local_scan: align local_scan.h and docs re. store_get()
[exim.git] / src / src / auths / call_pam.c
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1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4
f9ba5e22 5/* Copyright (c) University of Cambridge 1995 - 2018 */
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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
11defined by Sun for Solaris and also available for Linux and other OS.
12
13We can't just compile this code and allow the library mechanism to omit the
14functions if they are not wanted, because we need to have the PAM headers
15available for compiling. Therefore, compile these functions only if SUPPORT_PAM
16is defined. However, some compilers don't like compiling empty modules, so keep
17them happy with a dummy when skipping the rest. Make it reference itself to
18stop picky compilers complaining that it is unused, and put in a dummy argument
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19to stop even pickier compilers complaining about infinite loops.
20Then use a mutually-recursive pair as gcc is just getting stupid. */
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21
22#ifndef SUPPORT_PAM
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23static void dummy(int x);
24static void dummy2(int x) { dummy(x-1); }
25static void dummy(int x) { dummy2(x-1); }
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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
35data pointer passed to the conversation function. However, I was unable to get
36this to work on Solaris 2.6, so static variables are used instead. */
37
38static int pam_conv_had_error;
93a6fce2 39static const uschar *pam_args;
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40static 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
49back when it wants data from the client. The string list is in pam_args. When
50we reach the end, we pass back an empty string once. If this function is called
51again, it will give an error response. This is protection against something
52crazy happening.
53
54Arguments:
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
62Returns: a PAM return code
63*/
64
65static int
66pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg,
67 struct pam_response **resp, void *appdata_ptr)
68{
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69int sep = 0;
70struct pam_response *reply;
71
72if (pam_arg_ended) return PAM_CONV_ERR;
73
f3ebb786 74reply = store_get(sizeof(struct pam_response) * num_msg, FALSE);
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d7978c0f 76for (int i = 0; i < num_msg; i++)
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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 }
f3ebb786 89 reply[i].resp = CS string_copy_perm(arg, FALSE); /* PAM frees resp */
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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... */
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100 pam_conv_had_error = TRUE;
101 return PAM_CONV_ERR;
102 }
103 }
104
105*resp = reply;
106return PAM_SUCCESS;
107}
108
109
110
111/*************************************************
112* Perform PAM authentication *
113*************************************************/
114
115/* This function calls the PAM authentication mechanism, passing over one or
116more data strings.
117
118Arguments:
119 s a colon-separated list of strings
120 errptr where to point an error message
121
122Returns: OK if authentication succeeded
123 FAIL if authentication failed
124 ERROR some other error condition
125*/
126
127int
93a6fce2 128auth_call_pam(const uschar *s, uschar **errptr)
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129{
130pam_handle_t *pamh = NULL;
131struct pam_conv pamc;
132int pam_error;
133int sep = 0;
134uschar *user;
135
136/* Set up the input data structure: the address of the conversation function,
137and a pointer to application data, which we don't use because I couldn't get it
138to work under Solaris 2.6 - it always arrived in pam_converse() as NULL. */
139
140pamc.conv = pam_converse;
141pamc.appdata_ptr = NULL;
142
143/* Initialize the static data - the current input data, the error flag, and the
144flag for data end. */
145
146pam_args = s;
147pam_conv_had_error = FALSE;
148pam_arg_ended = FALSE;
149
150/* The first string in the list is the user. If this is an empty string, we
151fail. PAM doesn't support authentication with an empty user (it prompts for it,
152causing a potential mis-interpretation). */
153
154user = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
155if (user == NULL || user[0] == 0) return FAIL;
156
157/* Start off PAM interaction */
158
159DEBUG(D_auth)
160 debug_printf("Running PAM authentication for user \"%s\"\n", user);
161
162pam_error = pam_start ("exim", CS user, &pamc, &pamh);
163
164/* Do the authentication - the pam_authenticate() will call pam_converse() to
165get the data it wants. After successful authentication we call pam_acct_mgmt()
166to apply any other restrictions (e.g. only some times of day). */
167
168if (pam_error == PAM_SUCCESS)
169 {
170 pam_error = pam_authenticate (pamh, PAM_SILENT);
171 if (pam_error == PAM_SUCCESS && !pam_conv_had_error)
172 pam_error = pam_acct_mgmt (pamh, PAM_SILENT);
173 }
174
175/* Finish the PAM interaction - this causes it to clean up store etc. Unclear
176what should be passed as the second argument. */
177
178pam_end(pamh, PAM_SUCCESS);
179
180/* Sort out the return code. If not success, set the error message. */
181
182if (pam_error == PAM_SUCCESS)
183 {
184 DEBUG(D_auth) debug_printf("PAM success\n");
185 return OK;
186 }
187
5903c6ff 188*errptr = US pam_strerror(pamh, pam_error);
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189DEBUG(D_auth) debug_printf("PAM error: %s\n", *errptr);
190
191if (pam_error == PAM_USER_UNKNOWN ||
192 pam_error == PAM_AUTH_ERR ||
193 pam_error == PAM_ACCT_EXPIRED)
194 return FAIL;
195
196return ERROR;
197}
198
199#endif /* SUPPORT_PAM */
200
201/* End of call_pam.c */