Unix: harden OpenBSD doas authentication startup

Keep OpenBSD doas stderr on the private authentication PTY because doas requires stderr to be a terminal while prompting. Capture authentication-terminal diagnostics, strip prompts from user-facing errors, and fail promptly on explicit authentication denial. Wait for actual prompt bytes before sending the password so OpenBSD PTY POLLIN|POLLHUP before slave open cannot race with readpassphrase terminal flushing.
2026-06-09 21:22:41 +00:00 · 2026-06-30 11:03:54 +09:00
parent 409d349856
commit 5381c1b365
1 changed files with 312 additions and 23 deletions
@@ -211,7 +211,7 @@ namespace VeraCrypt
 		}
 	}

-	static void AttachDoasAuthTerminal (const string &slavePath)
+	static void AttachDoasAuthTerminal (const string &slavePath, bool keepStderrOnTerminal)
 	{
 		throw_sys_if (setsid () == -1);
 #ifdef O_CLOEXEC
@@ -253,7 +253,34 @@ namespace VeraCrypt
 			throw SystemException (SRC_POS, "Failed to set doas authentication terminal as controlling terminal");
 		}
 #endif
-		close (ttyFd);
+#ifdef TC_OPENBSD
+		if (tcsetpgrp (ttyFd, getpgrp()) == -1)
+		{
+			int err = errno;
+			close (ttyFd);
+			errno = err;
+			throw SystemException (SRC_POS, "Failed to set doas authentication terminal foreground process group");
+		}
+#else
+		tcsetpgrp (ttyFd, getpgrp());
+#endif
+		bool ttyFdKeptOnStderr = keepStderrOnTerminal && ttyFd == STDERR_FILENO;
+		if (keepStderrOnTerminal)
+		{
+			try
+			{
+				DupToStandardFd (ttyFd, STDERR_FILENO);
+			}
+			catch (...)
+			{
+				if (!ttyFdKeptOnStderr)
+					close (ttyFd);
+				throw;
+			}
+		}
+
+		if (!ttyFdKeptOnStderr)
+			close (ttyFd);
 	}

 	static void ReapChildProcessAsync (int pid)
@@ -334,6 +361,115 @@ namespace VeraCrypt
 		return string (errOutput.begin(), errOutput.end());
 	}

+	static string NormalizeTerminalOutput (const string &terminalOutput)
+	{
+		string normalized;
+		bool previousNewline = false;
+
+		for (size_t i = 0; i < terminalOutput.size(); ++i)
+		{
+			char c = terminalOutput[i];
+			if (c == '\r')
+			{
+				if (i + 1 < terminalOutput.size() && terminalOutput[i + 1] == '\n')
+					continue;
+				c = '\n';
+			}
+
+			if (c == '\n')
+			{
+				if (previousNewline)
+					continue;
+				previousNewline = true;
+			}
+			else
+				previousNewline = false;
+
+			normalized += c;
+		}
+
+		while (!normalized.empty() && normalized[0] == '\n')
+			normalized.erase (0, 1);
+		while (!normalized.empty() && normalized[normalized.size() - 1] == '\n')
+			normalized.erase (normalized.size() - 1);
+
+		return normalized;
+	}
+
+	static bool StringEndsWith (const string &str, const string &suffix)
+	{
+		return str.size() >= suffix.size() && str.compare (str.size() - suffix.size(), suffix.size(), suffix) == 0;
+	}
+
+	static string TrimTerminalLine (const string &line)
+	{
+		size_t first = line.find_first_not_of (" \t");
+		if (first == string::npos)
+			return string();
+
+		size_t last = line.find_last_not_of (" \t");
+		return line.substr (first, last - first + 1);
+	}
+
+	static bool IsDoasPasswordPromptLine (const string &line)
+	{
+		string trimmed = TrimTerminalLine (line);
+		return trimmed.find ("doas (") == 0 && StringEndsWith (trimmed, " password:");
+	}
+
+	static string NormalizeDoasAuthTerminalOutput (const string &terminalOutput)
+	{
+		string normalized = NormalizeTerminalOutput (terminalOutput);
+		string filtered;
+		size_t lineStart = 0;
+
+		while (lineStart <= normalized.size())
+		{
+			size_t lineEnd = normalized.find ('\n', lineStart);
+			string line = lineEnd == string::npos ? normalized.substr (lineStart) : normalized.substr (lineStart, lineEnd - lineStart);
+
+			if (!IsDoasPasswordPromptLine (line))
+			{
+				if (!filtered.empty())
+					filtered += '\n';
+				filtered += line;
+			}
+
+			if (lineEnd == string::npos)
+				break;
+
+			lineStart = lineEnd + 1;
+		}
+
+		return NormalizeTerminalOutput (filtered);
+	}
+
+	static bool DoasAuthenticationFailed (const vector <char> &authOutput)
+	{
+		return ErrorOutputToString (authOutput).find ("doas: Authentication failed") != string::npos;
+	}
+
+	static string CombineElevationErrorOutput (const vector <char> &errOutput, const vector <char> &authOutput)
+	{
+		string output = ErrorOutputToString (errOutput);
+		string authText = NormalizeDoasAuthTerminalOutput (ErrorOutputToString (authOutput));
+
+		if (!authText.empty())
+		{
+			if (!output.empty() && output[output.size() - 1] != '\n')
+				output += "\n";
+			output += authText;
+		}
+
+		return output;
+	}
+
+	static void ReadAvailableDataIfAny (int fd, vector <char> &output)
+	{
+		if (fd != -1)
+			ReadAvailableData (fd, output);
+	}
+
 	static void ThrowSerializedExceptionIfAny (const vector <char> &errOutput)
 	{
 		if (errOutput.empty())
@@ -354,8 +490,10 @@ namespace VeraCrypt
 			deserializedException->Throw();
 	}

-	static void WriteAllBestEffort (int fd, const char *data, size_t size)
+	static void WriteAllBestEffort (int fd, const char *data, size_t size, int retryTimeout = 0)
 	{
+		const int retryDelay = 50;
+		int retryTimeLeft = retryTimeout;
 		size_t offset = 0;
 		while (offset < size)
 		{
@@ -369,11 +507,97 @@ namespace VeraCrypt
 			if (bytesWritten == -1 && errno == EINTR)
 				continue;

+			if (bytesWritten == -1 && retryTimeLeft > 0 && (errno == EIO || errno == EAGAIN || errno == EWOULDBLOCK))
+			{
+				Thread::Sleep (retryDelay);
+				retryTimeLeft -= retryDelay;
+				continue;
+			}
+
 			return;
 		}
 	}

-	static void SendElevatedServiceSyncWithTimeout (shared_ptr <Stream> inputStream, int outputFd, int errorFd, int childPid, const string &helperName, int timeout)
+#ifdef TC_OPENBSD
+	static bool ReadDoasAuthTerminalPromptData (int fd, vector <char> &authOutput)
+	{
+		char buffer[256];
+		bool dataRead = false;
+
+		while (true)
+		{
+			ssize_t bytesRead = read (fd, buffer, sizeof (buffer));
+			if (bytesRead > 0)
+			{
+				authOutput.insert (authOutput.end(), buffer, buffer + bytesRead);
+				dataRead = true;
+				continue;
+			}
+
+			if (bytesRead == -1 && errno == EINTR)
+				continue;
+
+			if (bytesRead == -1 && (errno == EAGAIN || errno == EWOULDBLOCK))
+				return dataRead;
+
+			return dataRead;
+		}
+	}
+
+	static void WaitForDoasAuthTerminalPrompt (int fd, vector <char> &authOutput, int timeout)
+	{
+		const int pollInterval = 50;
+		int timeLeft = timeout;
+		int terminalFlags = fcntl (fd, F_GETFL, 0);
+		if (terminalFlags == -1)
+			return;
+
+		bool restoreFlags = (terminalFlags & O_NONBLOCK) == 0;
+		if (restoreFlags && fcntl (fd, F_SETFL, terminalFlags | O_NONBLOCK) == -1)
+			return;
+
+		while (timeLeft > 0)
+		{
+			struct pollfd pfd;
+			memset (&pfd, 0, sizeof (pfd));
+			pfd.fd = fd;
+			pfd.events = POLLIN;
+
+			int pollTimeout = timeLeft < pollInterval ? timeLeft : pollInterval;
+			int pollResult;
+			do
+			{
+				pollResult = poll (&pfd, 1, pollTimeout);
+			} while (pollResult == -1 && errno == EINTR);
+
+			if (pollResult == -1)
+				break;
+
+			if (pollResult == 0)
+			{
+				timeLeft -= pollTimeout;
+				continue;
+			}
+
+			if ((pfd.revents & POLLIN) && ReadDoasAuthTerminalPromptData (fd, authOutput))
+				break;
+
+			if (pfd.revents & (POLLERR | POLLNVAL))
+				break;
+
+			// On OpenBSD a PTY master reports POLLIN|POLLHUP before the
+			// slave is opened. A zero-byte read distinguishes that state from
+			// the real doas prompt; wait real time instead of spinning.
+			Thread::Sleep (pollTimeout);
+			timeLeft -= pollTimeout;
+		}
+
+		if (restoreFlags)
+			fcntl (fd, F_SETFL, terminalFlags);
+	}
+#endif
+
+	static void SendElevatedServiceSyncWithTimeout (shared_ptr <Stream> inputStream, int outputFd, int errorFd, int authFd, vector <char> authOutput, int childPid, const string &helperName, int timeout)
 	{
 		vector <char> errOutput;
 		uint8 sync[] = { 0, 0x11, 0x22 };
@@ -384,35 +608,71 @@ namespace VeraCrypt
 		}
 		catch (...)
 		{
-			ReadAvailableData (errorFd, errOutput);
+			ReadAvailableDataIfAny (errorFd, errOutput);
+			ReadAvailableDataIfAny (authFd, authOutput);
 			TerminateChildProcessAsync (childPid);
 			ThrowSerializedExceptionIfAny (errOutput);
-			throw ElevationFailed (SRC_POS, helperName, 1, ErrorOutputToString (errOutput));
+			throw ElevationFailed (SRC_POS, helperName, 1, CombineElevationErrorOutput (errOutput, authOutput));
 		}

 		const int pollInterval = 200;
 		int timeLeft = timeout;
+		bool errorFdActive = errorFd != -1;
+		bool authFdActive = authFd != -1;
 		while (timeLeft > 0)
 		{
-			struct pollfd fds[2];
+			struct pollfd fds[3];
 			memset (fds, 0, sizeof (fds));
 			fds[0].fd = outputFd;
 			fds[0].events = POLLIN;
-			fds[1].fd = errorFd;
-			fds[1].events = POLLIN;
+			nfds_t fdCount = 1;
+			nfds_t errorFdIndex = 0;
+			nfds_t authFdIndex = 0;
+			if (errorFdActive)
+			{
+				errorFdIndex = fdCount;
+				fds[fdCount].fd = errorFd;
+				fds[fdCount].events = POLLIN;
+				++fdCount;
+			}
+			if (authFdActive)
+			{
+				authFdIndex = fdCount;
+				fds[fdCount].fd = authFd;
+				fds[fdCount].events = POLLIN;
+				++fdCount;
+			}

 			int pollTimeout = timeLeft < pollInterval ? timeLeft : pollInterval;
 			int pollResult;
 			do
 			{
-				pollResult = poll (fds, array_capacity (fds), pollTimeout);
+				pollResult = poll (fds, fdCount, pollTimeout);
 			} while (pollResult == -1 && errno == EINTR);

 			throw_sys_if (pollResult == -1);
 			timeLeft -= pollTimeout;

-			if (fds[1].revents & (POLLIN | POLLHUP | POLLERR))
+			if (errorFdActive && (fds[errorFdIndex].revents & (POLLIN | POLLHUP | POLLERR)))
+			{
+				size_t previousErrOutputSize = errOutput.size();
 				ReadAvailableData (errorFd, errOutput);
+				if ((fds[errorFdIndex].revents & (POLLHUP | POLLERR)) && errOutput.size() == previousErrOutputSize)
+					errorFdActive = false;
+			}
+			if (authFdActive && (fds[authFdIndex].revents & (POLLIN | POLLHUP | POLLERR)))
+			{
+				size_t previousAuthOutputSize = authOutput.size();
+				ReadAvailableData (authFd, authOutput);
+				if ((fds[authFdIndex].revents & (POLLHUP | POLLERR)) && authOutput.size() == previousAuthOutputSize)
+					authFdActive = false;
+			}
+			if (DoasAuthenticationFailed (authOutput))
+			{
+				TerminateChildProcessAsync (childPid);
+				ThrowSerializedExceptionIfAny (errOutput);
+				throw ElevationFailed (SRC_POS, helperName, 1, CombineElevationErrorOutput (errOutput, authOutput));
+			}

 			if (fds[0].revents & POLLIN)
 			{
@@ -428,7 +688,7 @@ namespace VeraCrypt

 				TerminateChildProcessAsync (childPid);
 				ThrowSerializedExceptionIfAny (errOutput);
-				throw ElevationFailed (SRC_POS, helperName, 1, ErrorOutputToString (errOutput));
+				throw ElevationFailed (SRC_POS, helperName, 1, CombineElevationErrorOutput (errOutput, authOutput));
 			}

 			int status;
@@ -440,10 +700,11 @@ namespace VeraCrypt

 			if (waitRes == childPid)
 			{
-				ReadAvailableData (errorFd, errOutput);
+				ReadAvailableDataIfAny (errorFd, errOutput);
+				ReadAvailableDataIfAny (authFd, authOutput);
 				ThrowSerializedExceptionIfAny (errOutput);
 				int exitCode = WIFEXITED (status) ? WEXITSTATUS (status) : 1;
-				throw ElevationFailed (SRC_POS, helperName, exitCode, ErrorOutputToString (errOutput));
+				throw ElevationFailed (SRC_POS, helperName, exitCode, CombineElevationErrorOutput (errOutput, authOutput));
 			}

 			throw_sys_if (waitRes == -1);
@@ -452,13 +713,14 @@ namespace VeraCrypt
 			{
 				TerminateChildProcessAsync (childPid);
 				ThrowSerializedExceptionIfAny (errOutput);
-				throw ElevationFailed (SRC_POS, helperName, 1, ErrorOutputToString (errOutput));
+				throw ElevationFailed (SRC_POS, helperName, 1, CombineElevationErrorOutput (errOutput, authOutput));
 			}
 		}

-		ReadAvailableData (errorFd, errOutput);
+		ReadAvailableDataIfAny (errorFd, errOutput);
+		ReadAvailableDataIfAny (authFd, authOutput);
 		ThrowSerializedExceptionIfAny (errOutput);
-		string errorOutput = ErrorOutputToString (errOutput);
+		string errorOutput = CombineElevationErrorOutput (errOutput, authOutput);
 		if (errorOutput.empty())
 			errorOutput = "Timed out while waiting for the elevated VeraCrypt service to start";

@@ -1068,14 +1330,26 @@ namespace VeraCrypt
                        appPath = appImageEnv;
                    }
 #endif
-					if (privilegeHelper.IsDoas() && !useCallerDoasTerminal)
+					bool useDoasAuthTerminal = privilegeHelper.IsDoas() && !useCallerDoasTerminal;
+#ifdef TC_OPENBSD
+					// OpenBSD doas requires stderr to be a terminal while it
+					// prompts for the password. Keeping the private PTY slave
+					// on stderr satisfies that while stdin/stdout stay as the
+					// service pipes.
+					bool keepDoasStderrOnAuthTerminal = useDoasAuthTerminal;
+#else
+					bool keepDoasStderrOnAuthTerminal = false;
+#endif
+					if (useDoasAuthTerminal)
 					{
-						AttachDoasAuthTerminal (doasAuthTerminalPath);
+						AttachDoasAuthTerminal (doasAuthTerminalPath, keepDoasStderrOnAuthTerminal);
 					}
-					if (doasAuthTerminal != -1)
+					bool doasAuthTerminalReplacedByStderr = keepDoasStderrOnAuthTerminal && doasAuthTerminal == STDERR_FILENO;
+					if (doasAuthTerminal != -1 && !doasAuthTerminalReplacedByStderr)
 						close (doasAuthTerminal);

-					DupToStandardFd (errPipe.GetWriteFD(), STDERR_FILENO);
+					if (!keepDoasStderrOnAuthTerminal)
+						DupToStandardFd (errPipe.GetWriteFD(), STDERR_FILENO);
 					DupToStandardFd (inPipe->GetReadFD(), STDIN_FILENO);
 					DupToStandardFd (outPipe->GetWriteFD(), STDOUT_FILENO);

@@ -1131,6 +1405,7 @@ namespace VeraCrypt
 			Memory::Copy (&adminPassword.front(), request.AdminPassword.c_str(), request.AdminPassword.size());
 			adminPassword[request.AdminPassword.size()] = '\n';
 		}
+		vector <char> authOutput;

 #if defined(TC_LINUX )
 		Thread::Sleep (1000); // wait 1 second for the forked privilege helper to start
@@ -1142,7 +1417,10 @@ namespace VeraCrypt
 		else if (doasAuthTerminal != -1 && !doasNoPasswordAttempt)
 		{
 			// doas reads authentication from the controlling terminal, not stdin.
-			WriteAllBestEffort (doasAuthTerminal, &adminPassword.front(), adminPassword.size());
+#ifdef TC_OPENBSD
+			WaitForDoasAuthTerminalPrompt (doasAuthTerminal, authOutput, 2000);
+#endif
+			WriteAllBestEffort (doasAuthTerminal, &adminPassword.front(), adminPassword.size(), 2000);
 		}

 		burn (&adminPassword.front(), adminPassword.size());
@@ -1154,8 +1432,19 @@ namespace VeraCrypt
 		{
 			shared_ptr <Stream> inputStream (new FileStream (serviceInputFd));
 			shared_ptr <Stream> outputStream (new FileStream (serviceOutputFd));
+			int authOutputFd = -1;

-			SendElevatedServiceSyncWithTimeout (inputStream, serviceOutputFd, errPipe.GetReadFD(), forkedPid, privilegeHelper.Name, timeout);
+#ifdef TC_OPENBSD
+			if (doasAuthTerminal != -1)
+			{
+				int authTerminalFlags = fcntl (doasAuthTerminal, F_GETFL, 0);
+				throw_sys_if (authTerminalFlags == -1);
+				throw_sys_if (fcntl (doasAuthTerminal, F_SETFL, authTerminalFlags | O_NONBLOCK) == -1);
+				authOutputFd = doasAuthTerminal;
+			}
+#endif
+
+			SendElevatedServiceSyncWithTimeout (inputStream, serviceOutputFd, errPipe.GetReadFD(), authOutputFd, authOutput, forkedPid, privilegeHelper.Name, timeout);
 			throw_sys_if (fcntl (serviceOutputFd, F_SETFL, 0) == -1);
 			ReapChildProcessAsync (forkedPid);