Fix OOB reads of the TGA decompression buffer

It is possible to craft TGA files which will overflow the decompression
buffer, but not the image's bitmap. Therefore we also have to check for
potential decompression buffer overflows.

This issue had been reported by Ibrahim El-Sayed to security@libgd.org;
a modified case exposing an off-by-one error of the first patch had been
provided by Konrad Beckmann.

This commit is an amendment to commit fb0e0cce, so we use CVE-2016-6906
as well.

4 files changed, 14 insertions, 5 deletions

diff --git a/tests/tga/Makemodule.am b/tests/tga/Makemodule.am
index 916d707..ab08dbf 100644
--- a/tests/tga/Makemodule.am
+++ b/tests/tga/Makemodule.am
@@ -15,7 +15,8 @@ EXTRA_DIST += \
 	tga/bug00247a.tga \
 	tga/bug00248.tga \
 	tga/bug00248a.tga \
-	tga/heap_overflow.tga \
+	tga/heap_overflow_1.tga \
+	tga/heap_overflow_2.tga \
 	tga/tga_read_rgb.png \
 	tga/tga_read_rgb.tga \
 	tga/tga_read_rgb_rle.tga
diff --git a/tests/tga/heap_overflow.c b/tests/tga/heap_overflow.c
index 0e9a2d0..ddd4b63 100644
--- a/tests/tga/heap_overflow.c
+++ b/tests/tga/heap_overflow.c
@@ -1,5 +1,5 @@
 /**
- * Test that the crafted TGA file doesn't trigger OOB reads.
+ * Test that crafted TGA files don't trigger OOB reads.
  */
 
 
@@ -7,21 +7,29 @@
 #include "gdtest.h"
 
 
+static void check_file(char *basename);
 static size_t read_test_file(char **buffer, char *basename);
 
 
 int main()
 {
+    check_file("heap_overflow_1.tga");
+    check_file("heap_overflow_2.tga");
+
+    return gdNumFailures();
+}
+
+
+static void check_file(char *basename)
+{
     gdImagePtr im;
     char *buffer;
     size_t size;
 
-    size = read_test_file(&buffer, "heap_overflow.tga");
+    size = read_test_file(&buffer, basename);
     im = gdImageCreateFromTgaPtr(size, (void *) buffer);
     gdTestAssert(im == NULL);
     free(buffer);
-
-    return gdNumFailures();
 }
 
 
diff --git a/tests/tga/heap_overflow_1.tga b/tests/tga/heap_overflow_1.tga
new file mode 100644
index 0000000..e9bc0ec
--- /dev/null
+++ b/tests/tga/heap_overflow_1.tga
diff --git a/tests/tga/heap_overflow_2.tga b/tests/tga/heap_overflow_2.tga
new file mode 100644
index 0000000..2b681f2
--- /dev/null
+++ b/tests/tga/heap_overflow_2.tga