xref: /freebsd/contrib/openpam/lib/libpam/pam_get_authtok.c (revision 3b8f08459569bf0faa21473e5cec2491e95c9349)
1 /*-
2  * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
3  * Copyright (c) 2004-2011 Dag-Erling Smørgrav
4  * All rights reserved.
5  *
6  * This software was developed for the FreeBSD Project by ThinkSec AS and
7  * Network Associates Laboratories, the Security Research Division of
8  * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
9  * ("CBOSS"), as part of the DARPA CHATS research program.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 3. The name of the author may not be used to endorse or promote
20  *    products derived from this software without specific prior written
21  *    permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  *
35  * $Id: pam_get_authtok.c 670 2013-03-17 19:26:07Z des $
36  */
37 
38 #ifdef HAVE_CONFIG_H
39 # include "config.h"
40 #endif
41 
42 #include <sys/param.h>
43 
44 #include <stdlib.h>
45 #include <string.h>
46 
47 #include <security/pam_appl.h>
48 #include <security/openpam.h>
49 
50 #include "openpam_impl.h"
51 
52 static const char authtok_prompt[] = "Password:";
53 static const char authtok_prompt_remote[] = "Password for %u@%h:";
54 static const char oldauthtok_prompt[] = "Old Password:";
55 static const char newauthtok_prompt[] = "New Password:";
56 
57 /*
58  * OpenPAM extension
59  *
60  * Retrieve authentication token
61  */
62 
63 int
64 pam_get_authtok(pam_handle_t *pamh,
65 	int item,
66 	const char **authtok,
67 	const char *prompt)
68 {
69 	char prompt_buf[1024];
70 	size_t prompt_size;
71 	const void *oldauthtok, *prevauthtok, *promptp;
72 	const char *prompt_option, *default_prompt;
73 	const void *lhost, *rhost;
74 	char *resp, *resp2;
75 	int pitem, r, style, twice;
76 
77 	ENTER();
78 	if (pamh == NULL || authtok == NULL)
79 		RETURNC(PAM_SYSTEM_ERR);
80 	*authtok = NULL;
81 	twice = 0;
82 	switch (item) {
83 	case PAM_AUTHTOK:
84 		pitem = PAM_AUTHTOK_PROMPT;
85 		prompt_option = "authtok_prompt";
86 		default_prompt = authtok_prompt;
87 		r = pam_get_item(pamh, PAM_RHOST, &rhost);
88 		if (r == PAM_SUCCESS && rhost != NULL) {
89 			r = pam_get_item(pamh, PAM_HOST, &lhost);
90 			if (r == PAM_SUCCESS && lhost != NULL) {
91 				if (strcmp(rhost, lhost) != 0)
92 					default_prompt = authtok_prompt_remote;
93 			}
94 		}
95 		r = pam_get_item(pamh, PAM_OLDAUTHTOK, &oldauthtok);
96 		if (r == PAM_SUCCESS && oldauthtok != NULL) {
97 			default_prompt = newauthtok_prompt;
98 			twice = 1;
99 		}
100 		break;
101 	case PAM_OLDAUTHTOK:
102 		pitem = PAM_OLDAUTHTOK_PROMPT;
103 		prompt_option = "oldauthtok_prompt";
104 		default_prompt = oldauthtok_prompt;
105 		twice = 0;
106 		break;
107 	default:
108 		RETURNC(PAM_SYMBOL_ERR);
109 	}
110 	if (openpam_get_option(pamh, "try_first_pass") ||
111 	    openpam_get_option(pamh, "use_first_pass")) {
112 		r = pam_get_item(pamh, item, &prevauthtok);
113 		if (r == PAM_SUCCESS && prevauthtok != NULL) {
114 			*authtok = prevauthtok;
115 			RETURNC(PAM_SUCCESS);
116 		} else if (openpam_get_option(pamh, "use_first_pass")) {
117 			RETURNC(r == PAM_SUCCESS ? PAM_AUTH_ERR : r);
118 		}
119 	}
120 	/* pam policy overrides the module's choice */
121 	if ((promptp = openpam_get_option(pamh, prompt_option)) != NULL)
122 		prompt = promptp;
123 	/* no prompt provided, see if there is one tucked away somewhere */
124 	if (prompt == NULL)
125 		if (pam_get_item(pamh, pitem, &promptp) && promptp != NULL)
126 			prompt = promptp;
127 	/* fall back to hardcoded default */
128 	if (prompt == NULL)
129 		prompt = default_prompt;
130 	/* expand */
131 	prompt_size = sizeof prompt_buf;
132 	r = openpam_subst(pamh, prompt_buf, &prompt_size, prompt);
133 	if (r == PAM_SUCCESS && prompt_size <= sizeof prompt_buf)
134 		prompt = prompt_buf;
135 	style = openpam_get_option(pamh, "echo_pass") ?
136 	    PAM_PROMPT_ECHO_ON : PAM_PROMPT_ECHO_OFF;
137 	r = pam_prompt(pamh, style, &resp, "%s", prompt);
138 	if (r != PAM_SUCCESS)
139 		RETURNC(r);
140 	if (twice) {
141 		r = pam_prompt(pamh, style, &resp2, "Retype %s", prompt);
142 		if (r != PAM_SUCCESS) {
143 			FREE(resp);
144 			RETURNC(r);
145 		}
146 		if (strcmp(resp, resp2) != 0)
147 			FREE(resp);
148 		FREE(resp2);
149 	}
150 	if (resp == NULL)
151 		RETURNC(PAM_TRY_AGAIN);
152 	r = pam_set_item(pamh, item, resp);
153 	FREE(resp);
154 	if (r != PAM_SUCCESS)
155 		RETURNC(r);
156 	r = pam_get_item(pamh, item, (const void **)authtok);
157 	RETURNC(r);
158 }
159 
160 /*
161  * Error codes:
162  *
163  *	=pam_get_item
164  *	=pam_prompt
165  *	=pam_set_item
166  *	!PAM_SYMBOL_ERR
167  *	PAM_TRY_AGAIN
168  */
169 
170 /**
171  * The =pam_get_authtok function either prompts the user for an
172  * authentication token or retrieves a cached authentication token,
173  * depending on circumstances.
174  * Either way, a pointer to the authentication token is stored in the
175  * location pointed to by the =authtok argument, and the corresponding PAM
176  * item is updated.
177  *
178  * The =item argument must have one of the following values:
179  *
180  *	=PAM_AUTHTOK:
181  *		Returns the current authentication token, or the new token
182  *		when changing authentication tokens.
183  *	=PAM_OLDAUTHTOK:
184  *		Returns the previous authentication token when changing
185  *		authentication tokens.
186  *
187  * The =prompt argument specifies a prompt to use if no token is cached.
188  * If it is =NULL, the =PAM_AUTHTOK_PROMPT or =PAM_OLDAUTHTOK_PROMPT item,
189  * as appropriate, will be used.
190  * If that item is also =NULL, a hardcoded default prompt will be used.
191  * Additionally, when =pam_get_authtok is called from a service module,
192  * the prompt may be affected by module options as described below.
193  * The prompt is then expanded using =openpam_subst before it is passed to
194  * the conversation function.
195  *
196  * If =item is set to =PAM_AUTHTOK and there is a non-null =PAM_OLDAUTHTOK
197  * item, =pam_get_authtok will ask the user to confirm the new token by
198  * retyping it.
199  * If there is a mismatch, =pam_get_authtok will return =PAM_TRY_AGAIN.
200  *
201  * MODULE OPTIONS
202  *
203  * When called by a service module, =pam_get_authtok will recognize the
204  * following module options:
205  *
206  *	;authtok_prompt:
207  *		Prompt to use when =item is set to =PAM_AUTHTOK.
208  *		This option overrides both the =prompt argument and the
209  *		=PAM_AUTHTOK_PROMPT item.
210  *	;echo_pass:
211  *		If the application's conversation function allows it, this
212  *		lets the user see what they are typing.
213  *		This should only be used for non-reusable authentication
214  *		tokens.
215  *	;oldauthtok_prompt:
216  *		Prompt to use when =item is set to =PAM_OLDAUTHTOK.
217  *		This option overrides both the =prompt argument and the
218  *		=PAM_OLDAUTHTOK_PROMPT item.
219  *	;try_first_pass:
220  *		If the requested item is non-null, return it without
221  *		prompting the user.
222  *		Typically, the service module will verify the token, and
223  *		if it does not match, clear the item before calling
224  *		=pam_get_authtok a second time.
225  *	;use_first_pass:
226  *		Do not prompt the user at all; just return the cached
227  *		value, or =PAM_AUTH_ERR if there is none.
228  *
229  * >pam_conv
230  * >pam_get_item
231  * >pam_get_user
232  * >openpam_get_option
233  * >openpam_subst
234  */
235