1 files changed, 292 insertions, 0 deletions
diff --git a/vendor/github.com/jackc/pgx/v5/pgproto3/backend.go b/vendor/github.com/jackc/pgx/v5/pgproto3/backend.go
new file mode 100644
index 0000000..d146c33
--- /dev/null
+++ b/vendor/github.com/jackc/pgx/v5/pgproto3/backend.go
@@ -0,0 +1,292 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+// Backend acts as a server for the PostgreSQL wire protocol version 3.
+type Backend struct {
+	cr *chunkReader
+	w  io.Writer
+
+	// tracer is used to trace messages when Send or Receive is called. This means an outbound message is traced
+	// before it is actually transmitted (i.e. before Flush).
+	tracer *tracer
+
+	wbuf        []byte
+	encodeError error
+
+	// Frontend message flyweights
+	bind           Bind
+	cancelRequest  CancelRequest
+	_close         Close
+	copyFail       CopyFail
+	copyData       CopyData
+	copyDone       CopyDone
+	describe       Describe
+	execute        Execute
+	flush          Flush
+	functionCall   FunctionCall
+	gssEncRequest  GSSEncRequest
+	parse          Parse
+	query          Query
+	sslRequest     SSLRequest
+	startupMessage StartupMessage
+	sync           Sync
+	terminate      Terminate
+
+	bodyLen    int
+	maxBodyLen int // maxBodyLen is the maximum length of a message body in octets. If a message body exceeds this length, Receive will return an error.
+	msgType    byte
+	partialMsg bool
+	authType   uint32
+}
+
+const (
+	minStartupPacketLen = 4     // minStartupPacketLen is a single 32-bit int version or code.
+	maxStartupPacketLen = 10000 // maxStartupPacketLen is MAX_STARTUP_PACKET_LENGTH from PG source.
+)
+
+// NewBackend creates a new Backend.
+func NewBackend(r io.Reader, w io.Writer) *Backend {
+	cr := newChunkReader(r, 0)
+	return &Backend{cr: cr, w: w}
+}
+
+// Send sends a message to the frontend (i.e. the client). The message is buffered until Flush is called. Any error
+// encountered will be returned from Flush.
+func (b *Backend) Send(msg BackendMessage) {
+	if b.encodeError != nil {
+		return
+	}
+
+	prevLen := len(b.wbuf)
+	newBuf, err := msg.Encode(b.wbuf)
+	if err != nil {
+		b.encodeError = err
+		return
+	}
+	b.wbuf = newBuf
+
+	if b.tracer != nil {
+		b.tracer.traceMessage('B', int32(len(b.wbuf)-prevLen), msg)
+	}
+}
+
+// Flush writes any pending messages to the frontend (i.e. the client).
+func (b *Backend) Flush() error {
+	if err := b.encodeError; err != nil {
+		b.encodeError = nil
+		b.wbuf = b.wbuf[:0]
+		return &writeError{err: err, safeToRetry: true}
+	}
+
+	n, err := b.w.Write(b.wbuf)
+
+	const maxLen = 1024
+	if len(b.wbuf) > maxLen {
+		b.wbuf = make([]byte, 0, maxLen)
+	} else {
+		b.wbuf = b.wbuf[:0]
+	}
+
+	if err != nil {
+		return &writeError{err: err, safeToRetry: n == 0}
+	}
+
+	return nil
+}
+
+// Trace starts tracing the message traffic to w. It writes in a similar format to that produced by the libpq function
+// PQtrace.
+func (b *Backend) Trace(w io.Writer, options TracerOptions) {
+	b.tracer = &tracer{
+		w:             w,
+		buf:           &bytes.Buffer{},
+		TracerOptions: options,
+	}
+}
+
+// Untrace stops tracing.
+func (b *Backend) Untrace() {
+	b.tracer = nil
+}
+
+// ReceiveStartupMessage receives the initial connection message. This method is used of the normal Receive method
+// because the initial connection message is "special" and does not include the message type as the first byte. This
+// will return either a StartupMessage, SSLRequest, GSSEncRequest, or CancelRequest.
+func (b *Backend) ReceiveStartupMessage() (FrontendMessage, error) {
+	buf, err := b.cr.Next(4)
+	if err != nil {
+		return nil, err
+	}
+	msgSize := int(binary.BigEndian.Uint32(buf) - 4)
+
+	if msgSize < minStartupPacketLen || msgSize > maxStartupPacketLen {
+		return nil, fmt.Errorf("invalid length of startup packet: %d", msgSize)
+	}
+
+	buf, err = b.cr.Next(msgSize)
+	if err != nil {
+		return nil, translateEOFtoErrUnexpectedEOF(err)
+	}
+
+	code := binary.BigEndian.Uint32(buf)
+
+	switch code {
+	case ProtocolVersionNumber:
+		err = b.startupMessage.Decode(buf)
+		if err != nil {
+			return nil, err
+		}
+		return &b.startupMessage, nil
+	case sslRequestNumber:
+		err = b.sslRequest.Decode(buf)
+		if err != nil {
+			return nil, err
+		}
+		return &b.sslRequest, nil
+	case cancelRequestCode:
+		err = b.cancelRequest.Decode(buf)
+		if err != nil {
+			return nil, err
+		}
+		return &b.cancelRequest, nil
+	case gssEncReqNumber:
+		err = b.gssEncRequest.Decode(buf)
+		if err != nil {
+			return nil, err
+		}
+		return &b.gssEncRequest, nil
+	default:
+		return nil, fmt.Errorf("unknown startup message code: %d", code)
+	}
+}
+
+// Receive receives a message from the frontend. The returned message is only valid until the next call to Receive.
+func (b *Backend) Receive() (FrontendMessage, error) {
+	if !b.partialMsg {
+		header, err := b.cr.Next(5)
+		if err != nil {
+			return nil, translateEOFtoErrUnexpectedEOF(err)
+		}
+
+		b.msgType = header[0]
+		b.bodyLen = int(binary.BigEndian.Uint32(header[1:])) - 4
+		if b.maxBodyLen > 0 && b.bodyLen > b.maxBodyLen {
+			return nil, &ExceededMaxBodyLenErr{b.maxBodyLen, b.bodyLen}
+		}
+		b.partialMsg = true
+	}
+
+	var msg FrontendMessage
+	switch b.msgType {
+	case 'B':
+		msg = &b.bind
+	case 'C':
+		msg = &b._close
+	case 'D':
+		msg = &b.describe
+	case 'E':
+		msg = &b.execute
+	case 'F':
+		msg = &b.functionCall
+	case 'f':
+		msg = &b.copyFail
+	case 'd':
+		msg = &b.copyData
+	case 'c':
+		msg = &b.copyDone
+	case 'H':
+		msg = &b.flush
+	case 'P':
+		msg = &b.parse
+	case 'p':
+		switch b.authType {
+		case AuthTypeSASL:
+			msg = &SASLInitialResponse{}
+		case AuthTypeSASLContinue:
+			msg = &SASLResponse{}
+		case AuthTypeSASLFinal:
+			msg = &SASLResponse{}
+		case AuthTypeGSS, AuthTypeGSSCont:
+			msg = &GSSResponse{}
+		case AuthTypeCleartextPassword, AuthTypeMD5Password:
+			fallthrough
+		default:
+			// to maintain backwards compatibility
+			msg = &PasswordMessage{}
+		}
+	case 'Q':
+		msg = &b.query
+	case 'S':
+		msg = &b.sync
+	case 'X':
+		msg = &b.terminate
+	default:
+		return nil, fmt.Errorf("unknown message type: %c", b.msgType)
+	}
+
+	msgBody, err := b.cr.Next(b.bodyLen)
+	if err != nil {
+		return nil, translateEOFtoErrUnexpectedEOF(err)
+	}
+
+	b.partialMsg = false
+
+	err = msg.Decode(msgBody)
+	if err != nil {
+		return nil, err
+	}
+
+	if b.tracer != nil {
+		b.tracer.traceMessage('F', int32(5+len(msgBody)), msg)
+	}
+
+	return msg, nil
+}
+
+// SetAuthType sets the authentication type in the backend.
+// Since multiple message types can start with 'p', SetAuthType allows
+// contextual identification of FrontendMessages. For example, in the
+// PG message flow documentation for PasswordMessage:
+//
+//			Byte1('p')
+//
+//	     Identifies the message as a password response. Note that this is also used for
+//			GSSAPI, SSPI and SASL response messages. The exact message type can be deduced from
+//			the context.
+//
+// Since the Frontend does not know about the state of a backend, it is important
+// to call SetAuthType() after an authentication request is received by the Frontend.
+func (b *Backend) SetAuthType(authType uint32) error {
+	switch authType {
+	case AuthTypeOk,
+		AuthTypeCleartextPassword,
+		AuthTypeMD5Password,
+		AuthTypeSCMCreds,
+		AuthTypeGSS,
+		AuthTypeGSSCont,
+		AuthTypeSSPI,
+		AuthTypeSASL,
+		AuthTypeSASLContinue,
+		AuthTypeSASLFinal:
+		b.authType = authType
+	default:
+		return fmt.Errorf("authType not recognized: %d", authType)
+	}
+
+	return nil
+}
+
+// SetMaxBodyLen sets the maximum length of a message body in octets. If a message body exceeds this length, Receive will return
+// an error. This is useful for protecting against malicious clients that send large messages with the intent of
+// causing memory exhaustion.
+// The default value is 0.
+// If maxBodyLen is 0, then no maximum is enforced.
+func (b *Backend) SetMaxBodyLen(maxBodyLen int) {
+	b.maxBodyLen = maxBodyLen
+}