src/src/auths/call_pam.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2015 */
   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 Then use a mutually-recursive pair as gcc is just getting stupid. */
  21
  22 #ifndef SUPPORT_PAM
  23 static void dummy(int x);
  24 static void dummy2(int x) { dummy(x-1); }
  25 static void dummy(int x) { dummy2(x-1); }
  26 #else  /* SUPPORT_PAM */
  27
  28 #ifdef PAM_H_IN_PAM
  29 #include <pam/pam_appl.h>
  30 #else
  31 #include <security/pam_appl.h>
  32 #endif
  33
  34 /* According to the specification, it should be possible to have an application
  35 data pointer passed to the conversation function. However, I was unable to get
  36 this to work on Solaris 2.6, so static variables are used instead. */
  37
  38 static int pam_conv_had_error;
  39 static const uschar *pam_args;
  40 static BOOL pam_arg_ended;
  41
  42
  43
  44 /*************************************************
  45 *           PAM conversation function            *
  46 *************************************************/
  47
  48 /* This function is passed to the PAM authentication function, and it calls it
  49 back when it wants data from the client. The string list is in pam_args. When
  50 we reach the end, we pass back an empty string once. If this function is called
  51 again, it will give an error response. This is protection against something
  52 crazy happening.
  53
  54 Arguments:
  55   num_msg        number of messages associated with the call
  56   msg            points to an array of length num_msg of pam_message structures
  57   resp           set to point to the response block, which has to be got by
  58                    this function
  59   appdata_ptr    the application data pointer - not used because in Solaris
  60                    2.6 it always arrived in pam_converse() as NULL
  61
  62 Returns:         a PAM return code
  63 */
  64
  65 static int
  66 pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg,
  67   struct pam_response **resp, void *appdata_ptr)
  68 {
  69 int i;
  70 int sep = 0;
  71 struct pam_response *reply;
  72
  73 if (pam_arg_ended) return PAM_CONV_ERR;
  74
  75 reply = malloc(sizeof(struct pam_response) * num_msg);
  76
  77 if (reply == NULL) return PAM_CONV_ERR;
  78
  79 for (i = 0; i < num_msg; i++)
  80   {
  81   uschar *arg;
  82   switch (msg[i]->msg_style)
  83     {
  84     case PAM_PROMPT_ECHO_ON:
  85     case PAM_PROMPT_ECHO_OFF:
  86     arg = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
  87     if (arg == NULL)
  88       {
  89       arg = US"";
  90       pam_arg_ended = TRUE;
  91       }
  92     reply[i].resp = CS string_copy_malloc(arg); /* PAM frees resp */
  93     reply[i].resp_retcode = PAM_SUCCESS;
  94     break;
  95
  96     case PAM_TEXT_INFO:    /* Just acknowledge messages */
  97     case PAM_ERROR_MSG:
  98     reply[i].resp_retcode = PAM_SUCCESS;
  99     reply[i].resp = NULL;
 100     break;
 101
 102     default:  /* Must be an error of some sort... */
 103     free (reply);
 104     pam_conv_had_error = TRUE;
 105     return PAM_CONV_ERR;
 106     }
 107   }
 108
 109 *resp = reply;
 110 return PAM_SUCCESS;
 111 }
 112
 113
 114
 115 /*************************************************
 116 *              Perform PAM authentication        *
 117 *************************************************/
 118
 119 /* This function calls the PAM authentication mechanism, passing over one or
 120 more data strings.
 121
 122 Arguments:
 123   s        a colon-separated list of strings
 124   errptr   where to point an error message
 125
 126 Returns:   OK if authentication succeeded
 127            FAIL if authentication failed
 128            ERROR some other error condition
 129 */
 130
 131 int
 132 auth_call_pam(const uschar *s, uschar **errptr)
 133 {
 134 pam_handle_t *pamh = NULL;
 135 struct pam_conv pamc;
 136 int pam_error;
 137 int sep = 0;
 138 uschar *user;
 139
 140 /* Set up the input data structure: the address of the conversation function,
 141 and a pointer to application data, which we don't use because I couldn't get it
 142 to work under Solaris 2.6 - it always arrived in pam_converse() as NULL. */
 143
 144 pamc.conv = pam_converse;
 145 pamc.appdata_ptr = NULL;
 146
 147 /* Initialize the static data - the current input data, the error flag, and the
 148 flag for data end. */
 149
 150 pam_args = s;
 151 pam_conv_had_error = FALSE;
 152 pam_arg_ended = FALSE;
 153
 154 /* The first string in the list is the user. If this is an empty string, we
 155 fail. PAM doesn't support authentication with an empty user (it prompts for it,
 156 causing a potential mis-interpretation). */
 157
 158 user = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
 159 if (user == NULL || user[0] == 0) return FAIL;
 160
 161 /* Start off PAM interaction */
 162
 163 DEBUG(D_auth)
 164   debug_printf("Running PAM authentication for user \"%s\"\n", user);
 165
 166 pam_error = pam_start ("exim", CS user, &pamc, &pamh);
 167
 168 /* Do the authentication - the pam_authenticate() will call pam_converse() to
 169 get the data it wants. After successful authentication we call pam_acct_mgmt()
 170 to apply any other restrictions (e.g. only some times of day). */
 171
 172 if (pam_error == PAM_SUCCESS)
 173   {
 174   pam_error = pam_authenticate (pamh, PAM_SILENT);
 175   if (pam_error == PAM_SUCCESS && !pam_conv_had_error)
 176     pam_error = pam_acct_mgmt (pamh, PAM_SILENT);
 177   }
 178
 179 /* Finish the PAM interaction - this causes it to clean up store etc. Unclear
 180 what should be passed as the second argument. */
 181
 182 pam_end(pamh, PAM_SUCCESS);
 183
 184 /* Sort out the return code. If not success, set the error message. */
 185
 186 if (pam_error == PAM_SUCCESS)
 187   {
 188   DEBUG(D_auth) debug_printf("PAM success\n");
 189   return OK;
 190   }
 191
 192 *errptr = (uschar *)pam_strerror(pamh, pam_error);
 193 DEBUG(D_auth) debug_printf("PAM error: %s\n", *errptr);
 194
 195 if (pam_error == PAM_USER_UNKNOWN ||
 196     pam_error == PAM_AUTH_ERR ||
 197     pam_error == PAM_ACCT_EXPIRED)
 198   return FAIL;
 199
 200 return ERROR;
 201 }
 202
 203 #endif  /* SUPPORT_PAM */
 204
 205 /* End of call_pam.c */