From d98e5a2ace46adcefa093c029663575fd677bf05 Mon Sep 17 00:00:00 2001

From: Ondrej Dubaj <odubaj@redhat.com>

Date: Tue, 4 Jun 2019 13:05:57 +0200

Subject: [PATCH] Potential double-free in gdImage*Ptr()

Whenever `gdImage*Ptr()` calls `gdImage*Ctx()` and the latter fails, we

must not call `gdDPExtractData()`; otherwise a double-free would

happen.  Since `gdImage*Ctx()` are void functions, and we can't change

that for BC reasons, we're introducing static helpers which are used

internally.

We're adding a regression test for `gdImageJpegPtr()`, but not for

`gdImageGifPtr()` and `gdImageWbmpPtr()` since we don't know how to

trigger failure of the respective `gdImage*Ctx()` calls.

This potential security issue has been reported by Solmaz Salimi (aka.

Rooney).

---

 src/gd_gif_out.c                  | 19 +++++++++++++++----

 src/gd_jpeg.c                     | 20 ++++++++++++++++----

 src/gd_wbmp.c                     | 21 ++++++++++++++++++---

 tests/jpeg/CMakeLists.txt         |  1 +

 tests/jpeg/Makemodule.am          |  3 ++-

 tests/jpeg/jpeg_ptr_double_free.c | 31 +++++++++++++++++++++++++++++++

 6 files changed, 83 insertions(+), 12 deletions(-)

 create mode 100644 tests/jpeg/jpeg_ptr_double_free.c

diff --git a/src/gd_gif_out.c b/src/gd_gif_out.c

index 6fe707d..4a05c09 100755

--- a/src/gd_gif_out.c

+++ b/src/gd_gif_out.c

@@ -99,7 +99,7 @@ static void char_init(GifCtx *ctx);

 static void char_out(int c, GifCtx *ctx);

 static void flush_char(GifCtx *ctx);

-

+static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out);

 /*

@@ -131,8 +131,11 @@ BGD_DECLARE(void *) gdImageGifPtr(gdImagePtr im, int *size)

 	void *rv;

 	gdIOCtx *out = gdNewDynamicCtx(2048, NULL);

 	if (out == NULL) return NULL;

-	gdImageGifCtx(im, out);

-	rv = gdDPExtractData(out, size);

+	if (!_gdImageGifCtx(im, out)) {

+        rv = gdDPExtractData(out, size);

+    } else {

+        rv = NULL;

+    }

 	out->gd_free(out);

 	return rv;

 }

@@ -220,6 +223,12 @@ BGD_DECLARE(void) gdImageGif(gdImagePtr im, FILE *outFile)

 */

 BGD_DECLARE(void) gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)

+{

+    _gdImageGifCtx(im, out);

+}

+

+/* returns 0 on success, 1 on failure */

+static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)

 {

 	gdImagePtr pim = 0, tim = im;

 	int interlace, BitsPerPixel;

@@ -231,7 +240,7 @@ BGD_DECLARE(void) gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)

 		based temporary image. */

 		pim = gdImageCreatePaletteFromTrueColor(im, 1, 256);

 		if(!pim) {

-			return;

+			return 1;

 		}

 		tim = pim;

 	}

@@ -247,6 +256,8 @@ BGD_DECLARE(void) gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)

 		/* Destroy palette based temporary image. */

 		gdImageDestroy(	pim);

 	}

+

+    return 0;

 }

diff --git a/src/gd_jpeg.c b/src/gd_jpeg.c

index 271ef46..bd8fc27 100755

--- a/src/gd_jpeg.c

+++ b/src/gd_jpeg.c

@@ -123,6 +123,8 @@ static void fatal_jpeg_error(j_common_ptr cinfo)

 	exit(99);

 }

+static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality);

+

 /*

  * Write IM to OUTFILE as a JFIF-formatted JPEG image, using quality

  * QUALITY.  If QUALITY is in the range 0-100, increasing values

@@ -237,8 +239,11 @@ BGD_DECLARE(void *) gdImageJpegPtr(gdImagePtr im, int *size, int quality)

 	void *rv;

 	gdIOCtx *out = gdNewDynamicCtx(2048, NULL);

 	if (out == NULL) return NULL;

-	gdImageJpegCtx(im, out, quality);

-	rv = gdDPExtractData(out, size);

+	if (!_gdImageJpegCtx(im, out, quality)) {

+		rv = gdDPExtractData(out, size);

+	} else {

+		rv = NULL;

+	}

 	out->gd_free(out);

 	return rv;

 }

@@ -259,6 +264,12 @@ void jpeg_gdIOCtx_dest(j_compress_ptr cinfo, gdIOCtx *outfile);

 */

 BGD_DECLARE(void) gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)

+{

+	_gdImageJpegCtx(im, outfile, quality);

+}

+

+/* returns 0 on success, 1 on failure */

+static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)

 {

 	struct jpeg_compress_struct cinfo;

 	struct jpeg_error_mgr jerr;

@@ -293,7 +304,7 @@ BGD_DECLARE(void) gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)

 		if(row) {

 			gdFree(row);

 		}

-		return;

+		return 1;

 	}

 	cinfo.err->emit_message = jpeg_emit_message;

@@ -334,7 +345,7 @@ BGD_DECLARE(void) gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)

 	if(row == 0) {

 		gd_error("gd-jpeg: error: unable to allocate JPEG row structure: gdCalloc returns NULL\n");

 		jpeg_destroy_compress(&cinfo);

-		return;

+		return 1;

 	}

 	rowptr[0] = row;

@@ -411,6 +422,7 @@ BGD_DECLARE(void) gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)

 	jpeg_finish_compress(&cinfo);

 	jpeg_destroy_compress(&cinfo);

 	gdFree(row);

+	return 0;

 }

diff --git a/src/gd_wbmp.c b/src/gd_wbmp.c

index 0028273..341ff6e 100755

--- a/src/gd_wbmp.c

+++ b/src/gd_wbmp.c

@@ -88,6 +88,8 @@ int gd_getin(void *in)

 	return (gdGetC((gdIOCtx *)in));

 }

+static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out);

+

 /*

 	Function: gdImageWBMPCtx

@@ -100,6 +102,12 @@ int gd_getin(void *in)

 		out   - the stream where to write

 */

 BGD_DECLARE(void) gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)

+{

+	_gdImageWBMPCtx(image, fg, out);

+}

+

+/* returns 0 on success, 1 on failure */

+static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)

 {

 	int x, y, pos;

 	Wbmp *wbmp;

@@ -107,7 +115,7 @@ BGD_DECLARE(void) gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)

 	/* create the WBMP */

 	if((wbmp = createwbmp(gdImageSX(image), gdImageSY(image), WBMP_WHITE)) == NULL) {

 		gd_error("Could not create WBMP\n");

-		return;

+		return 1;

 	}

 	/* fill up the WBMP structure */

@@ -123,11 +131,15 @@ BGD_DECLARE(void) gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)

 	/* write the WBMP to a gd file descriptor */

 	if(writewbmp(wbmp, &gd_putout, out)) {

+		freewbmp(wbmp);

 		gd_error("Could not save WBMP\n");

+		return 1;

 	}

 	/* des submitted this bugfix: gdFree the memory. */

 	freewbmp(wbmp);

+

+	return 0;

 }

 /*

@@ -271,8 +283,11 @@ BGD_DECLARE(void *) gdImageWBMPPtr(gdImagePtr im, int *size, int fg)

 	void *rv;

 	gdIOCtx *out = gdNewDynamicCtx(2048, NULL);

 	if (out == NULL) return NULL;

-	gdImageWBMPCtx(im, fg, out);

-	rv = gdDPExtractData(out, size);

+	if (!_gdImageWBMPCtx(im, fg, out)) {

+		rv = gdDPExtractData(out, size);

+	} else {

+		rv = NULL;

+	}

 	out->gd_free(out);

 	return rv;

 }

diff --git a/tests/jpeg/CMakeLists.txt b/tests/jpeg/CMakeLists.txt

index 19964b0..a8d8162 100755

--- a/tests/jpeg/CMakeLists.txt

+++ b/tests/jpeg/CMakeLists.txt

@@ -2,6 +2,7 @@ IF(JPEG_FOUND)

 LIST(APPEND TESTS_FILES

 	jpeg_empty_file

 	jpeg_im2im

+	jpeg_ptr_double_free

 	jpeg_null

 )

diff --git a/tests/jpeg/Makemodule.am b/tests/jpeg/Makemodule.am

index 7e5d317..b89e169 100755

--- a/tests/jpeg/Makemodule.am

+++ b/tests/jpeg/Makemodule.am

@@ -2,7 +2,8 @@ if HAVE_LIBJPEG

 libgd_test_programs += \

 	jpeg/jpeg_empty_file \

 	jpeg/jpeg_im2im \

-	jpeg/jpeg_null

+	jpeg/jpeg_null \

+	jpeg/jpeg_ptr_double_free

 if HAVE_LIBPNG

 libgd_test_programs += \

diff --git a/tests/jpeg/jpeg_ptr_double_free.c b/tests/jpeg/jpeg_ptr_double_free.c

new file mode 100644

index 0000000..c80aeb6

--- /dev/null

+++ b/tests/jpeg/jpeg_ptr_double_free.c

@@ -0,0 +1,31 @@

+/**

+ * Test that failure to convert to JPEG returns NULL

+ *

+ * We are creating an image, set its width to zero, and pass this image to

+ * `gdImageJpegPtr()` which is supposed to fail, and as such should return NULL.

+ *

+ * See also <https://github.com/libgd/libgd/issues/381>

+ */

+

+

+#include "gd.h"

+#include "gdtest.h"

+

+

+int main()

+{

+    gdImagePtr src, dst;

+    int size;

+

+    src = gdImageCreateTrueColor(1, 10);

+    gdTestAssert(src != NULL);

+

+    src->sx = 0; /* this hack forces gdImageJpegPtr() to fail */

+

+    dst = gdImageJpegPtr(src, &size, 0);

+    gdTestAssert(dst == NULL);

+

+    gdImageDestroy(src);

+

+    return gdNumFailures();

+}

\ No newline at end of file

-- 

2.17.1