libexif: convert to fetchpatch
This commit is contained in:
Vladimír Čunát
parent
6310531fe2
commit
233f36303b
@ -1,115 +0,0 @@
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From 6aa11df549114ebda520dde4cdaea2f9357b2c89 Mon Sep 17 00:00:00 2001
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From: Dan Fandrich <dan@coneharvesters.com>
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Date: Fri, 12 Oct 2018 16:01:45 +0200
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Subject: [PATCH] Improve deep recursion detection in
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exif_data_load_data_content.
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The existing detection was still vulnerable to pathological cases
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causing DoS by wasting CPU. The new algorithm takes the number of tags
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into account to make it harder to abuse by cases using shallow recursion
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but with a very large number of tags. This improves on commit 5d28011c
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which wasn't sufficient to counter this kind of case.
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The limitation in the previous fix was discovered by Laurent Delosieres,
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Secunia Research at Flexera (Secunia Advisory SA84652) and is assigned
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the identifier CVE-2018-20030.
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---
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NEWS | 1 +
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libexif/exif-data.c | 45 +++++++++++++++++++++++++++++++++++++--------
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2 files changed, 38 insertions(+), 8 deletions(-)
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diff --git a/libexif/exif-data.c b/libexif/exif-data.c
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index e35403d..a6f9c94 100644
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--- a/libexif/exif-data.c
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+++ b/libexif/exif-data.c
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@@ -35,6 +35,7 @@
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#include <libexif/olympus/exif-mnote-data-olympus.h>
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#include <libexif/pentax/exif-mnote-data-pentax.h>
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+#include <math.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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@@ -350,6 +351,20 @@ if (data->ifd[(i)]->count) { \
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break; \
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}
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+/*! Calculate the recursion cost added by one level of IFD loading.
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+ *
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+ * The work performed is related to the cost in the exponential relation
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+ * work=1.1**cost
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+ */
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+static unsigned int
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+level_cost(unsigned int n)
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+{
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+ static const double log_1_1 = 0.09531017980432493;
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+
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+ /* Adding 0.1 protects against the case where n==1 */
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+ return ceil(log(n + 0.1)/log_1_1);
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+}
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+
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/*! Load data for an IFD.
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*
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* \param[in,out] data #ExifData
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@@ -357,13 +372,13 @@ if (data->ifd[(i)]->count) { \
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* \param[in] d pointer to buffer containing raw IFD data
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* \param[in] ds size of raw data in buffer at \c d
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* \param[in] offset offset into buffer at \c d at which IFD starts
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- * \param[in] recursion_depth number of times this function has been
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- * recursively called without returning
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+ * \param[in] recursion_cost factor indicating how expensive this recursive
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+ * call could be
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*/
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static void
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exif_data_load_data_content (ExifData *data, ExifIfd ifd,
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const unsigned char *d,
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- unsigned int ds, unsigned int offset, unsigned int recursion_depth)
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+ unsigned int ds, unsigned int offset, unsigned int recursion_cost)
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{
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ExifLong o, thumbnail_offset = 0, thumbnail_length = 0;
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ExifShort n;
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@@ -378,9 +393,20 @@ exif_data_load_data_content (ExifData *data, ExifIfd ifd,
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if ((((int)ifd) < 0) || ( ((int)ifd) >= EXIF_IFD_COUNT))
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return;
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- if (recursion_depth > 12) {
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+ if (recursion_cost > 170) {
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+ /*
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+ * recursion_cost is a logarithmic-scale indicator of how expensive this
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+ * recursive call might end up being. It is an indicator of the depth of
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+ * recursion as well as the potential for worst-case future recursive
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+ * calls. Since it's difficult to tell ahead of time how often recursion
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+ * will occur, this assumes the worst by assuming every tag could end up
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+ * causing recursion.
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+ * The value of 170 was chosen to limit typical EXIF structures to a
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+ * recursive depth of about 6, but pathological ones (those with very
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+ * many tags) to only 2.
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+ */
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exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData",
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- "Deep recursion detected!");
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+ "Deep/expensive recursion detected!");
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return;
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}
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@@ -422,15 +448,18 @@ exif_data_load_data_content (ExifData *data, ExifIfd ifd,
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switch (tag) {
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case EXIF_TAG_EXIF_IFD_POINTER:
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CHECK_REC (EXIF_IFD_EXIF);
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- exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o, recursion_depth + 1);
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+ exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o,
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+ recursion_cost + level_cost(n));
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break;
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case EXIF_TAG_GPS_INFO_IFD_POINTER:
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CHECK_REC (EXIF_IFD_GPS);
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- exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o, recursion_depth + 1);
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+ exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o,
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+ recursion_cost + level_cost(n));
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break;
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case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
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CHECK_REC (EXIF_IFD_INTEROPERABILITY);
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- exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o, recursion_depth + 1);
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+ exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o,
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+ recursion_cost + level_cost(n));
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break;
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case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
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thumbnail_offset = o;
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@ -19,10 +19,12 @@ stdenv.mkDerivation rec {
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url = "https://github.com/libexif/libexif/commit/5d28011c40ec86cf52cffad541093d37c263898a.patch";
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sha256 = "1wv8s962wmbn2m2xypgirf12g6msrbplpsmd5bh86irfwhkcppj3";
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})
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# This is basically
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# https://github.com/libexif/libexif/commit/6aa11df549114ebda520dde4cdaea2f9357b2c89.patch,
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# but without the addition to ./NEWS
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./CVE-2018-20030-2.patch
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(fetchpatch {
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name = "CVE-2018-20030-2.patch";
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url = "https://github.com/libexif/libexif/commit/6aa11df549114ebda520dde4cdaea2f9357b2c89.patch";
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sha256 = "01aqvz63glwq6wg0wr7ykqqghb4abgq77ghvhizbzadg1k4h7drx";
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excludes = [ "NEWS" ];
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})
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];
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buildInputs = [ gettext ];
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