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Simplify the way to pass the glyph drawing instructions from the work…
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…er to the main thread

and remove the use of eval in the font loader.
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@calixteman
calixteman committed Apr 27, 2024
1 parent 90d4b9c commit 551e639
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Showing 5 changed files with 150 additions and 61 deletions.
11 changes: 10 additions & 1 deletion src/core/evaluator.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4391,6 +4391,15 @@ class PartialEvaluator {
}
}

let fontMatrix = dict.getArray("FontMatrix");
if (
!Array.isArray(fontMatrix) ||
fontMatrix.length !== 6 ||
fontMatrix.some(x => typeof x !== "number")
) {
fontMatrix = FONT_IDENTITY_MATRIX;
}

const properties = {
type,
name: fontName.name,
Expand All @@ -4403,7 +4412,7 @@ class PartialEvaluator {
loadedName: baseDict.loadedName,
composite,
fixedPitch: false,
fontMatrix: dict.getArray("FontMatrix") || FONT_IDENTITY_MATRIX,
fontMatrix,
firstChar,
lastChar,
toUnicode,
Expand Down
77 changes: 51 additions & 26 deletions src/core/font_renderer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
import {
bytesToString,
FONT_IDENTITY_MATRIX,
FontRenderOps,
FormatError,
unreachable,
warn,
Expand Down Expand Up @@ -180,13 +181,13 @@ function lookupCmap(ranges, unicode) {

function compileGlyf(code, cmds, font) {
function moveTo(x, y) {
cmds.push({ cmd: "moveTo", args: [x, y] });
cmds.add(FontRenderOps.MOVE_TO, [x, y]);
}
function lineTo(x, y) {
cmds.push({ cmd: "lineTo", args: [x, y] });
cmds.add(FontRenderOps.LINE_TO, [x, y]);
}
function quadraticCurveTo(xa, ya, x, y) {
cmds.push({ cmd: "quadraticCurveTo", args: [xa, ya, x, y] });
cmds.add(FontRenderOps.QUADRATIC_CURVE_TO, [xa, ya, x, y]);
}

let i = 0;
Expand Down Expand Up @@ -247,20 +248,22 @@ function compileGlyf(code, cmds, font) {
if (subglyph) {
// TODO: the transform should be applied only if there is a scale:
// https://github.com/freetype/freetype/blob/edd4fedc5427cf1cf1f4b045e53ff91eb282e9d4/src/truetype/ttgload.c#L1205
cmds.push(
{ cmd: "save" },
{
cmd: "transform",
args: [scaleX, scale01, scale10, scaleY, x, y],
}
);
cmds.add(FontRenderOps.SAVE);
cmds.add(FontRenderOps.TRANSFORM, [
scaleX,
scale01,
scale10,
scaleY,
x,
y,
]);

if (!(flags & 0x02)) {
// TODO: we must use arg1 and arg2 to make something similar to:
// https://github.com/freetype/freetype/blob/edd4fedc5427cf1cf1f4b045e53ff91eb282e9d4/src/truetype/ttgload.c#L1209
}
compileGlyf(subglyph, cmds, font);
cmds.push({ cmd: "restore" });
cmds.add(FontRenderOps.RESTORE);
}
} while (flags & 0x20);
} else {
Expand Down Expand Up @@ -365,13 +368,13 @@ function compileGlyf(code, cmds, font) {

function compileCharString(charStringCode, cmds, font, glyphId) {
function moveTo(x, y) {
cmds.push({ cmd: "moveTo", args: [x, y] });
cmds.add(FontRenderOps.MOVE_TO, [x, y]);
}
function lineTo(x, y) {
cmds.push({ cmd: "lineTo", args: [x, y] });
cmds.add(FontRenderOps.LINE_TO, [x, y]);
}
function bezierCurveTo(x1, y1, x2, y2, x, y) {
cmds.push({ cmd: "bezierCurveTo", args: [x1, y1, x2, y2, x, y] });
cmds.add(FontRenderOps.BEZIER_CURVE_TO, [x1, y1, x2, y2, x, y]);
}

const stack = [];
Expand Down Expand Up @@ -544,7 +547,8 @@ function compileCharString(charStringCode, cmds, font, glyphId) {
const bchar = stack.pop();
y = stack.pop();
x = stack.pop();
cmds.push({ cmd: "save" }, { cmd: "translate", args: [x, y] });
cmds.add(FontRenderOps.SAVE);
cmds.add(FontRenderOps.TRANSLATE, [x, y]);
let cmap = lookupCmap(
font.cmap,
String.fromCharCode(font.glyphNameMap[StandardEncoding[achar]])
Expand All @@ -555,7 +559,7 @@ function compileCharString(charStringCode, cmds, font, glyphId) {
font,
cmap.glyphId
);
cmds.push({ cmd: "restore" });
cmds.add(FontRenderOps.RESTORE);

cmap = lookupCmap(
font.cmap,
Expand Down Expand Up @@ -741,6 +745,27 @@ function compileCharString(charStringCode, cmds, font, glyphId) {

const NOOP = [];

class Commands {
cmds = [];

add(cmd, args) {
if (args) {
if (args.some(arg => typeof arg !== "number")) {
warn(
`Commands.add - "${cmd}" has at least one non-number arg: "${args}".`
);
// "Fix" the wrong args by replacing them with 0.
const newArgs = args.map(arg => (typeof arg === "number" ? arg : 0));
this.cmds.push(cmd, ...newArgs);
} else {
this.cmds.push(cmd, ...args);
}
} else {
this.cmds.push(cmd);
}
}
}

class CompiledFont {
constructor(fontMatrix) {
if (this.constructor === CompiledFont) {
Expand All @@ -757,8 +782,10 @@ class CompiledFont {
let fn = this.compiledGlyphs[glyphId];
if (!fn) {
try {
fn = this.compileGlyph(this.glyphs[glyphId], glyphId);
this.compiledGlyphs[glyphId] = fn;
fn = this.compiledGlyphs[glyphId] = this.compileGlyph(
this.glyphs[glyphId],
glyphId
);
} catch (ex) {
// Avoid attempting to re-compile a corrupt glyph.
this.compiledGlyphs[glyphId] = NOOP;
Expand Down Expand Up @@ -793,16 +820,14 @@ class CompiledFont {
}
}

const cmds = [
{ cmd: "save" },
{ cmd: "transform", args: fontMatrix.slice() },
{ cmd: "scale", args: ["size", "-size"] },
];
const cmds = new Commands();
cmds.add(FontRenderOps.SAVE);
cmds.add(FontRenderOps.TRANSFORM, fontMatrix.slice());
cmds.add(FontRenderOps.SCALE);
this.compileGlyphImpl(code, cmds, glyphId);
cmds.add(FontRenderOps.RESTORE);

cmds.push({ cmd: "restore" });

return cmds;
return cmds.cmds;
}

compileGlyphImpl() {
Expand Down
6 changes: 2 additions & 4 deletions src/display/api.js
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Original file line number Diff line number Diff line change
Expand Up @@ -169,8 +169,8 @@ const DefaultStandardFontDataFactory =
* pixels, i.e. width * height. Images above this value will not be rendered.
* Use -1 for no limit, which is also the default value.
* @property {boolean} [isEvalSupported] - Determines if we can evaluate strings
* as JavaScript. Primarily used to improve performance of font rendering, and
* when parsing PDF functions. The default value is `true`.
* as JavaScript. Primarily used to improve performance of PDF functions.
* The default value is `true`.
* @property {boolean} [isOffscreenCanvasSupported] - Determines if we can use
* `OffscreenCanvas` in the worker. Primarily used to improve performance of
* image conversion/rendering.
Expand Down Expand Up @@ -384,7 +384,6 @@ function getDocument(src) {
};
const transportParams = {
ignoreErrors,
isEvalSupported,
disableFontFace,
fontExtraProperties,
enableXfa,
Expand Down Expand Up @@ -2744,7 +2743,6 @@ class WorkerTransport {
? (font, url) => globalThis.FontInspector.fontAdded(font, url)
: null;
const font = new FontFaceObject(exportedData, {
isEvalSupported: params.isEvalSupported,
disableFontFace: params.disableFontFace,
ignoreErrors: params.ignoreErrors,
inspectFont,
Expand Down
104 changes: 74 additions & 30 deletions src/display/font_loader.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
import {
assert,
bytesToString,
FeatureTest,
FontRenderOps,
isNodeJS,
shadow,
string32,
Expand Down Expand Up @@ -362,19 +362,13 @@ class FontLoader {
class FontFaceObject {
constructor(
translatedData,
{
isEvalSupported = true,
disableFontFace = false,
ignoreErrors = false,
inspectFont = null,
}
{ disableFontFace = false, ignoreErrors = false, inspectFont = null }
) {
this.compiledGlyphs = Object.create(null);
// importing translated data
for (const i in translatedData) {
this[i] = translatedData[i];
}
this.isEvalSupported = isEvalSupported !== false;
this.disableFontFace = disableFontFace === true;
this.ignoreErrors = ignoreErrors === true;
this._inspectFont = inspectFont;
Expand Down Expand Up @@ -440,35 +434,85 @@ class FontFaceObject {
throw ex;
}
warn(`getPathGenerator - ignoring character: "${ex}".`);
}

if (!Array.isArray(cmds) || cmds.length === 0) {
return (this.compiledGlyphs[character] = function (c, size) {
// No-op function, to allow rendering to continue.
});
}

// If we can, compile cmds into JS for MAXIMUM SPEED...
if (this.isEvalSupported && FeatureTest.isEvalSupported) {
const jsBuf = [];
for (const current of cmds) {
const args = current.args !== undefined ? current.args.join(",") : "";
jsBuf.push("c.", current.cmd, "(", args, ");\n");
const commands = [];
for (let i = 0, ii = cmds.length; i < ii; ) {
switch (cmds[i++]) {
case FontRenderOps.BEZIER_CURVE_TO:
{
const [a, b, c, d, e, f] = cmds.slice(i, i + 6);
commands.push(ctx => ctx.bezierCurveTo(a, b, c, d, e, f));
i += 6;
}
break;
case FontRenderOps.MOVE_TO:
{
const [a, b] = cmds.slice(i, i + 2);
commands.push(ctx => ctx.moveTo(a, b));
i += 2;
}
break;
case FontRenderOps.LINE_TO:
{
const [a, b] = cmds.slice(i, i + 2);
commands.push(ctx => ctx.lineTo(a, b));
i += 2;
}
break;
case FontRenderOps.QUADRATIC_CURVE_TO:
{
const [a, b, c, d] = cmds.slice(i, i + 4);
commands.push(ctx => ctx.quadraticCurveTo(a, b, c, d));
i += 4;
}
break;
case FontRenderOps.RESTORE:
commands.push(ctx => ctx.restore());
break;
case FontRenderOps.SAVE:
commands.push(ctx => ctx.save());
break;
case FontRenderOps.SCALE:
// The scale command must be at the third position, after save and
// transform (for the font matrix) commands (see also
// font_renderer.js).
// The goal is to just scale the canvas and then run the commands loop
// without the need to pass the size parameter to each command.
assert(
commands.length === 2,
"Scale command is only valid at the third position."
);
break;
case FontRenderOps.TRANSFORM:
{
const [a, b, c, d, e, f] = cmds.slice(i, i + 6);
commands.push(ctx => ctx.transform(a, b, c, d, e, f));
i += 6;
}
break;
case FontRenderOps.TRANSLATE:
{
const [a, b] = cmds.slice(i, i + 2);
commands.push(ctx => ctx.translate(a, b));
i += 2;
}
break;
}
// eslint-disable-next-line no-new-func
return (this.compiledGlyphs[character] = new Function(
"c",
"size",
jsBuf.join("")
));
}
// ... but fall back on using Function.prototype.apply() if we're
// blocked from using eval() for whatever reason (like CSP policies).
return (this.compiledGlyphs[character] = function (c, size) {
for (const current of cmds) {
if (current.cmd === "scale") {
current.args = [size, -size];
}
// eslint-disable-next-line prefer-spread
c[current.cmd].apply(c, current.args);
}

return (this.compiledGlyphs[character] = function glyphDrawer(ctx, size) {
commands[0](ctx);
commands[1](ctx);
ctx.scale(size, -size);
for (let i = 2, ii = commands.length; i < ii; i++) {
commands[i](ctx);
}
});
}
Expand Down
13 changes: 13 additions & 0 deletions src/shared/util.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1073,6 +1073,18 @@ function getUuid() {

const AnnotationPrefix = "pdfjs_internal_id_";

const FontRenderOps = {
BEZIER_CURVE_TO: 0,
MOVE_TO: 1,
LINE_TO: 2,
QUADRATIC_CURVE_TO: 3,
RESTORE: 4,
SAVE: 5,
SCALE: 6,
TRANSFORM: 7,
TRANSLATE: 8,
};

export {
AbortException,
AnnotationActionEventType,
Expand All @@ -1095,6 +1107,7 @@ export {
DocumentActionEventType,
FeatureTest,
FONT_IDENTITY_MATRIX,
FontRenderOps,
FormatError,
getModificationDate,
getUuid,
Expand Down

1 comment on commit 551e639

@mildsunrise
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(in case someone is confused, this is the fix for CVE-2024-4367)

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