sprompt.c

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/*-------------------------------------------------------------------------
 *
 * sprompt.c
 *    simple_prompt() routine
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/port/sprompt.c
 *
 *-------------------------------------------------------------------------
 */
#include "c.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)
 * destination: buffer in which to store result
 * destlen:     allocated length of destination
 * echo:        Set to false if you want to hide what is entered (for passwords)
 *
 * The input (without trailing newline) is returned in the destination buffer,
 * with a '\0' appended.
 */
void
simple_prompt(const char *prompt, char *destination, size_t destlen, bool echo)
{
    int         length;
    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);
    }

    if (fgets(destination, destlen, termin) == NULL)
        destination[0] = '\0';

    length = strlen(destination);
    if (length > 0 && destination[length - 1] != '\n')
    {
        /* eat rest of the line */
        char        buf[128];
        int         buflen;

        do
        {
            if (fgets(buf, sizeof(buf), termin) == NULL)
                break;
            buflen = strlen(buf);
        } while (buflen > 0 && buf[buflen - 1] != '\n');
    }

    /* strip trailing newline, including \r in case we're on Windows */
    while (length > 0 &&
           (destination[length - 1] == '\n' ||
            destination[length - 1] == '\r'))
        destination[--length] = '\0';

    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);
    }
}