Attempt to detect inline images which contain "EI" sequence in the actual image data (issue 11124)

This should reduce the possibility of accidentally truncating some inline images, while *not* causing the "EI" detection to become significantly slower.[1]
There's obviously a possibility that these added checks are not sufficient to catch *every* single case of "EI" sequences within the actual inline image data, but without specific test-cases I decided against over-engineering the solution here.

*Please note:* The interpolation issues are somewhat orthogonal to the main issue here, which is the truncated image, and it's already tracked elsewhere.

---
[1] I've looked at the issue a few times, and this is the first approach that I was able to come up with that didn't cause *unacceptable* performance regressions in e.g. issue 2618.

src/core/parser.js

@@ -203,10 +203,11 @@ class Parser {
       I = 0x49,
       SPACE = 0x20,
       LF = 0xa,
-      CR = 0xd;
-    const n = 10,
+      CR = 0xd,
       NUL = 0x0;
-    const startPos = stream.pos;
+    const lexer = this.lexer,
+      startPos = stream.pos,
+      n = 10;
     let state = 0,
       ch,
       maybeEIPos;
@@ -243,6 +244,25 @@ class Parser {
               break;
             }
           }
+
+          if (state !== 2) {
+            continue;
+          }
+          // Check that the "EI" sequence isn't part of the image data, since
+          // that would cause the image to be truncated (fixes issue11124.pdf).
+          if (lexer.knownCommands) {
+            const nextObj = lexer.peekObj();
+            if (nextObj instanceof Cmd && !lexer.knownCommands[nextObj.cmd]) {
+              // Not a valid command, i.e. the inline image data *itself*
+              // contains an "EI" sequence. Resetting the state.
+              state = 0;
+            }
+          } else {
+            warn(
+              "findDefaultInlineStreamEnd - `lexer.knownCommands` is undefined."
+            );
+          }
+
           if (state === 2) {
             break; // Finished!
           }
@@ -1276,6 +1296,28 @@ class Lexer {
     return Cmd.get(str);
   }
 
+  peekObj() {
+    const streamPos = this.stream.pos,
+      currentChar = this.currentChar,
+      beginInlineImagePos = this.beginInlineImagePos;
+
+    let nextObj;
+    try {
+      nextObj = this.getObj();
+    } catch (ex) {
+      if (ex instanceof MissingDataException) {
+        throw ex;
+      }
+      warn(`peekObj: ${ex}`);
+    }
+    // Ensure that we reset *all* relevant `Lexer`-instance state.
+    this.stream.pos = streamPos;
+    this.currentChar = currentChar;
+    this.beginInlineImagePos = beginInlineImagePos;
+
+    return nextObj;
+  }
+
   skipToNextLine() {
     let ch = this.currentChar;
     while (ch >= 0) {

test/pdfs/.gitignore

@@ -254,6 +254,7 @@
 !issue6336.pdf
 !issue6387.pdf
 !issue6410.pdf
+!issue11124.pdf
 !issue8586.pdf
 !jbig2_symbol_offset.pdf
 !gradientfill.pdf

test/pdfs/issue11124.pdf

@@ -0,0 +1,33 @@
+%PDF-1.3
+%âãÏÓ
+1 0 obj<</Type/Catalog/Pages 3 0 R>>
+endobj
+2 0 obj<</CreationDate(D:20190906183146+02'00')/Producer(PoDoFo - http://podofo.sf.net)>>
+endobj
+3 0 obj<</Type/Pages/Count 1/Kids[ 4 0 R]>>
+endobj
+4 0 obj<</Type/Page/Contents 5 0 R/MediaBox[ 0 0 100 100]/Parent 3 0 R/Resources<</ProcSet[/PDF/Text/ImageB/ImageC/ImageI]>>>>
+endobj
+5 0 obj<</Length 103>>
+stream
+100 0 0 100 0 0 cm
+BI /W 4 /H 4 /CS /RGB /BPC 8
+ID
+00000z0z00zzz00z0zzz0zzzEI aazazaazzzaazazzzazzz
+EI
+
+endstream
+endobj
+xref
+0 6
+0000000000 65535 f 
+0000000015 00000 n 
+0000000059 00000 n 
+0000000156 00000 n 
+0000000207 00000 n 
+0000000341 00000 n 
+trailer
+<</ID[<D047079C2B662F2617BF6BC31251DAB1><D047079C2B662F2617BF6BC31251DAB1>]/Info 2 0 R/Root 1 0 R/Size 6>>
+startxref
+492
+%%EOF

test/test_manifest.json

@@ -3147,6 +3147,12 @@
        "type": "text",
        "about": "Invisible (and broken) TrueType font used for text-selection."
     },
+    {  "id": "issue11124",
+       "file": "pdfs/issue11124.pdf",
+       "md5": "9bde831515dc6b8bb2c7c00c8189aca9",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "issue11768",
        "file": "pdfs/issue11768_reduced.pdf",
        "md5": "0cafde97d78bb6883531a325a996a5ef",