From f4f57913fff5de97da347a22558bbb74a1166369 Mon Sep 17 00:00:00 2001
From: matthias wandel <matthias@woodgears.ca>
Date: Wed, 1 Sep 2021 18:59:15 -0300
Subject: [PATCH] If exif header is complete garbage, don't keep it.  Fixes
 issue 36

(cherry picked from commit c761620767ae72e5d61c697a73de262aebe0b591)
---
 exif.c    | 12 +++++++-----
 jhead.h   |  2 +-
 jpgfile.c |  5 ++++-
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/exif.c b/exif.c
index ba066b5..d250a8d 100755
--- a/exif.c
+++ b/exif.c
@@ -1005,7 +1005,7 @@ void Clear_EXIF ()
 // Process a EXIF marker
 // Describes all the drivel that most digital cameras include...
 //--------------------------------------------------------------------------
-void process_EXIF (unsigned char * ExifSection, int length)
+int process_EXIF (unsigned char * ExifSection, int length)
 {
     int FirstOffset;
     
@@ -1020,7 +1020,7 @@ void process_EXIF (unsigned char * ExifSection, int length)
         static uchar ExifHeader[] = "Exif\0\0";
         if (memcmp(ExifSection+2, ExifHeader,6)){
             ErrNonfatal("Incorrect Exif header",0,0);
-            return;
+            return 0;
         }
     }
 
@@ -1033,21 +1033,21 @@ void process_EXIF (unsigned char * ExifSection, int length)
             MotorolaOrder = 1;
         }else{
             ErrNonfatal("Invalid Exif alignment marker.",0,0);
-            return;
+            return 0;
         }
     }
 
     // Check the next value for correctness.
     if (Get16u(ExifSection+10) != 0x2a){
         ErrNonfatal("Invalid Exif start (1)",0,0);
-        return;
+        return 0;
     }
 
     FirstOffset = (int)Get32u(ExifSection+12);
     if (FirstOffset < 8 || FirstOffset > 16){
         if (FirstOffset < 16 || FirstOffset > length-16 || length < 16){
             ErrNonfatal("invalid offset for first Exif IFD value",0,0);
-            return;
+            return 0;
         }
         // Usually set to 8, but other values valid too.
         ErrNonfatal("Suspicious offset of first Exif IFD value",0,0);
@@ -1086,6 +1086,7 @@ void process_EXIF (unsigned char * ExifSection, int length)
             ImageInfo.FocalLength35mmEquiv = (int)(ImageInfo.FocalLength/ImageInfo.CCDWidth*36 + 0.5);
         }
     }
+	return 1;
 }
 
 
@@ -1235,6 +1236,7 @@ void create_EXIF(void)
 const char * ClearOrientation(void)
 {
     int a;
+
     if (NumOrientations == 0) return NULL;
 
     for (a=0;a<NumOrientations;a++){
diff --git a/jhead.h b/jhead.h
index 3d620d9..03987e2 100644
--- a/jhead.h
+++ b/jhead.h
@@ -163,7 +163,7 @@ void FileTimeAsString(char * TimeStr);
 // Prototypes for exif.c functions.
 int Exif2tm(struct tm * timeptr, char * ExifTime);
 void Clear_EXIF();
-void process_EXIF (unsigned char * CharBuf, int length);
+int process_EXIF (unsigned char * CharBuf, int length);
 void ShowImageInfo(int ShowFileInfo);
 void ShowConciseImageInfo(void);
 const char * ClearOrientation(void);
diff --git a/jpgfile.c b/jpgfile.c
index 097d2f1..af2d7bc 100644
--- a/jpgfile.c
+++ b/jpgfile.c
@@ -286,7 +286,10 @@ int ReadJpegSections (FILE * infile, ReadMode_t ReadMode)
                 // There can be different section using the same marker.
                 if (ReadMode & READ_METADATA){
                     if (memcmp(Data+2, "Exif", 4) == 0){
-                        process_EXIF(Data, itemlen);
+                        if (!process_EXIF(Data, itemlen)){
+                            // malformatted exif sections, discard.
+                            free(Sections[--SectionsRead].Data);
+						}
                         break;
                     }else if (memcmp(Data+2, "http:", 5) == 0){
                         Sections[SectionsRead-1].Type = M_XMP; // Change tag for internal purposes.
-- 
2.39.2