81a4940d25
Fixes the following security issues: - CVE-2016-6328: A vulnerability was found in libexif. An integer overflow when parsing the MNOTE entry data of the input file. This can cause Denial-of-Service (DoS) and Information Disclosure (disclosing some critical heap chunk metadata, even other applications' private data). - CVE-2017-7544: libexif through 0.6.21 is vulnerable to out-of-bounds heap read vulnerability in exif_data_save_data_entry function in libexif/exif-data.c caused by improper length computation of the allocated data of an ExifMnote entry which can cause denial-of-service or possibly information disclosure. - CVE-2018-20030: An error when processing the EXIF_IFD_INTEROPERABILITY and EXIF_IFD_EXIF tags within libexif version 0.6.21 can be exploited to exhaust available CPU resources. - CVE-2019-9278: In libexif, there is a possible out of bounds write due to an integer overflow. This could lead to remote escalation of privilege in the media content provider with no additional execution privileges needed. User interaction is needed for exploitation. Signed-off-by: Peter Korsgaard <peter@korsgaard.com> Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
121 lines
4.5 KiB
Diff
121 lines
4.5 KiB
Diff
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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[Peter: drop NEWS change]
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Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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---
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libexif/exif-data.c | 45 +++++++++++++++++++++++++++++++++++++--------
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1 file changed, 37 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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--
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2.20.1
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