niceSOFT/libssh | Gitverse

src/getpass.c
284 строки7 KB
Andreas Schneider
getpass: Use explicit_bzero()
04 сен 2018, 20:57
04 сен 2018, 20:57a6d5981
/*
 * getpass.c - platform independent getpass function.
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2011-2013    by Andreas Schneider <mail@cryptomilk.org>
 *
 * The SSH Library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * The SSH Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#include "config.h"

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libssh/priv.h>

/**
 * @internal
 *
 * @brief Get the password from the console.
 *
 * @param[in]  prompt   The prompt to display.
 *
 * @param[in]  buf      The buffer to fill.
 *
 * @param[in]  len      The length of the buffer.
 *
 * @param[in]  verify   Should the password be verified?
 *
 * @return              1 on success, 0 on error.
 */
static int ssh_gets(const char *prompt, char *buf, size_t len, int verify) {
    char *tmp;
    char *ptr = NULL;
    int ok = 0;

    tmp = calloc(1, len);
    if (tmp == NULL) {
        return 0;
    }

    /* read the password */
    while (!ok) {
        if (buf[0] != '\0') {
            fprintf(stdout, "%s[%s] ", prompt, buf);
        } else {
            fprintf(stdout, "%s", prompt);
        }
        fflush(stdout);
        if (fgets(tmp, len, stdin) == NULL) {
            free(tmp);
            return 0;
        }

        if ((ptr = strchr(tmp, '\n'))) {
            *ptr = '\0';
        }
        fprintf(stdout, "\n");

        if (*tmp) {
            strncpy(buf, tmp, len);
        }

        if (verify) {
            char *key_string;

            key_string = calloc(1, len);
            if (key_string == NULL) {
                break;
            }

            fprintf(stdout, "\nVerifying, please re-enter. %s", prompt);
            fflush(stdout);
            if (! fgets(key_string, len, stdin)) {
                explicit_bzero(key_string, len);
                SAFE_FREE(key_string);
                clearerr(stdin);
                continue;
            }
            if ((ptr = strchr(key_string, '\n'))) {
                *ptr = '\0';
            }
            fprintf(stdout, "\n");
            if (strcmp(buf, key_string)) {
                printf("\n\07\07Mismatch - try again\n");
                explicit_bzero(key_string, len);
                SAFE_FREE(key_string);
                fflush(stdout);
                continue;
            }
            explicit_bzero(key_string, len);
            SAFE_FREE(key_string);
        }
        ok = 1;
    }
    explicit_bzero(tmp, len);
    free(tmp);

    return ok;
}

#ifdef _WIN32
#include <windows.h>

int ssh_getpass(const char *prompt,
                char *buf,
                size_t len,
                int echo,
                int verify) {
    HANDLE h;
    DWORD mode = 0;
    int ok;

    /* fgets needs at least len - 1 */
    if (prompt == NULL || buf == NULL || len < 2) {
        return -1;
    }

    /* get stdin and mode */
    h = GetStdHandle(STD_INPUT_HANDLE);
    if (!GetConsoleMode(h, &mode)) {
        return -1;
    }

    /* disable echo */
    if (!echo) {
        if (!SetConsoleMode(h, mode & ~ENABLE_ECHO_INPUT)) {
            return -1;
        }
    }

    ok = ssh_gets(prompt, buf, len, verify);

    /* reset echo */
    SetConsoleMode(h, mode);

    if (!ok) {
        explicit_bzero(buf, len);
        return -1;
    }

    /* force termination */
    buf[len - 1] = '\0';

    return 0;
}

#else

#include <fcntl.h>
#ifdef HAVE_TERMIOS_H
#include <termios.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

/**
 * @ingroup libssh_misc
 *
 * @brief Get a password from the console.
 *
 * You should make sure that the buffer is an empty string!
 *
 * You can also use this function to ask for a username. Then you can fill the
 * buffer with the username and it is shows to the users. If the users just
 * presses enter the buffer will be untouched.
 *
 * @code
 *   char username[128];
 *
 *   snprintf(username, sizeof(username), "john");
 *
 *   ssh_getpass("Username:", username, sizeof(username), 1, 0);
 * @endcode
 *
 * The prompt will look like this:
 *
 *   Username: [john]
 *
 * If you press enter then john is used as the username, or you can type it in
 * to change it.
 *
 * @param[in]  prompt   The prompt to show to ask for the password.
 *
 * @param[out] buf    The buffer the password should be stored. It NEEDS to be
 *                      empty or filled out.
 *
 * @param[in]  len      The length of the buffer.
 *
 * @param[in]  echo     Should we echo what you type.
 *
 * @param[in]  verify   Should we ask for the password twice.
 *
 * @return              0 on success, -1 on error.
 */
int ssh_getpass(const char *prompt,
                char *buf,
                size_t len,
                int echo,
                int verify) {
    struct termios attr;
    struct termios old_attr;
    int ok = 0;
    int fd = -1;

    /* fgets needs at least len - 1 */
    if (prompt == NULL || buf == NULL || len < 2) {
        return -1;
    }

    if (isatty(STDIN_FILENO)) {
        ZERO_STRUCT(attr);
        ZERO_STRUCT(old_attr);

        /* get local terminal attributes */
        if (tcgetattr(STDIN_FILENO, &attr) < 0) {
            perror("tcgetattr");
            return -1;
        }

        /* save terminal attributes */
        memcpy(&old_attr, &attr, sizeof(attr));
        if((fd = fcntl(0, F_GETFL, 0)) < 0) {
            perror("fcntl");
            return -1;
        }

        /* disable echo */
        if (!echo) {
            attr.c_lflag &= ~(ECHO);
        }

        /* write attributes to terminal */
        if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &attr) < 0) {
            perror("tcsetattr");
            return -1;
        }
    }

    /* disable nonblocking I/O */
    if (fd & O_NDELAY) {
        fcntl(0, F_SETFL, fd & ~O_NDELAY);
    }

    ok = ssh_gets(prompt, buf, len, verify);

    if (isatty(STDIN_FILENO)) {
        /* reset terminal */
        tcsetattr(STDIN_FILENO, TCSANOW, &old_attr);
    }

    /* close fd */
    if (fd & O_NDELAY) {
        fcntl(0, F_SETFL, fd);
    }

    if (!ok) {
        explicit_bzero(buf, len);
        return -1;
    }

    /* force termination */
    buf[len - 1] = '\0';

    return 0;
}

#endif