[perl] Fix CVE-2013-1667

[Petr Pisar]

commit 338a23705e0ab4b6c573330c83216585fdd16f4a
Author: Petr Písař <ppisar(a)redhat.com&gt;
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(a)gmail.com&gt;
+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(a)redhat.com&gt; - 4:5.16.2-260
+- Fix CVE-2013-1667 (DoS in rehashing code) (bug #918008)
+
 * Mon Feb 18 2013 Petr Pisar <ppisar(a)redhat.com&gt; - 4:5.16.2-259
 - Sub-package autodie (bug #911226)
 - Add NAME headings to CPAN modules (bug #908113)