src/common/sprompt.c

/*-------------------------------------------------------------------------
 *
 * sprompt.c
 *	  simple_prompt() routine
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/common/sprompt.c
 *
 *-------------------------------------------------------------------------
 */
#include "c.h"

#include "common/fe_memutils.h"
#include "common/string.h"

#ifdef HAVE_TERMIOS_H
#include <termios.h>
#endif


/*
 * simple_prompt
 *
 * Generalized function especially intended for reading in usernames and
 * passwords interactively.  Reads from /dev/tty or stdin/stderr.
 *
 * prompt:		The prompt to print, or NULL if none (automatically localized)
 * echo:		Set to false if you want to hide what is entered (for passwords)
 *
 * The input (without trailing newline) is returned as a malloc'd string.
 * Caller is responsible for freeing it when done.
 */
char *
simple_prompt(const char *prompt, bool echo)
{
	char	   *result;
	FILE	   *termin,
			   *termout;
#if defined(HAVE_TERMIOS_H)
	struct termios t_orig,
				t;
#elif defined(WIN32)
	HANDLE		t = NULL;
	DWORD		t_orig = 0;
#endif

#ifdef WIN32

	/*
	 * A Windows console has an "input code page" and an "output code page";
	 * these usually match each other, but they rarely match the "Windows ANSI
	 * code page" defined at system boot and expected of "char *" arguments to
	 * Windows API functions.  The Microsoft CRT write() implementation
	 * automatically converts text between these code pages when writing to a
	 * console.  To identify such file descriptors, it calls GetConsoleMode()
	 * on the underlying HANDLE, which in turn requires GENERIC_READ access on
	 * the HANDLE.  Opening termout in mode "w+" allows that detection to
	 * succeed.  Otherwise, write() would not recognize the descriptor as a
	 * console, and non-ASCII characters would display incorrectly.
	 *
	 * XXX fgets() still receives text in the console's input code page.  This
	 * makes non-ASCII credentials unportable.
	 *
	 * Unintuitively, we also open termin in mode "w+", even though we only
	 * read it; that's needed for SetConsoleMode() to succeed.
	 */
	termin = fopen("CONIN$", "w+");
	termout = fopen("CONOUT$", "w+");
#else

	/*
	 * Do not try to collapse these into one "w+" mode file. Doesn't work on
	 * some platforms (eg, HPUX 10.20).
	 */
	termin = fopen("/dev/tty", "r");
	termout = fopen("/dev/tty", "w");
#endif
	if (!termin || !termout
#ifdef WIN32

	/*
	 * Direct console I/O does not work from the MSYS 1.0.10 console.  Writes
	 * reach nowhere user-visible; reads block indefinitely.  XXX This affects
	 * most Windows terminal environments, including rxvt, mintty, Cygwin
	 * xterm, Cygwin sshd, and PowerShell ISE.  Switch to a more-generic test.
	 */
		|| (getenv("OSTYPE") && strcmp(getenv("OSTYPE"), "msys") == 0)
#endif
		)
	{
		if (termin)
			fclose(termin);
		if (termout)
			fclose(termout);
		termin = stdin;
		termout = stderr;
	}

	if (!echo)
	{
#if defined(HAVE_TERMIOS_H)
		/* disable echo via tcgetattr/tcsetattr */
		tcgetattr(fileno(termin), &t);
		t_orig = t;
		t.c_lflag &= ~ECHO;
		tcsetattr(fileno(termin), TCSAFLUSH, &t);
#elif defined(WIN32)
		/* need the file's HANDLE to turn echo off */
		t = (HANDLE) _get_osfhandle(_fileno(termin));

		/* save the old configuration first */
		GetConsoleMode(t, &t_orig);

		/* set to the new mode */
		SetConsoleMode(t, ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
#endif
	}

	if (prompt)
	{
		fputs(_(prompt), termout);
		fflush(termout);
	}

	result = pg_get_line(termin);

	/* If we failed to read anything, just return an empty string */
	if (result == NULL)
		result = pg_strdup("");

	/* strip trailing newline, including \r in case we're on Windows */
	(void) pg_strip_crlf(result);

	if (!echo)
	{
		/* restore previous echo behavior, then echo \n */
#if defined(HAVE_TERMIOS_H)
		tcsetattr(fileno(termin), TCSAFLUSH, &t_orig);
		fputs("\n", termout);
		fflush(termout);
#elif defined(WIN32)
		SetConsoleMode(t, t_orig);
		fputs("\n", termout);
		fflush(termout);
#endif
	}

	if (termin != stdin)
	{
		fclose(termin);
		fclose(termout);
	}

	return result;
}