Issue 747 (and others?): Avoid OOB read when parsing multiple long lines

The mtree bidder needs to look several lines ahead
in the input.  It does this by extending the read-ahead
and parsing subsequent lines from the same growing buffer.
A bookkeeping error when extending the read-ahead would
sometimes lead it to significantly over-count the
size of the line being read.

4 files changed, 61 insertions, 1 deletions

diff --git a/libarchive/archive_read_support_format_mtree.c b/libarchive/archive_read_support_format_mtree.c
index 8c3be9a2..ae58e875 100644
--- a/libarchive/archive_read_support_format_mtree.c
+++ b/libarchive/archive_read_support_format_mtree.c
@@ -301,6 +301,15 @@ get_line_size(const char *b, ssize_t avail, ssize_t *nlsize)
 	return (avail);
 }
 
+/*
+ *  <---------------- ravail --------------------->
+ *  <-- diff ------> <---  avail ----------------->
+ *                   <---- len ----------->
+ * | Previous lines | line being parsed  nl extra |
+ *                  ^
+ *                  b
+ *
+ */
 static ssize_t
 next_line(struct archive_read *a,
     const char **b, ssize_t *avail, ssize_t *ravail, ssize_t *nl)
@@ -339,7 +348,7 @@ next_line(struct archive_read *a,
 		*b += diff;
 		*avail -= diff;
 		tested = len;/* Skip some bytes we already determinated. */
-		len = get_line_size(*b, *avail, nl);
+		len = get_line_size(*b + len, *avail - len, nl);
 		if (len >= 0)
 			len += tested;
 	}
diff --git a/libarchive/test/CMakeLists.txt b/libarchive/test/CMakeLists.txt
index 345e42af..0cb5966d 100644
--- a/libarchive/test/CMakeLists.txt
+++ b/libarchive/test/CMakeLists.txt
@@ -138,6 +138,7 @@ IF(ENABLE_TEST)
     test_read_format_lha_bugfix_0.c
     test_read_format_lha_filename.c
     test_read_format_mtree.c
+    test_read_format_mtree_crash747.c
     test_read_format_pax_bz2.c
     test_read_format_rar.c
     test_read_format_rar_encryption_data.c
diff --git a/libarchive/test/test_read_format_mtree_crash747.c b/libarchive/test/test_read_format_mtree_crash747.c
new file mode 100644
index 00000000..c0828455
--- /dev/null
+++ b/libarchive/test/test_read_format_mtree_crash747.c
@@ -0,0 +1,44 @@
+/*-
+ * Copyright (c) 2003-2016 Tim Kientzle
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "test.h"
+
+
+/*
+ * Reproduce the crash reported in Github Issue #747.
+ */
+DEFINE_TEST(test_read_format_mtree_crash747)
+{
+	const char *reffile = "test_read_format_mtree_crash747.mtree.bz2";
+	struct archive *a;
+
+	extract_reference_file(reffile);
+
+	assert((a = archive_read_new()) != NULL);
+	assertEqualIntA(a, ARCHIVE_OK, archive_read_support_filter_bzip2(a));
+	assertEqualIntA(a, ARCHIVE_OK, archive_read_support_format_mtree(a));
+	assertEqualIntA(a, ARCHIVE_FATAL, archive_read_open_filename(a, reffile, 10240));
+	assertEqualInt(ARCHIVE_OK, archive_read_free(a));
+}
+
diff --git a/libarchive/test/test_read_format_mtree_crash747.mtree.bz2.uu b/libarchive/test/test_read_format_mtree_crash747.mtree.bz2.uu
new file mode 100644
index 00000000..84f38955
--- /dev/null
+++ b/libarchive/test/test_read_format_mtree_crash747.mtree.bz2.uu
@@ -0,0 +1,6 @@
+begin 600 test_read_format_mtree_crash747.mtree.bz2
+M0EIH.3%!62936:OH@(@``'/[@,`0`@!``'^```)A@9\`$`@@`'4)049!IIH!
+MM021-0,F@&@6````9%>$(K!GIC*XFR0`$```J0+:$XP```!D-F)H[#SE9+2'
+4+E"L=ASXUI%R(I"HD'ZA(5?1`Q``
+`
+end