[clang] [clang][analyzer] Add checker 'security.SetgidSetuidOrder' (PR #91445)

[Balázs Kéri via cfe-commits]

================
@@ -0,0 +1,185 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,security.SetgidSetuidOrder -verify %s
+
+typedef int uid_t;
+typedef int gid_t;
+
+int setuid(uid_t);
+int setgid(gid_t);
+int seteuid(uid_t);
+int setegid(gid_t);
+int setreuid(uid_t, uid_t);
+int setregid(gid_t, gid_t);
+int setresuid(uid_t, uid_t, uid_t);
+int setresgid(gid_t, gid_t, gid_t);
+
+uid_t getuid();
+gid_t getgid();
+
+
+
+void correct_order() {
+  if (setgid(getgid()) == -1)
+    return;
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void incorrect_order() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1) // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void warn_at_second_time() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1) // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
+    return;
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1) // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
+    return;
+}
+
+uid_t f_uid();
+gid_t f_gid();
+
+void setuid_other() {
+  if (setuid(f_uid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setgid_other() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(f_gid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setuid_other_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setuid(f_uid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setgid_with_getuid() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setgid(getuid()) == -1)
+    return;
+}
+
+void setuid_with_getgid() {
+  if (setuid(getgid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+int f_setuid() {
+  return setuid(getuid());
+}
+
+int f_setgid() {
+  return setgid(getgid()); // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
+}
+
+void function_calls() {
+  if (f_setuid() == -1)
+    return;
+  if (f_setgid() == -1)
+    return;
+}
+
+void seteuid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (seteuid(getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setegid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setegid(getgid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setreuid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setreuid(getuid(), getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setregid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setregid(getgid(), getgid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setresuid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setresuid(getuid(), getuid(), getuid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void setresgid_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  if (setresgid(getgid(), getgid(), getgid()) == -1)
+    return;
+  if (setgid(getgid()) == -1)
+    return;
+}
+
+void other_system_function_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  gid_t g = getgid();
+  if (setgid(getgid()) == -1) // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
+    return;
+}
+
+void f_extern();
+
+void other_unknown_function_between() {
+  if (setuid(getuid()) == -1)
+    return;
+  f_extern();
+  if (setgid(getgid()) == -1) // expected-warning{{A 'setgid(getgid())' call following a 'setuid(getuid())' call is likely to fail}}
----------------
balazske wrote:

This was a question for me to filter out this case from warning generation. But it is likely that if the extern function calls the `setgid(getgid())` there should be not a next call to this again.

https://github.com/llvm/llvm-project/pull/91445