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getpass.c revision 1.21 
      1 /*	$NetBSD: getpass.c,v 1.21 2012/04/13 02:20:50 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2012 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Christos Zoulas.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 #include <sys/cdefs.h>
     32 #if defined(LIBC_SCCS) && !defined(lint)
     33 __RCSID("$NetBSD: getpass.c,v 1.21 2012/04/13 02:20:50 christos Exp $");
     34 #endif /* LIBC_SCCS and not lint */
     35 
     36 #include "namespace.h"
     37 
     38 #include <assert.h>
     39 #ifdef TEST
     40 #include <stdio.h>
     41 #endif
     42 #include <errno.h>
     43 #include <signal.h>
     44 #include <string.h>
     45 #include <paths.h>
     46 #include <stdbool.h>
     47 #include <stdlib.h>
     48 #include <termios.h>
     49 #include <unistd.h>
     50 #include <fcntl.h>
     51 
     52 #ifdef __weak_alias
     53 __weak_alias(getpassfd,_getpassfd)
     54 __weak_alias(getpass_r,_getpass_r)
     55 __weak_alias(getpass,_getpass)
     56 #endif
     57 
     58 /*
     59  * Notes:
     60  *	- There is no getpass_r in POSIX
     61  *	- Historically EOF is documented to be treated as EOL, we provide a
     62  *	  tunable for that GETPASS_FAIL_EOF to disable this.
     63  *	- Historically getpass ate extra characters silently, we provide
     64  *	  a tunable for that GETPASS_BUF_LIMIT to disable this.
     65  *	- Historically getpass "worked" by echoing characters when turning
     66  *	  off echo failed, we provide a tunable GETPASS_NEED_TTY to
     67  *	  disable this.
     68  *	- Some implementations say that on interrupt the program shall
     69  *	  receive an interrupt signal before the function returns. We
     70  *	  send all the tty signals before we return, but we don't expect
     71  *	  suspend to do something useful unless the caller calls us again.
     72  *	  We also provide a tunable to disable signal delivery
     73  *	  GETPASS_NO_SIGNAL.
     74  *	- GETPASS_NO_BEEP disables beeping.
     75  *	- GETPASS_ECHO_STAR will echo '*' for each character of the password
     76  *	- GETPASS_ECHO will echo the password (as pam likes it)
     77  */
     78 char *
     79 /*ARGSUSED*/
     80 getpassfd(const char *prompt, char *buf, size_t len, int fd[], int flags)
     81 {
     82 	struct termios gt;
     83 	char c;
     84 	int sig;
     85 	bool lnext, havetty, allocated;
     86 
     87 	_DIAGASSERT(prompt != NULL);
     88 
     89 	sig = 0;
     90 
     91 	allocated = buf == NULL;
     92 	if (tcgetattr(fd[0], &gt) == -1) {
     93 		havetty = false;
     94 		if (flags & GETPASS_NEED_TTY)
     95 			goto out;
     96 		memset(&gt, -1, sizeof(gt));
     97 	} else
     98 		havetty = true;
     99 
    100 
    101 	if (havetty) {
    102 		struct termios st = gt;
    103 
    104 		st.c_lflag &= ~(ECHO|ECHOK|ECHOE|ECHOKE|ECHOCTL|ISIG|ICANON);
    105 		st.c_cc[VMIN] = 1;
    106 		st.c_cc[VTIME] = 0;
    107 		if (tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &st) == -1)
    108 			goto out;
    109 	}
    110 
    111 	if (prompt != NULL) {
    112 		size_t plen = strlen(prompt);
    113 		(void)write(fd[1], prompt, plen);
    114 	}
    115 
    116 	if (allocated) {
    117 		len = 1024;
    118 		if ((buf = malloc(len)) == NULL)
    119 			goto restore;
    120 	}
    121 
    122 	c = '\1';
    123 	lnext = false;
    124 	for (size_t l = 0; c != '\0'; ) {
    125 		if (read(fd[0], &c, 1) != 1)
    126 			goto restore;
    127 
    128 #define beep() do \
    129 	if (flags & GETPASS_NO_BEEP) \
    130 		(void)write(fd[2], "\a", 1); \
    131 	while (/*CONSTCOND*/ 0)
    132 #define erase() (void)write(fd[1], "\b \b", 3)
    133 
    134 #define C(a, b) (gt.c_cc[(a)] == _POSIX_VDISABLE ? (b) : gt.c_cc[(a)])
    135 
    136 		if (lnext) {
    137 			lnext = false;
    138 			goto add;
    139 		}
    140 
    141 		/* Ignored */
    142 		if (c == C(VREPRINT, CTRL('r')) || c == C(VSTART, CTRL('q')) ||
    143 		    c == C(VSTOP, CTRL('s')) || c == C(VSTATUS, CTRL('t')) ||
    144 		    c == C(VDISCARD, CTRL('o')))
    145 			continue;
    146 
    147 		/* Literal next */
    148 		if (c == C(VLNEXT, CTRL('v'))) {
    149 			lnext = true;
    150 			continue;
    151 		}
    152 
    153 		/* Line or word kill, treat as reset */
    154 		if (c == C(VKILL, CTRL('u')) || c == C(VWERASE, CTRL('w'))) {
    155 			if (flags & (GETPASS_ECHO | GETPASS_ECHO_STAR)) {
    156 				while (l--)
    157 					erase();
    158 			}
    159 			l = 0;
    160 			continue;
    161 		}
    162 
    163 		/* Character erase */
    164 		if (c == C(VERASE, CTRL('h'))) {
    165 			if (l == 0)
    166 				beep();
    167 			else {
    168 				l--;
    169 				if (flags & (GETPASS_ECHO | GETPASS_ECHO_STAR))
    170 					erase();
    171 			}
    172 			continue;
    173 		}
    174 
    175 		/* tty signal characters */
    176 		if (c == C(VINTR, CTRL('c'))) {
    177 			sig = SIGINT;
    178 			goto out;
    179 		}
    180 		if (c == C(VQUIT, CTRL('\\'))) {
    181 			sig = SIGQUIT;
    182 			goto out;
    183 		}
    184 		if (c == C(VSUSP, CTRL('z')) || c == C(VDSUSP, CTRL('y'))) {
    185 			sig = SIGTSTP;
    186 			goto out;
    187 		}
    188 
    189 		/* EOF */
    190 		if (c == C(VEOF, CTRL('d')))  {
    191 			if (flags & GETPASS_FAIL_EOF) {
    192 				errno = ENODATA;
    193 				goto out;
    194 			} else {
    195 				c = '\0';
    196 				goto add;
    197 			}
    198 		}
    199 
    200 		/* End of line */
    201 		if (c == C(VEOL, CTRL('j')) || c == C(VEOL2, CTRL('l')))
    202 			c = '\0';
    203 add:
    204 		if (l >= len) {
    205 			if (allocated) {
    206 				char *b;
    207 				len += 1024;
    208 				b = realloc(buf, len);
    209 				if (b == NULL)
    210 					goto restore;
    211 				buf = b;
    212 			} else {
    213 				if (flags & GETPASS_BUF_LIMIT) {
    214 					beep();
    215 					continue;
    216 				}
    217 				if (c == '\0' && l > 0)
    218 					l--;
    219 				else
    220 					continue;
    221 			}
    222 		}
    223 		buf[l++] = c;
    224 		if (c) {
    225 			if (flags & GETPASS_ECHO_STAR)
    226 				(void)write(fd[1], "*", 1);
    227 			else if (flags & GETPASS_ECHO)
    228 				(void)write(fd[1], &c, 1);
    229 		}
    230 	}
    231 
    232 	if (havetty)
    233 		(void)tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &gt);
    234 	return buf;
    235 restore:
    236 	if (havetty) {
    237 		c = errno;
    238 		(void)tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &gt);
    239 		errno = c;
    240 	}
    241 out:
    242 	if (sig) {
    243 		if ((flags & GETPASS_NO_SIGNAL) == 0)
    244 			(void)raise(sig);
    245 		errno = EINTR;
    246 	}
    247 	memset(buf, 0, len);
    248 	if (allocated)
    249 		free(buf);
    250 	return NULL;
    251 }
    252 
    253 char *
    254 getpass_r(const char *prompt, char *buf, size_t len)
    255 {
    256 	bool opentty;
    257 	int fd[3];
    258 	char *rv;
    259 
    260 	/*
    261 	 * Try to use /dev/tty if possible; otherwise read from stdin and
    262 	 * write to stderr.
    263 	 */
    264 	if ((fd[0] = fd[1] = fd[2] = open(_PATH_TTY, O_RDWR)) == -1) {
    265 		opentty = false;
    266 		fd[0] = STDIN_FILENO;
    267 		fd[1] = fd[2] = STDERR_FILENO;
    268 	} else
    269 		opentty = true;
    270 
    271 	rv = getpassfd(prompt, buf, len, fd, 0);
    272 
    273 	if (opentty) {
    274 		int serrno = errno;
    275 		(void)close(fd[0]);
    276 		errno = serrno;
    277 	}
    278 	return rv;
    279 }
    280 
    281 char *
    282 getpass(const char *prompt)
    283 {
    284 	static char e[] = "";
    285 	static char *buf;
    286 	static long bufsiz;
    287 	char *rv;
    288 
    289 	/*
    290 	 * Strictly speaking we could double allocate here, if we get
    291 	 * called at the same time, but this function is not re-entrant
    292 	 * anyway and it is not supposed to work if called concurrently.
    293 	 */
    294 	if (buf == NULL) {
    295 		if ((bufsiz = sysconf(_SC_PASS_MAX)) == -1)
    296 			return e;
    297 		if ((buf = malloc((size_t)bufsiz)) == NULL)
    298 			return e;
    299 	}
    300 
    301 	if ((rv = getpass_r(prompt, buf, (size_t)bufsiz)) == NULL)
    302 		return e;
    303 
    304 	return rv;
    305 }
    306 
    307 #ifdef TEST
    308 int
    309 main(int argc, char *argv[])
    310 {
    311 	char buf[28];
    312 	int fd[3] = { 0, 1, 2 };
    313 	printf("[%s]\n", getpassfd("foo>", buf, sizeof(buf), fd,
    314 	    GETPASS_ECHO_STAR));
    315 	return 0;
    316 }
    317 #endif
    318