add support for PrivateBin format v2

getpaste

@@ -301,6 +301,36 @@ sub follow {
 # }}}
 # decoders {{{
 
+sub decode_base58 {
+	my ($str, $alpha) = @_;
+	# Source: https://metacpan.org/pod/Encode::Base58
+
+	use bigint;
+	use integer;
+
+	my @alpha = split(//, $alpha);
+	my $i = 0;
+	my %alpha = map { $_ => $i++ } @alpha;
+
+	my $decoded = 0;
+	my $multi   = 1;
+	my $base    = @alpha;
+
+	while (length $str > 0) {
+		my $digit = chop $str;
+		$decoded += $multi * $alpha{$digit};
+		$multi   *= $base;
+	}
+
+	return $decoded->to_bytes;
+}
+
+sub decode_privatebin_base58 {
+	my ($str) = @_;
+
+	return decode_base58($str, "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz");
+}
+
 sub decode_sour_base64 {
 	my ($str) = @_;
 
@@ -637,6 +667,64 @@ sub unwrap_openssl_aes {
 	return Crypt::Mode::CBC->new("AES")->decrypt($data, $key, $iv);
 }
 
+sub unwrap_privatebin_v2 {
+	eval {
+		require Crypt::AuthEnc::GCM;
+		require Crypt::KeyDerivation;
+	} or _die("missing Perl package 'CryptX'");
+
+	Crypt::AuthEnc::GCM->import(":all");
+	Crypt::KeyDerivation->import("pbkdf2");
+
+	# serialization: JSON
+	# key derivation: PBKDF2-SHA256
+	# encryption: AES256-GCM
+
+	my ($data, $passwd) = @_;
+
+	if ($data->{v} != 2) {
+		_die("incorrect paste format version ".$data->{v});
+	}
+
+	my $cparams = $data->{adata}->[0];
+	my $ct     = decode_base64($data->{ct});
+	my $iv     = decode_base64($cparams->[0]);
+	my $salt   = decode_base64($cparams->[1]);
+	my $iter   = $cparams->[2];
+	my $ks     = $cparams->[3] / 8;
+	my $ts     = $cparams->[4] / 8;
+	my $cipher = $cparams->[5];
+	my $mode   = $cparams->[6];
+	my $comp   = $cparams->[7];
+
+	unless ($cipher eq "aes") {
+		_die("unsupported cipher ".$cipher);
+	}
+	unless ($mode eq "gcm") {
+		_die("unsupported cipher mode ".$mode);
+	}
+	unless ($comp eq "zlib") {
+		_die("unsupported compression ".$comp);
+	}
+
+	my $ikey = decode_privatebin_base58($passwd);
+	my $dkey = pbkdf2($ikey, $salt, $iter, "SHA256", $ks);
+
+	my $hdr = encode_json($data->{adata});
+	my $tag = substr($ct, -$ts, $ts, "");
+
+	if ($mode eq "gcm") {
+		$data = gcm_decrypt_verify("AES", $dkey, $iv, $hdr, $ct, $tag)
+		       // _die("decryption failed");
+	}
+	if ($comp eq "zlib") {
+		$data = decompress_deflate($data);
+	}
+	$data = decode_json($data)->{paste};
+
+	return $data;
+}
+
 sub unwrap_sjcl {
 	eval {
 		require Crypt::AuthEnc::CCM;
@@ -904,14 +992,24 @@ sub dl_privatebin {
 	my $body = get($url) // return;
 	$body = decode_json($body);
 
-	my $data = $body->{data};
-	$data = unwrap_sjcl($data, $frag);
-	$data = decode_base64($data);
-	# The example code that comes with js-deflate mistakenly encodes binary
-	# data as UTF-8, and of course PrivateBin just used it verbatim.
-	$data = encode("latin1", decode("utf-8", $data));
-	$data = decompress_deflate($data);
-	return $data;
+	if ($body->{v} == 2) {
+		my $data = $body;
+		$data = unwrap_privatebin_v2($data, $frag);
+		return $data;
+	}
+	elsif ($body->{data}) {
+		my $data = $body->{data} // $body;
+		$data = unwrap_sjcl($data, $frag);
+		$data = decode_base64($data);
+		# The example code that comes with js-deflate mistakenly encodes binary
+		# data as UTF-8, and of course PrivateBin just used it verbatim.
+		$data = encode("latin1", decode("utf-8", $data));
+		$data = decompress_deflate($data);
+		return $data;
+	}
+	else {
+		_die("unrecognized PrivateBin format (did they change things up again?)");
+	}
 }
 
 sub dl_riseup {