[analyzer] Make socket accept() propagate taint (#66074)

This allows to track taint on real code from `socket()`
to reading into a buffer using `recv()`.

#66074

Author: steakhal

clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp

@@ -621,6 +621,7 @@ void GenericTaintChecker::initTaintRules(CheckerContext &C) const {
       {{{"getlogin_r"}}, TR::Source({{0}})},
 
       // Props
+      {{{"accept"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
       {{{"atoi"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
       {{{"atol"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
       {{{"atoll"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},

clang/test/Analysis/taint-generic.c

@@ -544,6 +544,10 @@ void testFread(const char *fname, int *buffer, size_t size, size_t count) {
 }
 
 ssize_t recv(int sockfd, void *buf, size_t len, int flags);
+int accept(int fd, struct sockaddr *addr, socklen_t *addrlen);
+int bind(int fd, const struct sockaddr *addr, socklen_t addrlen);
+int listen(int fd, int backlog);
+
 void testRecv(int *buf, size_t len, int flags) {
   int fd;
   scanf("%d", &fd); // fake a tainted a file descriptor
@@ -1107,3 +1111,10 @@ void testProctitle2(char *real_argv[]) {
   setproctitle_init(1, argv, 0);         // expected-warning {{Untrusted data is passed to a user-defined sink}}
   setproctitle_init(1, real_argv, argv); // expected-warning {{Untrusted data is passed to a user-defined sink}}
 }
+
+void testAcceptPropagates() {
+  int listenSocket = socket(2, 1, 6);
+  clang_analyzer_isTainted_int(listenSocket); // expected-warning {{YES}}
+  int acceptSocket = accept(listenSocket, 0, 0);
+  clang_analyzer_isTainted_int(acceptSocket); // expected-warning {{YES}}
+}