aboutsummaryrefslogtreecommitdiff
path: root/package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch
diff options
context:
space:
mode:
Diffstat (limited to 'package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch')
-rw-r--r--package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch120
1 files changed, 120 insertions, 0 deletions
diff --git a/package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch b/package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch
new file mode 100644
index 0000000000..ff991541fe
--- /dev/null
+++ b/package/libexif/0004-Improve-deep-recursion-detection-in-exif_data_load_d.patch
@@ -0,0 +1,120 @@
+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.
+
+[Peter: drop NEWS change]
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+---
+ libexif/exif-data.c | 45 +++++++++++++++++++++++++++++++++++++--------
+ 1 file changed, 37 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 > 12) {
++ 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;
+--
+2.20.1
+