C++: Add GVN.

Author: geoffw0

cpp/ql/src/Security/CWE/CWE-319/UseOfHttp.ql

@@ -12,6 +12,7 @@
 
 import cpp
 import semmle.code.cpp.dataflow.TaintTracking
+import semmle.code.cpp.valuenumbering.GlobalValueNumbering
 import DataFlow::PathGraph
 
 /**
@@ -61,7 +62,7 @@ class HttpStringToUrlOpenConfig extends TaintTracking::Configuration {
     // block taint starting at `strstr`, which is likely testing an existing URL, rather than constructing an HTTP URL.
     not exists(FunctionCall fc |
       fc.getTarget().getName() = ["strstr", "strcasestr"] and
-      fc.getAnArgument() = src.asExpr()
+      fc.getArgument(1) = globalValueNumber(src.asExpr()).getAnExpr()
     )
   }
 

cpp/ql/test/query-tests/Security/CWE/CWE-319/UseOfHttp/UseOfHttp.expected

@@ -7,8 +7,6 @@ edges
 | test.cpp:40:11:40:17 | access to array | test.cpp:11:26:11:28 | url |
 | test.cpp:46:18:46:26 | http:// | test.cpp:49:11:49:16 | buffer |
 | test.cpp:49:11:49:16 | buffer | test.cpp:11:26:11:28 | url |
-| test.cpp:93:28:93:36 | http:// | test.cpp:104:11:104:13 | ptr |
-| test.cpp:104:11:104:13 | ptr | test.cpp:11:26:11:28 | url |
 | test.cpp:110:21:110:40 | http://example.com | test.cpp:121:11:121:13 | ptr |
 | test.cpp:121:11:121:13 | ptr | test.cpp:11:26:11:28 | url |
 nodes
@@ -21,8 +19,6 @@ nodes
 | test.cpp:40:11:40:17 | access to array | semmle.label | access to array |
 | test.cpp:46:18:46:26 | http:// | semmle.label | http:// |
 | test.cpp:49:11:49:16 | buffer | semmle.label | buffer |
-| test.cpp:93:28:93:36 | http:// | semmle.label | http:// |
-| test.cpp:104:11:104:13 | ptr | semmle.label | ptr |
 | test.cpp:110:21:110:40 | http://example.com | semmle.label | http://example.com |
 | test.cpp:121:11:121:13 | ptr | semmle.label | ptr |
 subpaths
@@ -31,5 +27,4 @@ subpaths
 | test.cpp:35:23:35:42 | http://example.com | test.cpp:35:23:35:42 | http://example.com | test.cpp:15:30:15:32 | url | A URL may be constructed with the HTTP protocol. |
 | test.cpp:36:26:36:45 | http://example.com | test.cpp:36:26:36:45 | http://example.com | test.cpp:15:30:15:32 | url | A URL may be constructed with the HTTP protocol. |
 | test.cpp:46:18:46:26 | http:// | test.cpp:46:18:46:26 | http:// | test.cpp:15:30:15:32 | url | A URL may be constructed with the HTTP protocol. |
-| test.cpp:93:28:93:36 | http:// | test.cpp:93:28:93:36 | http:// | test.cpp:15:30:15:32 | url | A URL may be constructed with the HTTP protocol. |
 | test.cpp:110:21:110:40 | http://example.com | test.cpp:110:21:110:40 | http://example.com | test.cpp:15:30:15:32 | url | A URL may be constructed with the HTTP protocol. |

cpp/ql/test/query-tests/Security/CWE/CWE-319/UseOfHttp/test.cpp

@@ -90,7 +90,7 @@ void test3(char *url)
 void test4(char *url)
 {
 	const char *https_string = "https://"; // GOOD (https)
-	const char *http_string = "http://"; // GOOD (we are not constructing the URL) [FALSE POSITIVE]
+	const char *http_string = "http://"; // GOOD (we are not constructing the URL)
 	char *ptr;
 
 	ptr = strstr(url, https_string);