nfs-utils/SOURCES/nfs-utils-1.3.0/utils/gssd/gssd_proc.c

/*
  gssd_proc.c

  Copyright (c) 2000-2004 The Regents of the University of Michigan.
  All rights reserved.

  Copyright (c) 2000 Dug Song <dugsong@UMICH.EDU>.
  Copyright (c) 2001 Andy Adamson <andros@UMICH.EDU>.
  Copyright (c) 2002 Marius Aamodt Eriksen <marius@UMICH.EDU>.
  Copyright (c) 2002 Bruce Fields <bfields@UMICH.EDU>
  Copyright (c) 2004 Kevin Coffman <kwc@umich.edu>
  All rights reserved, all wrongs reversed.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:

  1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
  3. Neither the name of the University nor the names of its
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif	/* HAVE_CONFIG_H */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <sys/param.h>
#include <rpc/rpc.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/fsuid.h>
#include <sys/resource.h>

#include <stdio.h>
#include <stdlib.h>
#include <pwd.h>
#include <grp.h>
#include <string.h>
#include <dirent.h>
#include <poll.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <gssapi/gssapi.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "gssd.h"
#include "err_util.h"
#include "gss_util.h"
#include "krb5_util.h"
#include "context.h"
#include "nfsrpc.h"
#include "nfslib.h"

/*
 * pollarray:
 *      array of struct pollfd suitable to pass to poll. initialized to
 *      zero - a zero struct is ignored by poll() because the events mask is 0.
 *
 * clnt_list:
 *      linked list of struct clnt_info which associates a clntXXX directory
 *	with an index into pollarray[], and other basic data about that client.
 *
 * Directory structure: created by the kernel
 *      {rpc_pipefs}/{dir}/clntXX         : one per rpc_clnt struct in the kernel
 *      {rpc_pipefs}/{dir}/clntXX/krb5    : read uid for which kernel wants
 *					    a context, write the resulting context
 *      {rpc_pipefs}/{dir}/clntXX/info    : stores info such as server name
 *      {rpc_pipefs}/{dir}/clntXX/gssd    : pipe for all gss mechanisms using
 *					    a text-based string of parameters
 *
 * Algorithm:
 *      Poll all {rpc_pipefs}/{dir}/clntXX/YYYY files.  When data is ready,
 *      read and process; performs rpcsec_gss context initialization protocol to
 *      get a cred for that user.  Writes result to corresponding krb5 file
 *      in a form the kernel code will understand.
 *      In addition, we make sure we are notified whenever anything is
 *      created or destroyed in {rpc_pipefs} or in any of the clntXX directories,
 *      and rescan the whole {rpc_pipefs} when this happens.
 */

struct pollfd * pollarray;

unsigned long pollsize;  /* the size of pollaray (in pollfd's) */

/* Avoid DNS reverse lookups on server names */
int avoid_dns = 1;

/*
 * convert a presentation address string to a sockaddr_storage struct. Returns
 * true on success or false on failure.
 *
 * Note that we do not populate the sin6_scope_id field here for IPv6 addrs.
 * gssd nececessarily relies on hostname resolution and DNS AAAA records
 * do not generally contain scope-id's. This means that GSSAPI auth really
 * can't work with IPv6 link-local addresses.
 *
 * We *could* consider changing this if we did something like adopt the
 * Microsoft "standard" of using the ipv6-literal.net domainname, but it's
 * not really feasible at present.
 */
static int
addrstr_to_sockaddr(struct sockaddr *sa, const char *node, const char *port)
{
	int rc;
	struct addrinfo *res;
	struct addrinfo hints = { .ai_flags = AI_NUMERICHOST | AI_NUMERICSERV };

#ifndef IPV6_SUPPORTED
	hints.ai_family = AF_INET;
#endif /* IPV6_SUPPORTED */

	rc = getaddrinfo(node, port, &hints, &res);
	if (rc) {
		printerr(0, "ERROR: unable to convert %s|%s to sockaddr: %s\n",
			 node, port, rc == EAI_SYSTEM ? strerror(errno) :
						gai_strerror(rc));
		return 0;
	}

#ifdef IPV6_SUPPORTED
	/*
	 * getnameinfo ignores the scopeid. If the address turns out to have
	 * a non-zero scopeid, we can't use it -- the resolved host might be
	 * completely different from the one intended.
	 */
	if (res->ai_addr->sa_family == AF_INET6) {
		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)res->ai_addr;
		if (sin6->sin6_scope_id) {
			printerr(0, "ERROR: address %s has non-zero "
				    "sin6_scope_id!\n", node);
			freeaddrinfo(res);
			return 0;
		}
	}
#endif /* IPV6_SUPPORTED */

	memcpy(sa, res->ai_addr, res->ai_addrlen);
	freeaddrinfo(res);
	return 1;
}

/*
 * convert a sockaddr to a hostname
 */
static char *
get_servername(const char *name, const struct sockaddr *sa, const char *addr)
{
	socklen_t		addrlen;
	int			err;
	char			*hostname;
	char			hbuf[NI_MAXHOST];
	unsigned char		buf[sizeof(struct in6_addr)];

	if (avoid_dns) {
		/*
		 * Determine if this is a server name, or an IP address.
		 * If it is an IP address, do the DNS lookup otherwise
		 * skip the DNS lookup.
		 */
		int is_fqdn = 1;
		if (strchr(name, '.') == NULL)
			is_fqdn = 0; /* local name */
		else if (inet_pton(AF_INET, name, buf) == 1)
			is_fqdn = 0; /* IPv4 address */
		else if (inet_pton(AF_INET6, name, buf) == 1)
			is_fqdn = 0; /* IPv6 addrss */

		if (is_fqdn) {
			return strdup(name);
		}
		/* Sorry, cannot avoid dns after all */
	}

	switch (sa->sa_family) {
	case AF_INET:
		addrlen = sizeof(struct sockaddr_in);
		break;
#ifdef IPV6_SUPPORTED
	case AF_INET6:
		addrlen = sizeof(struct sockaddr_in6);
		break;
#endif /* IPV6_SUPPORTED */
	default:
		printerr(0, "ERROR: unrecognized addr family %d\n",
			 sa->sa_family);
		return NULL;
	}

	err = getnameinfo(sa, addrlen, hbuf, sizeof(hbuf), NULL, 0,
			  NI_NAMEREQD);
	if (err) {
		printerr(0, "ERROR: unable to resolve %s to hostname: %s\n",
			 addr, err == EAI_SYSTEM ? strerror(err) :
						   gai_strerror(err));
		return NULL;
	}

	hostname = strdup(hbuf);

	return hostname;
}

/* XXX buffer problems: */
static int
read_service_info(char *info_file_name, char **servicename, char **servername,
		  int *prog, int *vers, char **protocol,
		  struct sockaddr *addr) {
#define INFOBUFLEN 256
	char		buf[INFOBUFLEN + 1];
	static char	server[128];
	int		nbytes;
	static char	service[128];
	static char	address[128];
	char		program[16];
	char		version[16];
	char		protoname[16];
	char		port[128];
	char		*p;
	int		fd = -1;
	int		numfields;

	*servicename = *servername = *protocol = NULL;

	if ((fd = open(info_file_name, O_RDONLY)) == -1) {
		printerr(0, "ERROR: can't open %s: %s\n", info_file_name,
			 strerror(errno));
		goto fail;
	}
	if ((nbytes = read(fd, buf, INFOBUFLEN)) == -1)
		goto fail;
	close(fd);
	fd = -1;
	buf[nbytes] = '\0';

	numfields = sscanf(buf,"RPC server: %127s\n"
		   "service: %127s %15s version %15s\n"
		   "address: %127s\n"
		   "protocol: %15s\n",
		   server,
		   service, program, version,
		   address,
		   protoname);

	if (numfields == 5) {
		strcpy(protoname, "tcp");
	} else if (numfields != 6) {
		goto fail;
	}

	port[0] = '\0';
	if ((p = strstr(buf, "port")) != NULL)
		sscanf(p, "port: %127s\n", port);

	/* get program, and version numbers */
	*prog = atoi(program + 1); /* skip open paren */
	*vers = atoi(version);

	if (!addrstr_to_sockaddr(addr, address, port))
		goto fail;

	*servername = get_servername(server, addr, address);
	if (*servername == NULL)
		goto fail;

	nbytes = snprintf(buf, INFOBUFLEN, "%s@%s", service, *servername);
	if (nbytes > INFOBUFLEN)
		goto fail;

	if (!(*servicename = calloc(strlen(buf) + 1, 1)))
		goto fail;
	memcpy(*servicename, buf, strlen(buf));

	if (!(*protocol = strdup(protoname)))
		goto fail;
	return 0;
fail:
	printerr(0, "ERROR: failed to read service info\n");
	if (fd != -1) close(fd);
	free(*servername);
	free(*servicename);
	free(*protocol);
	*servicename = *servername = *protocol = NULL;
	return -1;
}

static void
destroy_client(struct clnt_info *clp)
{
	if (clp->krb5_poll_index != -1)
		memset(&pollarray[clp->krb5_poll_index], 0,
					sizeof(struct pollfd));
	if (clp->gssd_poll_index != -1)
		memset(&pollarray[clp->gssd_poll_index], 0,
					sizeof(struct pollfd));
	if (clp->dir_fd != -1) close(clp->dir_fd);
	if (clp->krb5_fd != -1) close(clp->krb5_fd);
	if (clp->gssd_fd != -1) close(clp->gssd_fd);
	free(clp->dirname);
	free(clp->pdir);
	free(clp->servicename);
	free(clp->servername);
	free(clp->protocol);
	free(clp);
}

static struct clnt_info *
insert_new_clnt(void)
{
	struct clnt_info	*clp = NULL;

	if (!(clp = (struct clnt_info *)calloc(1,sizeof(struct clnt_info)))) {
		printerr(0, "ERROR: can't malloc clnt_info: %s\n",
			 strerror(errno));
		goto out;
	}
	clp->krb5_poll_index = -1;
	clp->gssd_poll_index = -1;
	clp->krb5_fd = -1;
	clp->gssd_fd = -1;
	clp->dir_fd = -1;

	TAILQ_INSERT_HEAD(&clnt_list, clp, list);
out:
	return clp;
}

static int
process_clnt_dir_files(struct clnt_info * clp)
{
	char	name[PATH_MAX];
	char	gname[PATH_MAX];
	char	info_file_name[PATH_MAX];

	if (clp->gssd_close_me) {
		printerr(2, "Closing 'gssd' pipe for %s\n", clp->dirname);
		close(clp->gssd_fd);
		memset(&pollarray[clp->gssd_poll_index], 0,
			sizeof(struct pollfd));
		clp->gssd_fd = -1;
		clp->gssd_poll_index = -1;
		clp->gssd_close_me = 0;
	}
	if (clp->krb5_close_me) {
		printerr(2, "Closing 'krb5' pipe for %s\n", clp->dirname);
		close(clp->krb5_fd);
		memset(&pollarray[clp->krb5_poll_index], 0,
			sizeof(struct pollfd));
		clp->krb5_fd = -1;
		clp->krb5_poll_index = -1;
		clp->krb5_close_me = 0;
	}

	if (clp->gssd_fd == -1) {
		snprintf(gname, sizeof(gname), "%s/gssd", clp->dirname);
		clp->gssd_fd = open(gname, O_RDWR);
	}
	if (clp->gssd_fd == -1) {
		if (clp->krb5_fd == -1) {
			snprintf(name, sizeof(name), "%s/krb5", clp->dirname);
			clp->krb5_fd = open(name, O_RDWR);
		}

		/* If we opened a gss-specific pipe, let's try opening
		 * the new upcall pipe again. If we succeed, close
		 * gss-specific pipe(s).
		 */
		if (clp->krb5_fd != -1) {
			clp->gssd_fd = open(gname, O_RDWR);
			if (clp->gssd_fd != -1) {
				if (clp->krb5_fd != -1)
					close(clp->krb5_fd);
				clp->krb5_fd = -1;
			}
		}
	}

	if ((clp->krb5_fd == -1) && (clp->gssd_fd == -1))
		return -1;
	snprintf(info_file_name, sizeof(info_file_name), "%s/info",
			clp->dirname);
	if (clp->prog == 0)
		read_service_info(info_file_name, &clp->servicename,
				  &clp->servername, &clp->prog, &clp->vers,
				  &clp->protocol, (struct sockaddr *) &clp->addr);
	return 0;
}

static int
get_poll_index(int *ind)
{
	unsigned int i;

	*ind = -1;
	for (i=0; i<pollsize; i++) {
		if (pollarray[i].events == 0) {
			*ind = i;
			break;
		}
	}
	if (*ind == -1) {
		printerr(0, "ERROR: No pollarray slots open\n");
		return -1;
	}
	return 0;
}


static int
insert_clnt_poll(struct clnt_info *clp)
{
	if ((clp->gssd_fd != -1) && (clp->gssd_poll_index == -1)) {
		if (get_poll_index(&clp->gssd_poll_index)) {
			printerr(0, "ERROR: Too many gssd clients\n");
			return -1;
		}
		pollarray[clp->gssd_poll_index].fd = clp->gssd_fd;
		pollarray[clp->gssd_poll_index].events |= POLLIN;
	}

	if ((clp->krb5_fd != -1) && (clp->krb5_poll_index == -1)) {
		if (get_poll_index(&clp->krb5_poll_index)) {
			printerr(0, "ERROR: Too many krb5 clients\n");
			return -1;
		}
		pollarray[clp->krb5_poll_index].fd = clp->krb5_fd;
		pollarray[clp->krb5_poll_index].events |= POLLIN;
	}

	return 0;
}

static void
process_clnt_dir(char *dir, char *pdir)
{
	struct clnt_info *	clp;

	if (!(clp = insert_new_clnt()))
		goto fail_destroy_client;

	if (!(clp->pdir = strdup(pdir)))
		goto fail_destroy_client;

	/* An extra for the '/', and an extra for the null */
	if (!(clp->dirname = calloc(strlen(dir) + strlen(pdir) + 2, 1))) {
		goto fail_destroy_client;
	}
	sprintf(clp->dirname, "%s/%s", pdir, dir);
	if ((clp->dir_fd = open(clp->dirname, O_RDONLY)) == -1) {
		if (errno != ENOENT)
			printerr(0, "ERROR: can't open %s: %s\n",
				 clp->dirname, strerror(errno));
		goto fail_destroy_client;
	}
	fcntl(clp->dir_fd, F_SETSIG, DNOTIFY_SIGNAL);
	fcntl(clp->dir_fd, F_NOTIFY, DN_CREATE | DN_DELETE | DN_MULTISHOT);

	if (process_clnt_dir_files(clp))
		goto fail_keep_client;

	if (insert_clnt_poll(clp))
		goto fail_destroy_client;

	return;

fail_destroy_client:
	if (clp) {
		TAILQ_REMOVE(&clnt_list, clp, list);
		destroy_client(clp);
	}
fail_keep_client:
	/* We couldn't find some subdirectories, but we keep the client
	 * around in case we get a notification on the directory when the
	 * subdirectories are created. */
	return;
}

void
init_client_list(void)
{
	struct rlimit rlim;
	TAILQ_INIT(&clnt_list);
	/* Eventually plan to grow/shrink poll array: */
	pollsize = FD_ALLOC_BLOCK;
	if (getrlimit(RLIMIT_NOFILE, &rlim) == 0 &&
	    rlim.rlim_cur != RLIM_INFINITY)
		pollsize = rlim.rlim_cur;
	pollarray = calloc(pollsize, sizeof(struct pollfd));
}

/*
 * This is run after a DNOTIFY signal, and should clear up any
 * directories that are no longer around, and re-scan any existing
 * directories, since the DNOTIFY could have been in there.
 */
static void
update_old_clients(struct dirent **namelist, int size, char *pdir)
{
	struct clnt_info *clp;
	void *saveprev;
	int i, stillhere;
	char fname[PATH_MAX];

	for (clp = clnt_list.tqh_first; clp != NULL; clp = clp->list.tqe_next) {
		/* only compare entries in the global list that are from the
		 * same pipefs parent directory as "pdir"
		 */
		if (strcmp(clp->pdir, pdir) != 0) continue;

		stillhere = 0;
		for (i=0; i < size; i++) {
			snprintf(fname, sizeof(fname), "%s/%s",
				 pdir, namelist[i]->d_name);
			if (strcmp(clp->dirname, fname) == 0) {
				stillhere = 1;
				break;
			}
		}
		if (!stillhere) {
			printerr(2, "destroying client %s\n", clp->dirname);
			saveprev = clp->list.tqe_prev;
			TAILQ_REMOVE(&clnt_list, clp, list);
			destroy_client(clp);
			clp = saveprev;
		}
	}
	for (clp = clnt_list.tqh_first; clp != NULL; clp = clp->list.tqe_next) {
		if (!process_clnt_dir_files(clp))
			insert_clnt_poll(clp);
	}
}

/* Search for a client by directory name, return 1 if found, 0 otherwise */
static int
find_client(char *dirname, char *pdir)
{
	struct clnt_info	*clp;
	char fname[PATH_MAX];

	for (clp = clnt_list.tqh_first; clp != NULL; clp = clp->list.tqe_next) {
		snprintf(fname, sizeof(fname), "%s/%s", pdir, dirname);
		if (strcmp(clp->dirname, fname) == 0)
			return 1;
	}
	return 0;
}

static int
process_pipedir(char *pipe_name)
{
	struct dirent **namelist;
	int i, j;

	if (chdir(pipe_name) < 0) {
		printerr(0, "ERROR: can't chdir to %s: %s\n",
			 pipe_name, strerror(errno));
		return -1;
	}

	j = scandir(pipe_name, &namelist, NULL, alphasort);
	if (j < 0) {
		printerr(0, "ERROR: can't scandir %s: %s\n",
			 pipe_name, strerror(errno));
		return -1;
	}

	update_old_clients(namelist, j, pipe_name);
	for (i=0; i < j; i++) {
		if (!strncmp(namelist[i]->d_name, "clnt", 4)
		    && !find_client(namelist[i]->d_name, pipe_name))
			process_clnt_dir(namelist[i]->d_name, pipe_name);
		free(namelist[i]);
	}

	free(namelist);

	return 0;
}

/* Used to read (and re-read) list of clients, set up poll array. */
int
update_client_list(void)
{
	int retval = -1;
	struct topdirs_info *tdi;

	TAILQ_FOREACH(tdi, &topdirs_list, list) {
		retval = process_pipedir(tdi->dirname);
		if (retval)
			printerr(1, "WARNING: error processing %s\n",
				 tdi->dirname);

	}
	return retval;
}

/* Encryption types supported by the kernel rpcsec_gss code */
int num_krb5_enctypes = 0;
krb5_enctype *krb5_enctypes = NULL;

/*
 * Parse the supported encryption type information
 */
static int
parse_enctypes(char *enctypes)
{
	int n = 0;
	char *curr, *comma;
	int i;
	static char *cached_types;

	if (cached_types && strcmp(cached_types, enctypes) == 0)
		return 0;
	free(cached_types);

	if (krb5_enctypes != NULL) {
		free(krb5_enctypes);
		krb5_enctypes = NULL;
		num_krb5_enctypes = 0;
	}

	/* count the number of commas */
	for (curr = enctypes; curr && *curr != '\0'; curr = ++comma) {
		comma = strchr(curr, ',');
		if (comma != NULL)
			n++;
		else
			break;
	}
	/* If no more commas and we're not at the end, there's one more value */
	if (*curr != '\0')
		n++;

	/* Empty string, return an error */
	if (n == 0)
		return ENOENT;

	/* Allocate space for enctypes array */
	if ((krb5_enctypes = (int *) calloc(n, sizeof(int))) == NULL) {
		return ENOMEM;
	}

	/* Now parse each value into the array */
	for (curr = enctypes, i = 0; curr && *curr != '\0'; curr = ++comma) {
		krb5_enctypes[i++] = atoi(curr);
		comma = strchr(curr, ',');
		if (comma == NULL)
			break;
	}

	num_krb5_enctypes = n;
	if ((cached_types = malloc(strlen(enctypes)+1)))
		strcpy(cached_types, enctypes);

	return 0;
}

static int
do_downcall(int k5_fd, uid_t uid, struct authgss_private_data *pd,
	    gss_buffer_desc *context_token, OM_uint32 lifetime_rec)
{
	char    *buf = NULL, *p = NULL, *end = NULL;
	unsigned int timeout = context_timeout;
	unsigned int buf_size = 0;

	printerr(1, "doing downcall lifetime_rec %u\n", lifetime_rec);
	buf_size = sizeof(uid) + sizeof(timeout) + sizeof(pd->pd_seq_win) +
		sizeof(pd->pd_ctx_hndl.length) + pd->pd_ctx_hndl.length +
		sizeof(context_token->length) + context_token->length;
	p = buf = malloc(buf_size);
	end = buf + buf_size;

	/* context_timeout set by -t option overrides context lifetime */
	if (timeout == 0)
		timeout = lifetime_rec;
	if (WRITE_BYTES(&p, end, uid)) goto out_err;
	if (WRITE_BYTES(&p, end, timeout)) goto out_err;
	if (WRITE_BYTES(&p, end, pd->pd_seq_win)) goto out_err;
	if (write_buffer(&p, end, &pd->pd_ctx_hndl)) goto out_err;
	if (write_buffer(&p, end, context_token)) goto out_err;

	if (write(k5_fd, buf, p - buf) < p - buf) goto out_err;
	if (buf) free(buf);
	return 0;
out_err:
	if (buf) free(buf);
	printerr(1, "Failed to write downcall!\n");
	return -1;
}

static int
do_error_downcall(int k5_fd, uid_t uid, int err)
{
	char	buf[1024];
	char	*p = buf, *end = buf + 1024;
	unsigned int timeout = 0;
	int	zero = 0;

	printerr(1, "doing error downcall\n");

	if (WRITE_BYTES(&p, end, uid)) goto out_err;
	if (WRITE_BYTES(&p, end, timeout)) goto out_err;
	/* use seq_win = 0 to indicate an error: */
	if (WRITE_BYTES(&p, end, zero)) goto out_err;
	if (WRITE_BYTES(&p, end, err)) goto out_err;

	if (write(k5_fd, buf, p - buf) < p - buf) goto out_err;
	return 0;
out_err:
	printerr(1, "Failed to write error downcall!\n");
	return -1;
}

/*
 * If the port isn't already set, do an rpcbind query to the remote server
 * using the program and version and get the port.
 *
 * Newer kernels send the value of the port= mount option in the "info"
 * file for the upcall or '0' for NFSv2/3. For NFSv4 it sends the value
 * of the port= option or '2049'. The port field in a new sockaddr should
 * reflect the value that was sent by the kernel.
 */
static int
populate_port(struct sockaddr *sa, const socklen_t salen,
	      const rpcprog_t program, const rpcvers_t version,
	      const unsigned short protocol)
{
	struct sockaddr_in	*s4 = (struct sockaddr_in *) sa;
#ifdef IPV6_SUPPORTED
	struct sockaddr_in6	*s6 = (struct sockaddr_in6 *) sa;
#endif /* IPV6_SUPPORTED */
	unsigned short		port;

	/*
	 * Newer kernels send the port in the upcall. If we already have
	 * the port, there's no need to look it up.
	 */
	switch (sa->sa_family) {
	case AF_INET:
		if (s4->sin_port != 0) {
			printerr(2, "DEBUG: port already set to %d\n",
				 ntohs(s4->sin_port));
			return 1;
		}
		break;
#ifdef IPV6_SUPPORTED
	case AF_INET6:
		if (s6->sin6_port != 0) {
			printerr(2, "DEBUG: port already set to %d\n",
				 ntohs(s6->sin6_port));
			return 1;
		}
		break;
#endif /* IPV6_SUPPORTED */
	default:
		printerr(0, "ERROR: unsupported address family %d\n",
			    sa->sa_family);
		return 0;
	}

	/*
	 * Newer kernels that send the port in the upcall set the value to
	 * 2049 for NFSv4 mounts when one isn't specified. The check below is
	 * only for kernels that don't send the port in the upcall. For those
	 * we either have to do an rpcbind query or set it to the standard
	 * port. Doing a query could be problematic (firewalls, etc), so take
	 * the latter approach.
	 */
	if (program == 100003 && version == 4) {
		port = 2049;
		goto set_port;
	}

	port = nfs_getport(sa, salen, program, version, protocol);
	if (!port) {
		printerr(0, "ERROR: unable to obtain port for prog %ld "
			    "vers %ld\n", program, version);
		return 0;
	}

set_port:
	printerr(2, "DEBUG: setting port to %hu for prog %lu vers %lu\n", port,
		 program, version);

	switch (sa->sa_family) {
	case AF_INET:
		s4->sin_port = htons(port);
		break;
#ifdef IPV6_SUPPORTED
	case AF_INET6:
		s6->sin6_port = htons(port);
		break;
#endif /* IPV6_SUPPORTED */
	}

	return 1;
}

/*
 * Create an RPC connection and establish an authenticated
 * gss context with a server.
 */
static int
create_auth_rpc_client(struct clnt_info *clp,
		       char *tgtname,
		       CLIENT **clnt_return,
		       AUTH **auth_return,
		       uid_t uid,
		       int authtype,
		       gss_cred_id_t cred)
{
	CLIENT			*rpc_clnt = NULL;
	struct rpc_gss_sec	sec;
	AUTH			*auth = NULL;
	int			retval = -1;
	OM_uint32		min_stat;
	char			rpc_errmsg[1024];
	int			protocol;
	struct timeval		timeout = {5, 0};
	struct sockaddr		*addr = (struct sockaddr *) &clp->addr;
	socklen_t		salen;

	sec.qop = GSS_C_QOP_DEFAULT;
	sec.svc = RPCSEC_GSS_SVC_NONE;
	sec.cred = cred;
	sec.req_flags = 0;
	if (authtype == AUTHTYPE_KRB5) {
		sec.mech = (gss_OID)&krb5oid;
		sec.req_flags = GSS_C_MUTUAL_FLAG;
	}
	else {
		printerr(0, "ERROR: Invalid authentication type (%d) "
			"in create_auth_rpc_client\n", authtype);
		goto out_fail;
	}


	if (authtype == AUTHTYPE_KRB5) {
#ifdef HAVE_SET_ALLOWABLE_ENCTYPES
		/*
		 * Do this before creating rpc connection since we won't need
		 * rpc connection if it fails!
		 */
		if (limit_krb5_enctypes(&sec)) {
			printerr(1, "WARNING: Failed while limiting krb5 "
				    "encryption types for user with uid %d\n",
				 uid);
			goto out_fail;
		}
#endif
	}

	/* create an rpc connection to the nfs server */

	printerr(2, "creating %s client for server %s\n", clp->protocol,
			clp->servername);

	if ((strcmp(clp->protocol, "tcp")) == 0) {
		protocol = IPPROTO_TCP;
	} else if ((strcmp(clp->protocol, "udp")) == 0) {
		protocol = IPPROTO_UDP;
	} else {
		printerr(0, "WARNING: unrecognized protocol, '%s', requested "
			 "for connection to server %s for user with uid %d\n",
			 clp->protocol, clp->servername, uid);
		goto out_fail;
	}

	switch (addr->sa_family) {
	case AF_INET:
		salen = sizeof(struct sockaddr_in);
		break;
#ifdef IPV6_SUPPORTED
	case AF_INET6:
		salen = sizeof(struct sockaddr_in6);
		break;
#endif /* IPV6_SUPPORTED */
	default:
		printerr(1, "ERROR: Unknown address family %d\n",
			 addr->sa_family);
		goto out_fail;
	}

	if (!populate_port(addr, salen, clp->prog, clp->vers, protocol))
		goto out_fail;

	rpc_clnt = nfs_get_rpcclient(addr, salen, protocol, clp->prog,
				     clp->vers, &timeout);
	if (!rpc_clnt) {
		snprintf(rpc_errmsg, sizeof(rpc_errmsg),
			 "WARNING: can't create %s rpc_clnt to server %s for "
			 "user with uid %d",
			 protocol == IPPROTO_TCP ? "tcp" : "udp",
			 clp->servername, uid);
		printerr(0, "%s\n",
			 clnt_spcreateerror(rpc_errmsg));
		goto out_fail;
	}
	if (!tgtname)
		tgtname = clp->servicename;

	printerr(2, "creating context with server %s\n", tgtname);
	auth = authgss_create_default(rpc_clnt, tgtname, &sec);
	if (!auth) {
		/* Our caller should print appropriate message */
		printerr(2, "WARNING: Failed to create krb5 context for "
			    "user with uid %d for server %s\n",
			 uid, tgtname);
		goto out_fail;
	}

	/* Success !!! */
	rpc_clnt->cl_auth = auth;
	*clnt_return = rpc_clnt;
	*auth_return = auth;
	retval = 0;

  out:
	if (sec.cred != GSS_C_NO_CREDENTIAL)
		gss_release_cred(&min_stat, &sec.cred);
	return retval;

  out_fail:
	/* Only destroy here if failure.  Otherwise, caller is responsible */
	if (rpc_clnt) clnt_destroy(rpc_clnt);

	goto out;
}

/*
 * Create the context as the user (not as root).
 *
 * Note that we change the *real* uid here, as changing the effective uid is
 * not sufficient. This is due to an unfortunate historical error in the MIT
 * krb5 libs, where they used %{uid} in the default_ccache_name. Changing that
 * now might break some applications so we're sort of stuck with it.
 *
 * Unfortunately, doing this leaves the forked child vulnerable to signals and
 * renicing, but this is the best we can do. In the event that a child is
 * signalled before downcalling, the kernel will just eventually time out the
 * upcall attempt.
 */
static int
change_identity(uid_t uid)
{
	struct passwd	*pw;

	/* drop list of supplimentary groups first */
	if (setgroups(0, NULL) != 0) {
		printerr(0, "WARNING: unable to drop supplimentary groups!");
		return errno;
	}

	/* try to get pwent for user */
	pw = getpwuid(uid);
	if (!pw) {
		/* if that doesn't work, try to get one for "nobody" */
		errno = 0;
		pw = getpwnam("nobody");
		if (!pw) {
			printerr(0, "WARNING: unable to determine gid for uid %u\n", uid);
			return errno ? errno : ENOENT;
		}
	}

	/*
	 * Switch the GIDs. Note that we leave the saved-set-gid alone in an
	 * attempt to prevent attacks via ptrace()
	 */
	if (setresgid(pw->pw_gid, pw->pw_gid, -1) != 0) {
		printerr(0, "WARNING: failed to set gid to %u!\n", pw->pw_gid);
		return errno;
	}

	/*
	 * Switch UIDs, but leave saved-set-uid alone to prevent ptrace() by
	 * other processes running with this uid.
	 */
	if (setresuid(uid, uid, -1) != 0) {
		printerr(0, "WARNING: Failed to setuid for user with uid %u\n",
				uid);
		return errno;
	}

	return 0;
}

/*
 * this code uses the userland rpcsec gss library to create a krb5
 * context on behalf of the kernel
 */
static void
process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname,
		    char *service)
{
	CLIENT			*rpc_clnt = NULL;
	AUTH			*auth = NULL;
	struct authgss_private_data pd;
	gss_buffer_desc		token;
	char			**credlist = NULL;
	char			**ccname;
	char			**dirname;
	int			create_resp = -1;
	int			err, downcall_err = -EACCES;
	gss_cred_id_t		gss_cred;
	OM_uint32		maj_stat, min_stat, lifetime_rec;
	pid_t			pid;

	pid = fork();
	switch(pid) {
	case 0:
		/* Child: fall through to rest of function */
		break;
	case -1:
		/* fork() failed! */
		printerr(0, "WARNING: unable to fork() to handle upcall: %s\n",
				strerror(errno));
		return;
	default:
		/* Parent: just wait on child to exit and return */
		do {
			pid = wait(&err);
		} while(pid == -1 && errno != -ECHILD);

		if (WIFSIGNALED(err))
			printerr(0, "WARNING: forked child was killed with signal %d\n",
					WTERMSIG(err));
		return;
	}

	printerr(1, "handling krb5 upcall (%s)\n", clp->dirname);

	token.length = 0;
	token.value = NULL;
	memset(&pd, 0, sizeof(struct authgss_private_data));

	/*
	 * If "service" is specified, then the kernel is indicating that
	 * we must use machine credentials for this request.  (Regardless
	 * of the uid value or the setting of root_uses_machine_creds.)
	 * If the service value is "*", then any service name can be used.
	 * Otherwise, it specifies the service name that should be used.
	 * (For now, the values of service will only be "*" or "nfs".)
	 *
	 * Restricting gssd to use "nfs" service name is needed for when
	 * the NFS server is doing a callback to the NFS client.  In this
	 * case, the NFS server has to authenticate itself as "nfs" --
	 * even if there are other service keys such as "host" or "root"
	 * in the keytab.
	 *
	 * Another case when the kernel may specify the service attribute
	 * is when gssd is being asked to create the context for a
	 * SETCLIENT_ID operation.  In this case, machine credentials
	 * must be used for the authentication.  However, the service name
	 * used for this case is not important.
	 *
	 */
	printerr(2, "%s: service is '%s'\n", __func__,
		 service ? service : "<null>");
	if (uid != 0 || (uid == 0 && root_uses_machine_creds == 0 &&
				service == NULL)) {

		err = change_identity(uid);
		if (err) {
			printerr(0, "WARNING: failed to change identity: %s",
				 strerror(err));
			goto out_return_error;
		}

		/* Tell krb5 gss which credentials cache to use */
		/* Try first to acquire credentials directly via GSSAPI */
		err = gssd_acquire_user_cred(&gss_cred);
		if (!err)
			create_resp = create_auth_rpc_client(clp, tgtname, &rpc_clnt, &auth, uid,
							     AUTHTYPE_KRB5, gss_cred);
		/* if create_auth_rplc_client fails try the traditional method of
		 * trolling for credentials */
		for (dirname = ccachesearch; create_resp != 0 && *dirname != NULL; dirname++) {
			err = gssd_setup_krb5_user_gss_ccache(uid, clp->servername, *dirname);
			if (err == -EKEYEXPIRED)
				downcall_err = -EKEYEXPIRED;
			else if (!err)
				create_resp = create_auth_rpc_client(clp, tgtname, &rpc_clnt, &auth, uid,
							     AUTHTYPE_KRB5, GSS_C_NO_CREDENTIAL);
		}
	}
	if (create_resp != 0) {
		if (uid == 0 && (root_uses_machine_creds == 1 ||
				service != NULL)) {
			int nocache = 0;
			int success = 0;
			do {
				gssd_refresh_krb5_machine_credential(clp->servername,
								     NULL, service);
				/*
				 * Get a list of credential cache names and try each
				 * of them until one works or we've tried them all
				 */
				if (gssd_get_krb5_machine_cred_list(&credlist)) {
					printerr(0, "ERROR: No credentials found "
						 "for connection to server %s\n",
						 clp->servername);
					goto out_return_error;
				}
				for (ccname = credlist; ccname && *ccname; ccname++) {
					gssd_setup_krb5_machine_gss_ccache(*ccname);
					if ((create_auth_rpc_client(clp, tgtname, &rpc_clnt,
								    &auth, uid,
								    AUTHTYPE_KRB5,
								    GSS_C_NO_CREDENTIAL)) == 0) {
						/* Success! */
						success++;
						break;
					}
					printerr(2, "WARNING: Failed to create machine krb5 context "
						 "with credentials cache %s for server %s\n",
						 *ccname, clp->servername);
				}
				gssd_free_krb5_machine_cred_list(credlist);
				if (!success) {
					if(nocache == 0) {
						nocache++;
						printerr(2, "WARNING: Machine cache is prematurely expired or corrupted "
						            "trying to recreate cache for server %s\n", clp->servername);
					} else {
						printerr(1, "WARNING: Failed to create machine krb5 context "
						 "with any credentials cache for server %s\n",
						 clp->servername);
						goto out_return_error;
					}
				}
			} while(!success);
		} else {
			printerr(1, "WARNING: Failed to create krb5 context "
				 "for user with uid %d for server %s\n",
				 uid, clp->servername);
			goto out_return_error;
		}
	}

	if (!authgss_get_private_data(auth, &pd)) {
		printerr(1, "WARNING: Failed to obtain authentication "
			    "data for user with uid %d for server %s\n",
			 uid, clp->servername);
		goto out_return_error;
	}

	/* Grab the context lifetime to pass to the kernel. lifetime_rec
	 * is set to zero on error */
	maj_stat = gss_inquire_context(&min_stat, pd.pd_ctx, NULL, NULL,
				       &lifetime_rec, NULL, NULL, NULL, NULL);

	if (maj_stat)
		printerr(1, "WARNING: Failed to inquire context for lifetme "
			    "maj_stat %u\n", maj_stat);

	if (serialize_context_for_kernel(&pd.pd_ctx, &token, &krb5oid, NULL)) {
		printerr(0, "WARNING: Failed to serialize krb5 context for "
			    "user with uid %d for server %s\n",
			 uid, clp->servername);
		goto out_return_error;
	}

	do_downcall(fd, uid, &pd, &token, lifetime_rec);

out:
	if (token.value)
		free(token.value);
#ifdef HAVE_AUTHGSS_FREE_PRIVATE_DATA
	if (pd.pd_ctx_hndl.length != 0 || pd.pd_ctx != 0)
		authgss_free_private_data(&pd);
#endif
	if (auth)
		AUTH_DESTROY(auth);
	if (rpc_clnt)
		clnt_destroy(rpc_clnt);
	exit(0);

out_return_error:
	do_error_downcall(fd, uid, downcall_err);
	goto out;
}

void
handle_krb5_upcall(struct clnt_info *clp)
{
	uid_t			uid;

	if (read(clp->krb5_fd, &uid, sizeof(uid)) < (ssize_t)sizeof(uid)) {
		printerr(0, "WARNING: failed reading uid from krb5 "
			    "upcall pipe: %s\n", strerror(errno));
		return;
	}

	process_krb5_upcall(clp, uid, clp->krb5_fd, NULL, NULL);
}

void
handle_gssd_upcall(struct clnt_info *clp)
{
	uid_t			uid;
	char			*lbuf = NULL;
	int			lbuflen = 0;
	char			*p;
	char			*mech = NULL;
	char			*target = NULL;
	char			*service = NULL;
	char			*enctypes = NULL;

	printerr(1, "handling gssd upcall (%s)\n", clp->dirname);

	if (readline(clp->gssd_fd, &lbuf, &lbuflen) != 1) {
		printerr(0, "WARNING: handle_gssd_upcall: "
			    "failed reading request\n");
		return;
	}
	printerr(2, "%s: '%s'\n", __func__, lbuf);

	/* find the mechanism name */
	if ((p = strstr(lbuf, "mech=")) != NULL) {
		mech = malloc(lbuflen);
		if (!mech)
			goto out;
		if (sscanf(p, "mech=%s", mech) != 1) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				    "failed to parse gss mechanism name "
				    "in upcall string '%s'\n", lbuf);
			goto out;
		}
	} else {
		printerr(0, "WARNING: handle_gssd_upcall: "
			    "failed to find gss mechanism name "
			    "in upcall string '%s'\n", lbuf);
		goto out;
	}

	/* read uid */
	if ((p = strstr(lbuf, "uid=")) != NULL) {
		if (sscanf(p, "uid=%d", &uid) != 1) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				    "failed to parse uid "
				    "in upcall string '%s'\n", lbuf);
			goto out;
		}
	} else {
		printerr(0, "WARNING: handle_gssd_upcall: "
			    "failed to find uid "
			    "in upcall string '%s'\n", lbuf);
		goto out;
	}

	/* read supported encryption types if supplied */
	if ((p = strstr(lbuf, "enctypes=")) != NULL) {
		enctypes = malloc(lbuflen);
		if (!enctypes)
			goto out;
		if (sscanf(p, "enctypes=%s", enctypes) != 1) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				    "failed to parse encryption types "
				    "in upcall string '%s'\n", lbuf);
			goto out;
		}
		if (parse_enctypes(enctypes) != 0) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				"parsing encryption types failed: errno %d\n", errno);
		}
	}

	/* read target name */
	if ((p = strstr(lbuf, "target=")) != NULL) {
		target = malloc(lbuflen);
		if (!target)
			goto out;
		if (sscanf(p, "target=%s", target) != 1) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				    "failed to parse target name "
				    "in upcall string '%s'\n", lbuf);
			goto out;
		}
	}

	/*
	 * read the service name
	 *
	 * The presence of attribute "service=" indicates that machine
	 * credentials should be used for this request.  If the value
	 * is "*", then any machine credentials available can be used.
	 * If the value is anything else, then machine credentials for
	 * the specified service name (always "nfs" for now) should be
	 * used.
	 */
	if ((p = strstr(lbuf, "service=")) != NULL) {
		service = malloc(lbuflen);
		if (!service)
			goto out;
		if (sscanf(p, "service=%s", service) != 1) {
			printerr(0, "WARNING: handle_gssd_upcall: "
				    "failed to parse service type "
				    "in upcall string '%s'\n", lbuf);
			goto out;
		}
	}

	if (strcmp(mech, "krb5") == 0 && clp->servername)
		process_krb5_upcall(clp, uid, clp->gssd_fd, target, service);
	else {
		if (clp->servername)
			printerr(0, "WARNING: handle_gssd_upcall: "
				 "received unknown gss mech '%s'\n", mech);
		do_error_downcall(clp->gssd_fd, uid, -EACCES);
	}

out:
	free(lbuf);
	free(mech);
	free(enctypes);
	free(target);
	free(service);
	return;
}