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authorthestig <thestig@chromium.org>2016-09-01 10:08:30 -0700
committerCommit bot <commit-bot@chromium.org>2016-09-01 10:08:30 -0700
commit5e2d5c7ca2d084b2151b3c2e82eea18c189bef0a (patch)
tree72f7808a095dadb1e3b5b13ac65ed08343017abf /core
parent543651f9d8d8cb9ec45dce5fe3d06c2e6013de7d (diff)
downloadpdfium-5e2d5c7ca2d084b2151b3c2e82eea18c189bef0a.tar.xz
Better validate hint table header bits entries.
BUG=637119 Review-Url: https://codereview.chromium.org/2305443003
Diffstat (limited to 'core')
-rw-r--r--core/fpdfapi/fpdf_parser/cpdf_hint_tables.cpp35
1 files changed, 18 insertions, 17 deletions
diff --git a/core/fpdfapi/fpdf_parser/cpdf_hint_tables.cpp b/core/fpdfapi/fpdf_parser/cpdf_hint_tables.cpp
index 316361aced..3b0d2afbe0 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_hint_tables.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_hint_tables.cpp
@@ -21,6 +21,13 @@ bool CanReadFromBitStream(const CFX_BitStream* hStream,
return bits.IsValid() && hStream->BitsRemaining() >= bits.ValueOrDie();
}
+// Sanity check values from the page table header. The note in the PDF 1.7
+// reference for Table F.3 says the valid range is only 0 through 32. Though 0
+// is not useful either.
+bool IsValidPageOffsetHintTableBitCount(uint32_t bits) {
+ return bits > 0 && bits <= 32;
+}
+
} // namespace
CPDF_HintTables::CPDF_HintTables(CPDF_DataAvail* pDataAvail,
@@ -80,19 +87,19 @@ bool CPDF_HintTables::ReadPageHintTable(CFX_BitStream* hStream) {
// Item 3: The number of bits needed to represent the difference
// between the greatest and least number of objects in a page.
const uint32_t dwDeltaObjectsBits = hStream->GetBits(16);
- if (!dwDeltaObjectsBits)
- return FALSE;
+ if (!IsValidPageOffsetHintTableBitCount(dwDeltaObjectsBits))
+ return false;
// Item 4: The least length of a page in bytes.
const uint32_t dwPageLeastLen = hStream->GetBits(32);
if (!dwPageLeastLen)
- return FALSE;
+ return false;
// Item 5: The number of bits needed to represent the difference
// between the greatest and least length of a page, in bytes.
const uint32_t dwDeltaPageLenBits = hStream->GetBits(16);
- if (!dwDeltaPageLenBits)
- return FALSE;
+ if (!IsValidPageOffsetHintTableBitCount(dwDeltaPageLenBits))
+ return false;
// Skip Item 6, 7, 8, 9 total 96 bits.
hStream->SkipBits(96);
@@ -100,32 +107,26 @@ bool CPDF_HintTables::ReadPageHintTable(CFX_BitStream* hStream) {
// Item 10: The number of bits needed to represent the greatest
// number of shared object references.
const uint32_t dwSharedObjBits = hStream->GetBits(16);
+ if (!IsValidPageOffsetHintTableBitCount(dwSharedObjBits))
+ return false;
// Item 11: The number of bits needed to represent the numerically
// greatest shared object identifier used by the pages.
const uint32_t dwSharedIdBits = hStream->GetBits(16);
- if (!dwSharedObjBits)
- return FALSE;
+ if (!IsValidPageOffsetHintTableBitCount(dwSharedIdBits))
+ return false;
// Item 12: The number of bits needed to represent the numerator of
// the fractional position for each shared object reference. For each
// shared object referenced from a page, there is an indication of
// where in the page's content stream the object is first referenced.
const uint32_t dwSharedNumeratorBits = hStream->GetBits(16);
- if (!dwSharedIdBits)
- return FALSE;
+ if (!IsValidPageOffsetHintTableBitCount(dwSharedNumeratorBits))
+ return false;
// Item 13: Skip Item 13 which has 16 bits.
hStream->SkipBits(16);
- // Sanity check values from the page table header. 2^|kMaxBits| should be more
- // than enough to represent most of the values here.
- constexpr uint32_t kMaxBits = 34;
- if (dwSharedObjBits > kMaxBits || dwDeltaObjectsBits > kMaxBits ||
- dwDeltaPageLenBits > kMaxBits || dwSharedIdBits > kMaxBits) {
- return false;
- }
-
const int nPages = GetNumberOfPages();
if (nPages < 1 || nPages >= FPDF_PAGE_MAX_NUM)
return false;