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proxy.go
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proxy.go
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package proxy
import (
"fmt"
"log"
"net"
"github.com/jackc/pgproto3/v2"
"github.com/sergi/go-diff/diffmatchpatch"
)
type PgRewriteProxy struct {
backend *pgproto3.Backend
frontend *pgproto3.Frontend
clientConn net.Conn
upstreamConn net.Conn
rewriterFactory QueryRewriterFactory
}
func NewPgRewriteProxy(clientConn, upstreamConn net.Conn, rewriterFactory QueryRewriterFactory) *PgRewriteProxy {
return &PgRewriteProxy{
backend: pgproto3.NewBackend(pgproto3.NewChunkReader(clientConn), clientConn),
frontend: pgproto3.NewFrontend(pgproto3.NewChunkReader(upstreamConn), upstreamConn),
rewriterFactory: rewriterFactory,
clientConn: clientConn,
upstreamConn: upstreamConn,
}
}
func (p *PgRewriteProxy) Run() error {
// Startup message is special
var startupMessage pgproto3.FrontendMessage
var err error
for {
startupMessage, err = p.backend.ReceiveStartupMessage()
if err != nil {
return fmt.Errorf("error receiving startup message: %w", err)
}
// We can't support SSL otherwise we can't modify queries
_, isSsl := startupMessage.(*pgproto3.SSLRequest)
_, isGss := startupMessage.(*pgproto3.GSSEncRequest)
if isSsl || isGss {
_, err = p.clientConn.Write([]byte("N"))
if err != nil {
return fmt.Errorf("error sending deny SSL request: %w", err)
}
} else {
break
}
}
// Pass on the startup message
err = p.frontend.Send(startupMessage)
if err != nil {
return err
}
// Boot two loops, one for inbound, one for outbound
errc := make(chan error)
go func() {
rewriter, err := p.rewriterFactory.Create()
if err != nil {
errc <- err
return
}
for {
msg, err := p.backend.Receive()
if err != nil {
errc <- err
return
}
if queryMsg, ok := msg.(*pgproto3.Query); ok {
newQuery, rewriteErr := rewriter.RewriteQuery(queryMsg.String)
if rewriteErr != nil {
err := p.sendRewriteError(rewriteErr)
if err != nil {
errc <- err
return
}
} else {
if queryMsg.String != newQuery {
err = p.sendRewriteNotice(queryMsg.String, newQuery)
if err != nil {
errc <- err
return
}
}
queryMsg.String = newQuery
}
}
if parseMsg, ok := msg.(*pgproto3.Parse); ok {
newQuery, rewriteErr := rewriter.RewriteParse(parseMsg.Query)
if rewriteErr != nil {
err := p.sendRewriteError(rewriteErr)
if err != nil {
errc <- err
return
}
} else {
if parseMsg.Query != newQuery {
err = p.sendRewriteNotice(parseMsg.Query, newQuery)
if err != nil {
errc <- err
return
}
}
parseMsg.Query = newQuery
}
}
// don't support rewriting parameters just yet (not sure if I need to)
//if _, ok := msg.(*pgproto3.Bind); ok {
//}
err = p.frontend.Send(msg)
if err != nil {
errc <- err
return
}
}
}()
go func() {
for {
bm, err := p.frontend.Receive()
if err != nil {
errc <- err
return
}
err = p.backend.Send(bm)
if err != nil {
errc <- err
return
}
}
}()
// Wait for either loop to exit
err = <-errc
return err
}
/// Be nice and tell the user we rewrote their query
func (p *PgRewriteProxy) sendRewriteNotice(original, new string) error {
dmp := diffmatchpatch.New()
diffs := dmp.DiffMain(original, new, false)
detail := dmp.DiffPrettyText(diffs)
not := &pgproto3.NoticeResponse{
Severity: "NOTICE",
Message: "Query was rewritten",
Detail: detail,
}
return p.backend.Send(not)
}
/// Be nice and tell the user we failed to rewrite their query
func (p *PgRewriteProxy) sendRewriteError(rewriteErr error) error {
not := &pgproto3.NoticeResponse{
Severity: "WARNING",
Message: "Failed to rewrite query",
Detail: rewriteErr.Error(),
}
return p.backend.Send(not)
}
func (p *PgRewriteProxy) Close() error {
err := p.clientConn.Close()
err2 := p.upstreamConn.Close()
if err != nil {
return err
} else if err2 != nil {
return err2
}
return nil
}
func RunProxy(ln net.Listener, upstream string, rewriterFactory QueryRewriterFactory) error {
for {
conn, err := ln.Accept()
if err != nil {
return err
}
upstreamConn, err := net.Dial("tcp", upstream)
if err == nil {
b := NewPgRewriteProxy(conn, upstreamConn, rewriterFactory)
go func() {
defer b.Close()
err := b.Run()
if err != nil {
log.Println(err)
}
log.Println("Closed connection from", conn.RemoteAddr())
}()
} else {
log.Println(err)
}
}
}