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sftp: Allow password entry

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This was a bit tricky: We start the ssh binary, but we want it to ignore
SIGINT. In contrast, restic itself should process SIGINT and clean up
properly. Before, we used `setsid()` to give the ssh process its own
process group, but that means it cannot prompt the user for a password
because the tty is gone.

So, now we're passing in two functions that ignore SIGINT just before
the ssh process is started and re-install it after start.
This commit is contained in:
Alexander Neumann
2017-09-23 11:21:27 +02:00
parent 45a09c76ff
commit fb9729fdb9
6 changed files with 24 additions and 41 deletions
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31
internal/backend/sftp/sftp.go
View File

@@ -36,7 +36,7 @@ var _ restic.Backend = &SFTP{}
const defaultLayout = "default"
func startClient(program string, args ...string) (*SFTP, error) {
func startClient(preExec, postExec func(), program string, args ...string) (*SFTP, error) {
debug.Log("start client %v %v", program, args)
// Connect to a remote host and request the sftp subsystem via the 'ssh'
// command. This assumes that passwordless login is correctly configured.
@@ -55,9 +55,6 @@ func startClient(program string, args ...string) (*SFTP, error) {
}
}()
// ignore signals sent to the parent (e.g. SIGINT)
cmd.SysProcAttr = ignoreSigIntProcAttr()
// get stdin and stdout
wr, err := cmd.StdinPipe()
if err != nil {
@@ -68,11 +65,19 @@ func startClient(program string, args ...string) (*SFTP, error) {
return nil, errors.Wrap(err, "cmd.StdoutPipe")
}
if preExec != nil {
preExec()
}
// start the process
if err := cmd.Start(); err != nil {
return nil, errors.Wrap(err, "cmd.Start")
}
if postExec != nil {
postExec()
}
// wait in a different goroutine
ch := make(chan error, 1)
go func() {
@@ -104,8 +109,9 @@ func (r *SFTP) clientError() error {
}
// Open opens an sftp backend as described by the config by running
// "ssh" with the appropriate arguments (or cfg.Command, if set).
func Open(cfg Config) (*SFTP, error) {
// "ssh" with the appropriate arguments (or cfg.Command, if set). The function
// preExec is run just before, postExec just after starting a program.
func Open(cfg Config, preExec, postExec func()) (*SFTP, error) {
debug.Log("open backend with config %#v", cfg)
cmd, args, err := buildSSHCommand(cfg)
@@ -113,7 +119,7 @@ func Open(cfg Config) (*SFTP, error) {
return nil, err
}
sftp, err := startClient(cmd, args...)
sftp, err := startClient(preExec, postExec, cmd, args...)
if err != nil {
debug.Log("unable to start program: %v", err)
return nil, err
@@ -225,15 +231,16 @@ func buildSSHCommand(cfg Config) (cmd string, args []string, err error) {
return cmd, args, nil
}
// Create creates an sftp backend as described by the config by running
// "ssh" with the appropriate arguments (or cfg.Command, if set).
func Create(cfg Config) (*SFTP, error) {
// Create creates an sftp backend as described by the config by running "ssh"
// with the appropriate arguments (or cfg.Command, if set). The function
// preExec is run just before, postExec just after starting a program.
func Create(cfg Config, preExec, postExec func()) (*SFTP, error) {
cmd, args, err := buildSSHCommand(cfg)
if err != nil {
return nil, err
}
sftp, err := startClient(cmd, args...)
sftp, err := startClient(preExec, postExec, cmd, args...)
if err != nil {
debug.Log("unable to start program: %v", err)
return nil, err
@@ -261,7 +268,7 @@ func Create(cfg Config) (*SFTP, error) {
}
// open backend
return Open(cfg)
return Open(cfg, preExec, postExec)
}
// Location returns this backend's location (the directory name).