xref: /dragonfly/lib/libc/gen/readpassphrase.3 (revision 1847e88f) 
1.\"	$OpenBSD: readpassphrase.3,v 1.7 2001/12/15 15:37:51 millert Exp $
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3.\" Copyright (c) 2000 Todd C. Miller <Todd.Miller@courtesan.com>
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28.\" $FreeBSD: src/lib/libc/gen/readpassphrase.3,v 1.4.2.3 2003/03/15 15:11:05 trhodes Exp $
29.\" $DragonFly: src/lib/libc/gen/readpassphrase.3,v 1.3 2006/02/17 19:35:06 swildner Exp $
30.\"
31.Dd December 7, 2001
32.Dt READPASSPHRASE 3
33.Os
34.Sh NAME
35.Nm readpassphrase
36.Nd get a passphrase from the user
37.Sh SYNOPSIS
38.In readpassphrase.h
39.Ft "char *"
40.Fn readpassphrase "const char *prompt" "char *buf" "size_t bufsiz" "int flags"
41.Sh DESCRIPTION
42The
43.Fn readpassphrase
44function displays a prompt to, and reads in a passphrase from,
45.Pa /dev/tty .
46If this file is inaccessible
47and the
48.Dv RPP_REQUIRE_TTY
49flag is not set,
50.Fn readpassphrase
51displays the prompt on the standard error output and reads from the standard
52input.
53In this case it is generally not possible to turn off echo.
54.Pp
55Up to
56.Fa bufsiz
57\- 1 characters (one is for the
58.Dv NUL )
59are read into the provided buffer
60.Fa buf .
61Any additional
62characters and the terminating newline (or return) character are discarded.
63.Pp
64The
65.Fn readpassphrase
66function
67takes the following optional
68.Fa flags :
69.Pp
70.Bl -tag -width ".Dv RPP_REQUIRE_TTY" -compact
71.It Dv RPP_ECHO_OFF
72turn off echo (default behavior)
73.It Dv RPP_ECHO_ON
74leave echo on
75.It Dv RPP_REQUIRE_TTY
76fail if there is no tty
77.It Dv RPP_FORCELOWER
78force input to lower case
79.It Dv RPP_FORCEUPPER
80force input to upper case
81.It Dv RPP_SEVENBIT
82strip the high bit from input
83.El
84.Pp
85The calling process should zero the passphrase as soon as possible to
86avoid leaving the cleartext passphrase visible in the process's address
87space.
88.Sh RETURN VALUES
89Upon successful completion,
90.Fn readpassphrase
91returns a pointer to the null-terminated passphrase.
92If an error is encountered, the terminal state is restored and
93a
94.Dv NULL
95pointer is returned.
96.Sh FILES
97.Bl -tag -width ".Pa /dev/tty" -compact
98.It Pa /dev/tty
99.El
100.Sh EXAMPLES
101The following code fragment will read a passphrase from
102.Pa /dev/tty
103into the buffer
104.Fa passbuf .
105.Bd -literal -offset indent
106char passbuf[1024];
107
108\&...
109
110if (readpassphrase("Response: ", passbuf, sizeof(passbuf),
111    RPP_REQUIRE_TTY) == NULL)
112	errx(1, "unable to read passphrase");
113
114if (compare(transform(passbuf), epass) != 0)
115	errx(1, "bad passphrase");
116
117\&...
118
119memset(passbuf, 0, sizeof(passbuf));
120.Ed
121.Sh ERRORS
122.Bl -tag -width Er
123.It Bq Er EINTR
124The
125.Fn readpassphrase
126function was interrupted by a signal.
127.It Bq Er EINVAL
128The
129.Fa bufsiz
130argument was zero.
131.It Bq Er EIO
132The process is a member of a background process attempting to read
133from its controlling terminal, the process is ignoring or blocking
134the
135.Dv SIGTTIN
136signal or the process group is orphaned.
137.It Bq Er EMFILE
138The process has already reached its limit for open file descriptors.
139.It Bq Er ENFILE
140The system file table is full.
141.It Bq Er ENOTTY
142There is no controlling terminal and the
143.Dv RPP_REQUIRE_TTY
144flag was specified.
145.El
146.Sh SIGNALS
147The
148.Fn readpassphrase
149function
150will catch the following signals:
151.Pp
152.Bl -tag -compact
153.It Dv SIGINT
154.It Dv SIGHUP
155.It Dv SIGQUIT
156.It Dv SIGTERM
157.It Dv SIGTSTP
158.It Dv SIGTTIN
159.It Dv SIGTTOU
160.El
161.Pp
162When one of the above signals is intercepted, terminal echo will
163be restored if it had previously been turned off.
164If a signal handler was installed for the signal when
165.Fn readpassphrase
166was called that handler is then executed.
167If no handler was previously installed for the signal then the
168default action is taken as per
169.Xr sigaction 2 .
170.Pp
171The
172.Dv SIGTSTP , SIGTTIN ,
173and
174.Dv SIGTTOU
175signals (stop signal generated from keyboard or due to terminal I/O
176from a background process) are treated specially.
177When the process is resumed after it has been stopped,
178.Fn readpassphrase
179will reprint the prompt and the user may then enter a passphrase.
180.Sh SEE ALSO
181.Xr sigaction 2 ,
182.Xr getpass 3
183.Sh STANDARDS
184The
185.Fn readpassphrase
186function is an
187extension and should not be used if portability is desired.
188.Sh HISTORY
189The
190.Fn readpassphrase
191function first appeared in
192.Ox 2.9 .
193