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Return an empty reader for zero-length streams before applying filters. This prevents "unexpected EOF" errors from zlib when processing empty FlateDecode streams in PDFs.
Limit the recursion depth in readObject() to prevent excessive resource consumption when parsing deeply nested PDF structures. Returns an error if parsing past the limit.
readToken returns io.EOF as a token value once the input is exhausted,
but readArray only broke out of its loop on nil or keyword("]"). On a
PDF whose content stream is truncated inside an unterminated array, the
loop unread the io.EOF token, read it back as an object, and appended
it to the array forever, allocating memory without bound (~7GB of heap
in 5 seconds observed on a real-world malformed PDF) and hanging every
text-extraction entry point (GetPlainText, Page.Content,
Page.GetTextByRow).
readDict already guards against io.EOF; give readArray the same guard.
Add a regression test that synthesizes a minimal single-page PDF whose
content stream ends inside an unterminated array and verifies that
GetPlainText returns instead of spinning. The test times out against
the previous code and passes with the fix.
…oder fix: ASCII85 decoder drops 'z' zero-groups and never signals EOF at ~> marker
fix: guard debug print behind DebugOn
…f-loopx Fix infinite loop / unbounded allocation in readArray on truncated PDFs
…ay-tokenization Fix tokens split across content streams
fix: add maximum nesting depth for PDF object parsing
fix: handle EOF and ] keyword
fix: handle empty streams to avoid zlib EOF errors
A font subsetter can emit a /ToUnicode CMap whose PostScript preamble is
malformed — e.g. a /CIDSystemInfo dict literal with a stray "def" after
every entry:
<</Registry (Vendor+Subset+0) def/Ordering (T1UV) def/Supplement 0 def>> def
This is invalid: a dictionary literal ("<< ... >>") should contain only
key/value pairs, never a "def" token between them. Interpret reads that
literal via readObject, which correctly treats it as a hard parse error
for a real PDF object — but that panic then escaped Interpret entirely,
taking down the WHOLE calling operation (e.g. reading a font's /ToUnicode
CMap via readCmap, then Font.Encoder, then Page.GetPlainText) even when
the font's actual beginbfchar/beginbfrange mapping data — the only part
GetPlainText's caller needs — was itself complete and well-formed.
Observed in the wild on a real health-insurance plan document: a
multi-language notice page embeds one Identity-H font per language, and
one language's font subset had this malformed preamble. The document's
other ~10 pages, and the other fonts on the same page, were unaffected —
but the single panic failed the whole page's text extraction.
Interpret already documents itself as "not a full-blown PostScript
interpreter... a limited PostScript subset for embedded CMap/function
data", so this fix keeps that spirit rather than tightening validation:
- the object read for an unrecognized operand is now recovered
(readObjectRecover) rather than allowed to panic past Interpret
- the "def" operator no longer panics when no dict has been opened via
"begin" (a case a malformed producer can reach); it now discards the
operand and continues, matching the existing sibling leniency for
"def" of a non-name key just above it
New test: TestInterpretToleratesMalformedCMapPreamble, built from the
exact byte-for-byte shape of the real malformed preamble (including its
"\r" line endings), asserting GetPlainText still recovers the font's
well-formed bfchar mapping data.
No existing test's behavior changes; the full suite is green.
…-panic fix: Interpret should not panic on a malformed CMap PostScript preamble
feat: Add support for "UniGB-UCS2-H" encoding.
…tream # Conflicts: # lex.go # page.go # ps.go
|
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Included review availability: 1 review is currently available. Your included PR review attempts over the past 7 days set your current allowance at 5 reviews per hour. 📝 WalkthroughWalkthroughThe change updates ASCII85 decoding, truncated-input handling, cross-reference processing, stream interpretation, text extraction, encryption validation, UTF-16 decoding, and regression coverage. ChangesPDF parser and text extraction
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Inline comments:
In `@page.go`:
- Line 239: Keep the exported Font.Encoder method on a value receiver so calls
on Font values and interface implementations remain supported. At internal
caching sites, invoke the existing private pointer-receiver method instead of
changing the exported method set.
- Line 345: Update utf16Decode to process only complete two-byte pairs and
append U+FFFD when the input contains a trailing unmatched byte, preventing the
final pair access from panicking. Add a regression test covering odd-length
input through ucs2Encoder.Decode or utf16Decode and verify the replacement
character is emitted.
- Line 245: Update Font.encoder to cache the computed encoding in f.enc only
when ctx.Err() is nil, so cancellation-related nopEncoder results do not prevent
later CMap retries when the same fonts map is reused.
In `@read.go`:
- Line 225: Update the xref traversal loop around the prev chain to track
visited offsets and return a malformed-PDF error when an offset repeats, before
invoking parse again; preserve normal traversal for unseen /Prev offsets and add
a regression test covering a self-referential xref /Prev chain.
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ascii85.goascii85_integration_test.goascii85_test.golex.golex_test.goopen_test.gopage.gopage_test.gopdfpasswd/main_test.gops.gops_malformed_cmap_test.gops_test.goread.gostack_test.gostream_test.govalue_test.go
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recoverTo (page.go) stringified every panic value, discarding the %w-wrapped context.Canceled/DeadlineExceeded and errObjectNestingDepth chains and breaking errors.Is checks on GetPlainText's error. readObjectRecover (ps.go), added upstream to tolerate malformed CMap preambles, was also silently swallowing errObjectNestingDepth panics raised while parsing content-stream objects, so the max-nesting-depth guard never surfaced as an error from Interpret.
…ref /Prev loop utf16Decode indexed one byte past an odd-length string; now it appends U+FFFD for the trailing unmatched byte instead of panicking. Font.encoder cached whatever getEncoder returned even when ctx had already been cancelled (e.g. the page byte cap firing mid-CMap-parse), permanently pinning a nopEncoder fallback onto a *Font shared across later pages in Reader.GetPlainText. Only cache when ctx.Err() is nil. readPrevXrefs had no cycle detection, so a self-referential or looping xref /Prev chain would spin forever; it now tracks visited offsets and errors on a repeat. Left Font.Encoder()'s pointer receiver as-is: it matches upstream's own (intentional, already-published) fix and the TestFontEncoderCaches test written for it, so reverting it to a value receiver would just diverge from upstream and break that test.
cpoile
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Sep 21, 2026
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Nice! Just a couple gaps in our specific changes. Thanks @fmartingr!
| // loop instead of returning a malformed-PDF error. | ||
| func TestNewReaderRejectsCyclicPrevXref(t *testing.T) { | ||
| data := selfReferentialPrevXrefPDF() | ||
| _, err := NewReader(bytes.NewReader(data), int64(len(data))) |
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iiuc, this test is part of our post-upstream follow-up for the infinite /Prev loop from upstream. Since NewReader runs synchronously here, that same regression would hang this test instead of giving us a clear failure. The production fix is fine, but the issue is limited to our new regression test.
| // Fonts are cached across pages (see Reader.GetPlainText), so a fallback | ||
| // caused by this call's ctx being cancelled must not be cached: it would | ||
| // permanently break decoding for later pages that pass a fresh, live ctx. | ||
| if ctx.Err() == nil { |
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Looks like this guard is our post-merge fix for the cancellation/cache interaction created when upstream font caching was combined with Mattermost context-aware CMap parsing. The upstream TestFontEncoderCaches only covers successful WinAnsi caching, so the canceled-parse/live-retry behavior fixed here is not covered. The implementation looks correct, but the issue is a coverage gap in our integration fix.
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Summary
Merges the latest changes from upstream ledongthuc/pdf, the project this repo is forked from.
Commits included: