is the TLS connection state if applicable.
 	ConnState *tls.ConnectionState `sentinel:""`
 }