sudo/plugins/sudoers/auth/pam.c

/*
 * Copyright (c) 1999-2005, 2007-2018 Todd C. Miller <Todd.Miller@sudo.ws>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

/*
 * This is an open source non-commercial project. Dear PVS-Studio, please check it.
 * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 */

#include <config.h>

#ifdef HAVE_PAM

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#include <unistd.h>
#include <pwd.h>
#include <errno.h>

#ifdef HAVE_PAM_PAM_APPL_H
# include <pam/pam_appl.h>
#else
# include <security/pam_appl.h>
#endif

#ifdef HAVE_LIBINTL_H
# if defined(__LINUX_PAM__)
#  define PAM_TEXT_DOMAIN	"Linux-PAM"
# elif defined(__sun__)
#  define PAM_TEXT_DOMAIN	"SUNW_OST_SYSOSPAM"
# endif
#endif

/* We don't want to translate the strings in the calls to dgt(). */
#ifdef PAM_TEXT_DOMAIN
# define dgt(d, t)	dgettext(d, t)
#endif

#include "sudoers.h"
#include "sudo_auth.h"

/* Only OpenPAM and Linux PAM use const qualifiers. */
#ifdef PAM_SUN_CODEBASE
# define PAM_CONST
#else
# define PAM_CONST	const
#endif

/* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
#ifdef PAM_SUN_CODEBASE
# define PAM_MSG_GET(msg, n) (*(msg) + (n))
#else
# define PAM_MSG_GET(msg, n) ((msg)[(n)])
#endif

#ifndef PAM_DATA_SILENT
#define PAM_DATA_SILENT	0
#endif

static int converse(int, PAM_CONST struct pam_message **,
		    struct pam_response **, void *);
static struct sudo_conv_callback *conv_callback;
static struct pam_conv pam_conv = { converse, &conv_callback };
static char *def_prompt = PASSPROMPT;
static bool getpass_error;
static pam_handle_t *pamh;

static int
sudo_pam_init2(struct passwd *pw, sudo_auth *auth, bool quiet)
{
    static int pam_status = PAM_SUCCESS;
    const char *tty = user_ttypath;
    int rc;
    debug_decl(sudo_pam_init, SUDOERS_DEBUG_AUTH)

    /* Stash pointer to last pam status. */
    auth->data = &pam_status;

#ifdef _AIX
    if (pamh != NULL) {
	/* Already initialized (may happen with AIX). */
	debug_return_int(AUTH_SUCCESS);
    }
#endif /* _AIX */

    /* Initial PAM setup */
    pam_status = pam_start(ISSET(sudo_mode, MODE_LOGIN_SHELL) ?
	def_pam_login_service : def_pam_service, pw->pw_name, &pam_conv, &pamh);
    if (pam_status != PAM_SUCCESS) {
	if (!quiet)
	    log_warning(0, N_("unable to initialize PAM"));
	debug_return_int(AUTH_FATAL);
    }

    /*
     * Set PAM_RUSER to the invoking user (the "from" user).
     * We set PAM_RHOST to avoid a bug in Solaris 7 and below.
     */
    rc = pam_set_item(pamh, PAM_RUSER, user_name);
    if (rc != PAM_SUCCESS) {
	const char *errstr = pam_strerror(pamh, rc);
	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
	    "pam_set_item(pamh, PAM_RUSER, %s): %s", user_name,
	    errstr ? errstr : "unknown error");
    }
#ifdef __sun__
    rc = pam_set_item(pamh, PAM_RHOST, user_host);
    if (rc != PAM_SUCCESS) {
	const char *errstr = pam_strerror(pamh, rc);
	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
	    "pam_set_item(pamh, PAM_RHOST, %s): %s", user_host,
	    errstr ? errstr : "unknown error");
    }
#endif

#if defined(__LINUX_PAM__) || defined(__sun__)
    /*
     * Some PAM modules assume PAM_TTY is set and will misbehave (or crash)
     * if it is not.  Known offenders include pam_lastlog and pam_time.
     */
    if (tty == NULL)
	tty = "";
#endif
    if (tty != NULL) {
	rc = pam_set_item(pamh, PAM_TTY, tty);
	if (rc != PAM_SUCCESS) {
	    const char *errstr = pam_strerror(pamh, rc);
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"pam_set_item(pamh, PAM_TTY, %s): %s", tty,
		errstr ? errstr : "unknown error");
	}
    }

    /*
     * If PAM session and setcred support is disabled we don't
     * need to keep a sudo process around to close the session.
     */
    if (!def_pam_session && !def_pam_setcred)
	auth->end_session = NULL;

    debug_return_int(AUTH_SUCCESS);
}

int
sudo_pam_init(struct passwd *pw, sudo_auth *auth)
{
    return sudo_pam_init2(pw, auth, false);
}

#ifdef _AIX
int
sudo_pam_init_quiet(struct passwd *pw, sudo_auth *auth)
{
    return sudo_pam_init2(pw, auth, true);
}
#endif /* _AIX */

int
sudo_pam_verify(struct passwd *pw, char *prompt, sudo_auth *auth, struct sudo_conv_callback *callback)
{
    const char *s;
    int *pam_status = (int *) auth->data;
    debug_decl(sudo_pam_verify, SUDOERS_DEBUG_AUTH)

    def_prompt = prompt;	/* for converse */
    getpass_error = false;	/* set by converse if user presses ^C */
    conv_callback = callback;	/* passed to conversation function */

    /* PAM_SILENT prevents the authentication service from generating output. */
    *pam_status = pam_authenticate(pamh, PAM_SILENT);
    if (getpass_error) {
	/* error or ^C from tgetpass() */
	debug_return_int(AUTH_INTR);
    }
    switch (*pam_status) {
	case PAM_SUCCESS:
	    debug_return_int(AUTH_SUCCESS);
	case PAM_AUTH_ERR:
	case PAM_AUTHINFO_UNAVAIL:
	case PAM_MAXTRIES:
	case PAM_PERM_DENIED:
	    sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
		"pam_authenticate: %d", *pam_status);
	    debug_return_int(AUTH_FAILURE);
	default:
	    if ((s = pam_strerror(pamh, *pam_status)) != NULL)
		log_warningx(0, N_("PAM authentication error: %s"), s);
	    debug_return_int(AUTH_FATAL);
    }
}

int
sudo_pam_approval(struct passwd *pw, sudo_auth *auth, bool exempt)
{
    const char *s;
    int rc, status = AUTH_SUCCESS;
    int *pam_status = (int *) auth->data;
    debug_decl(sudo_pam_approval, SUDOERS_DEBUG_AUTH)

    rc = pam_acct_mgmt(pamh, PAM_SILENT);
    switch (rc) {
	case PAM_SUCCESS:
	    break;
	case PAM_AUTH_ERR:
	    log_warningx(0, N_("account validation failure, "
		"is your account locked?"));
	    status = AUTH_FATAL;
	    break;
	case PAM_NEW_AUTHTOK_REQD:
	    /* Ignore if user is exempt from password restrictions. */
	    if (exempt) {
		rc = *pam_status;
		break;
	    }
	    /* New password required, try to change it. */
	    log_warningx(0, N_("Account or password is "
		"expired, reset your password and try again"));
	    rc = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
	    if (rc == PAM_SUCCESS)
		break;
	    if ((s = pam_strerror(pamh, rc)) == NULL)
		s = "unknown error";
	    log_warningx(0,
		N_("unable to change expired password: %s"), s);
	    status = AUTH_FAILURE;
	    break;
	case PAM_AUTHTOK_EXPIRED:
	    /* Ignore if user is exempt from password restrictions. */
	    if (exempt) {
		rc = *pam_status;
		break;
	    }
	    /* Password expired, cannot be updated by user. */
	    log_warningx(0,
		N_("Password expired, contact your system administrator"));
	    status = AUTH_FATAL;
	    break;
	case PAM_ACCT_EXPIRED:
	    log_warningx(0,
		N_("Account expired or PAM config lacks an \"account\" "
		"section for sudo, contact your system administrator"));
	    status = AUTH_FATAL;
	    break;
	case PAM_AUTHINFO_UNAVAIL:
	case PAM_MAXTRIES:
	case PAM_PERM_DENIED:
	    s = pam_strerror(pamh, rc);
	    log_warningx(0, N_("PAM account management error: %s"),
		s ? s : "unknown error");
	    status = AUTH_FAILURE;
	    break;
	default:
	    s = pam_strerror(pamh, rc);
	    log_warningx(0, N_("PAM account management error: %s"),
		s ? s : "unknown error");
	    status = AUTH_FATAL;
	    break;
    }
    *pam_status = rc;
    debug_return_int(status);
}

int
sudo_pam_cleanup(struct passwd *pw, sudo_auth *auth)
{
    int *pam_status = (int *) auth->data;
    debug_decl(sudo_pam_cleanup, SUDOERS_DEBUG_AUTH)

    /* If successful, we can't close the session until sudo_pam_end_session() */
    if (*pam_status != PAM_SUCCESS || auth->end_session == NULL) {
	*pam_status = pam_end(pamh, *pam_status | PAM_DATA_SILENT);
	pamh = NULL;
    }
    debug_return_int(*pam_status == PAM_SUCCESS ? AUTH_SUCCESS : AUTH_FAILURE);
}

int
sudo_pam_begin_session(struct passwd *pw, char **user_envp[], sudo_auth *auth)
{
    int rc, status = AUTH_SUCCESS;
    int *pam_status = (int *) auth->data;
    const char *errstr;
    debug_decl(sudo_pam_begin_session, SUDOERS_DEBUG_AUTH)

    /*
     * If there is no valid user we cannot open a PAM session.
     * This is not an error as sudo can run commands with arbitrary
     * uids, it just means we are done from a session management standpoint.
     */
    if (pw == NULL) {
	if (pamh != NULL) {
	    rc = pam_end(pamh, PAM_SUCCESS | PAM_DATA_SILENT);
	    if (rc != PAM_SUCCESS) {
		errstr = pam_strerror(pamh, rc);
		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		    "pam_end: %s", errstr ? errstr : "unknown error");
	    }
	    pamh = NULL;
	}
	goto done;
    }

    /*
     * Update PAM_USER to reference the user we are running the command
     * as, as opposed to the user we authenticated as.
     */
    rc = pam_set_item(pamh, PAM_USER, pw->pw_name);
    if (rc != PAM_SUCCESS) {
	errstr = pam_strerror(pamh, rc);
	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
	    "pam_set_item(pamh, PAM_USER, %s): %s", pw->pw_name,
	    errstr ? errstr : "unknown error");
    }

    /*
     * Reinitialize credentials when changing the user.
     * We don't worry about a failure from pam_setcred() since with
     * stacked PAM auth modules a failure from one module may override
     * PAM_SUCCESS from another.  For example, given a non-local user,
     * pam_unix will fail but pam_ldap or pam_sss may succeed, but if
     * pam_unix is first in the stack, pam_setcred() will fail.
     */
    if (def_pam_setcred) {
	rc = pam_setcred(pamh, PAM_REINITIALIZE_CRED);
	if (rc != PAM_SUCCESS) {
	    errstr = pam_strerror(pamh, rc);
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"pam_setcred: %s", errstr ? errstr : "unknown error");
	}
    }

    if (def_pam_session) {
	/*
	 * We use PAM_SILENT to prevent pam_lastlog from printing last login
	 * information except when explicitly running a shell.
	 */
	const bool silent = !ISSET(sudo_mode, MODE_SHELL|MODE_LOGIN_SHELL);
	rc = pam_open_session(pamh, silent ? PAM_SILENT : 0);
	switch (rc) {
	case PAM_SUCCESS:
	    break;
	case PAM_SESSION_ERR:
	    /* Treat PAM_SESSION_ERR as a non-fatal error. */
	    errstr = pam_strerror(pamh, rc);
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"pam_open_session: %s", errstr ? errstr : "unknown error");
	    /* Avoid closing session that was not opened. */
	    def_pam_session = false;
	    break;
	default:
	    /* Unexpected session failure, treat as fatal error. */
	    *pam_status = rc;
	    errstr = pam_strerror(pamh, *pam_status);
	    log_warningx(0, N_("%s: %s"), "pam_open_session",
		errstr ? errstr : "unknown error");
	    rc = pam_end(pamh, *pam_status | PAM_DATA_SILENT);
	    if (rc != PAM_SUCCESS) {
		errstr = pam_strerror(pamh, rc);
		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		    "pam_end: %s", errstr ? errstr : "unknown error");
	    }
	    pamh = NULL;
	    status = AUTH_FATAL;
	    goto done;
	}
    }

#ifdef HAVE_PAM_GETENVLIST
    /*
     * Update environment based on what is stored in pamh.
     * If no authentication is done we will only have environment
     * variables if pam_env is called via session.
     */
    if (user_envp != NULL) {
	char **pam_envp = pam_getenvlist(pamh);
	if (pam_envp != NULL) {
	    /* Merge pam env with user env. */
	    if (!env_init(*user_envp) || !env_merge(pam_envp))
		status = AUTH_FATAL;
	    *user_envp = env_get();
	    (void)env_init(NULL);
	    free(pam_envp);
	    /* XXX - we leak any duplicates that were in pam_envp */
	}
    }
#endif /* HAVE_PAM_GETENVLIST */

done:
    debug_return_int(status);
}

int
sudo_pam_end_session(struct passwd *pw, sudo_auth *auth)
{
    int rc, status = AUTH_SUCCESS;
    debug_decl(sudo_pam_end_session, SUDOERS_DEBUG_AUTH)

    if (pamh != NULL) {
	/*
	 * Update PAM_USER to reference the user we are running the command
	 * as, as opposed to the user we authenticated as.
	 * XXX - still needed now that session init is in parent?
	 */
	rc = pam_set_item(pamh, PAM_USER, pw->pw_name);
	if (rc != PAM_SUCCESS) {
	    const char *errstr = pam_strerror(pamh, rc);
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"pam_set_item(pamh, PAM_USER, %s): %s", pw->pw_name,
		errstr ? errstr : "unknown error");
	}
	if (def_pam_session) {
	    rc = pam_close_session(pamh, PAM_SILENT);
	    if (rc != PAM_SUCCESS) {
		const char *errstr = pam_strerror(pamh, rc);
		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		    "pam_close_session: %s", errstr ? errstr : "unknown error");
	    }
	}
	if (def_pam_setcred) {
	    rc = pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT);
	    if (rc != PAM_SUCCESS) {
		const char *errstr = pam_strerror(pamh, rc);
		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		    "pam_setcred: %s", errstr ? errstr : "unknown error");
	    }
	}
	rc = pam_end(pamh, PAM_SUCCESS | PAM_DATA_SILENT);
	if (rc != PAM_SUCCESS) {
	    const char *errstr = pam_strerror(pamh, rc);
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"pam_end: %s", errstr ? errstr : "unknown error");
	    status = AUTH_FATAL;
	}
	pamh = NULL;
    }

    debug_return_int(status);
}

#define PROMPT_IS_PASSWORD(_p) \
    (strncmp((_p), "Password:", 9) == 0 && \
	((_p)[9] == '\0' || ((_p)[9] == ' ' && (_p)[10] == '\0')))

#ifdef PAM_TEXT_DOMAIN
# define PAM_PROMPT_IS_PASSWORD(_p) \
    (strcmp((_p), dgt(PAM_TEXT_DOMAIN, "Password:")) == 0 || \
	strcmp((_p), dgt(PAM_TEXT_DOMAIN, "Password: ")) == 0 || \
	PROMPT_IS_PASSWORD(_p))
#else
# define PAM_PROMPT_IS_PASSWORD(_p)	PROMPT_IS_PASSWORD(_p)
#endif /* PAM_TEXT_DOMAIN */

/*
 * We use the PAM prompt in preference to sudo's as long
 * as passprompt_override is not set and:
 *  a) the (translated) sudo prompt matches /^Password: ?/
 * or:
 *  b) the PAM prompt itself *doesn't* match /^Password: ?/
 *     or /^username's Password: ?/
 *
 * The intent is to use the PAM prompt for things like
 * challenge-response, otherwise use sudo's prompt.
 * There may also be cases where a localized translation
 * of "Password: " exists for PAM but not for sudo.
 */
static bool
use_pam_prompt(const char *pam_prompt)
{
    size_t user_len;
    debug_decl(use_pam_prompt, SUDOERS_DEBUG_AUTH)

    /* Always use sudo prompt if passprompt_override is set. */
    if (def_passprompt_override)
	debug_return_bool(false);

    /* If sudo prompt matches "^Password: ?$", use PAM prompt. */
    if (PROMPT_IS_PASSWORD(def_prompt))
	debug_return_bool(true);

    /* If PAM prompt matches "^Password: ?$", use sudo prompt. */
    if (PAM_PROMPT_IS_PASSWORD(pam_prompt))
	debug_return_bool(false);

    /*
     * Some PAM modules use "^username's Password: ?$" instead of
     * "^Password: ?" so check for that too.
     */
    user_len = strlen(user_name);
    if (strncmp(pam_prompt, user_name, user_len) == 0) {
	const char *cp = pam_prompt + user_len;
	if (strncmp(cp, "'s Password:", 12) == 0 &&
	    (cp[12] == '\0' || (cp[12] == ' ' && cp[13] == '\0')))
	    debug_return_bool(false);
    }

    /* Otherwise, use the PAM prompt. */
    debug_return_bool(true);
}

/*
 * ``Conversation function'' for PAM <-> human interaction.
 */
static int
converse(int num_msg, PAM_CONST struct pam_message **msg,
    struct pam_response **reply_out, void *vcallback)
{
    struct sudo_conv_callback *callback = NULL;
    struct pam_response *reply;
    const char *prompt;
    char *pass;
    int n, type;
    int ret = PAM_SUCCESS;
    debug_decl(converse, SUDOERS_DEBUG_AUTH)

    if (num_msg <= 0 || num_msg > PAM_MAX_NUM_MSG) {
	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
	    "invalid number of PAM messages: %d", num_msg);
	debug_return_int(PAM_CONV_ERR);
    }
    sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
	"number of PAM messages: %d", num_msg);

    if ((reply = calloc(num_msg, sizeof(struct pam_response))) == NULL) {
	sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
	debug_return_int(PAM_BUF_ERR);
    }
    *reply_out = reply;

    if (vcallback != NULL)
	callback = *((struct sudo_conv_callback **)vcallback);

    for (n = 0; n < num_msg; n++) {
	PAM_CONST struct pam_message *pm = PAM_MSG_GET(msg, n);

	type = SUDO_CONV_PROMPT_ECHO_OFF;
	switch (pm->msg_style) {
	    case PAM_PROMPT_ECHO_ON:
		type = SUDO_CONV_PROMPT_ECHO_ON;
		/* FALLTHROUGH */
	    case PAM_PROMPT_ECHO_OFF:
		/* Error out if the last password read was interrupted. */
		if (getpass_error)
		    goto done;

		/* Choose either the sudo prompt or the PAM one. */
		prompt = use_pam_prompt(pm->msg) ? pm->msg : def_prompt;

		/* Read the password unless interrupted. */
		pass = auth_getpass(prompt, type, callback);
		if (pass == NULL) {
		    /* Error (or ^C) reading password, don't try again. */
		    getpass_error = true;
		    ret = PAM_CONV_ERR;
		    goto done;
		}
		if (strlen(pass) >= PAM_MAX_RESP_SIZE) {
		    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
			"password longer than %d", PAM_MAX_RESP_SIZE);
		    ret = PAM_CONV_ERR;
		    memset_s(pass, SUDO_CONV_REPL_MAX, 0, strlen(pass));
		    goto done;
		}
		reply[n].resp = pass;	/* auth_getpass() malloc's a copy */
		break;
	    case PAM_TEXT_INFO:
		if (pm->msg != NULL)
		    sudo_printf(SUDO_CONV_INFO_MSG, "%s\n", pm->msg);
		break;
	    case PAM_ERROR_MSG:
		if (pm->msg != NULL)
		    sudo_printf(SUDO_CONV_ERROR_MSG, "%s\n", pm->msg);
		break;
	    default:
		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		    "unsupported message style: %d", pm->msg_style);
		ret = PAM_CONV_ERR;
		goto done;
	}
    }

done:
    if (ret != PAM_SUCCESS) {
	/* Zero and free allocated memory and return an error. */
	for (n = 0; n < num_msg; n++) {
	    struct pam_response *pr = &reply[n];

	    if (pr->resp != NULL) {
		memset_s(pr->resp, SUDO_CONV_REPL_MAX, 0, strlen(pr->resp));
		free(pr->resp);
		pr->resp = NULL;
	    }
	}
	free(reply);
	*reply_out = NULL;
    }
    debug_return_int(ret);
}

#endif /* HAVE_PAM */