gnu: expat: Fix CVE-2012-6702 and CVE-2016-5300.

* gnu/packages/patches/expat-CVE-2012-6702-and-CVE-2016-5300.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/xml.scm (expat/fixed): Use it.

2 files changed, 144 insertions, 1 deletions

diff --git a/gnu/packages/patches/expat-CVE-2012-6702-and-CVE-2016-5300.patch b/gnu/packages/patches/expat-CVE-2012-6702-and-CVE-2016-5300.patch
new file mode 100644
index 0000000000..edc43f84f1
--- /dev/null
+++ b/gnu/packages/patches/expat-CVE-2012-6702-and-CVE-2016-5300.patch
@@ -0,0 +1,142 @@
+Fix CVE-2012-6702 and CVE-2016-5300.
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-6702
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5300
+
+Patch copied from:
+https://sources.debian.net/src/expat/2.1.0-6%2Bdeb8u3/debian/patches/cve-2012-6702-plus-cve-2016-5300-v1.patch/
+
+From cb31522769d11a375078a073cba94e7176cb48a4 Mon Sep 17 00:00:00 2001
+From: Sebastian Pipping <sebastian@pipping.org>
+Date: Wed, 16 Mar 2016 15:30:12 +0100
+Subject: [PATCH] Resolve call to srand, use more entropy (patch version 1.0)
+
+Squashed backport against vanilla Expat 2.1.1, addressing:
+* CVE-2012-6702 -- unanticipated internal calls to srand
+* CVE-2016-5300 -- use of too little entropy
+
+Since commit e3e81a6d9f0885ea02d3979151c358f314bf3d6d
+(released with Expat 2.1.0) Expat called srand by itself
+from inside generate_hash_secret_salt for an instance
+of XML_Parser if XML_SetHashSalt was either (a) not called
+for that instance or if (b) salt 0 was passed to XML_SetHashSalt
+prior to parsing.  That call to srand passed (rather litle)
+entropy extracted from the current time as a seed for srand.
+
+That call to srand (1) broke repeatability for code calling
+srand with a non-random seed prior to parsing with Expat,
+and (2) resulted in a rather small set of hashing salts in
+Expat in total.
+
+For a short- to mid-term fix, the new approach avoids calling
+srand altogether, extracts more entropy out of the clock and
+other sources, too.
+
+For a long term fix, we may want to read sizeof(long) bytes
+from a source like getrandom(..) on Linux, and from similar
+sources on other supported architectures.
+
+https://bugzilla.redhat.com/show_bug.cgi?id=1197087
+---
+ CMakeLists.txt |  3 +++
+ lib/xmlparse.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
+ 2 files changed, 44 insertions(+), 7 deletions(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 353627e..524d514 100755
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -41,6 +41,9 @@ include_directories(${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/lib)
+ if(MSVC)

+     add_definitions(-D_CRT_SECURE_NO_WARNINGS -wd4996)

+ endif(MSVC)

++if(WIN32)

++    add_definitions(-DCOMPILED_FROM_DSP)

++endif(WIN32)

+ 

+ set(expat_SRCS

+     lib/xmlparse.c

+diff --git a/lib/xmlparse.c b/lib/xmlparse.c
+index e308c79..c5f942f 100644
+--- a/lib/xmlparse.c
++++ b/lib/xmlparse.c
+@@ -6,7 +6,14 @@
+ #include <string.h>                     /* memset(), memcpy() */
+ #include <assert.h>
+ #include <limits.h>                     /* UINT_MAX */
+-#include <time.h>                       /* time() */
++
++#ifdef COMPILED_FROM_DSP
++#define getpid GetCurrentProcessId
++#else
++#include <sys/time.h>                   /* gettimeofday() */
++#include <sys/types.h>                  /* getpid() */
++#include <unistd.h>                     /* getpid() */
++#endif
+ 
+ #define XML_BUILDING_EXPAT 1
+ 
+@@ -432,7 +439,7 @@ static ELEMENT_TYPE *
+ getElementType(XML_Parser parser, const ENCODING *enc,
+                const char *ptr, const char *end);
+ 
+-static unsigned long generate_hash_secret_salt(void);
++static unsigned long generate_hash_secret_salt(XML_Parser parser);
+ static XML_Bool startParsing(XML_Parser parser);
+ 
+ static XML_Parser
+@@ -691,11 +698,38 @@ static const XML_Char implicitContext[] = {
+ };
+ 
+ static unsigned long
+-generate_hash_secret_salt(void)
++gather_time_entropy(void)
+ {
+-  unsigned int seed = time(NULL) % UINT_MAX;
+-  srand(seed);
+-  return rand();
++#ifdef COMPILED_FROM_DSP
++  FILETIME ft;
++  GetSystemTimeAsFileTime(&ft); /* never fails */
++  return ft.dwHighDateTime ^ ft.dwLowDateTime;
++#else
++  struct timeval tv;
++  int gettimeofday_res;
++
++  gettimeofday_res = gettimeofday(&tv, NULL);
++  assert (gettimeofday_res == 0);
++
++  /* Microseconds time is <20 bits entropy */
++  return tv.tv_usec;
++#endif
++}
++
++static unsigned long
++generate_hash_secret_salt(XML_Parser parser)
++{
++  /* Process ID is 0 bits entropy if attacker has local access
++   * XML_Parser address is few bits of entropy if attacker has local access */
++  const unsigned long entropy =
++      gather_time_entropy() ^ getpid() ^ (unsigned long)parser;
++
++  /* Factors are 2^31-1 and 2^61-1 (Mersenne primes M31 and M61) */
++  if (sizeof(unsigned long) == 4) {
++    return entropy * 2147483647;
++  } else {
++    return entropy * 2305843009213693951;
++  }
+ }
+ 
+ static XML_Bool  /* only valid for root parser */
+@@ -703,7 +737,7 @@ startParsing(XML_Parser parser)
+ {
+     /* hash functions must be initialized before setContext() is called */
+     if (hash_secret_salt == 0)
+-      hash_secret_salt = generate_hash_secret_salt();
++      hash_secret_salt = generate_hash_secret_salt(parser);
+     if (ns) {
+       /* implicit context only set for root parser, since child
+          parsers (i.e. external entity parsers) will inherit it
+-- 
+2.8.2
+
diff --git a/gnu/packages/xml.scm b/gnu/packages/xml.scm
index dc5c60dca8..d5967f7966 100644
--- a/gnu/packages/xml.scm
+++ b/gnu/packages/xml.scm
@@ -69,7 +69,8 @@ things the parser might find in the XML document (like start tags).")
     (inherit expat)
     (source (origin
               (inherit (package-source expat))
-              (patches (search-patches "expat-CVE-2015-1283.patch"
+              (patches (search-patches "expat-CVE-2012-6702-and-CVE-2016-5300.patch"
+                                       "expat-CVE-2015-1283.patch"
                                        "expat-CVE-2015-1283-refix.patch"
                                        "expat-CVE-2016-0718.patch"))))))