backends: Fix several security issues in the dvi-backend.

See CVE-2010-2640, CVE-2010-2641, CVE-2010-2642 and  CVE-2010-2643.

backend/dvi/mdvi-lib/afmparse.c

@@ -160,7 +160,7 @@ static char *token(FILE *stream)
     
     idx = 0;
     while (ch != EOF && ch != ' ' && ch != lineterm 
-           && ch != '\t' && ch != ':' && ch != ';') 
+           && ch != '\t' && ch != ':' && ch != ';' && idx < MAX_NAME)
     {
         ident[idx++] = ch;
         ch = fgetc(stream);

backend/dvi/mdvi-lib/dviread.c

@@ -1507,6 +1507,10 @@ int	special(DviContext *dvi, int opcode)
 	Int32	arg;
 	
 	arg = dugetn(dvi, opcode - DVI_XXX1 + 1);
+	if (arg <= 0) {
+		dvierr(dvi, _("malformed special length\n"));
+		return -1;
+	}
 	s = mdvi_malloc(arg + 1);
 	dread(dvi, s, arg);
 	s[arg] = 0;

backend/dvi/mdvi-lib/pk.c

@@ -469,6 +469,15 @@ static int pk_load_font(DviParams *unused, DviFont *font)
 			}
 			if(feof(p))
 				break;
+
+			/* Although the PK format support bigger char codes,
+                         * XeTeX and other extended TeX engines support charcodes up to
+                         * 65536, while normal TeX engine supports only charcode up to 255.*/
+			if (cc < 0 || cc > 65536) {
+				mdvi_error (_("%s: unexpected charcode (%d)\n"),
+					    font->fontname,cc);
+				goto error;
+			} 
 			if(cc < loc)
 				loc = cc;
 			if(cc > hic)
@@ -512,7 +521,7 @@ static int pk_load_font(DviParams *unused, DviFont *font)
 	}
 
 	/* resize font char data */
-	if(loc > 0 || hic < maxch-1) {
+	if(loc > 0 && hic < maxch-1) {
 		memmove(font->chars, font->chars + loc, 
 			(hic - loc + 1) * sizeof(DviFontChar));
 		font->chars = xresize(font->chars,

backend/dvi/mdvi-lib/tfmfile.c

@@ -172,7 +172,8 @@ int	tfm_load_file(const char *filename, TFMInfo *info)
 	/* We read the entire TFM file into core */
 	if(fstat(fileno(in), &st) < 0)
 		return -1;
-	if(st.st_size == 0)
+	/* according to the spec, TFM files are smaller than 16K */
+	if(st.st_size == 0 || st.st_size >= 16384)
 		goto bad_tfm;
 
 	/* allocate a word-aligned buffer to hold the file */

backend/dvi/mdvi-lib/vf.c

@@ -165,6 +165,12 @@ static int vf_load_font(DviParams *params, DviFont *font)
 			cc = fuget1(p);
 			tfm = fuget3(p);
 		}
+		if (cc < 0 || cc > 65536) {
+			/* TeX engines do not support char codes bigger than 65535 */
+			mdvi_error(_("(vf) %s: unexpected character %d\n"),
+				   font->fontname, cc);
+			goto error;
+		}
 		if(loc < 0 || cc < loc)
 			loc = cc;
 		if(hic < 0 || cc > hic)