ResStringPool: Fix security vulnerability
Adds detection of attacker-modified size and data fields passed to
ResStringPool::setTo(). These attacks are modified apks that AAPT would
not normally generate. In the rare case this occurs, the installation
cannot be allowed to continue.
Bug: 71361168
Bug: 71360999
Test: run cts -m CtsAppSecurityHostTestCases \
-t android.appsecurity.cts.CorruptApkTests
Change-Id: If7eb93a9e723b16c8a0556fc4e20006aa0391d57
Merged-In: If7eb93a9e723b16c8a0556fc4e20006aa0391d57
(cherry picked from commit 7e54c3f261d81316b75cb734075319108d8bc1d1)
diff --git a/libs/androidfw/ResourceTypes.cpp b/libs/androidfw/ResourceTypes.cpp
index 7cb4216..f608d7b 100644
--- a/libs/androidfw/ResourceTypes.cpp
+++ b/libs/androidfw/ResourceTypes.cpp
@@ -457,6 +457,22 @@
uninit();
+ // The chunk must be at least the size of the string pool header.
+ if (size < sizeof(ResStringPool_header)) {
+ LOG_ALWAYS_FATAL("Bad string block: data size %zu is too small to be a string block", size);
+ return (mError=BAD_TYPE);
+ }
+
+ // The data is at least as big as a ResChunk_header, so we can safely validate the other
+ // header fields.
+ // `data + size` is safe because the source of `size` comes from the kernel/filesystem.
+ if (validate_chunk(reinterpret_cast<const ResChunk_header*>(data), sizeof(ResStringPool_header),
+ reinterpret_cast<const uint8_t*>(data) + size,
+ "ResStringPool_header") != NO_ERROR) {
+ LOG_ALWAYS_FATAL("Bad string block: malformed block dimensions");
+ return (mError=BAD_TYPE);
+ }
+
const bool notDeviceEndian = htods(0xf0) != 0xf0;
if (copyData || notDeviceEndian) {
@@ -468,6 +484,8 @@
data = mOwnedData;
}
+ // The size has been checked, so it is safe to read the data in the ResStringPool_header
+ // data structure.
mHeader = (const ResStringPool_header*)data;
if (notDeviceEndian) {
