Lifted from SUSE: backport of two upstream commits

https://sourceforge.net/p/djvu/djvulibre-git/ci/970fb11a296b5bbdc5e8425851253d2c5913c45e
https://sourceforge.net/p/djvu/djvulibre-git/ci/89d71b01d606e57ecec2c2930c145bb20ba5bbe3
https://bugzilla.suse.com/show_bug.cgi?id=1146702#c3
https://build.opensuse.org/package/view_file/graphics/djvulibre/djvulibre-CVE-2019-15142.patch

Index: djvulibre-3.5.27/libdjvu/DjVmDir.cpp
===================================================================
--- djvulibre-3.5.27.orig/libdjvu/DjVmDir.cpp 2014-07-08 23:15:07.000000000 +0200
+++ djvulibre-3.5.27/libdjvu/DjVmDir.cpp 2019-09-02 13:46:28.076374501 +0200
@@ -300,36 +300,44 @@ DjVmDir::decode(const GP<ByteStream> &gs
          memcpy((char*) strings+strings_size, buffer, length);
       }
       DEBUG_MSG("size of decompressed names block=" << strings.size() << "\n");
-   
-         // Copy names into the files
+      int strings_size=strings.size();
+      strings.resize(strings_size+3);
+      memset((char*) strings+strings_size, 0, 4);
+      
+      // Copy names into the files
       const char * ptr=strings;
       for(pos=files_list;pos;++pos)
       {
          GP<File> file=files_list[pos];
-
+         if (ptr >= (const char*)strings + strings_size)
+           G_THROW( "DjVu document is corrupted (DjVmDir)" );
          file->id=ptr;
          ptr+=file->id.length()+1;
          if (file->flags & File::HAS_NAME)
          {
-            file->name=ptr;
-            ptr+=file->name.length()+1;
-         } else
+           file->name=ptr;
+           ptr+=file->name.length()+1;
+         }
+         else
          {
             file->name=file->id;
          }
          if (file->flags & File::HAS_TITLE)
          {
-            file->title=ptr;
-       ptr+=file->title.length()+1;
-         } else
-       file->title=file->id;
-   /* msr debug:  multipage file, file->title is null.  
+           file->title=ptr;
+           ptr+=file->title.length()+1;
+         }
+         else
+         {
+           file->title=file->id;
+         }
+         /* msr debug:  multipage file, file->title is null.  
          DEBUG_MSG(file->name << ", " << file->id << ", " << file->title << ", " <<
                    file->offset << ", " << file->size << ", " <<
                    file->is_page() << "\n"); */
       }
 
-         // Check that there is only one file with SHARED_ANNO flag on
+      // Check that there is only one file with SHARED_ANNO flag on
       int shared_anno_cnt=0;
       for(pos=files_list;pos;++pos)
       {
Index: djvulibre-3.5.27/libdjvu/miniexp.cpp
===================================================================
--- djvulibre-3.5.27.orig/libdjvu/miniexp.cpp 2015-02-11 05:35:37.000000000 +0100
+++ djvulibre-3.5.27/libdjvu/miniexp.cpp 2019-09-02 13:46:28.072374476 +0200
@@ -1028,7 +1028,7 @@ print_c_string(const char *s, char *d, i
     {
       if (char_quoted(c, flags))
         {
-          char buffer[10];
+          char buffer[16]; /* 10+1 */
           static const char *tr1 = "\"\\tnrbf";
           static const char *tr2 = "\"\\\t\n\r\b\f";
           buffer[0] = buffer[1] = 0;
Index: djvulibre-3.5.27/tools/csepdjvu.cpp
===================================================================
--- djvulibre-3.5.27.orig/tools/csepdjvu.cpp 2014-07-24 23:12:05.000000000 +0200
+++ djvulibre-3.5.27/tools/csepdjvu.cpp 2019-09-02 13:46:28.072374476 +0200
@@ -1814,7 +1814,7 @@ main(int argc, const char **argv)
                 ByteStream::create(GURL::Filename::UTF8(arg),"rb");
               BufferByteStream ibs(*fbs);
               do {
-                char pagename[16];
+                char pagename[20];
                 sprintf(pagename, "p%04d.djvu", ++pageno);
                 if (opts.verbose > 1)
                   DjVuPrintErrorUTF8("%s","--------------------\n");