qemu/fsdev/virtfs-proxy-helper.c
M. Mohan Kumar 17bff52b62 hw/9pfs: File system helper process for qemu 9p proxy FS
Provide root privilege access to QEMU 9p proxy filesystem using socket
communication.

Proxy helper is started by root user as:
~ # virtfs-proxy-helper -f|--fd <socket descriptor> -p|--path <path-to-share>

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2012-01-04 20:14:02 +05:30

301 lines
6.7 KiB
C

/*
* Helper for QEMU Proxy FS Driver
* Copyright IBM, Corp. 2011
*
* Authors:
* M. Mohan Kumar <mohan@in.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*/
#include <stdio.h>
#include <string.h>
#include <sys/un.h>
#include <limits.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <getopt.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/capability.h>
#include <sys/fsuid.h>
#include <stdarg.h>
#include <stdbool.h>
#include "qemu-common.h"
#include "virtio-9p-marshal.h"
#include "hw/9pfs/virtio-9p-proxy.h"
#define PROGNAME "virtfs-proxy-helper"
static struct option helper_opts[] = {
{"fd", required_argument, NULL, 'f'},
{"path", required_argument, NULL, 'p'},
{"nodaemon", no_argument, NULL, 'n'},
};
static bool is_daemon;
static void do_log(int loglevel, const char *format, ...)
{
va_list ap;
va_start(ap, format);
if (is_daemon) {
vsyslog(LOG_CRIT, format, ap);
} else {
vfprintf(stderr, format, ap);
}
va_end(ap);
}
static void do_perror(const char *string)
{
if (is_daemon) {
syslog(LOG_CRIT, "%s:%s", string, strerror(errno));
} else {
fprintf(stderr, "%s:%s\n", string, strerror(errno));
}
}
static int do_cap_set(cap_value_t *cap_value, int size, int reset)
{
cap_t caps;
if (reset) {
/*
* Start with an empty set and set permitted and effective
*/
caps = cap_init();
if (caps == NULL) {
do_perror("cap_init");
return -1;
}
if (cap_set_flag(caps, CAP_PERMITTED, size, cap_value, CAP_SET) < 0) {
do_perror("cap_set_flag");
goto error;
}
} else {
caps = cap_get_proc();
if (!caps) {
do_perror("cap_get_proc");
return -1;
}
}
if (cap_set_flag(caps, CAP_EFFECTIVE, size, cap_value, CAP_SET) < 0) {
do_perror("cap_set_flag");
goto error;
}
if (cap_set_proc(caps) < 0) {
do_perror("cap_set_proc");
goto error;
}
cap_free(caps);
return 0;
error:
cap_free(caps);
return -1;
}
static int init_capabilities(void)
{
/* helper needs following capbabilities only */
cap_value_t cap_list[] = {
CAP_CHOWN,
CAP_DAC_OVERRIDE,
CAP_FOWNER,
CAP_FSETID,
CAP_SETGID,
CAP_MKNOD,
CAP_SETUID,
};
return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 1);
}
static int socket_read(int sockfd, void *buff, ssize_t size)
{
ssize_t retval, total = 0;
while (size) {
retval = read(sockfd, buff, size);
if (retval == 0) {
return -EIO;
}
if (retval < 0) {
if (errno == EINTR) {
continue;
}
return -errno;
}
size -= retval;
buff += retval;
total += retval;
}
return total;
}
static int socket_write(int sockfd, void *buff, ssize_t size)
{
ssize_t retval, total = 0;
while (size) {
retval = write(sockfd, buff, size);
if (retval < 0) {
if (errno == EINTR) {
continue;
}
return -errno;
}
size -= retval;
buff += retval;
total += retval;
}
return total;
}
static int read_request(int sockfd, struct iovec *iovec, ProxyHeader *header)
{
int retval;
/*
* read the request header.
*/
iovec->iov_len = 0;
retval = socket_read(sockfd, iovec->iov_base, PROXY_HDR_SZ);
if (retval < 0) {
return retval;
}
iovec->iov_len = PROXY_HDR_SZ;
retval = proxy_unmarshal(iovec, 0, "dd", &header->type, &header->size);
if (retval < 0) {
return retval;
}
/*
* We can't process message.size > PROXY_MAX_IO_SZ.
* Treat it as fatal error
*/
if (header->size > PROXY_MAX_IO_SZ) {
return -ENOBUFS;
}
retval = socket_read(sockfd, iovec->iov_base + PROXY_HDR_SZ, header->size);
if (retval < 0) {
return retval;
}
iovec->iov_len += header->size;
return 0;
}
static void usage(char *prog)
{
fprintf(stderr, "usage: %s\n"
" -p|--path <path> 9p path to export\n"
" {-f|--fd <socket-descriptor>} socket file descriptor to be used\n"
" [-n|--nodaemon] Run as a normal program\n",
basename(prog));
}
static int process_requests(int sock)
{
int retval;
ProxyHeader header;
struct iovec in_iovec;
in_iovec.iov_base = g_malloc(PROXY_MAX_IO_SZ + PROXY_HDR_SZ);
in_iovec.iov_len = PROXY_MAX_IO_SZ + PROXY_HDR_SZ;
while (1) {
retval = read_request(sock, &in_iovec, &header);
if (retval < 0) {
goto error;
}
}
(void)socket_write;
error:
g_free(in_iovec.iov_base);
return -1;
}
int main(int argc, char **argv)
{
int sock;
char *rpath = NULL;
struct stat stbuf;
int c, option_index;
is_daemon = true;
sock = -1;
while (1) {
option_index = 0;
c = getopt_long(argc, argv, "p:nh?f:", helper_opts,
&option_index);
if (c == -1) {
break;
}
switch (c) {
case 'p':
rpath = strdup(optarg);
break;
case 'n':
is_daemon = false;
break;
case 'f':
sock = atoi(optarg);
break;
case '?':
case 'h':
default:
usage(argv[0]);
exit(EXIT_FAILURE);
}
}
/* Parameter validation */
if (sock == -1 || rpath == NULL) {
fprintf(stderr, "socket descriptor or path not specified\n");
usage(argv[0]);
exit(EXIT_FAILURE);
}
if (lstat(rpath, &stbuf) < 0) {
fprintf(stderr, "invalid path \"%s\" specified, %s\n",
rpath, strerror(errno));
exit(EXIT_FAILURE);
}
if (!S_ISDIR(stbuf.st_mode)) {
fprintf(stderr, "specified path \"%s\" is not directory\n", rpath);
exit(EXIT_FAILURE);
}
if (is_daemon) {
if (daemon(0, 0) < 0) {
fprintf(stderr, "daemon call failed\n");
exit(EXIT_FAILURE);
}
openlog(PROGNAME, LOG_PID, LOG_DAEMON);
}
do_log(LOG_INFO, "Started\n");
if (chdir("/") < 0) {
do_perror("chdir");
goto error;
}
if (chroot(rpath) < 0) {
do_perror("chroot");
goto error;
}
umask(0);
if (init_capabilities() < 0) {
goto error;
}
process_requests(sock);
error:
do_log(LOG_INFO, "Done\n");
closelog();
return 0;
}