From dc92574c10f3e2516ec6445b88c5d584f40df4e5 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Mon, 4 Jan 2021 11:55:28 -0500
Subject: Fix some pipelines to be safe if downstream write fails (fuzz issue
 28262)

---
 libqpdf/Pl_AES_PDF.cc         | 2 +-
 libqpdf/Pl_ASCII85Decoder.cc  | 7 +++++--
 libqpdf/Pl_ASCIIHexDecoder.cc | 6 ++++--
 libqpdf/Pl_Count.cc           | 2 +-
 4 files changed, 11 insertions(+), 6 deletions(-)

(limited to 'libqpdf')

diff --git a/libqpdf/Pl_AES_PDF.cc b/libqpdf/Pl_AES_PDF.cc
index 18cf3a4d..2865f804 100644
--- a/libqpdf/Pl_AES_PDF.cc
+++ b/libqpdf/Pl_AES_PDF.cc
@@ -238,6 +238,6 @@ Pl_AES_PDF::flush(bool strip_padding)
 	    }
 	}
     }
-    getNext()->write(this->outbuf, bytes);
     this->offset = 0;
+    getNext()->write(this->outbuf, bytes);
 }
diff --git a/libqpdf/Pl_ASCII85Decoder.cc b/libqpdf/Pl_ASCII85Decoder.cc
index b8df3e87..9d9f6704 100644
--- a/libqpdf/Pl_ASCII85Decoder.cc
+++ b/libqpdf/Pl_ASCII85Decoder.cc
@@ -119,10 +119,13 @@ Pl_ASCII85Decoder::flush()
 
     QTC::TC("libtests", "Pl_ASCII85Decoder partial flush",
 	    (this->pos == 5) ? 0 : 1);
-    getNext()->write(outbuf, this->pos - 1);
-
+    // Reset before calling getNext()->write in case that throws an
+    // exception.
+    auto t = this->pos - 1;
     this->pos = 0;
     memset(this->inbuf, 117, 5);
+
+    getNext()->write(outbuf, t);
 }
 
 void
diff --git a/libqpdf/Pl_ASCIIHexDecoder.cc b/libqpdf/Pl_ASCIIHexDecoder.cc
index f20a9769..7845268e 100644
--- a/libqpdf/Pl_ASCIIHexDecoder.cc
+++ b/libqpdf/Pl_ASCIIHexDecoder.cc
@@ -97,12 +97,14 @@ Pl_ASCIIHexDecoder::flush()
 
     QTC::TC("libtests", "Pl_ASCIIHexDecoder partial flush",
 	    (this->pos == 2) ? 0 : 1);
-    getNext()->write(&ch, 1);
-
+    // Reset before calling getNext()->write in case that throws an
+    // exception.
     this->pos = 0;
     this->inbuf[0] = '0';
     this->inbuf[1] = '0';
     this->inbuf[2] = '\0';
+
+    getNext()->write(&ch, 1);
 }
 
 void
diff --git a/libqpdf/Pl_Count.cc b/libqpdf/Pl_Count.cc
index 8077092a..c35619b8 100644
--- a/libqpdf/Pl_Count.cc
+++ b/libqpdf/Pl_Count.cc
@@ -27,8 +27,8 @@ Pl_Count::write(unsigned char* buf, size_t len)
     if (len)
     {
 	this->m->count += QIntC::to_offset(len);
-	getNext()->write(buf, len);
 	this->m->last_char = buf[len - 1];
+	getNext()->write(buf, len);
     }
 }
 
-- 
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