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authorRaph Levien <raph@google.com>2015-11-30 23:04:59 (GMT)
committerThe Android Automerger <android-build@google.com>2015-12-11 00:11:55 (GMT)
commit715e31e7334db3c196d64dd83e5bf2de4f1c711d (patch)
tree4952f4146f9b7a155d714db59c75a50c248ef160
parent86542797761632890092ef89b7fb58c2c2cdfc11 (diff)
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Avoid integer overflows in parsing fonts
A malformed TTF can cause size calculations to overflow. This patch checks the maximum reasonable value so that the total size fits in 32 bits. It also adds some explicit casting to avoid possible technical undefined behavior when parsing sized unsigned values. Bug: 25645298 Change-Id: Id4716132041a6f4f1fbb73ec4e445391cf7d9616 (cherry picked from commit 183c9ec2800baa2ce099ee260c6cbc6121cf1274)
-rw-r--r--libs/minikin/CmapCoverage.cpp9
1 files changed, 6 insertions, 3 deletions
diff --git a/libs/minikin/CmapCoverage.cpp b/libs/minikin/CmapCoverage.cpp
index 7503372..6431000 100644
--- a/libs/minikin/CmapCoverage.cpp
+++ b/libs/minikin/CmapCoverage.cpp
@@ -29,11 +29,12 @@ namespace android {
// These could perhaps be optimized to use __builtin_bswap16 and friends.
static uint32_t readU16(const uint8_t* data, size_t offset) {
- return data[offset] << 8 | data[offset + 1];
+ return ((uint32_t)data[offset]) << 8 | ((uint32_t)data[offset + 1]);
}
static uint32_t readU32(const uint8_t* data, size_t offset) {
- return data[offset] << 24 | data[offset + 1] << 16 | data[offset + 2] << 8 | data[offset + 3];
+ return ((uint32_t)data[offset]) << 24 | ((uint32_t)data[offset + 1]) << 16 |
+ ((uint32_t)data[offset + 2]) << 8 | ((uint32_t)data[offset + 3]);
}
static void addRange(vector<uint32_t> &coverage, uint32_t start, uint32_t end) {
@@ -101,11 +102,13 @@ static bool getCoverageFormat12(vector<uint32_t>& coverage, const uint8_t* data,
const size_t kGroupSize = 12;
const size_t kStartCharCodeOffset = 0;
const size_t kEndCharCodeOffset = 4;
+ const size_t kMaxNGroups = 0xfffffff0 / kGroupSize; // protection against overflow
+ // For all values < kMaxNGroups, kFirstGroupOffset + nGroups * kGroupSize fits in 32 bits.
if (kFirstGroupOffset > size) {
return false;
}
uint32_t nGroups = readU32(data, kNGroupsOffset);
- if (kFirstGroupOffset + nGroups * kGroupSize > size) {
+ if (nGroups >= kMaxNGroups || kFirstGroupOffset + nGroups * kGroupSize > size) {
return false;
}
for (uint32_t i = 0; i < nGroups; i++) {