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package Nix::SSH;
use strict;
use File::Temp qw(tempdir);
use IPC::Open2;
our @ISA = qw(Exporter);
our @EXPORT = qw(
sshOpts openSSHConnection closeSSHConnection
readN readInt readString readStrings
writeInt writeString writeStrings
connectToRemoteNix
);
our @sshOpts = split ' ', ($ENV{"NIX_SSHOPTS"} or "");
push @sshOpts, "-x";
my $sshStarted = 0;
my $sshHost;
# Open a master SSH connection to `host', unless there already is a
# running master connection (as determined by `-O check').
sub openSSHConnection {
my ($host) = @_;
die if $sshStarted;
$sshHost = $host;
return 1 if system("ssh $sshHost @sshOpts -O check 2> /dev/null") == 0;
my $tmpDir = tempdir("nix-ssh.XXXXXX", CLEANUP => 1, TMPDIR => 1)
or die "cannot create a temporary directory";
push @sshOpts, "-S", "$tmpDir/control";
# Start the master. We can't use the `-f' flag (fork into
# background after establishing the connection) because then the
# child continues to run if we are killed. So instead make SSH
# print "started" when it has established the connection, and wait
# until we see that.
open SSHPIPE, "ssh $sshHost @sshOpts -M -N -o LocalCommand='echo started' -o PermitLocalCommand=yes |" or die;
while (<SSHPIPE>) {
chomp;
if ($_ eq "started") {
$sshStarted = 1;
return 1;
}
}
return 0;
}
# Tell the master SSH client to exit.
sub closeSSHConnection {
if ($sshStarted) {
system("ssh $sshHost @sshOpts -O exit 2> /dev/null") == 0
or warn "unable to stop SSH master: $?";
$sshStarted = 0;
}
}
sub readN {
my ($bytes, $from) = @_;
my $res = "";
while ($bytes > 0) {
my $s;
my $n = sysread($from, $s, $bytes);
die "I/O error reading from remote side\n" if !defined $n;
die "got EOF while expecting $bytes bytes from remote side\n" if !$n;
$bytes -= $n;
$res .= $s;
}
return $res;
}
sub readInt {
my ($from) = @_;
return unpack("L<x4", readN(8, $from));
}
sub readString {
my ($from) = @_;
my $len = readInt($from);
my $s = readN($len, $from);
readN(8 - $len % 8, $from) if $len % 8; # skip padding
return $s;
}
sub readStrings {
my ($from) = @_;
my $n = readInt($from);
my @res;
push @res, readString($from) while $n--;
return @res;
}
sub writeInt {
my ($n, $to) = @_;
syswrite($to, pack("L<x4", $n)) or die;
}
sub writeString {
my ($s, $to) = @_;
my $len = length $s;
my $req .= pack("L<x4", $len);
$req .= $s;
$req .= "\000" x (8 - $len % 8) if $len % 8;
syswrite($to, $req) or die;
}
sub writeStrings {
my ($ss, $to) = @_;
writeInt(scalar(@{$ss}), $to);
writeString($_, $to) foreach @{$ss};
}
sub connectToRemoteNix {
my ($sshHost, $sshOpts, $extraFlags) = @_;
$extraFlags ||= "";
# Start ‘nix-store --serve’ on the remote host.
my ($from, $to);
# FIXME: don't start a shell, start ssh directly.
my $pid = open2($from, $to, "exec ssh $sshHost @{$sshOpts} nix-store --serve --write $extraFlags");
# Do the handshake.
my $SERVE_MAGIC_1 = 0x390c9deb; # FIXME
my $clientVersion = 0x200;
syswrite($to, pack("L<x4L<x4", $SERVE_MAGIC_1, $clientVersion)) or die;
die "did not get valid handshake from remote host\n" if readInt($from) != 0x5452eecb;
my $serverVersion = readInt($from);
die "unsupported server version\n" if $serverVersion < 0x200 || $serverVersion >= 0x300;
return ($from, $to, $pid);
}
END { my $saved = $?; closeSSHConnection; $? = $saved; }
1;
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