[perl] Fix CVE-2013-1667
Petr Pisar
ppisar at fedoraproject.org
Tue Mar 5 12:50:31 UTC 2013
commit 338a23705e0ab4b6c573330c83216585fdd16f4a
Author: Petr Písař <ppisar at redhat.com>
Date: Tue Mar 5 13:30:37 2013 +0100
Fix CVE-2013-1667
perl-5.16.2-CVE-2013-1667.patch | 170 +++++++++++++++++++++++++++++++++++++++
perl.spec | 10 ++-
2 files changed, 179 insertions(+), 1 deletions(-)
---
diff --git a/perl-5.16.2-CVE-2013-1667.patch b/perl-5.16.2-CVE-2013-1667.patch
new file mode 100644
index 0000000..61ed14b
--- /dev/null
+++ b/perl-5.16.2-CVE-2013-1667.patch
@@ -0,0 +1,170 @@
+From 6e79fe5714a72b1ef86dc890ff60746cdd19f854 Mon Sep 17 00:00:00 2001
+From: Yves Orton <demerphq at gmail.com>
+Date: Tue, 12 Feb 2013 10:53:05 +0100
+Subject: [PATCH] Prevent premature hsplit() calls, and only trigger REHASH
+ after hsplit()
+
+Triggering a hsplit due to long chain length allows an attacker
+to create a carefully chosen set of keys which can cause the hash
+to use 2 * (2**32) * sizeof(void *) bytes ram. AKA a DOS via memory
+exhaustion. Doing so also takes non trivial time.
+
+Eliminating this check, and only inspecting chain length after a
+normal hsplit() (triggered when keys>buckets) prevents the attack
+entirely, and makes such attacks relatively benign.
+---
+ ext/Hash-Util-FieldHash/t/10_hash.t | 18 ++++++++++++++++--
+ hv.c | 35 ++++++++---------------------------
+ t/op/hash.t | 20 +++++++++++++++++---
+ 3 files changed, 41 insertions(+), 32 deletions(-)
+
+diff --git a/ext/Hash-Util-FieldHash/t/10_hash.t b/ext/Hash-Util-FieldHash/t/10_hash.t
+index 2cfb4e8..d58f053 100644
+--- a/ext/Hash-Util-FieldHash/t/10_hash.t
++++ b/ext/Hash-Util-FieldHash/t/10_hash.t
+@@ -38,15 +38,29 @@ use constant START => "a";
+
+ # some initial hash data
+ fieldhash my %h2;
+-%h2 = map {$_ => 1} 'a'..'cc';
++my $counter= "a";
++$h2{$counter++}++ while $counter ne 'cd';
+
+ ok (!Internals::HvREHASH(%h2),
+ "starting with pre-populated non-pathological hash (rehash flag if off)");
+
+ my @keys = get_keys(\%h2);
++my $buckets= buckets(\%h2);
+ $h2{$_}++ for @keys;
++$h2{$counter++}++ while buckets(\%h2) == $buckets; # force a split
+ ok (Internals::HvREHASH(%h2),
+- scalar(@keys) . " colliding into the same bucket keys are triggering rehash");
++ scalar(@keys) . " colliding into the same bucket keys are triggering rehash after split");
++
++# returns the number of buckets in a hash
++sub buckets {
++ my $hr = shift;
++ my $keys_buckets= scalar(%$hr);
++ if ($keys_buckets=~m!/([0-9]+)\z!) {
++ return 0+$1;
++ } else {
++ return 8;
++ }
++}
+
+ sub get_keys {
+ my $hr = shift;
+diff --git a/hv.c b/hv.c
+index 6b66251..a031703 100644
+--- a/hv.c
++++ b/hv.c
+@@ -35,7 +35,8 @@ holds the key and hash value.
+ #define PERL_HASH_INTERNAL_ACCESS
+ #include "perl.h"
+
+-#define HV_MAX_LENGTH_BEFORE_SPLIT 14
++#define HV_MAX_LENGTH_BEFORE_REHASH 14
++#define SHOULD_DO_HSPLIT(xhv) ((xhv)->xhv_keys > (xhv)->xhv_max) /* HvTOTALKEYS(hv) > HvMAX(hv) */
+
+ static const char S_strtab_error[]
+ = "Cannot modify shared string table in hv_%s";
+@@ -798,29 +799,9 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
+ if (masked_flags & HVhek_ENABLEHVKFLAGS)
+ HvHASKFLAGS_on(hv);
+
+- {
+- const HE *counter = HeNEXT(entry);
+-
+- xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
+- if (!counter) { /* initial entry? */
+- } else if (xhv->xhv_keys > xhv->xhv_max) {
+- /* Use only the old HvUSEDKEYS(hv) > HvMAX(hv) condition to limit
+- bucket splits on a rehashed hash, as we're not going to
+- split it again, and if someone is lucky (evil) enough to
+- get all the keys in one list they could exhaust our memory
+- as we repeatedly double the number of buckets on every
+- entry. Linear search feels a less worse thing to do. */
+- hsplit(hv);
+- } else if(!HvREHASH(hv)) {
+- U32 n_links = 1;
+-
+- while ((counter = HeNEXT(counter)))
+- n_links++;
+-
+- if (n_links > HV_MAX_LENGTH_BEFORE_SPLIT) {
+- hsplit(hv);
+- }
+- }
++ xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
++ if ( SHOULD_DO_HSPLIT(xhv) ) {
++ hsplit(hv);
+ }
+
+ if (return_svp) {
+@@ -1197,7 +1178,7 @@ S_hsplit(pTHX_ HV *hv)
+
+
+ /* Pick your policy for "hashing isn't working" here: */
+- if (longest_chain <= HV_MAX_LENGTH_BEFORE_SPLIT /* split worked? */
++ if (longest_chain <= HV_MAX_LENGTH_BEFORE_REHASH /* split worked? */
+ || HvREHASH(hv)) {
+ return;
+ }
+@@ -2782,8 +2763,8 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
+
+ xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
+ if (!next) { /* initial entry? */
+- } else if (xhv->xhv_keys > xhv->xhv_max /* HvUSEDKEYS(hv) > HvMAX(hv) */) {
+- hsplit(PL_strtab);
++ } else if ( SHOULD_DO_HSPLIT(xhv) ) {
++ hsplit(PL_strtab);
+ }
+ }
+
+diff --git a/t/op/hash.t b/t/op/hash.t
+index ef757a3..97eb81b 100644
+--- a/t/op/hash.t
++++ b/t/op/hash.t
+@@ -39,22 +39,36 @@ use constant THRESHOLD => 14;
+ use constant START => "a";
+
+ # some initial hash data
+-my %h2 = map {$_ => 1} 'a'..'cc';
++my %h2;
++my $counter= "a";
++$h2{$counter++}++ while $counter ne 'cd';
+
+ ok (!Internals::HvREHASH(%h2),
+ "starting with pre-populated non-pathological hash (rehash flag if off)");
+
+ my @keys = get_keys(\%h2);
++my $buckets= buckets(\%h2);
+ $h2{$_}++ for @keys;
++$h2{$counter++}++ while buckets(\%h2) == $buckets; # force a split
+ ok (Internals::HvREHASH(%h2),
+- scalar(@keys) . " colliding into the same bucket keys are triggering rehash");
++ scalar(@keys) . " colliding into the same bucket keys are triggering rehash after split");
++
++# returns the number of buckets in a hash
++sub buckets {
++ my $hr = shift;
++ my $keys_buckets= scalar(%$hr);
++ if ($keys_buckets=~m!/([0-9]+)\z!) {
++ return 0+$1;
++ } else {
++ return 8;
++ }
++}
+
+ sub get_keys {
+ my $hr = shift;
+
+ # the minimum of bits required to mount the attack on a hash
+ my $min_bits = log(THRESHOLD)/log(2);
+-
+ # if the hash has already been populated with a significant amount
+ # of entries the number of mask bits can be higher
+ my $keys = scalar keys %$hr;
+--
+1.8.1.4
+
diff --git a/perl.spec b/perl.spec
index 5cecfed..def0214 100644
--- a/perl.spec
+++ b/perl.spec
@@ -29,7 +29,7 @@
Name: perl
Version: %{perl_version}
# release number must be even higher, because dual-lived modules will be broken otherwise
-Release: 259%{?dist}
+Release: 260%{?dist}
Epoch: %{perl_epoch}
Summary: Practical Extraction and Report Language
Group: Development/Languages
@@ -115,6 +115,9 @@ Patch20: perl-5.17.6-Fix-misparsing-of-maketext-strings.patch
# Add NAME heading into CPAN PODs, rhbz#908113, CPANRT#73396
Patch21: perl-5.16.2-cpan-CPAN-add-NAME-headings-in-modules-with-POD.patch
+# Fix CVE-2013-1667, rhbz#918008
+Patch22: perl-5.16.2-CVE-2013-1667.patch
+
# Update some of the bundled modules
# see http://fedoraproject.org/wiki/Perl/perl.spec for instructions
@@ -1583,6 +1586,7 @@ tarball from perl.org.
%patch19 -p1
%patch20 -p1
%patch21 -p1
+%patch22 -p1
#copy the example script
cp -a %{SOURCE5} .
@@ -1795,6 +1799,7 @@ pushd %{build_archlib}/CORE/
'Fedora Patch19: Do not crash when vivifying $|' \
'Fedora Patch20: Fix misparsing of maketext strings (CVE-2012-6329)' \
'Fedora Patch21: Add NAME headings to CPAN modules (CPANRT#73396)' \
+ 'Fedora Patch22: Fix DoS in rehashing code (CVE-2013-1667)' \
%{nil}
rm patchlevel.bak
@@ -3074,6 +3079,9 @@ sed \
# Old changelog entries are preserved in CVS.
%changelog
+* Tue Mar 05 2013 Petr Pisar <ppisar at redhat.com> - 4:5.16.2-260
+- Fix CVE-2013-1667 (DoS in rehashing code) (bug #918008)
+
* Mon Feb 18 2013 Petr Pisar <ppisar at redhat.com> - 4:5.16.2-259
- Sub-package autodie (bug #911226)
- Add NAME headings to CPAN modules (bug #908113)
More information about the scm-commits
mailing list