From ff0affd81d58cecfbe2cc2e3f5cc2d9895bf922b Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Fri, 31 Jan 2025 14:11:15 +0000
Subject: [PATCH] In QPDFWriter::willFilterStream on runtime error on first attempt retry without filtering

---
 libqpdf/QPDFWriter.cc                  | 23 ++++++++++++++++-------
 qpdf/qtest/qpdf/qjson-bad-data.out     |  2 ++
 qpdf/qtest/qpdf/qjson-bad-datafile.out |  2 ++
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index a38b213..4dda1dc 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -26,6 +26,8 @@
 #include <cstdlib>
 #include <stdexcept>
 
+using namespace std::literals;
+
 QPDFWriter::ProgressReporter::~ProgressReporter() // NOLINT (modernize-use-equals-default)
 {
     // Must be explicit and not inline -- see QPDF_DLL_CLASS in README-maintainer
@@ -1296,17 +1298,24 @@ QPDFWriter::willFilterStream(
                 !filter ? qpdf_dl_none : (uncompress ? qpdf_dl_all : m->stream_decode_level),
                 false,
                 first_attempt);
+            if (filter && !filtered) {
+                // Try again
+                filter = false;
+                stream.setFilterOnWrite(false);
+            } else {
+                break;
+            }
         } catch (std::runtime_error& e) {
+            if (filter && first_attempt) {
+                stream.warnIfPossible("error while getting stream data: "s + e.what());
+                stream.warnIfPossible("qpdf will attempt to write the damaged stream unchanged");
+                filter = false;
+                stream.setFilterOnWrite(false);
+                continue;
+            }
             throw std::runtime_error(
                 "error while getting stream data for " + stream.unparse() + ": " + e.what());
         }
-        if (filter && !filtered) {
-            // Try again
-            filter = false;
-            stream.setFilterOnWrite(false);
-        } else {
-            break;
-        }
     }
     if (!filtered) {
         compress_stream = false;
diff --git a/qpdf/qtest/qpdf/qjson-bad-data.out b/qpdf/qtest/qpdf/qjson-bad-data.out
index e5cf46b..3a3c9c5 100644
--- a/qpdf/qtest/qpdf/qjson-bad-data.out
+++ b/qpdf/qtest/qpdf/qjson-bad-data.out
@@ -1 +1,3 @@
+WARNING: qjson-bad-data.json, obj:4 0 R at offset 0: error while getting stream data: base64-decode: base64 decode: invalid input
+WARNING: qjson-bad-data.json, obj:4 0 R at offset 0: qpdf will attempt to write the damaged stream unchanged
 qpdf: error while getting stream data for 4 0 R: base64-decode: base64 decode: invalid input
diff --git a/qpdf/qtest/qpdf/qjson-bad-datafile.out b/qpdf/qtest/qpdf/qjson-bad-datafile.out
index 1ef4f02..cd39770 100644
--- a/qpdf/qtest/qpdf/qjson-bad-datafile.out
+++ b/qpdf/qtest/qpdf/qjson-bad-datafile.out
@@ -1 +1,3 @@
+WARNING: qjson-bad-datafile.json, obj:4 0 R at offset 0: error while getting stream data: open file does not exist: No such file or directory
+WARNING: qjson-bad-datafile.json, obj:4 0 R at offset 0: qpdf will attempt to write the damaged stream unchanged
 qpdf: error while getting stream data for 4 0 R: open file does not exist: No such file or directory
--
libgit2 0.21.4