diff options
author | EuAndreh <eu@euandre.org> | 2024-08-08 18:48:25 -0300 |
---|---|---|
committer | EuAndreh <eu@euandre.org> | 2024-08-08 18:48:25 -0300 |
commit | 81ebc234678af08692aad7f3c2d1128f6c2f75c4 (patch) | |
tree | fc5ba312b456d2b2ef20424572d9ca4a9a76edc8 /src/binder.go | |
parent | rm go.mod (diff) | |
download | binder-81ebc234678af08692aad7f3c2d1128f6c2f75c4.tar.gz binder-81ebc234678af08692aad7f3c2d1128f6c2f75c4.tar.xz |
Makefile: Use "go tool {compile,link}" over "go {build,test}"
Diffstat (limited to 'src/binder.go')
-rw-r--r-- | src/binder.go | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/src/binder.go b/src/binder.go new file mode 100644 index 0000000..8950c29 --- /dev/null +++ b/src/binder.go @@ -0,0 +1,133 @@ +package binder + +import ( + "fmt" + "net" + "os" + "os/user" + "strconv" + "syscall" + + g "gobang" +) + + + +type CLIArgs struct { + FromAddr string + ToAddr string +} + + + +const USER = "nobody" + + + +var EmitActiveConnection = g.MakeGauge("active-connections") + + + +func dropPrivileges(username string) { + g.Info("Dropping privileges", "drop-root-init") + + user, err := user.Lookup(username) + g.FatalIf(err) + + gid, err := strconv.Atoi(user.Gid) + g.FatalIf(err) + + uid, err := strconv.Atoi(user.Uid) + g.FatalIf(err) + + err = syscall.Setgid(gid) + g.FatalIf(err) + + err = syscall.Setgroups([]int{}) + g.FatalIf(err) + + err = syscall.Setuid(uid) + g.FatalIf(err) + + g.Info("Privileges dropped", "drop-root-end") +} + +func isRunningAsRoot() bool { + return os.Geteuid() == 0 +} + +func ParseArgs(args []string) CLIArgs { + if len(args) != 3 { + fmt.Fprintf( + os.Stderr, + "Usage: %s FROM-ADDRESS TO-ADDRESS\n", + args[0], + ) + os.Exit(2) + } + return CLIArgs { + FromAddr: args[1], + ToAddr: args[2], + } +} + +func Listen(fromAddr string) net.Listener { + listener, err := net.Listen("tcp", fromAddr) + g.FatalIf(err) + g.Info("Started listening", "listen-start", "from-address", fromAddr) + return listener +} + +func DropRoot() { + if isRunningAsRoot() { + dropPrivileges(USER) + if isRunningAsRoot() { + panic("Failed to drop privileges") + } + } +} + +func Start(toAddr string, listener net.Listener) { + for { + connFrom, err := listener.Accept() + if err != nil { + g.Warning( + "Error accepting connection", + "accept-connection-error", + "err", err, + ) + continue + } + defer connFrom.Close() + EmitActiveConnection.Inc() + + connTo, err := net.Dial("unix", toAddr) + if err != nil { + g.Warning( + "Error dialing connection", + "dial-connection-error", + "err", err, + ) + connFrom.Close() + continue + } + defer connTo.Close() + + c := make(chan g.CopyResult) + go g.CopyData(c, "c2s", connFrom, connTo) + go g.CopyData(c, "s2c", connTo, connFrom) + go func() { + <- c + EmitActiveConnection.Dec() + }() + } +} + + +func Main() { + g.Init() + args := ParseArgs(os.Args) + listener := Listen(args.FromAddr) + DropRoot() + Start(args.ToAddr, listener) +} |