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113 lines
3.2 KiB
Perl
113 lines
3.2 KiB
Perl
# File: ValidateString.pm
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#
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# Purpose: ensures that a given string conforms to PBot's limitations
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# for internal strings. This means ensuring the string is not too long,
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# does not have undesired characters, etc.
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# SPDX-FileCopyrightText: 2021 Pragmatic Software <pragma78@gmail.com>
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# SPDX-License-Identifier: MIT
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package PBot::Core::Utils::ValidateString;
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use PBot::Imports;
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# export validate_string subroutine
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require Exporter;
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our @ISA = qw/Exporter/;
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our @EXPORT = qw/validate_string/;
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use JSON;
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use Encode;
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use Unicode::Truncate;
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# validate_string converts a given string to one that conforms to
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# PBot's limitations for internal strings. This means ensuring the
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# string is not too long, does not have undesired characters, etc.
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#
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# If the given string contains a JSON structure, it will be parsed
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# and each value will be validated. JSON structures must have a depth
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# of one level only.
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#
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# Note that $max_length represents bytes, not characters. The string
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# is encoded to utf8, validated, and then decoded back. Truncation
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# uses Unicode::Truncate to find the longest Unicode string that can
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# fit within $max_length bytes without corruption of the characters.
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#
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# if $max_length is undefined, it defaults to 8k.
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#
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# if $max_length is 0, no truncation occurs.
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sub validate_string {
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my ($string, $max_length) = @_;
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if (not defined $string or not length $string) {
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# nothing to validate; return as-is.
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return $string;
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}
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# set default max length if none given
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$max_length //= 1024 * 8;
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local $@;
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eval {
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# attempt to decode as a JSON string
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# throws exception if fails
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my $data = decode_json($string);
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# no exception thrown, must be JSON.
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# so we validate all of its values.
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if (not defined $data) {
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# decode_json decodes "null" to undef. so we just
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# go ahead and return "null" as-is. otherwise, if we allow
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# encode_json to encode it back to a string, the string
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# will be "{}". bit weird.
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return 'null';
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}
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# validate values
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foreach my $key (keys %$data) {
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$data->{$key} = validate_this_string($data->{$key}, $max_length);
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}
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# encode back to a JSON string
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$string = encode_json($data);
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};
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if ($@) {
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# not a JSON string, so validate as a normal string.
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$string = validate_this_string($string, $max_length);
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}
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# all validated!
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return $string;
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}
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# validates the string.
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# safely performs Unicode truncation given a byte length, handles
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# unwanted characters, etc.
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sub validate_this_string {
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my ($string, $max_length) = @_;
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# truncate safely
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if ($max_length > 0) {
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$string = encode('UTF-8', $string);
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$string = truncate_egc $string, $max_length;
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}
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# allow only these characters.
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# TODO: probably going to delete this code.
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# replace any extraneous characters with escaped-hexadecimal representation
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# $string =~ s/(\P{PosixGraph})/
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# my $ch = $1;
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# if ($ch =~ m{[\s\x03\x02\x1d\x1f\x16\x0f]}) {
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# $ch;
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# } else {
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# sprintf "\\x%02X", ord $ch;
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# }/gxe;
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return $string;
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}
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1;
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