Run pg_upgrade and pg_resetxlog with restricted token on Windows

As with initdb these programs need to run with a restricted token, and
if they don't pg_upgrade will fail when run as a user with Adminstrator
privileges.

Backpatch to all live branches. On the development branch the code is
reorganized so that the restricted token code is now in a single
location. On the stable bramches a less invasive change is made by
simply copying the relevant code to pg_upgrade.c and pg_resetxlog.c.

Patches and bug report from Muhammad Asif Naeem, reviewed by Michael
Paquier, slightly edited by me.

src/common/Makefile

@@ -26,7 +26,7 @@ LIBS += $(PTHREAD_LIBS)
 OBJS_COMMON = exec.o pg_crc.o pg_lzcompress.o pgfnames.o psprintf.o relpath.o \
 	rmtree.o string.o username.o wait_error.o
 
-OBJS_FRONTEND = $(OBJS_COMMON) fe_memutils.o
+OBJS_FRONTEND = $(OBJS_COMMON) fe_memutils.o restricted_token.o
 
 OBJS_SRV = $(OBJS_COMMON:%.o=%_srv.o)
 

src/common/restricted_token.c

@@ -0,0 +1,193 @@
+/*-------------------------------------------------------------------------
+ *
+ * restricted_token.c
+ *		helper routine to ensure restricted token on Windows
+ *
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/common/restricted_token.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#error "This file is not expected to be compiled for backend code"
+#endif
+
+#include "postgres_fe.h"
+
+#include "common/restricted_token.h"
+
+#ifdef WIN32
+
+/* internal vars */
+char	*restrict_env;
+
+typedef BOOL (WINAPI * __CreateRestrictedToken) (HANDLE, DWORD, DWORD, PSID_AND_ATTRIBUTES, DWORD, PLUID_AND_ATTRIBUTES, DWORD, PSID_AND_ATTRIBUTES, PHANDLE);
+
+/* Windows API define missing from some versions of MingW headers */
+#ifndef  DISABLE_MAX_PRIVILEGE
+#define DISABLE_MAX_PRIVILEGE	0x1
+#endif
+
+/*
+ * Create a restricted token and execute the specified process with it.
+ *
+ * Returns restricted token on success and 0 on failure.
+ *
+ * On NT4, or any other system not containing the required functions, will
+ * NOT execute anything.
+ */
+HANDLE
+CreateRestrictedProcess(char *cmd, PROCESS_INFORMATION *processInfo, const char *progname)
+{
+	BOOL		b;
+	STARTUPINFO si;
+	HANDLE		origToken;
+	HANDLE		restrictedToken;
+	SID_IDENTIFIER_AUTHORITY NtAuthority = {SECURITY_NT_AUTHORITY};
+	SID_AND_ATTRIBUTES dropSids[2];
+	__CreateRestrictedToken _CreateRestrictedToken = NULL;
+	HANDLE		Advapi32Handle;
+
+	ZeroMemory(&si, sizeof(si));
+	si.cb = sizeof(si);
+
+	Advapi32Handle = LoadLibrary("ADVAPI32.DLL");
+	if (Advapi32Handle != NULL)
+	{
+		_CreateRestrictedToken = (__CreateRestrictedToken) GetProcAddress(Advapi32Handle, "CreateRestrictedToken");
+	}
+
+	if (_CreateRestrictedToken == NULL)
+	{
+		fprintf(stderr, _("%s: WARNING: cannot create restricted tokens on this platform\n"), progname);
+		if (Advapi32Handle != NULL)
+			FreeLibrary(Advapi32Handle);
+		return 0;
+	}
+
+	/* Open the current token to use as a base for the restricted one */
+	if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &origToken))
+	{
+		fprintf(stderr, _("%s: could not open process token: error code %lu\n"), progname, GetLastError());
+		return 0;
+	}
+
+	/* Allocate list of SIDs to remove */
+	ZeroMemory(&dropSids, sizeof(dropSids));
+	if (!AllocateAndInitializeSid(&NtAuthority, 2,
+		 SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS, 0, 0, 0, 0, 0,
+								  0, &dropSids[0].Sid) ||
+		!AllocateAndInitializeSid(&NtAuthority, 2,
+	SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_POWER_USERS, 0, 0, 0, 0, 0,
+								  0, &dropSids[1].Sid))
+	{
+		fprintf(stderr, _("%s: could not allocate SIDs: error code %lu\n"),
+				progname, GetLastError());
+		return 0;
+	}
+
+	b = _CreateRestrictedToken(origToken,
+							   DISABLE_MAX_PRIVILEGE,
+							   sizeof(dropSids) / sizeof(dropSids[0]),
+							   dropSids,
+							   0, NULL,
+							   0, NULL,
+							   &restrictedToken);
+
+	FreeSid(dropSids[1].Sid);
+	FreeSid(dropSids[0].Sid);
+	CloseHandle(origToken);
+	FreeLibrary(Advapi32Handle);
+
+	if (!b)
+	{
+		fprintf(stderr, _("%s: could not create restricted token: error code %lu\n"),
+				progname, GetLastError());
+		return 0;
+	}
+
+#ifndef __CYGWIN__
+	AddUserToTokenDacl(restrictedToken);
+#endif
+
+	if (!CreateProcessAsUser(restrictedToken,
+							 NULL,
+							 cmd,
+							 NULL,
+							 NULL,
+							 TRUE,
+							 CREATE_SUSPENDED,
+							 NULL,
+							 NULL,
+							 &si,
+							 processInfo))
+
+	{
+		fprintf(stderr, _("%s: could not start process for command \"%s\": error code %lu\n"), progname, cmd, GetLastError());
+		return 0;
+	}
+
+	ResumeThread(processInfo->hThread);
+	return restrictedToken;
+}
+#endif
+
+/*
+ * On Windows make sure that we are running with a restricted token,
+ * On other platforms do nothing.
+ */
+void
+get_restricted_token(const char *progname)
+{
+#ifdef WIN32
+	HANDLE		restrictedToken;
+
+	/*
+	 * Before we execute another program, make sure that we are running with a
+	 * restricted token. If not, re-execute ourselves with one.
+	 */
+
+	if ((restrict_env = getenv("PG_RESTRICT_EXEC")) == NULL
+		|| strcmp(restrict_env, "1") != 0)
+	{
+		PROCESS_INFORMATION pi;
+		char	   *cmdline;
+
+		ZeroMemory(&pi, sizeof(pi));
+
+		cmdline = pg_strdup(GetCommandLine());
+
+		putenv("PG_RESTRICT_EXEC=1");
+
+		if ((restrictedToken = CreateRestrictedProcess(cmdline, &pi, progname)) == 0)
+		{
+			fprintf(stderr, _("%s: could not re-execute with restricted token: error code %lu\n"), progname, GetLastError());
+		}
+		else
+		{
+			/*
+			 * Successfully re-execed. Now wait for child process to capture
+			 * exitcode.
+			 */
+			DWORD		x;
+
+			CloseHandle(restrictedToken);
+			CloseHandle(pi.hThread);
+			WaitForSingleObject(pi.hProcess, INFINITE);
+
+			if (!GetExitCodeProcess(pi.hProcess, &x))
+			{
+				fprintf(stderr, _("%s: could not get exit code from subprocess: error code %lu\n"), progname, GetLastError());
+				exit(1);
+			}
+			exit(x);
+		}
+	}
+#endif
+}