gen/FreeBSD/readpassphrase.3

   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 1.6 2002/12/27 12:15:28 schweikh Exp $
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  30 .Dd December 7, 2001
  31 .Dt READPASSPHRASE 3
  32 .Os
  33 .Sh NAME
  34 .Nm readpassphrase
  35 .Nd get a passphrase from the user
  36 .Sh SYNOPSIS
  37 .In readpassphrase.h
  38 .Ft "char *"
  39 .Fn readpassphrase "const char *prompt" "char *buf" "size_t bufsiz" "int flags"
  40 .Sh DESCRIPTION
  41 The
  42 .Fn readpassphrase
  43 function displays a prompt to, and reads in a passphrase from,
  44 .Pa /dev/tty .
  45 If this file is inaccessible
  46 and the
  47 .Dv RPP_REQUIRE_TTY
  48 flag is not set,
  49 .Fn readpassphrase
  50 displays the prompt on the standard error output and reads from the standard
  51 input.
  52 In this case it is generally not possible to turn off echo.
  53 .Pp
  54 Up to
  55 .Fa bufsiz
  56 \- 1 characters (one is for the
  57 .Dv NUL )
  58 are read into the provided buffer
  59 .Fa buf .
  60 Any additional
  61 characters and the terminating newline (or return) character are discarded.
  62 .Pp
  63 The
  64 .Fn readpassphrase
  65 function
  66 takes the following optional
  67 .Fa flags :
  68 .Pp
  69 .Bl -tag -width ".Dv RPP_REQUIRE_TTY" -compact
  70 .It Dv RPP_ECHO_OFF
  71 turn off echo (default behavior)
  72 .It Dv RPP_ECHO_ON
  73 leave echo on
  74 .It Dv RPP_REQUIRE_TTY
  75 fail if there is no tty
  76 .It Dv RPP_FORCELOWER
  77 force input to lower case
  78 .It Dv RPP_FORCEUPPER
  79 force input to upper case
  80 .It Dv RPP_SEVENBIT
  81 strip the high bit from input
  82 .El
  83 .Pp
  84 The calling process should zero the passphrase as soon as possible to
  85 avoid leaving the cleartext passphrase visible in the process's address
  86 space.
  87 .Sh RETURN VALUES
  88 Upon successful completion,
  89 .Fn readpassphrase
  90 returns a pointer to the null-terminated passphrase.
  91 If an error is encountered, the terminal state is restored and
  92 a
  93 .Dv NULL
  94 pointer is returned.
  95 .Sh ERRORS
  96 .Bl -tag -width Er
  97 .It Bq Er EINTR
  98 The
  99 .Fn readpassphrase
 100 function was interrupted by a signal.
 101 .It Bq Er EINVAL
 102 The
 103 .Fa bufsiz
 104 argument was zero.
 105 .It Bq Er EIO
 106 The process is a member of a background process attempting to read
 107 from its controlling terminal, the process is ignoring or blocking
 108 the
 109 .Dv SIGTTIN
 110 signal or the process group is orphaned.
 111 .It Bq Er EMFILE
 112 The process has already reached its limit for open file descriptors.
 113 .It Bq Er ENFILE
 114 The system file table is full.
 115 .It Bq Er ENOTTY
 116 There is no controlling terminal and the
 117 .Dv RPP_REQUIRE_TTY
 118 flag was specified.
 119 .El
 120 .Sh EXAMPLES
 121 The following code fragment will read a passphrase from
 122 .Pa /dev/tty
 123 into the buffer
 124 .Fa passbuf .
 125 .Bd -literal -offset indent
 126 char passbuf[1024];
 127
 128 \&...
 129
 130 if (readpassphrase("Response: ", passbuf, sizeof(passbuf),
 131     RPP_REQUIRE_TTY) == NULL)
 132         errx(1, "unable to read passphrase");
 133
 134 if (compare(transform(passbuf), epass) != 0)
 135         errx(1, "bad passphrase");
 136
 137 \&...
 138
 139 memset(passbuf, 0, sizeof(passbuf));
 140 .Ed
 141 .Sh SIGNALS
 142 The
 143 .Fn readpassphrase
 144 function
 145 will catch the following signals:
 146 .Pp
 147 .Bl -tag -compact
 148 .It Dv SIGINT
 149 .It Dv SIGHUP
 150 .It Dv SIGQUIT
 151 .It Dv SIGTERM
 152 .It Dv SIGTSTP
 153 .It Dv SIGTTIN
 154 .It Dv SIGTTOU
 155 .El
 156 .Pp
 157 When one of the above signals is intercepted, terminal echo will
 158 be restored if it had previously been turned off.
 159 If a signal handler was installed for the signal when
 160 .Fn readpassphrase
 161 was called that handler is then executed.
 162 If no handler was previously installed for the signal then the
 163 default action is taken as per
 164 .Xr sigaction 2 .
 165 .Pp
 166 The
 167 .Dv SIGTSTP , SIGTTIN ,
 168 and
 169 .Dv SIGTTOU
 170 signals (stop signal generated from keyboard or due to terminal I/O
 171 from a background process) are treated specially.
 172 When the process is resumed after it has been stopped,
 173 .Fn readpassphrase
 174 will reprint the prompt and the user may then enter a passphrase.
 175 .Sh FILES
 176 .Bl -tag -width ".Pa /dev/tty" -compact
 177 .It Pa /dev/tty
 178 .El
 179 .Sh SEE ALSO
 180 .Xr sigaction 2 ,
 181 .Xr getpass 3
 182 .Sh STANDARDS
 183 The
 184 .Fn readpassphrase
 185 function is an
 186 extension and should not be used if portability is desired.
 187 .Sh HISTORY
 188 The
 189 .Fn readpassphrase
 190 function first appeared in
 191 .Ox 2.9 .