| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2018 */ |
| 6 | /* Copyright (c) The Exim Maintainers 2020 */ |
| 7 | /* See the file NOTICE for conditions of use and distribution. */ |
| 8 | |
| 9 | #include "../exim.h" |
| 10 | |
| 11 | /* This module contains functions that call the PAM authentication mechanism |
| 12 | defined by Sun for Solaris and also available for Linux and other OS. |
| 13 | |
| 14 | We can't just compile this code and allow the library mechanism to omit the |
| 15 | functions if they are not wanted, because we need to have the PAM headers |
| 16 | available for compiling. Therefore, compile these functions only if SUPPORT_PAM |
| 17 | is defined. However, some compilers don't like compiling empty modules, so keep |
| 18 | them happy with a dummy when skipping the rest. Make it reference itself to |
| 19 | stop picky compilers complaining that it is unused, and put in a dummy argument |
| 20 | to stop even pickier compilers complaining about infinite loops. |
| 21 | Then use a mutually-recursive pair as gcc is just getting stupid. */ |
| 22 | |
| 23 | #ifndef SUPPORT_PAM |
| 24 | static void dummy(int x); |
| 25 | static void dummy2(int x) { dummy(x-1); } |
| 26 | static void dummy(int x) { dummy2(x-1); } |
| 27 | #else /* SUPPORT_PAM */ |
| 28 | |
| 29 | #ifdef PAM_H_IN_PAM |
| 30 | #include <pam/pam_appl.h> |
| 31 | #else |
| 32 | #include <security/pam_appl.h> |
| 33 | #endif |
| 34 | |
| 35 | /* According to the specification, it should be possible to have an application |
| 36 | data pointer passed to the conversation function. However, I was unable to get |
| 37 | this to work on Solaris 2.6, so static variables are used instead. */ |
| 38 | |
| 39 | static int pam_conv_had_error; |
| 40 | static const uschar *pam_args; |
| 41 | static BOOL pam_arg_ended; |
| 42 | |
| 43 | |
| 44 | |
| 45 | /************************************************* |
| 46 | * PAM conversation function * |
| 47 | *************************************************/ |
| 48 | |
| 49 | /* This function is passed to the PAM authentication function, and it calls it |
| 50 | back when it wants data from the client. The string list is in pam_args. When |
| 51 | we reach the end, we pass back an empty string once. If this function is called |
| 52 | again, it will give an error response. This is protection against something |
| 53 | crazy happening. |
| 54 | |
| 55 | Arguments: |
| 56 | num_msg number of messages associated with the call |
| 57 | msg points to an array of length num_msg of pam_message structures |
| 58 | resp set to point to the response block, which has to be got by |
| 59 | this function |
| 60 | appdata_ptr the application data pointer - not used because in Solaris |
| 61 | 2.6 it always arrived in pam_converse() as NULL |
| 62 | |
| 63 | Returns: a PAM return code |
| 64 | */ |
| 65 | |
| 66 | static int |
| 67 | pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg, |
| 68 | struct pam_response **resp, void *appdata_ptr) |
| 69 | { |
| 70 | int sep = 0; |
| 71 | struct pam_response *reply; |
| 72 | |
| 73 | /* It seems that PAM frees reply[] */ |
| 74 | |
| 75 | if ( pam_arg_ended |
| 76 | || !(reply = malloc(sizeof(struct pam_response) * num_msg))) |
| 77 | return PAM_CONV_ERR; |
| 78 | |
| 79 | for (int 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) |
| 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 = US 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 */ |