Fix bug #77380 (Global out of bounds read in xmlrpc base64 code)

(cherry picked from commit 1cc2182bcc)

NEWS

@@ -72,6 +72,7 @@ PHP                                                                        NEWS
 
 - Xmlrpc:
   . Fixed bug #77242 (heap out of bounds read in xmlrpc_decode()). (cmb)
+  . Fixed bug #77380 (Global out of bounds read in xmlrpc base64 code). (Stas)
 
 06 Dec 2018, PHP 7.3.0
 

ext/xmlrpc/libxmlrpc/base64.c

@@ -74,7 +74,7 @@ void base64_encode_xmlrpc(struct buffer_st *b, const char *source, int length)
 
   while (!hiteof) {
     unsigned char igroup[3], ogroup[4];
-    int c, n;
+	int c, n;
 
     igroup[0] = igroup[1] = igroup[2] = 0;
     for (n = 0; n < 3; n++) {
@@ -166,7 +166,7 @@ void base64_decode_xmlrpc(struct buffer_st *bfr, const char *source, int length)
 		return;
 	    }
 
-	    if (dtable[c] & 0x80) {
+	    if (dtable[(unsigned char)c] & 0x80) {
 	      /*
 	      fprintf(stderr, "Offset %i length %i\n", offset, length);
 	      fprintf(stderr, "character '%c:%x:%c' in input file.\n", c, c, dtable[c]);

ext/xmlrpc/tests/bug77380.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Bug #77380 (Global out of bounds read in xmlrpc base64 code)
+--SKIPIF--
+<?php
+if (!extension_loaded("xmlrpc")) print "skip";
+?>
+--FILE--
+<?php
+var_dump(xmlrpc_decode(base64_decode("PGJhc2U2ND7CkzwvYmFzZTY0Pgo=")));
+?>
+--EXPECT--
+object(stdClass)#1 (2) {
+  ["scalar"]=>
+  string(0) ""
+  ["xmlrpc_type"]=>
+  string(6) "base64"
+}