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LibGfx: Handle malformed Platform ID during TTF parsing

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This should fix one of the OSS Fuzz crashes that occurs during
TTF file format parsing.

See: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=37263
This commit is contained in:
Brian Gianforcaro 2021-12-16 04:55:35 -08:00 • committed by Andreas Kling
parent 3a6f550b24
commit c710d52afa
3 changed files with 8 additions and 4 deletions
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4
Userland/Libraries/LibGfx/TrueTypeFont/Cmap.cpp
View file

@ -13,7 +13,7 @@ extern u16 be_u16(u8 const*);
extern u32 be_u32(u8 const*); extern u32 be_u32(u8 const*);
extern i16 be_i16(u8 const*); extern i16 be_i16(u8 const*);
Cmap::Subtable::Platform Cmap::Subtable::platform_id() const Optional<Cmap::Subtable::Platform> Cmap::Subtable::platform_id() const
{ {
switch (m_raw_platform_id) { switch (m_raw_platform_id) {
case 0: case 0:
@ -25,7 +25,7 @@ Cmap::Subtable::Platform Cmap::Subtable::platform_id() const
case 4: case 4:
return Platform::Custom; return Platform::Custom;
default: default:
VERIFY_NOT_REACHED(); return {};
} }
} }

2
Userland/Libraries/LibGfx/TrueTypeFont/Cmap.h
View file

@ -45,7 +45,7 @@ public:
} }
// Returns 0 if glyph not found. This corresponds to the "missing glyph" // Returns 0 if glyph not found. This corresponds to the "missing glyph"
u32 glyph_id_for_code_point(u32 code_point) const; u32 glyph_id_for_code_point(u32 code_point) const;
Platform platform_id() const; Optional<Platform> platform_id() const;
u16 encoding_id() const { return m_encoding_id; } u16 encoding_id() const { return m_encoding_id; }
Format format() const; Format format() const;

6
Userland/Libraries/LibGfx/TrueTypeFont/Font.cpp
View file

@ -368,7 +368,11 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
continue; continue;
} }
auto subtable = opt_subtable.value(); auto subtable = opt_subtable.value();
if (subtable.platform_id() == Cmap::Subtable::Platform::Windows) { auto platform = subtable.platform_id();
if (!platform.has_value())
return Error::from_string_literal("Invalid Platform ID"sv);
if (platform.value() == Cmap::Subtable::Platform::Windows) {
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) { if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) {
cmap.set_active_index(i); cmap.set_active_index(i);
break; break;