Truncate too long /Decode map entries (issue 20668)

Author: Snuffleupagus

src/core/colorspace.js

@@ -116,6 +116,23 @@ function copyRgbaImage(src, dest, alpha01) {
   }
 }
 
+function isDefaultDecodeHelper(decode, expectedLen) {
+  if (!Array.isArray(decode)) {
+    return true;
+  }
+  const decodeLen = decode.length;
+
+  if (decodeLen < expectedLen) {
+    warn("Decode map length is too short.");
+    return true;
+  }
+  if (decodeLen > expectedLen) {
+    info("Truncating too long decode map.");
+    decode.length = expectedLen;
+  }
+  return false;
+}
+
 class ColorSpace {
   static #rgbBuf = new Uint8ClampedArray(3);
 
@@ -185,8 +202,8 @@ class ColorSpace {
   /**
    * Refer to the static `ColorSpace.isDefaultDecode` method below.
    */
-  isDefaultDecode(decodeMap, bpc) {
-    return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
+  isDefaultDecode(decode, bpc) {
+    return ColorSpace.isDefaultDecode(decode, this.numComps);
   }
 
   /**
@@ -322,11 +339,7 @@ class ColorSpace {
    * @param {number} numComps - Number of components the color space has.
    */
   static isDefaultDecode(decode, numComps) {
-    if (!Array.isArray(decode)) {
-      return true;
-    }
-    if (numComps * 2 !== decode.length) {
-      warn("The decode map is not the correct length");
+    if (isDefaultDecodeHelper(decode, numComps * 2)) {
       return true;
     }
     for (let i = 0, ii = decode.length; i < ii; i += 2) {
@@ -424,7 +437,7 @@ class PatternCS extends ColorSpace {
     this.base = baseCS;
   }
 
-  isDefaultDecode(decodeMap, bpc) {
+  isDefaultDecode(decode, bpc) {
     unreachable("Should not call PatternCS.isDefaultDecode");
   }
 }
@@ -489,19 +502,15 @@ class IndexedCS extends ColorSpace {
     return this.base.getOutputLength(inputLength * this.base.numComps, alpha01);
   }
 
-  isDefaultDecode(decodeMap, bpc) {
-    if (!Array.isArray(decodeMap)) {
-      return true;
-    }
-    if (decodeMap.length !== 2) {
-      warn("Decode map length is not correct");
+  isDefaultDecode(decode, bpc) {
+    if (isDefaultDecodeHelper(decode, 2)) {
       return true;
     }
     if (!Number.isInteger(bpc) || bpc < 1) {
       warn("Bits per component is not correct");
       return true;
     }
-    return decodeMap[0] === 0 && decodeMap[1] === (1 << bpc) - 1;
+    return decode[0] === 0 && decode[1] === (1 << bpc) - 1;
   }
 }
 
@@ -1282,7 +1291,7 @@ class LabCS extends ColorSpace {
     return ((inputLength * (3 + alpha01)) / 3) | 0;
   }
 
-  isDefaultDecode(decodeMap, bpc) {
+  isDefaultDecode(decode, bpc) {
     // XXX: Decoding is handled with the lab conversion because of the strange
     // ranges that are used.
     return true;

test/pdfs/.gitignore

@@ -873,4 +873,3 @@
 !Brotli-Prototype-FileA.pdf
 !bug2013793.pdf
 !bug2014080.pdf
-!issue20246.pdf

test/pdfs/issue20668.pdf.link

@@ -0,0 +1 @@
+https://github.com/user-attachments/files/25338956/CE651A-_-HPP1102-specs.pdf

test/test_manifest.json

@@ -13945,5 +13945,14 @@
     "link": true,
     "lastPage": 1,
     "type": "eq"
+  },
+  {
+    "id": "issue20668",
+    "file": "pdfs/issue20668.pdf",
+    "md5": "70233922a9354c3708637902a8e22e70",
+    "rounds": 1,
+    "link": true,
+    "lastPage": 1,
+    "type": "eq"
   }
 ]