debian experimental exim-daemon-heavy config
[exim.git] / src / src / auths / call_pam.c
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 */