Windows: Make pg_ctl reliably detect service status

alvherre · alvherre · commit 744d01c9a188 · 2016-01-07T11:59:08.000-03:00
pg_ctl is using isatty() to verify whether the process is running in a
terminal, and if not it sends its output to Windows' Event Log ... which
does the wrong thing when the output has been redirected to a pipe, as
reported in bug #13592.

To fix, make pg_ctl use the code we already have to detect service-ness:
in the master branch, move src/backend/port/win32/security.c to src/port
(with suitable tweaks so that it runs properly in backend and frontend
environments); pg_ctl already has access to pgport so it Just Works.  In
older branches, that's likely to cause trouble, so instead duplicate the
required code in pg_ctl.c.

Author: Michael Paquier
Bug report and diagnosis: Egon Kocjan
Backpatch: all supported branches
diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
@@ -149,6 +149,10 @@ static void WINAPI pgwin32_ServiceHandler(DWORD);
 static void WINAPI pgwin32_ServiceMain(DWORD, LPTSTR *);
 static void pgwin32_doRunAsService(void);
 static int	CreateRestrictedProcess(char *cmd, PROCESS_INFORMATION *processInfo, bool as_service);
+static bool pgwin32_get_dynamic_tokeninfo(HANDLE token,
+							  TOKEN_INFORMATION_CLASS class,
+							  char **InfoBuffer, char *errbuf, int errsize);
+static int pgwin32_is_service(void);
 #endif
 
 static pgpid_t get_pgpid(bool is_status_request);
@@ -216,7 +220,7 @@ write_stderr(const char *fmt,...)
 	 * On Win32, we print to stderr if running on a console, or write to
 	 * eventlog if running as a service
 	 */
-	if (!isatty(fileno(stderr)))	/* Running as a service */
+	if (!pgwin32_is_service())	/* Running as a service */
 	{
 		char		errbuf[2048];		/* Arbitrary size? */
 
@@ -1689,6 +1693,160 @@ pgwin32_doRunAsService(void)
 	}
 }
 
+/*
+ * Call GetTokenInformation() on a token and return a dynamically sized
+ * buffer with the information in it. This buffer must be free():d by
+ * the calling function!
+ */
+static bool
+pgwin32_get_dynamic_tokeninfo(HANDLE token, TOKEN_INFORMATION_CLASS class,
+							  char **InfoBuffer, char *errbuf, int errsize)
+{
+	DWORD		InfoBufferSize;
+
+	if (GetTokenInformation(token, class, NULL, 0, &InfoBufferSize))
+	{
+		snprintf(errbuf, errsize, "could not get token information: got zero size\n");
+		return false;
+	}
+
+	if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+	{
+		snprintf(errbuf, errsize, "could not get token information: error code %lu\n",
+				 GetLastError());
+		return false;
+	}
+
+	*InfoBuffer = malloc(InfoBufferSize);
+	if (*InfoBuffer == NULL)
+	{
+		snprintf(errbuf, errsize, "could not allocate %d bytes for token information\n",
+				 (int) InfoBufferSize);
+		return false;
+	}
+
+	if (!GetTokenInformation(token, class, *InfoBuffer,
+							 InfoBufferSize, &InfoBufferSize))
+	{
+		snprintf(errbuf, errsize, "could not get token information: error code %lu\n",
+				 GetLastError());
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * We consider ourselves running as a service if one of the following is
+ * true:
+ *
+ * 1) We are running as Local System (only used by services)
+ * 2) Our token contains SECURITY_SERVICE_RID (automatically added to the
+ *	  process token by the SCM when starting a service)
+ *
+ * Return values:
+ *	 0 = Not service
+ *	 1 = Service
+ *	-1 = Error
+ *
+ * Note: we can't report errors via write_stderr (because that calls this)
+ * We are therefore reduced to writing directly on stderr, which sucks, but
+ * we have few alternatives.
+ */
+int
+pgwin32_is_service(void)
+{
+	static int	_is_service = -1;
+	HANDLE		AccessToken;
+	char	   *InfoBuffer = NULL;
+	char		errbuf[256];
+	PTOKEN_GROUPS Groups;
+	PTOKEN_USER User;
+	PSID		ServiceSid;
+	PSID		LocalSystemSid;
+	SID_IDENTIFIER_AUTHORITY NtAuthority = {SECURITY_NT_AUTHORITY};
+	UINT		x;
+
+	/* Only check the first time */
+	if (_is_service != -1)
+		return _is_service;
+
+	if (!OpenProcessToken(GetCurrentProcess(), TOKEN_READ, &AccessToken))
+	{
+		fprintf(stderr, "could not open process token: error code %lu\n",
+				GetLastError());
+		return -1;
+	}
+
+	/* First check for local system */
+	if (!pgwin32_get_dynamic_tokeninfo(AccessToken, TokenUser, &InfoBuffer,
+									   errbuf, sizeof(errbuf)))
+	{
+		fprintf(stderr, "%s", errbuf);
+		return -1;
+	}
+
+	User = (PTOKEN_USER) InfoBuffer;
+
+	if (!AllocateAndInitializeSid(&NtAuthority, 1,
+							  SECURITY_LOCAL_SYSTEM_RID, 0, 0, 0, 0, 0, 0, 0,
+								  &LocalSystemSid))
+	{
+		fprintf(stderr, "could not get SID for local system account\n");
+		CloseHandle(AccessToken);
+		return -1;
+	}
+
+	if (EqualSid(LocalSystemSid, User->User.Sid))
+	{
+		FreeSid(LocalSystemSid);
+		free(InfoBuffer);
+		CloseHandle(AccessToken);
+		_is_service = 1;
+		return _is_service;
+	}
+
+	FreeSid(LocalSystemSid);
+	free(InfoBuffer);
+
+	/* Now check for group SID */
+	if (!pgwin32_get_dynamic_tokeninfo(AccessToken, TokenGroups, &InfoBuffer,
+									   errbuf, sizeof(errbuf)))
+	{
+		fprintf(stderr, "%s", errbuf);
+		return -1;
+	}
+
+	Groups = (PTOKEN_GROUPS) InfoBuffer;
+
+	if (!AllocateAndInitializeSid(&NtAuthority, 1,
+								  SECURITY_SERVICE_RID, 0, 0, 0, 0, 0, 0, 0,
+								  &ServiceSid))
+	{
+		fprintf(stderr, "could not get SID for service group\n");
+		free(InfoBuffer);
+		CloseHandle(AccessToken);
+		return -1;
+	}
+
+	_is_service = 0;
+	for (x = 0; x < Groups->GroupCount; x++)
+	{
+		if (EqualSid(ServiceSid, Groups->Groups[x].Sid))
+		{
+			_is_service = 1;
+			break;
+		}
+	}
+
+	free(InfoBuffer);
+	FreeSid(ServiceSid);
+
+	CloseHandle(AccessToken);
+
+	return _is_service;
+}
+
 
 /*
  * Mingw headers are incomplete, and so are the libraries. So we have to load
