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package sshd
import (
"context"
"time"
"golang.org/x/crypto/ssh"
"golang.org/x/sync/semaphore"
"gitlab.com/gitlab-org/gitlab-shell/internal/metrics"
"gitlab.com/gitlab-org/labkit/log"
)
type connection struct {
begin time.Time
concurrentSessions *semaphore.Weighted
remoteAddr string
}
type channelHandler func(context.Context, ssh.Channel, <-chan *ssh.Request)
func newConnection(maxSessions int64, remoteAddr string) *connection {
return &connection{
begin: time.Now(),
concurrentSessions: semaphore.NewWeighted(maxSessions),
remoteAddr: remoteAddr,
}
}
func (c *connection) handle(ctx context.Context, chans <-chan ssh.NewChannel, handler channelHandler) {
defer metrics.SshdConnectionDuration.Observe(time.Since(c.begin).Seconds())
for newChannel := range chans {
if newChannel.ChannelType() != "session" {
newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
continue
}
if !c.concurrentSessions.TryAcquire(1) {
newChannel.Reject(ssh.ResourceShortage, "too many concurrent sessions")
metrics.SshdHitMaxSessions.Inc()
continue
}
channel, requests, err := newChannel.Accept()
if err != nil {
log.WithError(err).Info("could not accept channel")
c.concurrentSessions.Release(1)
continue
}
go func() {
defer c.concurrentSessions.Release(1)
// Prevent a panic in a single session from taking out the whole server
defer func() {
if err := recover(); err != nil {
log.WithFields(log.Fields{"recovered_error": err}).Warnf("panic handling session from %s", c.remoteAddr)
}
}()
handler(ctx, channel, requests)
}()
}
}
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