Fix CVE-2013-1667
This commit is contained in:
Petr Písař
parent
c1f404d101
commit
338a23705e
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@ -0,0 +1,170 @@
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From 6e79fe5714a72b1ef86dc890ff60746cdd19f854 Mon Sep 17 00:00:00 2001
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From: Yves Orton <demerphq@gmail.com>
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Date: Tue, 12 Feb 2013 10:53:05 +0100
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Subject: [PATCH] Prevent premature hsplit() calls, and only trigger REHASH
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after hsplit()
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Triggering a hsplit due to long chain length allows an attacker
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to create a carefully chosen set of keys which can cause the hash
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to use 2 * (2**32) * sizeof(void *) bytes ram. AKA a DOS via memory
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exhaustion. Doing so also takes non trivial time.
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Eliminating this check, and only inspecting chain length after a
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normal hsplit() (triggered when keys>buckets) prevents the attack
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entirely, and makes such attacks relatively benign.
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---
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ext/Hash-Util-FieldHash/t/10_hash.t | 18 ++++++++++++++++--
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hv.c | 35 ++++++++---------------------------
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t/op/hash.t | 20 +++++++++++++++++---
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3 files changed, 41 insertions(+), 32 deletions(-)
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diff --git a/ext/Hash-Util-FieldHash/t/10_hash.t b/ext/Hash-Util-FieldHash/t/10_hash.t
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index 2cfb4e8..d58f053 100644
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--- a/ext/Hash-Util-FieldHash/t/10_hash.t
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+++ b/ext/Hash-Util-FieldHash/t/10_hash.t
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@@ -38,15 +38,29 @@ use constant START => "a";
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# some initial hash data
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fieldhash my %h2;
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-%h2 = map {$_ => 1} 'a'..'cc';
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+my $counter= "a";
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+$h2{$counter++}++ while $counter ne 'cd';
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ok (!Internals::HvREHASH(%h2),
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"starting with pre-populated non-pathological hash (rehash flag if off)");
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my @keys = get_keys(\%h2);
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+my $buckets= buckets(\%h2);
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$h2{$_}++ for @keys;
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+$h2{$counter++}++ while buckets(\%h2) == $buckets; # force a split
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ok (Internals::HvREHASH(%h2),
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- scalar(@keys) . " colliding into the same bucket keys are triggering rehash");
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+ scalar(@keys) . " colliding into the same bucket keys are triggering rehash after split");
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+
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+# returns the number of buckets in a hash
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+sub buckets {
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+ my $hr = shift;
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+ my $keys_buckets= scalar(%$hr);
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+ if ($keys_buckets=~m!/([0-9]+)\z!) {
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+ return 0+$1;
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+ } else {
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+ return 8;
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+ }
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+}
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sub get_keys {
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my $hr = shift;
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diff --git a/hv.c b/hv.c
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index 6b66251..a031703 100644
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--- a/hv.c
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+++ b/hv.c
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@@ -35,7 +35,8 @@ holds the key and hash value.
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#define PERL_HASH_INTERNAL_ACCESS
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#include "perl.h"
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-#define HV_MAX_LENGTH_BEFORE_SPLIT 14
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+#define HV_MAX_LENGTH_BEFORE_REHASH 14
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+#define SHOULD_DO_HSPLIT(xhv) ((xhv)->xhv_keys > (xhv)->xhv_max) /* HvTOTALKEYS(hv) > HvMAX(hv) */
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static const char S_strtab_error[]
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= "Cannot modify shared string table in hv_%s";
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@@ -798,29 +799,9 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
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if (masked_flags & HVhek_ENABLEHVKFLAGS)
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HvHASKFLAGS_on(hv);
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- {
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- const HE *counter = HeNEXT(entry);
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-
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- xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
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- if (!counter) { /* initial entry? */
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- } else if (xhv->xhv_keys > xhv->xhv_max) {
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- /* Use only the old HvUSEDKEYS(hv) > HvMAX(hv) condition to limit
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- bucket splits on a rehashed hash, as we're not going to
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- split it again, and if someone is lucky (evil) enough to
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- get all the keys in one list they could exhaust our memory
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- as we repeatedly double the number of buckets on every
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- entry. Linear search feels a less worse thing to do. */
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- hsplit(hv);
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- } else if(!HvREHASH(hv)) {
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- U32 n_links = 1;
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-
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- while ((counter = HeNEXT(counter)))
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- n_links++;
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-
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- if (n_links > HV_MAX_LENGTH_BEFORE_SPLIT) {
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- hsplit(hv);
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- }
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- }
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+ xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
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+ if ( SHOULD_DO_HSPLIT(xhv) ) {
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+ hsplit(hv);
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}
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if (return_svp) {
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@@ -1197,7 +1178,7 @@ S_hsplit(pTHX_ HV *hv)
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/* Pick your policy for "hashing isn't working" here: */
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- if (longest_chain <= HV_MAX_LENGTH_BEFORE_SPLIT /* split worked? */
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+ if (longest_chain <= HV_MAX_LENGTH_BEFORE_REHASH /* split worked? */
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|| HvREHASH(hv)) {
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return;
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}
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@@ -2782,8 +2763,8 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
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xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
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if (!next) { /* initial entry? */
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- } else if (xhv->xhv_keys > xhv->xhv_max /* HvUSEDKEYS(hv) > HvMAX(hv) */) {
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- hsplit(PL_strtab);
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+ } else if ( SHOULD_DO_HSPLIT(xhv) ) {
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+ hsplit(PL_strtab);
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}
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}
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diff --git a/t/op/hash.t b/t/op/hash.t
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index ef757a3..97eb81b 100644
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--- a/t/op/hash.t
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+++ b/t/op/hash.t
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@@ -39,22 +39,36 @@ use constant THRESHOLD => 14;
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use constant START => "a";
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# some initial hash data
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-my %h2 = map {$_ => 1} 'a'..'cc';
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+my %h2;
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+my $counter= "a";
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+$h2{$counter++}++ while $counter ne 'cd';
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ok (!Internals::HvREHASH(%h2),
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"starting with pre-populated non-pathological hash (rehash flag if off)");
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my @keys = get_keys(\%h2);
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+my $buckets= buckets(\%h2);
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$h2{$_}++ for @keys;
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+$h2{$counter++}++ while buckets(\%h2) == $buckets; # force a split
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ok (Internals::HvREHASH(%h2),
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- scalar(@keys) . " colliding into the same bucket keys are triggering rehash");
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+ scalar(@keys) . " colliding into the same bucket keys are triggering rehash after split");
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+
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+# returns the number of buckets in a hash
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+sub buckets {
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+ my $hr = shift;
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+ my $keys_buckets= scalar(%$hr);
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+ if ($keys_buckets=~m!/([0-9]+)\z!) {
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+ return 0+$1;
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+ } else {
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+ return 8;
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+ }
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+}
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sub get_keys {
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my $hr = shift;
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# the minimum of bits required to mount the attack on a hash
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my $min_bits = log(THRESHOLD)/log(2);
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-
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# if the hash has already been populated with a significant amount
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# of entries the number of mask bits can be higher
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my $keys = scalar keys %$hr;
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--
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1.8.1.4
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10
perl.spec
10
perl.spec
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@ -29,7 +29,7 @@
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Name: perl
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Version: %{perl_version}
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# release number must be even higher, because dual-lived modules will be broken otherwise
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Release: 259%{?dist}
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Release: 260%{?dist}
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Epoch: %{perl_epoch}
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Summary: Practical Extraction and Report Language
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Group: Development/Languages
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@ -115,6 +115,9 @@ Patch20: perl-5.17.6-Fix-misparsing-of-maketext-strings.patch
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# Add NAME heading into CPAN PODs, rhbz#908113, CPANRT#73396
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Patch21: perl-5.16.2-cpan-CPAN-add-NAME-headings-in-modules-with-POD.patch
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# Fix CVE-2013-1667, rhbz#918008
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Patch22: perl-5.16.2-CVE-2013-1667.patch
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# Update some of the bundled modules
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# see http://fedoraproject.org/wiki/Perl/perl.spec for instructions
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@ -1583,6 +1586,7 @@ tarball from perl.org.
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%patch19 -p1
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%patch20 -p1
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%patch21 -p1
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%patch22 -p1
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#copy the example script
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cp -a %{SOURCE5} .
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@ -1795,6 +1799,7 @@ pushd %{build_archlib}/CORE/
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'Fedora Patch19: Do not crash when vivifying $|' \
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'Fedora Patch20: Fix misparsing of maketext strings (CVE-2012-6329)' \
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'Fedora Patch21: Add NAME headings to CPAN modules (CPANRT#73396)' \
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'Fedora Patch22: Fix DoS in rehashing code (CVE-2013-1667)' \
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%{nil}
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rm patchlevel.bak
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@ -3074,6 +3079,9 @@ sed \
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# Old changelog entries are preserved in CVS.
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%changelog
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* Tue Mar 05 2013 Petr Pisar <ppisar@redhat.com> - 4:5.16.2-260
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- Fix CVE-2013-1667 (DoS in rehashing code) (bug #918008)
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* Mon Feb 18 2013 Petr Pisar <ppisar@redhat.com> - 4:5.16.2-259
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- Sub-package autodie (bug #911226)
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- Add NAME headings to CPAN modules (bug #908113)
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