emit an audit event with file transfer statistics when an SFTP sessio…

…n is completed (#48051)

* emit an audit event with file transfer statistics when an SFTP session is completed

* remove unused SFTP event codes, don't embed os.File

* send oneof events to parent process to make event unmarshaling easier to reason about

* protect tracked files with mutex

api/proto/teleport/legacy/types/events/events.proto

@@ -1892,6 +1892,54 @@ message SFTP {
   string Error = 12 [(gogoproto.jsontag) = "error,omitempty"];
 }
 
+// SFTPSummary is emitted at the end of an SFTP transfer
+message SFTPSummary {
+  // Metadata is a common event metadata
+  Metadata Metadata = 1 [
+    (gogoproto.nullable) = false,
+    (gogoproto.embed) = true,
+    (gogoproto.jsontag) = ""
+  ];
+
+  // User is a common user event metadata
+  UserMetadata User = 2 [
+    (gogoproto.nullable) = false,
+    (gogoproto.embed) = true,
+    (gogoproto.jsontag) = ""
+  ];
+
+  // ConnectionMetadata holds information about the connection
+  ConnectionMetadata Connection = 3 [
+    (gogoproto.nullable) = false,
+    (gogoproto.embed) = true,
+    (gogoproto.jsontag) = ""
+  ];
+
+  // SessionMetadata is a common event session metadata
+  SessionMetadata Session = 4 [
+    (gogoproto.nullable) = false,
+    (gogoproto.embed) = true,
+    (gogoproto.jsontag) = ""
+  ];
+
+  // ServerMetadata is a common server metadata
+  ServerMetadata Server = 5 [
+    (gogoproto.nullable) = false,
+    (gogoproto.embed) = true,
+    (gogoproto.jsontag) = ""
+  ];
+
+  // FileTransferStats contains statistics about transferred files
+  repeated FileTransferStat FileTransferStats = 6 [(gogoproto.jsontag) = "file_transfer_stats"];
+}
+
+// FileTransferStat is statistics about a transferred file
+message FileTransferStat {
+  string Path = 1 [(gogoproto.jsontag) = "path"];
+  uint64 BytesRead = 2 [(gogoproto.jsontag) = "bytes_read"];
+  uint64 BytesWritten = 3 [(gogoproto.jsontag) = "bytes_written"];
+}
+
 // Subsystem is emitted when a user requests a new subsystem.
 message Subsystem {
   // Metadata is a common event metadata
@@ -4615,6 +4663,7 @@ message OneOf {
     events.UserTaskCreate UserTaskCreate = 188;
     events.UserTaskUpdate UserTaskUpdate = 189;
     events.UserTaskDelete UserTaskDelete = 190;
+    events.SFTPSummary SFTPSummary = 191;
   }
 }
 

api/types/events/events.go

@@ -2302,3 +2302,29 @@ func (m *UserTaskUpdate) TrimToMaxSize(_ int) AuditEvent {
 func (m *UserTaskDelete) TrimToMaxSize(_ int) AuditEvent {
 	return m
 }
+
+func (m *SFTPSummary) TrimToMaxSize(maxSize int) AuditEvent {
+	size := m.Size()
+	if size <= maxSize {
+		return m
+	}
+
+	out := utils.CloneProtoMsg(m)
+
+	var customFieldsCount int
+	for i := range out.FileTransferStats {
+		if out.FileTransferStats[i].Path != "" {
+			customFieldsCount++
+			out.FileTransferStats[i].Path = ""
+		}
+	}
+
+	maxSize = adjustedMaxSize(out, maxSize)
+	maxFieldsSize := maxSizePerField(maxSize, customFieldsCount)
+
+	for i := range out.FileTransferStats {
+		out.FileTransferStats[i].Path = trimStr(out.FileTransferStats[i].Path, maxFieldsSize)
+	}
+
+	return out
+}