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libgit2/managed: fix race conditions in ssh transport #753

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merged 1 commit into from
Jun 2, 2022
Merged

libgit2/managed: fix race conditions in ssh transport #753

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89 changes: 57 additions & 32 deletions pkg/git/libgit2/managed/ssh.go
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Original file line number Diff line number Diff line change
Expand Up @@ -46,12 +46,14 @@ package managed
import (
"context"
"crypto/sha256"
"errors"
"fmt"
"io"
"net"
"net/url"
"runtime"
"strings"
"sync"
"time"

"golang.org/x/crypto/ssh"
Expand Down Expand Up @@ -83,16 +85,22 @@ func sshSmartSubtransportFactory(remote *git2go.Remote, transport *git2go.Transp
type sshSmartSubtransport struct {
transport *git2go.Transport

lastAction git2go.SmartServiceAction
lastAction git2go.SmartServiceAction
stdin io.WriteCloser
stdout io.Reader
addr string
ctx context.Context

con connection
}

type connection struct {
conn net.Conn
client *ssh.Client
session *ssh.Session
stdin io.WriteCloser
stdout io.Reader
currentStream *sshSmartSubtransportStream
addr string
connected bool
ctx context.Context
m sync.Mutex
}

func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.SmartServiceAction) (git2go.SmartSubtransportStream, error) {
Expand Down Expand Up @@ -128,17 +136,17 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
var cmd string
switch action {
case git2go.SmartServiceActionUploadpackLs, git2go.SmartServiceActionUploadpack:
if t.currentStream != nil {
if t.con.currentStream != nil {
if t.lastAction == git2go.SmartServiceActionUploadpackLs {
return t.currentStream, nil
return t.con.currentStream, nil
}
}
cmd = fmt.Sprintf("git-upload-pack '%s'", uPath)

case git2go.SmartServiceActionReceivepackLs, git2go.SmartServiceActionReceivepack:
if t.currentStream != nil {
if t.con.currentStream != nil {
if t.lastAction == git2go.SmartServiceActionReceivepackLs {
return t.currentStream, nil
return t.con.currentStream, nil
}
}
cmd = fmt.Sprintf("git-receive-pack '%s'", uPath)
Expand All @@ -147,7 +155,7 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
return nil, fmt.Errorf("unexpected action: %v", action)
}

if t.connected {
if t.con.connected {
// Disregard errors from previous stream, futher details inside Close().
_ = t.Close()
}
Expand Down Expand Up @@ -185,21 +193,23 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
if err != nil {
return nil, err
}
t.connected = true
t.con.m.Lock()
t.con.connected = true
t.con.m.Unlock()

traceLog.Info("[ssh]: creating new ssh session")
if t.session, err = t.client.NewSession(); err != nil {
if t.con.session, err = t.con.client.NewSession(); err != nil {
return nil, err
}

if t.stdin, err = t.session.StdinPipe(); err != nil {
if t.stdin, err = t.con.session.StdinPipe(); err != nil {
return nil, err
}

var w *io.PipeWriter
var reader io.Reader
t.stdout, w = io.Pipe()
if reader, err = t.session.StdoutPipe(); err != nil {
if reader, err = t.con.session.StdoutPipe(); err != nil {
return nil, err
}

Expand All @@ -208,7 +218,15 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
//
// xref: https:/golang/crypto/blob/eb4f295cb31f7fb5d52810411604a2638c9b19a2/ssh/session.go#L553-L558
go func() error {
defer w.Close()
defer func() {
w.Close()

// In case this goroutine panics, handle recovery.
if r := recover(); r != nil {
traceLog.Error(errors.New(r.(string)),
"[ssh]: recovered from libgit2 ssh smart subtransport panic", "address", t.addr)
}
}()

var cancel context.CancelFunc
ctx := t.ctx
Expand All @@ -226,9 +244,12 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
return nil

default:
if !t.connected {
t.con.m.Lock()
if !t.con.connected {
t.con.m.Unlock()
return nil
}
t.con.m.Unlock()

_, err := io.Copy(w, reader)
if err != nil {
Expand All @@ -240,16 +261,16 @@ func (t *sshSmartSubtransport) Action(transportOptionsURL string, action git2go.
}()

traceLog.Info("[ssh]: run on remote", "cmd", cmd)
if err := t.session.Start(cmd); err != nil {
if err := t.con.session.Start(cmd); err != nil {
return nil, err
}

t.lastAction = action
t.currentStream = &sshSmartSubtransportStream{
t.con.currentStream = &sshSmartSubtransportStream{
owner: t,
}

return t.currentStream, nil
return t.con.currentStream, nil
}

func (t *sshSmartSubtransport) createConn(addr string, sshConfig *ssh.ClientConfig) error {
Expand All @@ -265,8 +286,8 @@ func (t *sshSmartSubtransport) createConn(addr string, sshConfig *ssh.ClientConf
return err
}

t.conn = conn
t.client = ssh.NewClient(c, chans, reqs)
t.con.conn = conn
t.con.client = ssh.NewClient(c, chans, reqs)

return nil
}
Expand All @@ -282,31 +303,35 @@ func (t *sshSmartSubtransport) createConn(addr string, sshConfig *ssh.ClientConf
// SmartSubTransport (i.e. unreleased resources, staled connections).
func (t *sshSmartSubtransport) Close() error {
traceLog.Info("[ssh]: sshSmartSubtransport.Close()", "server", t.addr)
t.currentStream = nil
if t.client != nil && t.stdin != nil {
t.con.m.Lock()
defer t.con.m.Unlock()
t.con.currentStream = nil
if t.con.client != nil && t.stdin != nil {
_ = t.stdin.Close()
}
t.client = nil
t.con.client = nil

if t.session != nil {
if t.con.session != nil {
traceLog.Info("[ssh]: session.Close()", "server", t.addr)
_ = t.session.Close()
_ = t.con.session.Close()
}
t.session = nil
t.con.session = nil

return nil
}

func (t *sshSmartSubtransport) Free() {
traceLog.Info("[ssh]: sshSmartSubtransport.Free()")
if t.client != nil {
_ = t.client.Close()
if t.con.client != nil {
_ = t.con.client.Close()
}

if t.conn != nil {
_ = t.conn.Close()
if t.con.conn != nil {
_ = t.con.conn.Close()
}
t.connected = false
t.con.m.Lock()
t.con.connected = false
t.con.m.Unlock()
}

type sshSmartSubtransportStream struct {
Expand Down