gnu: libexif: Fix CVE-2018-20030.

* gnu/packages/photo.scm (libexif)[source]: Add patch.
* gnu/packages/patches/libexif-CVE-2018-20030.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

2 files changed, 123 insertions, 2 deletions

diff --git a/gnu/packages/patches/libexif-CVE-2018-20030.patch b/gnu/packages/patches/libexif-CVE-2018-20030.patch
new file mode 100644
index 0000000000..57e4746b58
--- /dev/null
+++ b/gnu/packages/patches/libexif-CVE-2018-20030.patch
@@ -0,0 +1,120 @@
+https://github.com/libexif/libexif/commit/6aa11df549114ebda520dde4cdaea2f9357b2c89.patch
+
+NEWS section was removed
+'12' -> '30' on line 79
+
+From 6aa11df549114ebda520dde4cdaea2f9357b2c89 Mon Sep 17 00:00:00 2001
+From: Dan Fandrich <dan@coneharvesters.com>
+Date: Fri, 12 Oct 2018 16:01:45 +0200
+Subject: [PATCH] Improve deep recursion detection in
+ exif_data_load_data_content.
+
+The existing detection was still vulnerable to pathological cases
+causing DoS by wasting CPU. The new algorithm takes the number of tags
+into account to make it harder to abuse by cases using shallow recursion
+but with a very large number of tags.  This improves on commit 5d28011c
+which wasn't sufficient to counter this kind of case.
+
+The limitation in the previous fix was discovered by Laurent Delosieres,
+Secunia Research at Flexera (Secunia Advisory SA84652) and is assigned
+the identifier CVE-2018-20030.
+---
+ NEWS                |  1 +
+ libexif/exif-data.c | 45 +++++++++++++++++++++++++++++++++++++--------
+ 2 files changed, 38 insertions(+), 8 deletions(-)
+
+diff --git a/libexif/exif-data.c b/libexif/exif-data.c
+index e35403d..a6f9c94 100644
+--- a/libexif/exif-data.c
++++ b/libexif/exif-data.c
+@@ -35,6 +35,7 @@
+ #include <libexif/olympus/exif-mnote-data-olympus.h>
+ #include <libexif/pentax/exif-mnote-data-pentax.h>
+ 
++#include <math.h>
+ #include <stdlib.h>
+ #include <stdio.h>
+ #include <string.h>
+@@ -350,6 +351,20 @@ if (data->ifd[(i)]->count) {				\
+ 	break;						\
+ }
+ 
++/*! Calculate the recursion cost added by one level of IFD loading.
++ *
++ * The work performed is related to the cost in the exponential relation
++ *   work=1.1**cost
++ */
++static unsigned int
++level_cost(unsigned int n)
++{
++    static const double log_1_1 = 0.09531017980432493;
++
++	/* Adding 0.1 protects against the case where n==1 */
++	return ceil(log(n + 0.1)/log_1_1);
++}
++
+ /*! Load data for an IFD.
+  *
+  * \param[in,out] data #ExifData
+@@ -357,13 +372,13 @@ if (data->ifd[(i)]->count) {				\
+  * \param[in] d pointer to buffer containing raw IFD data
+  * \param[in] ds size of raw data in buffer at \c d
+  * \param[in] offset offset into buffer at \c d at which IFD starts
+- * \param[in] recursion_depth number of times this function has been
+- * recursively called without returning
++ * \param[in] recursion_cost factor indicating how expensive this recursive
++ * call could be
+  */
+ static void
+ exif_data_load_data_content (ExifData *data, ExifIfd ifd,
+ 			     const unsigned char *d,
+-			     unsigned int ds, unsigned int offset, unsigned int recursion_depth)
++			     unsigned int ds, unsigned int offset, unsigned int recursion_cost)
+ {
+ 	ExifLong o, thumbnail_offset = 0, thumbnail_length = 0;
+ 	ExifShort n;
+@@ -378,9 +393,20 @@ exif_data_load_data_content (ExifData *data, ExifIfd ifd,
+ 	if ((((int)ifd) < 0) || ( ((int)ifd) >= EXIF_IFD_COUNT))
+ 	  return;
+ 
+-	if (recursion_depth > 30) {
++	if (recursion_cost > 170) {
++		/*
++		 * recursion_cost is a logarithmic-scale indicator of how expensive this
++		 * recursive call might end up being. It is an indicator of the depth of
++		 * recursion as well as the potential for worst-case future recursive
++		 * calls. Since it's difficult to tell ahead of time how often recursion
++		 * will occur, this assumes the worst by assuming every tag could end up
++		 * causing recursion.
++		 * The value of 170 was chosen to limit typical EXIF structures to a
++		 * recursive depth of about 6, but pathological ones (those with very
++		 * many tags) to only 2.
++		 */
+ 		exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData",
+-			  "Deep recursion detected!");
++			  "Deep/expensive recursion detected!");
+ 		return;
+ 	}
+ 
+@@ -422,15 +448,18 @@ exif_data_load_data_content (ExifData *data, ExifIfd ifd,
+ 			switch (tag) {
+ 			case EXIF_TAG_EXIF_IFD_POINTER:
+ 				CHECK_REC (EXIF_IFD_EXIF);
+-				exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o, recursion_depth + 1);
++				exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o,
++					recursion_cost + level_cost(n));
+ 				break;
+ 			case EXIF_TAG_GPS_INFO_IFD_POINTER:
+ 				CHECK_REC (EXIF_IFD_GPS);
+-				exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o, recursion_depth + 1);
++				exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o,
++					recursion_cost + level_cost(n));
+ 				break;
+ 			case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
+ 				CHECK_REC (EXIF_IFD_INTEROPERABILITY);
+-				exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o, recursion_depth + 1);
++				exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o,
++					recursion_cost + level_cost(n));
+ 				break;
+ 			case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
+ 				thumbnail_offset = o;
diff --git a/gnu/packages/photo.scm b/gnu/packages/photo.scm
index cf7da80642..cbfc2debd8 100644
--- a/gnu/packages/photo.scm
+++ b/gnu/packages/photo.scm
@@ -2,7 +2,7 @@
 ;;; Copyright © 2014, 2015, 2017, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2015, 2017 Andreas Enge <andreas@enge.fr>
-;;; Copyright © 2016, 2017, 2018 Efraim Flashner <efraim@flashner.co.il>
+;;; Copyright © 2016, 2017, 2018, 2019 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2017 Roel Janssen <roel@gnu.org>
 ;;; Copyright © 2018, 2019 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;; Copyright © 2018 Leo Famulari <leo@famulari.name>
@@ -117,7 +117,8 @@ cameras (CRW/CR2, NEF, RAF, DNG, and others).")
               (uri (string-append "mirror://sourceforge/libexif/libexif/"
                                   version "/libexif-" version ".tar.bz2"))
               (patches (search-patches "libexif-CVE-2016-6328.patch"
-                                       "libexif-CVE-2017-7544.patch"))
+                                       "libexif-CVE-2017-7544.patch"
+                                       "libexif-CVE-2018-20030.patch"))
               (sha256
                (base32
                 "06nlsibr3ylfwp28w8f5466l6drgrnydgxrm4jmxzrmk5svaxk8n"))))