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[v8] Fall back to "/" when home directory doesn't exist for tsh ssh (#9413) #9662

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merged 3 commits into from
Jan 20, 2022
Merged

[v8] Fall back to "/" when home directory doesn't exist for tsh ssh (#9413) #9662

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a96401b
Fall back to "/" when home directory doesn't exist for `tsh ssh` (#9413)
atburke Jan 5, 2022
40b198e
Merge branch 'branch/v8' into atburke/v8/missing-home-dir
russjones Jan 13, 2022
9c655e1
Merge branch 'branch/v8' into atburke/v8/missing-home-dir
atburke Jan 19, 2022
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15 changes: 12 additions & 3 deletions lib/srv/exec_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -178,7 +178,7 @@ func (s *ExecSuite) TestOSCommandPrep(c *check.C) {
// Empty command (simple shell).
execCmd, err := s.ctx.ExecCommand()
c.Assert(err, check.IsNil)
cmd, err := buildCommand(execCmd, nil, nil, nil)
cmd, err := buildCommand(execCmd, s.usr, nil, nil, nil)
c.Assert(err, check.IsNil)
c.Assert(cmd, check.NotNil)
c.Assert(cmd.Path, check.Equals, "/bin/sh")
Expand All @@ -191,7 +191,7 @@ func (s *ExecSuite) TestOSCommandPrep(c *check.C) {
s.ctx.ExecRequest.SetCommand("ls -lh /etc")
execCmd, err = s.ctx.ExecCommand()
c.Assert(err, check.IsNil)
cmd, err = buildCommand(execCmd, nil, nil, nil)
cmd, err = buildCommand(execCmd, s.usr, nil, nil, nil)
c.Assert(err, check.IsNil)
c.Assert(cmd, check.NotNil)
c.Assert(cmd.Path, check.Equals, "/bin/sh")
Expand All @@ -204,11 +204,20 @@ func (s *ExecSuite) TestOSCommandPrep(c *check.C) {
s.ctx.ExecRequest.SetCommand("top")
execCmd, err = s.ctx.ExecCommand()
c.Assert(err, check.IsNil)
cmd, err = buildCommand(execCmd, nil, nil, nil)
cmd, err = buildCommand(execCmd, s.usr, nil, nil, nil)
c.Assert(err, check.IsNil)
c.Assert(cmd.Path, check.Equals, "/bin/sh")
c.Assert(cmd.Args, check.DeepEquals, []string{"/bin/sh", "-c", "top"})
c.Assert(cmd.SysProcAttr.Pdeathsig, check.Equals, syscall.SIGKILL)

// Missing home directory
s.usr.HomeDir = "/wrong/place"
root := string(os.PathSeparator)
expectedEnv[2] = fmt.Sprintf("HOME=%s", root)
cmd, err = buildCommand(execCmd, s.usr, nil, nil, nil)
c.Assert(err, check.IsNil)
c.Assert(cmd.Dir, check.Equals, root)
c.Assert(cmd.Env, check.DeepEquals, expectedEnv)
}

func (s *ExecSuite) TestLoginDefsParser(c *check.C) {
Expand Down
26 changes: 17 additions & 9 deletions lib/srv/reexec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -215,8 +215,13 @@ func RunCommand() (io.Writer, int, error) {
pamEnvironment = pamContext.Environment()
}

localUser, err := user.Lookup(c.Login)
if err != nil {
return errorWriter, teleport.RemoteCommandFailure, trace.Wrap(err)
}

// Build the actual command that will launch the shell.
cmd, err := buildCommand(&c, tty, pty, pamEnvironment)
cmd, err := buildCommand(&c, localUser, tty, pty, pamEnvironment)
if err != nil {
return errorWriter, teleport.RemoteCommandFailure, trace.Wrap(err)
}
Expand Down Expand Up @@ -359,14 +364,10 @@ func RunAndExit(commandType string) {

// buildCommand constructs a command that will execute the users shell. This
// function is run by Teleport while it's re-executing.
func buildCommand(c *ExecCommand, tty *os.File, pty *os.File, pamEnvironment []string) (*exec.Cmd, error) {
func buildCommand(c *ExecCommand, localUser *user.User, tty *os.File, pty *os.File, pamEnvironment []string) (*exec.Cmd, error) {
var cmd exec.Cmd

// Lookup the UID and GID for the user.
localUser, err := user.Lookup(c.Login)
if err != nil {
return nil, trace.Wrap(err)
}
// Get UID and GID.
uid, err := strconv.Atoi(localUser.Uid)
if err != nil {
return nil, trace.Wrap(err)
Expand Down Expand Up @@ -423,11 +424,18 @@ func buildCommand(c *ExecCommand, tty *os.File, pty *os.File, pamEnvironment []s
cmd.Args = []string{shellPath, "-c", c.Command}
}

// Ensure that the user has a home directory.
// TODO: Generalize this to support Windows.
homeDir := string(os.PathSeparator)
if utils.IsDir(localUser.HomeDir) {
homeDir = localUser.HomeDir
}

// Create default environment for user.
cmd.Env = []string{
"LANG=en_US.UTF-8",
getDefaultEnvPath(localUser.Uid, defaultLoginDefsPath),
"HOME=" + localUser.HomeDir,
"HOME=" + homeDir,
"USER=" + c.Login,
"SHELL=" + shellPath,
}
Expand All @@ -450,7 +458,7 @@ func buildCommand(c *ExecCommand, tty *os.File, pty *os.File, pamEnvironment []s
cmd.Env = append(cmd.Env, pamEnvironment...)

// Set the home directory for the user.
cmd.Dir = localUser.HomeDir
cmd.Dir = homeDir

// If a terminal was requested, connect std{in,out,err} to the TTY and set
// the controlling TTY. Otherwise, connect std{in,out,err} to
Expand Down