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getpass.c revision 1.19 
      1 /*	$NetBSD: getpass.c,v 1.19 2012/04/12 22:07:44 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 1.19 2012/04/12 22:07:44 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 will echo the password (as pam likes it)
     76  */
     77 char *
     78 /*ARGSUSED*/
     79 getpassfd(const char *prompt, char *buf, size_t len, int fd[], int flags)
     80 {
     81 	struct termios gt;
     82 	char c;
     83 	int sig;
     84 	bool lnext, havetty, allocated;
     85 
     86 	_DIAGASSERT(prompt != NULL);
     87 
     88 	sig = 0;
     89 
     90 	allocated = buf == NULL;
     91 	if (tcgetattr(fd[0], &gt) == -1) {
     92 		havetty = false;
     93 		if (flags & GETPASS_NEED_TTY)
     94 			goto out;
     95 		memset(&gt, -1, sizeof(gt));
     96 	} else
     97 		havetty = true;
     98 
     99 
    100 	if (havetty) {
    101 		struct termios st = gt;
    102 
    103 		st.c_lflag &= ~(ECHO|ECHOK|ECHOE|ECHOKE|ECHOCTL|ISIG|ICANON);
    104 		st.c_cc[VMIN] = 1;
    105 		st.c_cc[VTIME] = 0;
    106 		if (tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &st) == -1)
    107 			goto out;
    108 	}
    109 
    110 	if (prompt != NULL) {
    111 		size_t plen = strlen(prompt);
    112 		(void)write(fd[1], prompt, plen);
    113 	}
    114 
    115 	if (allocated) {
    116 		len = 1024;
    117 		if ((buf = malloc(len)) == NULL)
    118 			goto restore;
    119 	}
    120 
    121 	c = '\1';
    122 	lnext = false;
    123 	for (size_t l = 0; c != '\0'; ) {
    124 		if (read(fd[0], &c, 1) != 1)
    125 			goto restore;
    126 
    127 #define beep() do \
    128 	if (flags & GETPASS_NO_BEEP) \
    129 		(void)write(fd[2], "\a", 1); \
    130 	while (/*CONSTCOND*/ 0)
    131 #define erase() (void)write(fd[1], "\b \b", 3)
    132 
    133 #define C(a, b) (gt.c_cc[(a)] == _POSIX_VDISABLE ? (b) : gt.c_cc[(a)])
    134 
    135 		if (lnext) {
    136 			lnext = false;
    137 			goto add;
    138 		}
    139 
    140 		/* Ignored */
    141 		if (c == C(VREPRINT, CTRL('r')) || c == C(VSTART, CTRL('q')) ||
    142 		    c == C(VSTOP, CTRL('s')) || c == C(VSTATUS, CTRL('t')) ||
    143 		    c == C(VDISCARD, CTRL('o')))
    144 			continue;
    145 
    146 		/* Literal next */
    147 		if (c == C(VLNEXT, CTRL('v'))) {
    148 			lnext = true;
    149 			continue;
    150 		}
    151 
    152 		/* Line or word kill, treat as reset */
    153 		if (c == C(VKILL, CTRL('u')) || c == C(VWERASE, CTRL('w'))) {
    154 			if (flags & GETPASS_ECHO) {
    155 				while (l--)
    156 					erase();
    157 			}
    158 			l = 0;
    159 			continue;
    160 		}
    161 
    162 		/* Character erase */
    163 		if (c == C(VERASE, CTRL('h'))) {
    164 			if (l == 0)
    165 				beep();
    166 			else {
    167 				l--;
    168 				if (flags & GETPASS_ECHO)
    169 					erase();
    170 			}
    171 			continue;
    172 		}
    173 
    174 		/* tty signal characters */
    175 		if (c == C(VINTR, CTRL('c'))) {
    176 			sig = SIGINT;
    177 			goto out;
    178 		}
    179 		if (c == C(VQUIT, CTRL('\\'))) {
    180 			sig = SIGQUIT;
    181 			goto out;
    182 		}
    183 		if (c == C(VSUSP, CTRL('z')) || c == C(VDSUSP, CTRL('y'))) {
    184 			sig = SIGTSTP;
    185 			goto out;
    186 		}
    187 
    188 		/* EOF */
    189 		if (c == C(VEOF, CTRL('d')))  {
    190 			if (flags & GETPASS_FAIL_EOF) {
    191 				errno = ENODATA;
    192 				goto out;
    193 			} else {
    194 				c = '\0';
    195 				goto add;
    196 			}
    197 		}
    198 
    199 		/* End of line */
    200 		if (c == C(VEOL, CTRL('j')) || c == C(VEOL2, CTRL('l')))
    201 			c = '\0';
    202 add:
    203 		if (l >= len) {
    204 			if (allocated) {
    205 				len += 1024;
    206 				char *b = realloc(buf, len);
    207 				if (b == NULL)
    208 					goto restore;
    209 				buf = b;
    210 			} else {
    211 				if (flags & GETPASS_BUF_LIMIT) {
    212 					beep();
    213 					continue;
    214 				}
    215 				if (c == '\0' && l > 0)
    216 					l--;
    217 				else
    218 					continue;
    219 			}
    220 		}
    221 		buf[l++] = c;
    222 		if (c && (flags & GETPASS_ECHO))
    223 		    (void)write(fd[1], &c, 1);
    224 	}
    225 
    226 	if (havetty)
    227 		(void)tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &gt);
    228 	return buf;
    229 restore:
    230 	if (havetty) {
    231 		c = errno;
    232 		(void)tcsetattr(fd[0], TCSAFLUSH|TCSASOFT, &gt);
    233 		errno = c;
    234 	}
    235 out:
    236 	if (sig) {
    237 		if ((flags & GETPASS_NO_SIGNAL) == 0)
    238 			(void)raise(sig);
    239 		errno = EINTR;
    240 	}
    241 	memset(buf, 0, len);
    242 	if (allocated)
    243 		free(buf);
    244 	return NULL;
    245 }
    246 
    247 char *
    248 getpass_r(const char *prompt, char *buf, size_t len)
    249 {
    250 	bool opentty;
    251 	int fd[3];
    252 	char *rv;
    253 
    254 	/*
    255 	 * Try to use /dev/tty if possible; otherwise read from stdin and
    256 	 * write to stderr.
    257 	 */
    258 	if ((fd[0] = fd[1] = fd[2] = open(_PATH_TTY, O_RDWR)) == -1) {
    259 		opentty = false;
    260 		fd[0] = STDIN_FILENO;
    261 		fd[1] = fd[2] = STDERR_FILENO;
    262 	} else
    263 		opentty = true;
    264 
    265 	rv = getpassfd(prompt, buf, len, fd, 0);
    266 
    267 	if (opentty) {
    268 		int serrno = errno;
    269 		(void)close(fd[0]);
    270 		errno = serrno;
    271 	}
    272 	return rv;
    273 }
    274 
    275 char *
    276 getpass(const char *prompt)
    277 {
    278 	static char e[] = "";
    279 	static char *buf;
    280 	static long bufsiz;
    281 	char *rv;
    282 
    283 	/*
    284 	 * Strictly speaking we could double allocate here, if we get
    285 	 * called at the same time, but this function is not re-entrant
    286 	 * anyway and it is not supposed to work if called concurrently.
    287 	 */
    288 	if (buf == NULL) {
    289 		if ((bufsiz = sysconf(_SC_PASS_MAX)) == -1)
    290 			return e;
    291 		if ((buf = malloc((size_t)bufsiz)) == NULL)
    292 			return e;
    293 	}
    294 
    295 	if ((rv = getpass_r(prompt, buf, (size_t)bufsiz)) == NULL)
    296 		return e;
    297 
    298 	return rv;
    299 }
    300 
    301 #ifdef TEST
    302 int
    303 main(int argc, char *argv[])
    304 {
    305 	char buf[28];
    306 	int fd[3] = { 0, 1, 2 };
    307 	printf("[%s]\n", getpassfd("foo>", buf, sizeof(buf), fd, GETPASS_ECHO));
    308 	return 0;
    309 }
    310 #endif
    311