1READPASSPHRASE(3bsd)                 LOCAL                READPASSPHRASE(3bsd)
2

NAME

4     readpassphrase — get a passphrase from the user
5

LIBRARY

7     Utility functions from BSD systems (libbsd, -lbsd)
8

SYNOPSIS

10     #include <readpassphrase.h>
11     (See libbsd(7) for include usage.)
12
13     char *
14     readpassphrase(const char *prompt, char *buf, size_t bufsiz, int flags);
15

DESCRIPTION

17     The readpassphrase() function displays a prompt to, and reads in a
18     passphrase from, /dev/tty.  If this file is inaccessible and the
19     RPP_REQUIRE_TTY flag is not set, readpassphrase() displays the prompt on
20     the standard error output and reads from the standard input.  In this
21     case it is generally not possible to turn off echo.
22
23     Up to bufsiz - 1 characters (one is for the NUL) are read into the pro‐
24     vided buffer buf.  Any additional characters and the terminating newline
25     (or return) character are discarded.
26
27     The flags argument is the bitwise OR of zero or more of the following
28     values:
29
30           RPP_ECHO_OFF            turn off echo (default behavior)
31           RPP_ECHO_ON             leave echo on
32           RPP_REQUIRE_TTY         fail if there is no tty
33           RPP_FORCELOWER          force input to lower case
34           RPP_FORCEUPPER          force input to upper case
35           RPP_SEVENBIT            strip the high bit from input
36           RPP_STDIN               read passphrase from stdin; ignore prompt
37
38     The calling process should zero the passphrase as soon as possible to
39     avoid leaving the cleartext passphrase visible in the process's address
40     space.
41

RETURN VALUES

43     Upon successful completion, readpassphrase() returns a pointer to the
44     NUL-terminated passphrase.  If an error is encountered, the terminal
45     state is restored and a null pointer is returned.
46

FILES

48     /dev/tty
49

EXAMPLES

51     The following code fragment will read a passphrase from /dev/tty into the
52     buffer passbuf.
53
54           char passbuf[1024];
55
56           ...
57
58           if (readpassphrase("Response: ", passbuf, sizeof(passbuf),
59               RPP_REQUIRE_TTY) == NULL)
60                   errx(1, "unable to read passphrase");
61
62           if (compare(transform(passbuf), epass) != 0)
63                   errx(1, "bad passphrase");
64
65           ...
66
67           explicit_bzero(passbuf, sizeof(passbuf));
68

ERRORS

70     [EINTR]            The readpassphrase() function was interrupted by a
71                        signal.
72
73     [EINVAL]           The bufsiz argument was zero.
74
75     [EIO]              The process is a member of a background process
76                        attempting to read from its controlling terminal, the
77                        process is ignoring or blocking the SIGTTIN signal, or
78                        the process group is orphaned.
79
80     [EMFILE]           The process has already reached its limit for open
81                        file descriptors.
82
83     [ENFILE]           The system file table is full.
84
85     [ENOTTY]           There is no controlling terminal and the
86                        RPP_REQUIRE_TTY flag was specified.
87

SIGNALS

89     readpassphrase() will catch the following signals:
90
91           SIGALRM         SIGHUP          SIGINT
92           SIGPIPE         SIGQUIT         SIGTERM
93           SIGTSTP         SIGTTIN         SIGTTOU
94
95     When one of the above signals is intercepted, terminal echo will be
96     restored if it had previously been turned off.  If a signal handler was
97     installed for the signal when readpassphrase() was called, that handler
98     is then executed.  If no handler was previously installed for the signal
99     then the default action is taken as per sigaction(2).
100
101     The SIGTSTP, SIGTTIN, and SIGTTOU signals (stop signals generated from
102     keyboard or due to terminal I/O from a background process) are treated
103     specially.  When the process is resumed after it has been stopped,
104     readpassphrase() will reprint the prompt and the user may then enter a
105     passphrase.
106

SEE ALSO

108     sigaction(2), getpass(3)
109

STANDARDS

111     The readpassphrase() function is an OpenBSD extension and should not be
112     used if portability is desired.
113

HISTORY

115     The readpassphrase() function first appeared in OpenBSD 2.9.
116
117BSD                              May 10, 2020                              BSD
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