Bug#494750: driftnet: driftnat dies with "libpng error: Invalid image width"

[Adam =?UTF-8?Q?Sj=C3=B8gren]

On Tue, 12 Aug 2008 20:08:38 +0200, Christoph wrote:

> Thanks for the bug report. Unfortuntely I'm not familiar with libpng and 
> driftnet has been abandoned upstream. So I'd appreciate a patch dealing 
> with the libpng return codes.

Attached is a patch that uses libpng's error-handling to catch the
error, clean up and continue.

(I haven't fiddled with libpng before, so I hope it isn't too far of. It
 works work me (I get error messages printed and no crashing)).


  Best regards,

    Adam

-- 
 "What looks large from a distance                            Adam Sjøgren
  Close up is never that big"                            [EMAIL PROTECTED]


--- hip/driftnet-0.1.6/png.c	2008-08-11 23:20:02.000000000 +0200
+++ hop/driftnet-0.1.6/png.c	2008-08-13 19:56:24.941247135 +0200
@@ -29,6 +29,24 @@
     }
 }
 
+/* png_catch_error: */
+/* Catch errors signalled by libpng, clean up and go on. */
+void png_catch_error(png_structp png_ptr, png_const_charp error_msg) {
+   jmp_buf *jmpbuf_ptr;
+   
+   fprintf(stderr, "libpng error: %s (skipping image).\n", error_msg);
+   fflush(stderr);
+
+   jmpbuf_ptr=png_jmpbuf(png_ptr);
+   if (jmpbuf_ptr==NULL) {
+      fprintf(stderr, "libpng unrecoverable error, terminating.\n");
+      fflush(stderr);
+      exit(20);
+   }
+
+   longjmp(jmpbuf_ptr, 1);
+}
+         
 /* png_load_hdr:
  * Load the header of a PNG file. */
 int png_load_hdr(img I) {
@@ -38,12 +56,19 @@
 	return 0;
     }
     I->us = p;
-    p->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
+    p->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, png_catch_error, NULL);
     if (p->png == 0) {
 	png_done(I);
 	I->err = IE_HDRFORMAT;
 	return 0;
     }
+
+    if (setjmp(png_jmpbuf(p->png))) {
+       png_done(I);
+       I->err = IE_HDRFORMAT;
+       return 0;
+    }
+
     p->info = png_create_info_struct(p->png);
     if (p->info == 0) {
 	png_done(I);