contrib/openpam/lib/openpam_subst.c

   1 /*-
   2  * Copyright (c) 2011 Dag-Erling Smørgrav
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer
  10  *    in this position and unchanged.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. The name of the author may not be used to endorse or promote
  15  *    products derived from this software without specific prior written
  16  *    permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  * $Id: openpam_subst.c 543 2012-03-31 22:11:34Z des $
  31  */
  32
  33 #ifdef HAVE_CONFIG_H
  34 # include "config.h"
  35 #endif
  36
  37 #include <security/pam_appl.h>
  38
  39 #include "openpam_impl.h"
  40
  41 #define subst_char(ch) do {                     \
  42         int ch_ = (ch);                         \
  43         if (buf && len < *bufsize)              \
  44                 *buf++ = ch_;                   \
  45         ++len;                                  \
  46 } while (0)
  47
  48 #define subst_string(s) do {                    \
  49         const char *s_ = (s);                   \
  50         while (*s_)                             \
  51                 subst_char(*s_++);              \
  52 } while (0)
  53
  54 #define subst_item(i) do {                      \
  55         int i_ = (i);                           \
  56         const void *p_;                         \
  57         ret = pam_get_item(pamh, i_, &p_);      \
  58         if (ret == PAM_SUCCESS && p_ != NULL)   \
  59                 subst_string(p_);               \
  60 } while (0)
  61
  62 /*
  63  * OpenPAM internal
  64  *
  65  * Substitute PAM item values in a string
  66  */
  67
  68 int
  69 openpam_subst(const pam_handle_t *pamh,
  70     char *buf, size_t *bufsize, const char *template)
  71 {
  72         size_t len;
  73         int ret;
  74
  75         ENTERS(template);
  76         if (template == NULL)
  77                 template = "(null)";
  78
  79         len = 1; /* initialize to 1 for terminating NUL */
  80         ret = PAM_SUCCESS;
  81         while (*template && ret == PAM_SUCCESS) {
  82                 if (template[0] == '%') {
  83                         ++template;
  84                         switch (*template) {
  85                         case 's':
  86                                 subst_item(PAM_SERVICE);
  87                                 break;
  88                         case 't':
  89                                 subst_item(PAM_TTY);
  90                                 break;
  91                         case 'h':
  92                                 subst_item(PAM_HOST);
  93                                 break;
  94                         case 'u':
  95                                 subst_item(PAM_USER);
  96                                 break;
  97                         case 'H':
  98                                 subst_item(PAM_RHOST);
  99                                 break;
 100                         case 'U':
 101                                 subst_item(PAM_RUSER);
 102                                 break;
 103                         case '\0':
 104                                 subst_char('%');
 105                                 break;
 106                         default:
 107                                 subst_char('%');
 108                                 subst_char(*template);
 109                         }
 110                         ++template;
 111                 } else {
 112                         subst_char(*template++);
 113                 }
 114         }
 115         if (buf)
 116                 *buf = '\0';
 117         if (ret == PAM_SUCCESS) {
 118                 if (len > *bufsize)
 119                         ret = PAM_TRY_AGAIN;
 120                 *bufsize = len;
 121         }
 122         RETURNC(ret);
 123 }
 124
 125 /*
 126  * Error codes:
 127  *
 128  *      =pam_get_item
 129  *      !PAM_SYMBOL_ERR
 130  *      PAM_TRY_AGAIN
 131  */
 132
 133 /**
 134  * The =openpam_subst function expands a string, substituting PAM item
 135  * values for all occurrences of specific substitution codes.
 136  * The =template argument points to the initial string.
 137  * The result is stored in the buffer pointed to by the =buf argument; the
 138  * =bufsize argument specifies the size of that buffer.
 139  * The actual size of the resulting string, including the terminating NUL
 140  * character, is stored in the location pointed to by the =bufsize
 141  * argument.
 142  *
 143  * If =buf is NULL, or if the buffer is too small to hold the expanded
 144  * string, =bufsize is updated to reflect the amount of space required to
 145  * hold the entire string, and =openpam_subst returns =PAM_TRY_AGAIN.
 146  *
 147  * If =openpam_subst fails for any other reason, the =bufsize argument is
 148  * untouched, but part of the buffer may still have been overwritten.
 149  *
 150  * Substitution codes are introduced by a percent character and correspond
 151  * to PAM items:
 152  *
 153  *      %H:
 154  *              Replaced by the current value of the =PAM_RHOST item.
 155  *      %h:
 156  *              Replaced by the current value of the =PAM_HOST item.
 157  *      %s:
 158  *              Replaced by the current value of the =PAM_SERVICE item.
 159  *      %t:
 160  *              Replaced by the current value of the =PAM_TTY item.
 161  *      %U:
 162  *              Replaced by the current value of the =PAM_RUSER item.
 163  *      %u:
 164  *              Replaced by the current value of the =PAM_USER item.
 165  *
 166  * >pam_get_authtok
 167  * >pam_get_item
 168  * >pam_get_user
 169  *
 170  * AUTHOR DES
 171  */