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#!/usr/bin/env perl
# Find functions making recursive calls to themselves.
# (Multiple recursion where a() calls b() which calls a() not covered.)
#
# When the recursion depth might depend on data controlled by the attacker in
# an unbounded way, those functions should use interation instead.
#
# Typical usage: scripts/recursion.pl library/*.c
use warnings;
use strict;
use utf8;
use open qw(:std utf8);
# exclude functions that are ok:
# - mpi_write_hlp: bounded by size of mbedtls_mpi, a compile-time constant
# - x509_crt_verify_child: bounded by MBEDTLS_X509_MAX_INTERMEDIATE_CA
my $known_ok = qr/mpi_write_hlp|x509_crt_verify_child/;
my $cur_name;
my $inside;
my @funcs;
die "Usage: $0 file.c [...]\n" unless @ARGV;
while (<>)
{
if( /^[^\/#{}\s]/ && ! /\[.*]/ ) {
chomp( $cur_name = $_ ) unless $inside;
} elsif( /^{/ && $cur_name ) {
$inside = 1;
$cur_name =~ s/.* ([^ ]*)\(.*/$1/;
} elsif( /^}/ && $inside ) {
undef $inside;
undef $cur_name;
} elsif( $inside && /\b\Q$cur_name\E\([^)]/ ) {
push @funcs, $cur_name unless /$known_ok/;
}
}
print "$_\n" for @funcs;
exit @funcs;
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