fixed possible bufferoverflow in get_next_char

malformed input to htmlentities/htmlspecialchars
with utf-8 encoding crashed the server

ex: htmlentities("\xfd...(30times)", ENT_NOQUOTES, "utf-8");

ext/standard/html.c

@@ -137,21 +137,38 @@ static const struct {
 	{ 0, NULL, 0, 0 }
 };
 	
+#define MB_RETURN { \
+			*newpos = pos;       \
+		  	mbseq[mbpos] = '\0'; \
+		  	*mbseqlen = mbpos;   \
+		  	return this_char; }
+					
+#define MB_WRITE(mbchar) { \
+			mbspace--;  \
+			if (mbspace == 0) {      \
+				MB_RETURN;           \
+			}                        \
+			mbseq[mbpos++] = (mbchar); }
 
 /* {{{ get_next_char
  */
 inline static unsigned short get_next_char(enum entity_charset charset,
-		unsigned char *str,
-		int *newpos,
-		unsigned char *mbseq,
-		int *mbseqlen
-)
+		unsigned char * str,
+		int * newpos,
+		unsigned char * mbseq,
+		int * mbseqlen)
 {
 	int pos = *newpos;
 	int mbpos = 0;
+	int mbspace = *mbseqlen;
 	unsigned short this_char = str[pos++];
 	
-	mbseq[mbpos++] = (unsigned char)this_char;
+	if (mbspace <= 0) {
+		*mbseqlen = 0;
+		return this_char;
+	}
+	
+	MB_WRITE((unsigned char)this_char);
 	
 	switch(charset)	{
 		case cs_utf_8:
@@ -232,7 +249,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					if (more)
 					{
 						this_char = str[pos++];
-						mbseq[mbpos++] = (unsigned char)this_char;
+						MB_WRITE((unsigned char)this_char);
 					}
 				} while(more);
 			}
@@ -250,7 +267,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					{
 						/* yes, this a wide char */
 						this_char <<= 8;
-						mbseq[mbpos++] = next_char;
+						MB_WRITE(next_char);
 						this_char |= next_char;
 						pos++;
 					}
@@ -271,7 +288,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					{
 						/* yes, this a wide char */
 						this_char <<= 8;
-						mbseq[mbpos++] = next_char;
+						MB_WRITE(next_char);
 						this_char |= next_char;
 						pos++;
 					}
@@ -289,7 +306,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					{
 						/* yes, this a jis kanji char */
 						this_char <<= 8;
-						mbseq[mbpos++] = next_char;
+						MB_WRITE(next_char);
 						this_char |= next_char;
 						pos++;
 					}
@@ -301,7 +318,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					{
 						/* JIS X 0201 kana */
 						this_char <<= 8;
-						mbseq[mbpos++] = next_char;
+						MB_WRITE(next_char);
 						this_char |= next_char;
 						pos++;
 					}
@@ -315,12 +332,13 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 					{
 						/* JIS X 0212 hojo-kanji */
 						this_char <<= 8;
-						mbseq[mbpos++] = next_char;
+						MB_WRITE(next_char);
 						this_char |= next_char;
+						pos++;
 						this_char <<= 8;
-						mbseq[mbpos++] = next2_char;
+						MB_WRITE(next2_char);
 						this_char |= next2_char;
-						pos+=2;
+						pos++;
 					}
 					
 				}
@@ -331,10 +349,7 @@ inline static unsigned short get_next_char(enum entity_charset charset,
 				break;
 			}
 	}
-	*newpos = pos;
-	mbseq[mbpos] = '\0';
-	*mbseqlen = mbpos;
-	return this_char;
+	MB_RETURN;
 }
 /* }}} */
 
@@ -489,8 +504,8 @@ PHPAPI char *php_escape_html_entities(unsigned char *old, int oldlen, int *newle
 
 	i = 0;
 	while (i < oldlen) {
-		int mbseqlen;
 		unsigned char mbsequence[16];	/* allow up to 15 characters in a multibyte sequence */
+		int mbseqlen = sizeof(mbsequence);
 		unsigned short this_char = get_next_char(charset, old, &i, mbsequence, &mbseqlen);
 
 		matches_map = 0;