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 1.7 2005/01/20 09:17:02 ru 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 FILES
  96 .Bl -tag -width ".Pa /dev/tty" -compact
  97 .It Pa /dev/tty
  98 .El
  99 .Sh EXAMPLES
 100 The following code fragment will read a passphrase from
 101 .Pa /dev/tty
 102 into the buffer
 103 .Fa passbuf .
 104 .Bd -literal -offset indent
 105 char passbuf[1024];
 106
 107 \&...
 108
 109 if (readpassphrase("Response: ", passbuf, sizeof(passbuf),
 110     RPP_REQUIRE_TTY) == NULL)
 111         errx(1, "unable to read passphrase");
 112
 113 if (compare(transform(passbuf), epass) != 0)
 114         errx(1, "bad passphrase");
 115
 116 \&...
 117
 118 memset(passbuf, 0, sizeof(passbuf));
 119 .Ed
 120 .Sh SIGNALS
 121 The
 122 .Fn readpassphrase
 123 function
 124 will catch the following signals:
 125 .Pp
 126 .Bl -tag -compact
 127 .It Dv SIGINT
 128 .It Dv SIGHUP
 129 .It Dv SIGQUIT
 130 .It Dv SIGTERM
 131 .It Dv SIGTSTP
 132 .It Dv SIGTTIN
 133 .It Dv SIGTTOU
 134 .El
 135 .Pp
 136 When one of the above signals is intercepted, terminal echo will
 137 be restored if it had previously been turned off.
 138 If a signal handler was installed for the signal when
 139 .Fn readpassphrase
 140 was called that handler is then executed.
 141 If no handler was previously installed for the signal then the
 142 default action is taken as per
 143 .Xr sigaction 2 .
 144 .Pp
 145 The
 146 .Dv SIGTSTP , SIGTTIN ,
 147 and
 148 .Dv SIGTTOU
 149 signals (stop signal generated from keyboard or due to terminal I/O
 150 from a background process) are treated specially.
 151 When the process is resumed after it has been stopped,
 152 .Fn readpassphrase
 153 will reprint the prompt and the user may then enter a passphrase.
 154 .Sh ERRORS
 155 .Bl -tag -width Er
 156 .It Bq Er EINTR
 157 The
 158 .Fn readpassphrase
 159 function was interrupted by a signal.
 160 .It Bq Er EINVAL
 161 The
 162 .Fa bufsiz
 163 argument was zero.
 164 .It Bq Er EIO
 165 The process is a member of a background process attempting to read
 166 from its controlling terminal, the process is ignoring or blocking
 167 the
 168 .Dv SIGTTIN
 169 signal or the process group is orphaned.
 170 .It Bq Er EMFILE
 171 The process has already reached its limit for open file descriptors.
 172 .It Bq Er ENFILE
 173 The system file table is full.
 174 .It Bq Er ENOTTY
 175 There is no controlling terminal and the
 176 .Dv RPP_REQUIRE_TTY
 177 flag was specified.
 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 .