src/src/auths/call_pam.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 #include "../exim.h"
   9
  10 /* This module contains functions that call the PAM authentication mechanism
  11 defined by Sun for Solaris and also available for Linux and other OS.
  12
  13 We can't just compile this code and allow the library mechanism to omit the
  14 functions if they are not wanted, because we need to have the PAM headers
  15 available for compiling. Therefore, compile these functions only if SUPPORT_PAM
  16 is defined. However, some compilers don't like compiling empty modules, so keep
  17 them happy with a dummy when skipping the rest. Make it reference itself to
  18 stop picky compilers complaining that it is unused, and put in a dummy argument
  19 to stop even pickier compilers complaining about infinite loops. */
  20
  21 #ifndef SUPPORT_PAM
  22 static void dummy(int x) { dummy(x-1); }
  23 #else  /* SUPPORT_PAM */
  24
  25 #ifdef PAM_H_IN_PAM
  26 #include <pam/pam_appl.h>
  27 #else
  28 #include <security/pam_appl.h>
  29 #endif
  30
  31 /* According to the specification, it should be possible to have an application
  32 data pointer passed to the conversation function. However, I was unable to get
  33 this to work on Solaris 2.6, so static variables are used instead. */
  34
  35 static int pam_conv_had_error;
  36 static uschar *pam_args;
  37 static BOOL pam_arg_ended;
  38
  39
  40
  41 /*************************************************
  42 *           PAM conversation function            *
  43 *************************************************/
  44
  45 /* This function is passed to the PAM authentication function, and it calls it
  46 back when it wants data from the client. The string list is in pam_args. When
  47 we reach the end, we pass back an empty string once. If this function is called
  48 again, it will give an error response. This is protection against something
  49 crazy happening.
  50
  51 Arguments:
  52   num_msg        number of messages associated with the call
  53   msg            points to an array of length num_msg of pam_message structures
  54   resp           set to point to the response block, which has to be got by
  55                    this function
  56   appdata_ptr    the application data pointer - not used because in Solaris
  57                    2.6 it always arrived in pam_converse() as NULL
  58
  59 Returns:         a PAM return code
  60 */
  61
  62 static int
  63 pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg,
  64   struct pam_response **resp, void *appdata_ptr)
  65 {
  66 int i;
  67 int sep = 0;
  68 struct pam_response *reply;
  69
  70 if (pam_arg_ended) return PAM_CONV_ERR;
  71
  72 reply = malloc(sizeof(struct pam_response) * num_msg);
  73
  74 if (reply == NULL) return PAM_CONV_ERR;
  75
  76 for (i = 0; i < num_msg; i++)
  77   {
  78   uschar *arg;
  79   switch (msg[i]->msg_style)
  80     {
  81     case PAM_PROMPT_ECHO_ON:
  82     case PAM_PROMPT_ECHO_OFF:
  83     arg = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
  84     if (arg == NULL)
  85       {
  86       arg = US"";
  87       pam_arg_ended = TRUE;
  88       }
  89     reply[i].resp = CS string_copy_malloc(arg); /* PAM frees resp */
  90     reply[i].resp_retcode = PAM_SUCCESS;
  91     break;
  92
  93     case PAM_TEXT_INFO:    /* Just acknowledge messages */
  94     case PAM_ERROR_MSG:
  95     reply[i].resp_retcode = PAM_SUCCESS;
  96     reply[i].resp = NULL;
  97     break;
  98
  99     default:  /* Must be an error of some sort... */
 100     free (reply);
 101     pam_conv_had_error = TRUE;
 102     return PAM_CONV_ERR;
 103     }
 104   }
 105
 106 *resp = reply;
 107 return PAM_SUCCESS;
 108 }
 109
 110
 111
 112 /*************************************************
 113 *              Perform PAM authentication        *
 114 *************************************************/
 115
 116 /* This function calls the PAM authentication mechanism, passing over one or
 117 more data strings.
 118
 119 Arguments:
 120   s        a colon-separated list of strings
 121   errptr   where to point an error message
 122
 123 Returns:   OK if authentication succeeded
 124            FAIL if authentication failed
 125            ERROR some other error condition
 126 */
 127
 128 int
 129 auth_call_pam(uschar *s, uschar **errptr)
 130 {
 131 pam_handle_t *pamh = NULL;
 132 struct pam_conv pamc;
 133 int pam_error;
 134 int sep = 0;
 135 uschar *user;
 136
 137 /* Set up the input data structure: the address of the conversation function,
 138 and a pointer to application data, which we don't use because I couldn't get it
 139 to work under Solaris 2.6 - it always arrived in pam_converse() as NULL. */
 140
 141 pamc.conv = pam_converse;
 142 pamc.appdata_ptr = NULL;
 143
 144 /* Initialize the static data - the current input data, the error flag, and the
 145 flag for data end. */
 146
 147 pam_args = s;
 148 pam_conv_had_error = FALSE;
 149 pam_arg_ended = FALSE;
 150
 151 /* The first string in the list is the user. If this is an empty string, we
 152 fail. PAM doesn't support authentication with an empty user (it prompts for it,
 153 causing a potential mis-interpretation). */
 154
 155 user = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
 156 if (user == NULL || user[0] == 0) return FAIL;
 157
 158 /* Start off PAM interaction */
 159
 160 DEBUG(D_auth)
 161   debug_printf("Running PAM authentication for user \"%s\"\n", user);
 162
 163 pam_error = pam_start ("exim", CS user, &pamc, &pamh);
 164
 165 /* Do the authentication - the pam_authenticate() will call pam_converse() to
 166 get the data it wants. After successful authentication we call pam_acct_mgmt()
 167 to apply any other restrictions (e.g. only some times of day). */
 168
 169 if (pam_error == PAM_SUCCESS)
 170   {
 171   pam_error = pam_authenticate (pamh, PAM_SILENT);
 172   if (pam_error == PAM_SUCCESS && !pam_conv_had_error)
 173     pam_error = pam_acct_mgmt (pamh, PAM_SILENT);
 174   }
 175
 176 /* Finish the PAM interaction - this causes it to clean up store etc. Unclear
 177 what should be passed as the second argument. */
 178
 179 pam_end(pamh, PAM_SUCCESS);
 180
 181 /* Sort out the return code. If not success, set the error message. */
 182
 183 if (pam_error == PAM_SUCCESS)
 184   {
 185   DEBUG(D_auth) debug_printf("PAM success\n");
 186   return OK;
 187   }
 188
 189 *errptr = (uschar *)pam_strerror(pamh, pam_error);
 190 DEBUG(D_auth) debug_printf("PAM error: %s\n", *errptr);
 191
 192 if (pam_error == PAM_USER_UNKNOWN ||
 193     pam_error == PAM_AUTH_ERR ||
 194     pam_error == PAM_ACCT_EXPIRED)
 195   return FAIL;
 196
 197 return ERROR;
 198 }
 199
 200 #endif  /* SUPPORT_PAM */
 201
 202 /* End of call_pam.c */