simcop2387/sys-linux-syscall-execve
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Final fixes to the env building, and encode not decode

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This commit is contained in:
Ryan Voots 2018-03-09 22:40:47 -08:00
parent 13b8f0e253
commit a53e20fa4b
2 changed files with 33 additions and 31 deletions
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62
lib/Sys/Linux/Syscall/Execve.pm
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@ -3,39 +3,37 @@ package Sys::Linux::Syscall::Execve;
use strict;
use warnings;
use Linux::Seccomp qw/syscall_resolve_name/;
use Encode qw/decode/;
use Encode qw/encode/;
use Exporter qw/import/;
use Config;
our $VERSION = "0.10";
our @EXPORT_OK = qw/execve execve_env execve_byref/;
my $ptr_int_type;
my $ptr_int_size;
my $ptr_int_size = $Config{ptrsize};
if ($ptr_int_size == 8) {
$ptr_int_type = "Q"; # 64bit pointer size, native endian
} elsif ($ptr_int_size == 4) {
$ptr_int_type = "L"; # 32bit pointer size native endian
} else {
die "Unknown pointer size $ptr_int_size";
}
my $execve_syscall = syscall_resolve_name('execve');
my $NULL = 0;
my $NULL_PTR = pack($ptr_int_type, $NULL);
BEGIN {
my $dummy = "dummy";
my $ptr_str = pack "p",$dummy;
$ptr_int_size = length $ptr_str;
if ($ptr_int_size == 8) {
$ptr_int_type = "Q"; # 64bit pointer size, native endian
} elsif ($ptr_int_size == 4) {
$ptr_int_type = "L"; # 32bit pointer size native endian
} else {
die "Unknown pointer size $ptr_int_size";
}
}
our $ERRNO = 0;
our $ERRSTR = "";
sub _execve {
my ($cmd_ptr, $arg_ptr, $env_ptr) = @_;
# printf "ptrs, 0x%08X 0x%08X 0x%08X\n\n", $cmd_ptr, $arg_ptr, $env_ptr;
my $ret = syscall $execve_syscall, 0+$cmd_ptr, 0+$arg_ptr, 0+$env_ptr;
$ERRNO = $!; # Preserve this for posterity.
$ERRSTR = "$!";
@ -67,39 +65,45 @@ sub _build_args {
{
# Because we have to format things, we have to do some tricks to ensure that perl can't ever garbage collect this data while we might use it.
my $env_internal;
my $env_internal_ptrs;
sub _build_env {
my $env_ref = shift;
my $length =()= keys %$env_ref;
# This weird buffer is also the start of the char *env[] that will be passed to execve()
# We're going to put out string data at the end of it, and we're going to need to calculate pointers.
$env_internal .= $NULL_PTR x ($length+1);
my @items = map {decode('utf-8', $_ . '=' . $env_ref->{$_})} keys %$env_ref;
my @items = map {encode('utf-8', $_ . '=' . $env_ref->{$_})} keys %$env_ref;
# Start the formatting of things, this is similar to how
# many C libraries do this. We take everything and put it in one large buffer
$env_internal .= join "\0", @items;
$env_internal = join "\0", @items;
$env_internal .= "\0";
# ok at this point the buffer is setup in place, with all the right lengths of things.
my $buf_ptr_origin = get_strptr_int(\$env_internal);
my $offset = ($length+1) * $ptr_int_size;
my $offset = 0;
my @ptrs;
# printf "START => 0x%08X + %6d => 0x%08X\n", $buf_ptr_origin, $offset, $buf_ptr_origin+$offset;
# This all starts at $buf_ptr_origin, and our strings start at +$offset.
for my $item (@items) {
$buf_ptr_origin = get_strptr_int(\$env_internal);
# printf " => 0x%08X + %6d => 0x%08X (%10d): %s\n", $buf_ptr_origin, $offset, $buf_ptr_origin+$offset, length($item)+1, $item;
push @ptrs, $buf_ptr_origin+$offset;
$offset += length($item) + 1; # account for \0 at the end of each string
}
my $new_ptrs = join '', map {pack_ptr($_)} @ptrs;
push @ptrs, 0;
substr $env_internal, 0, length($new_ptrs), $new_ptrs;
$env_internal_ptrs = join '', map {pack_ptr($_)} @ptrs;
return $env_internal;
my $buf_ptr_origin_new = get_strptr_int(\$env_internal_ptrs);
# printf " => 0x%08X\n", $buf_ptr_origin_new;
# print unpack("H*", $env_internal_ptrs), "\n";
return \$env_internal_ptrs;
}
}
@ -110,7 +114,7 @@ sub execve_byref {
my $_envbuf = _build_env($env_ref//{});
my $arg_ptr = get_strptr_int(\$_argbuf);
my $env_ptr = get_strptr_int(\$_envbuf);
my $env_ptr = get_strptr_int($_envbuf);
my $cmd_ptr = get_strptr_int($cmd_ref);
my $ret = _execve($cmd_ptr, $arg_ptr, $env_ptr);
@ -131,8 +135,6 @@ sub execve {
execve_byref(\$cmd, \@args, \%ENV);
}
print _build_env({foo => "bar", baz => "1....."});
1;
__END__

2
t/execve.t
View file

@ -17,7 +17,7 @@ sub test_exec {
die "Couldn't fork: $!" unless defined $pid;
if ($pid) {
waitpid $pid;
waitpid $pid, 0;
return $?>>8;
} else {
execve($cmd);