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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "gfxGraphiteShaper.h"
#include "nsString.h"
#include "gfxContext.h"
#include "gfxFontConstants.h"
#include "gfxTextRun.h"
#include "graphite2/Font.h"
#include "graphite2/GraphiteExtra.h"
#include "graphite2/Segment.h"
#include "harfbuzz/hb.h"
#include "mozilla/ScopeExit.h"
#include "ThebesRLBox.h"
#define FloatToFixed(f) (65536 * (f))
#define FixedToFloat(f) ((f) * (1.0 / 65536.0))
// Right shifts of negative (signed) integers are undefined, as are overflows
// when converting unsigned to negative signed integers.
// (If speed were an issue we could make some 2's complement assumptions.)
#define FixedToIntRound(f) \
((f) > 0 ? ((32768 + (f)) >> 16) : -((32767 - (f)) >> 16))
#define CopyAndVerifyOrFail(t, cond, failed) \
(t).copy_and_verify([&](auto val) { \
if (!(cond)) { \
*(failed) = true; \
} \
return val; \
})
using namespace mozilla; // for AutoSwap_* types
/*
* Creation and destruction; on deletion, release any font tables we're holding
*/
gfxGraphiteShaper::gfxGraphiteShaper(gfxFont* aFont)
: gfxFontShaper(aFont),
mGrFace(mFont->GetFontEntry()->GetGrFace()),
mSandbox(mFont->GetFontEntry()->GetGrSandbox()),
mCallback(mFont->GetFontEntry()->GetGrSandboxAdvanceCallbackHandle()),
mFallbackToSmallCaps(false) {
mCallbackData.mFont = aFont;
}
gfxGraphiteShaper::~gfxGraphiteShaper() {
auto t_mGrFont = rlbox::from_opaque(mGrFont);
if (t_mGrFont) {
sandbox_invoke(*mSandbox, gr_font_destroy, t_mGrFont);
}
mFont->GetFontEntry()->ReleaseGrFace(mGrFace);
}
/*static*/
thread_local gfxGraphiteShaper::CallbackData*
gfxGraphiteShaper::tl_GrGetAdvanceData = nullptr;
/*static*/
tainted_opaque_gr<float> gfxGraphiteShaper::GrGetAdvance(
rlbox_sandbox_gr& sandbox,
tainted_opaque_gr<const void*> /* appFontHandle */,
tainted_opaque_gr<uint16_t> t_glyphid) {
CallbackData* cb = tl_GrGetAdvanceData;
if (!cb) {
// GrGetAdvance callback called unexpectedly. Just return safe value.
tainted_gr<float> ret = 0;
return ret.to_opaque();
}
auto glyphid = rlbox::from_opaque(t_glyphid).unverified_safe_because(
"Here the only use of a glyphid is for lookup to get a width. "
"Implementations of GetGlyphWidth in this code base use a hashtable "
"which is robust to unknown keys. So no validation is required.");
tainted_gr<float> ret = FixedToFloat(cb->mFont->GetGlyphWidth(glyphid));
return ret.to_opaque();
}
static inline uint32_t MakeGraphiteLangTag(uint32_t aTag) {
uint32_t grLangTag = aTag;
// replace trailing space-padding with NULs for graphite
uint32_t mask = 0x000000FF;
while ((grLangTag & mask) == ' ') {
grLangTag &= ~mask;
mask <<= 8;
}
return grLangTag;
}
struct GrFontFeatures {
tainted_gr<gr_face*> mFace;
tainted_gr<gr_feature_val*> mFeatures;
rlbox_sandbox_gr* mSandbox;
};
static void AddFeature(uint32_t aTag, uint32_t aValue, void* aUserArg) {
GrFontFeatures* f = static_cast<GrFontFeatures*>(aUserArg);
tainted_gr<const gr_feature_ref*> fref =
sandbox_invoke(*(f->mSandbox), gr_face_find_fref, f->mFace, aTag);
if (fref) {
sandbox_invoke(*(f->mSandbox), gr_fref_set_feature_value, fref, aValue,
f->mFeatures);
}
}
// Count the number of Unicode characters in a UTF-16 string (i.e. surrogate
// pairs are counted as 1, although they are 2 code units).
// (Any isolated surrogates will count 1 each, because in decoding they would
// be replaced by individual U+FFFD REPLACEMENT CHARACTERs.)
static inline size_t CountUnicodes(const char16_t* aText, uint32_t aLength) {
size_t total = 0;
const char16_t* end = aText + aLength;
while (aText < end) {
if (NS_IS_HIGH_SURROGATE(*aText) && aText + 1 < end &&
NS_IS_LOW_SURROGATE(*(aText + 1))) {
aText += 2;
} else {
aText++;
}
total++;
}
return total;
}
bool gfxGraphiteShaper::ShapeText(DrawTarget* aDrawTarget,
const char16_t* aText, uint32_t aOffset,
uint32_t aLength, Script aScript,
nsAtom* aLanguage, bool aVertical,
RoundingFlags aRounding,
gfxShapedText* aShapedText) {
const gfxFontStyle* style = mFont->GetStyle();
auto t_mGrFace = rlbox::from_opaque(mGrFace);
auto t_mGrFont = rlbox::from_opaque(mGrFont);
if (!t_mGrFont) {
if (!t_mGrFace) {
return false;
}
if (mFont->ProvidesGlyphWidths()) {
auto p_ops = mSandbox->malloc_in_sandbox<gr_font_ops>();
if (!p_ops) {
return false;
}
auto clean_ops = MakeScopeExit([&] { mSandbox->free_in_sandbox(p_ops); });
p_ops->size = sizeof(*p_ops);
p_ops->glyph_advance_x = *mCallback;
p_ops->glyph_advance_y = nullptr; // vertical text not yet implemented
t_mGrFont = sandbox_invoke(
*mSandbox, gr_make_font_with_ops, mFont->GetAdjustedSize(),
// For security, we do not pass the callback data to this arg, and use
// a TLS var instead. However, gr_make_font_with_ops expects this to
// be a non null ptr, and changes its behavior if it isn't. Therefore,
// we should pass some dummy non null pointer which will be passed to
// the GrGetAdvance callback, but never used. Let's just pass p_ops
// again, as this is a non-null tainted pointer.
p_ops /* mCallbackData */, p_ops, t_mGrFace);
} else {
t_mGrFont = sandbox_invoke(*mSandbox, gr_make_font,
mFont->GetAdjustedSize(), t_mGrFace);
}
mGrFont = t_mGrFont.to_opaque();
if (!t_mGrFont) {
return false;
}
// determine whether petite-caps falls back to small-caps
if (style->variantCaps != NS_FONT_VARIANT_CAPS_NORMAL) {
switch (style->variantCaps) {
case NS_FONT_VARIANT_CAPS_ALLPETITE:
case NS_FONT_VARIANT_CAPS_PETITECAPS:
bool synLower, synUpper;
mFont->SupportsVariantCaps(aScript, style->variantCaps,
mFallbackToSmallCaps, synLower, synUpper);
break;
default:
break;
}
}
}
gfxFontEntry* entry = mFont->GetFontEntry();
uint32_t grLang = 0;
if (style->languageOverride) {
grLang = MakeGraphiteLangTag(style->languageOverride);
} else if (entry->mLanguageOverride) {
grLang = MakeGraphiteLangTag(entry->mLanguageOverride);
} else if (aLanguage) {
nsAutoCString langString;
aLanguage->ToUTF8String(langString);
grLang = GetGraphiteTagForLang(langString);
}
tainted_gr<gr_feature_val*> grFeatures =
sandbox_invoke(*mSandbox, gr_face_featureval_for_lang, t_mGrFace, grLang);
// insert any merged features into Graphite feature list
GrFontFeatures f = {t_mGrFace, grFeatures, mSandbox};
MergeFontFeatures(style, mFont->GetFontEntry()->mFeatureSettings,
aShapedText->DisableLigatures(),
mFont->GetFontEntry()->FamilyName(), mFallbackToSmallCaps,
AddFeature, &f);
// Graphite shaping doesn't map U+00a0 (nbsp) to space if it is missing
// from the font, so check for that possibility. (Most fonts double-map
// the space glyph to both 0x20 and 0xA0, so this won't often be needed;
// so we don't copy the text until we know it's required.)
nsAutoString transformed;
const char16_t NO_BREAK_SPACE = 0x00a0;
if (!entry->HasCharacter(NO_BREAK_SPACE)) {
nsDependentSubstring src(aText, aLength);
if (src.FindChar(NO_BREAK_SPACE) != kNotFound) {
transformed = src;
transformed.ReplaceChar(NO_BREAK_SPACE, ' ');
aText = transformed.BeginReading();
}
}
size_t numChars = CountUnicodes(aText, aLength);
gr_bidirtl grBidi = gr_bidirtl(
aShapedText->IsRightToLeft() ? (gr_rtl | gr_nobidi) : gr_nobidi);
tainted_gr<char16_t*> t_aText =
mSandbox->malloc_in_sandbox<char16_t>(aLength);
if (!t_aText) {
return false;
}
auto clean_txt = MakeScopeExit([&] { mSandbox->free_in_sandbox(t_aText); });
rlbox::memcpy(*mSandbox, t_aText, aText, aLength * sizeof(char16_t));
tl_GrGetAdvanceData = &mCallbackData;
auto clean_adv_data = MakeScopeExit([&] { tl_GrGetAdvanceData = nullptr; });
tainted_gr<gr_segment*> seg =
sandbox_invoke(*mSandbox, gr_make_seg, mGrFont, t_mGrFace, 0, grFeatures,
gr_utf16, t_aText, numChars, grBidi);
sandbox_invoke(*mSandbox, gr_featureval_destroy, grFeatures);
if (!seg) {
return false;
}
nsresult rv =
SetGlyphsFromSegment(aShapedText, aOffset, aLength, aText,
t_aText.to_opaque(), seg.to_opaque(), aRounding);
sandbox_invoke(*mSandbox, gr_seg_destroy, seg);
return NS_SUCCEEDED(rv);
}
nsresult gfxGraphiteShaper::SetGlyphsFromSegment(
gfxShapedText* aShapedText, uint32_t aOffset, uint32_t aLength,
const char16_t* aText, tainted_opaque_gr<char16_t*> t_aText,
tainted_opaque_gr<gr_segment*> aSegment, RoundingFlags aRounding) {
typedef gfxShapedText::CompressedGlyph CompressedGlyph;
int32_t dev2appUnits = aShapedText->GetAppUnitsPerDevUnit();
bool rtl = aShapedText->IsRightToLeft();
// identify clusters; graphite may have reordered/expanded/ligated glyphs.
tainted_gr<gr_glyph_to_char_association*> data =
sandbox_invoke(*mSandbox, gr_get_glyph_to_char_association, aSegment,
aLength, rlbox::from_opaque(t_aText));
if (!data) {
return NS_ERROR_FAILURE;
}
tainted_gr<gr_glyph_to_char_cluster*> clusters = data->clusters;
tainted_gr<uint16_t*> gids = data->gids;
tainted_gr<float*> xLocs = data->xLocs;
tainted_gr<float*> yLocs = data->yLocs;
CompressedGlyph* charGlyphs = aShapedText->GetCharacterGlyphs() + aOffset;
bool roundX = bool(aRounding & RoundingFlags::kRoundX);
bool roundY = bool(aRounding & RoundingFlags::kRoundY);
bool failedVerify = false;
// cIndex is primarily used to index into the clusters array which has size
// aLength below. As cIndex is not changing anymore, let's just verify it
// and remove the tainted wrapper.
uint32_t cIndex =
CopyAndVerifyOrFail(data->cIndex, val < aLength, &failedVerify);
if (failedVerify) {
return NS_ERROR_ILLEGAL_VALUE;
}
// now put glyphs into the textrun, one cluster at a time
for (uint32_t i = 0; i <= cIndex; ++i) {
// We makes a local copy of "clusters[i]" which is of type
// tainted_gr<gr_glyph_to_char_cluster> below. We do this intentionally
// rather than taking a reference. Taking a reference with the code
//
// tainted_volatile_gr<gr_glyph_to_char_cluster>& c = clusters[i];
//
// produces a tainted_volatile which means the value can change at any
// moment allowing for possible time-of-check-time-of-use vuln. We thus
// make a local copy to simplify the verification.
tainted_gr<gr_glyph_to_char_cluster> c = clusters[i];
tainted_gr<float> t_adv; // total advance of the cluster
if (rtl) {
if (i == 0) {
t_adv = sandbox_invoke(*mSandbox, gr_seg_advance_X, aSegment) -
xLocs[c.baseGlyph];
} else {
t_adv = xLocs[clusters[i - 1].baseGlyph] - xLocs[c.baseGlyph];
}
} else {
if (i == cIndex) {
t_adv = sandbox_invoke(*mSandbox, gr_seg_advance_X, aSegment) -
xLocs[c.baseGlyph];
} else {
t_adv = xLocs[clusters[i + 1].baseGlyph] - xLocs[c.baseGlyph];
}
}
float adv = t_adv.unverified_safe_because(
"glyphs. There are no a-priori limits on what that might be. Incorrect "
"values will tend to result in bad layout or missing text, or bad "
"nscoord values. But, these will not result in safety issues.");
// check unexpected offset - offs used to index into aText
uint32_t offs =
CopyAndVerifyOrFail(c.baseChar, val < aLength, &failedVerify);
if (failedVerify) {
return NS_ERROR_ILLEGAL_VALUE;
}
// Check for default-ignorable char that didn't get filtered, combined,
// etc by the shaping process, and skip it.
auto one_glyph = c.nGlyphs == static_cast<uint32_t>(1);
auto one_char = c.nChars == static_cast<uint32_t>(1);
if ((one_glyph && one_char)
.unverified_safe_because(
"using this boolean check to decide whether to ignore a "
"character or not. The worst that can happen is a bad "
"rendering.")) {
if (aShapedText->FilterIfIgnorable(aOffset + offs, aText[offs])) {
continue;
}
}
uint32_t appAdvance = roundX ? NSToIntRound(adv) * dev2appUnits
: NSToIntRound(adv * dev2appUnits);
const char gid_simple_value[] =
"maximum glyph ID supported by the font. However, out-of-range values "
"here should not lead to safety issues; they would simply result in "
"blank rendering, although this depends on the platform back-end.";
// gids[c.baseGlyph] is checked and used below. Since this is a
// tainted_volatile, which can change at any moment, we make a local copy
// first to prevent a time-of-check-time-of-use vuln.
uint16_t gid_of_base_glyph =
gids[c.baseGlyph].unverified_safe_because(gid_simple_value);
const char fast_path[] =
"Even if the number of glyphs set is an incorrect value, the else "
"branch is a more general purpose algorithm which can handle other "
"values of nGlyphs";
if (one_glyph.unverified_safe_because(fast_path) &&
CompressedGlyph::IsSimpleGlyphID(gid_of_base_glyph) &&
CompressedGlyph::IsSimpleAdvance(appAdvance) &&
charGlyphs[offs].IsClusterStart() &&
(yLocs[c.baseGlyph] == 0).unverified_safe_because(fast_path)) {
charGlyphs[offs].SetSimpleGlyph(appAdvance, gid_of_base_glyph);
} else {
// not a one-to-one mapping with simple metrics: use DetailedGlyph
AutoTArray<gfxShapedText::DetailedGlyph, 8> details;
float clusterLoc;
uint32_t glyph_end =
(c.baseGlyph + c.nGlyphs)
.unverified_safe_because(
"This only controls the total number of glyphs set for this "
"particular text. Worst that can happen is a bad rendering");
// check overflow - ensure loop start is before the end
uint32_t glyph_start =
CopyAndVerifyOrFail(c.baseGlyph, val <= glyph_end, &failedVerify);
if (failedVerify) {
return NS_ERROR_ILLEGAL_VALUE;
}
for (uint32_t j = glyph_start; j < glyph_end; ++j) {
gfxShapedText::DetailedGlyph* d = details.AppendElement();
d->mGlyphID = gids[j].unverified_safe_because(gid_simple_value);
const char safe_coordinates[] =
"There are no limits on coordinates. Worst case, bad values would "
"force rendering off-screen, but there are no memory safety "
"issues.";
float yLocs_j = yLocs[j].unverified_safe_because(safe_coordinates);
float xLocs_j = xLocs[j].unverified_safe_because(safe_coordinates);
d->mOffset.y = roundY ? NSToIntRound(-yLocs_j) * dev2appUnits
: -yLocs_j * dev2appUnits;
if (j == glyph_start) {
d->mAdvance = appAdvance;
clusterLoc = xLocs_j;
} else {
float dx =
rtl ? (xLocs_j - clusterLoc) : (xLocs_j - clusterLoc - adv);
d->mOffset.x =
roundX ? NSToIntRound(dx) * dev2appUnits : dx * dev2appUnits;
d->mAdvance = 0;
}
}
aShapedText->SetDetailedGlyphs(aOffset + offs, details.Length(),
details.Elements());
}
// check unexpected offset
uint32_t char_end = CopyAndVerifyOrFail(c.baseChar + c.nChars,
val <= aLength, &failedVerify);
// check overflow - ensure loop start is before the end
uint32_t char_start =
CopyAndVerifyOrFail(c.baseChar + 1, val <= char_end, &failedVerify);
if (failedVerify) {
return NS_ERROR_ILLEGAL_VALUE;
}
for (uint32_t j = char_start; j < char_end; ++j) {
CompressedGlyph& g = charGlyphs[j];
NS_ASSERTION(!g.IsSimpleGlyph(), "overwriting a simple glyph");
g.SetComplex(g.IsClusterStart(), false);
}
}
sandbox_invoke(*mSandbox, gr_free_char_association, data);
return NS_OK;
}
// for language tag validation - include list of tags from the IANA registry
#include "gfxLanguageTagList.cpp"
nsTHashSet<uint32_t>* gfxGraphiteShaper::sLanguageTags;
/*static*/
uint32_t gfxGraphiteShaper::GetGraphiteTagForLang(const nsCString& aLang) {
int len = aLang.Length();
if (len < 2) {
return 0;
}
// convert primary language subtag to a left-packed, NUL-padded integer
// for the Graphite API
uint32_t grLang = 0;
for (int i = 0; i < 4; ++i) {
grLang <<= 8;
if (i < len) {
uint8_t ch = aLang[i];
if (ch == '-') {
// found end of primary language subtag, truncate here
len = i;
continue;
}
if (ch < 'a' || ch > 'z') {
// invalid character in tag, so ignore it completely
return 0;
}
grLang += ch;
}
}
// valid tags must have length = 2 or 3
if (len < 2 || len > 3) {
return 0;
}
if (!sLanguageTags) {
// store the registered IANA tags in a hash for convenient validation
sLanguageTags = new nsTHashSet<uint32_t>(ArrayLength(sLanguageTagList));
for (const uint32_t* tag = sLanguageTagList; *tag != 0; ++tag) {
sLanguageTags->Insert(*tag);
}
}
// only accept tags known in the IANA registry
if (sLanguageTags->Contains(grLang)) {
return grLang;
}
return 0;
}
/*static*/
void gfxGraphiteShaper::Shutdown() {
#ifdef NS_FREE_PERMANENT_DATA
if (sLanguageTags) {
sLanguageTags->Clear();
delete sLanguageTags;
sLanguageTags = nullptr;
}
#endif
}