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18a10ddc16
libvirt/tools/virt-login-shell.c
Daniel P. Berrange 18a10ddc16 virt-login-shell: add ability to auto-detect shell from container 
Currently the shell must be looked up from the config setting in
/etc/libvirt/virt-login-shell.conf. This is inflexible if there
are containers where different users need different shells. Add
add a new 'auto-shell' config parameter which instructs us to
query the containers' /etc/passwd for the shell to be exec'd.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2016-06-10 11:03:02 +01:00

475 lines
13 KiB
C
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/*
* virt-login-shell.c: a shell to connect to a container
*
* Copyright (C) 2013-2014 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*
* Daniel Walsh <dwalsh@redhat.com>
*/
#include <config.h>
#include <errno.h>
#include <fnmatch.h>
#include <getopt.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "internal.h"
#include "virerror.h"
#include "virconf.h"
#include "virutil.h"
#include "virfile.h"
#include "virprocess.h"
#include "configmake.h"
#include "virstring.h"
#include "viralloc.h"
#include "vircommand.h"
#include "virgettext.h"
#define VIR_FROM_THIS VIR_FROM_NONE
static const char *conf_file = SYSCONFDIR "/libvirt/virt-login-shell.conf";
static int virLoginShellAllowedUser(virConfPtr conf,
const char *name,
gid_t *groups)
{
virConfValuePtr p;
int ret = -1;
char *ptr = NULL;
size_t i;
char *gname = NULL;
p = virConfGetValue(conf, "allowed_users");
if (p && p->type == VIR_CONF_LIST) {
virConfValuePtr pp;
/* Calc length and check items */
for (pp = p->list; pp; pp = pp->next) {
if (pp->type != VIR_CONF_STRING) {
virReportSystemError(EINVAL, "%s",
_("shell must be a list of strings"));
goto cleanup;
} else {
/*
If string begins with a % this indicates a linux group.
Check to see if the user is in the Linux Group.
*/
if (pp->str[0] == '%') {
ptr = &pp->str[1];
if (!*ptr)
continue;
for (i = 0; groups[i]; i++) {
if (!(gname = virGetGroupName(groups[i])))
continue;
if (fnmatch(ptr, gname, 0) == 0) {
ret = 0;
goto cleanup;
}
VIR_FREE(gname);
}
continue;
}
if (fnmatch(pp->str, name, 0) == 0) {
ret = 0;
goto cleanup;
}
}
}
}
virReportSystemError(EPERM,
_("%s not matched against 'allowed_users' in %s"),
name, conf_file);
cleanup:
VIR_FREE(gname);
return ret;
}
static int virLoginShellGetAutoShell(virConfPtr conf,
bool *autoshell)
{
virConfValuePtr p;
p = virConfGetValue(conf, "auto_shell");
if (!p) {
*autoshell = false;
} else if (p->type == VIR_CONF_LONG ||
p->type == VIR_CONF_ULONG) {
*autoshell = (p->l != 0);
} else {
virReportSystemError(EINVAL, "%s",
_("auto_shell must be a boolean value"));
return -1;
}
return 0;
}
static int virLoginShellGetShellArgv(virConfPtr conf,
char ***retshargv,
size_t *retshargvlen)
{
size_t i;
size_t len;
char **shargv = NULL;
virConfValuePtr p, pp;
p = virConfGetValue(conf, "shell");
if (!p) {
len = 1; /* /bin/sh */
} else if (p->type == VIR_CONF_LIST) {
/* Calc length and check items */
for (len = 0, pp = p->list; pp; len++, pp = pp->next) {
if (pp->type != VIR_CONF_STRING) {
virReportSystemError(EINVAL, "%s",
_("shell must be a list of strings"));
goto error;
}
}
} else if (p->type == VIR_CONF_STRING) {
len = 1; /* /path/to/shell */
} else {
virReportSystemError(EINVAL, "%s",
_("shell must be a list of strings"));
goto error;
}
len++; /* NULL terminator */
if (VIR_ALLOC_N(shargv, len) < 0)
goto error;
i = 0;
if (!p) {
if (VIR_STRDUP(shargv[i++], "/bin/sh") < 0)
goto error;
} else if (p->type == VIR_CONF_LIST) {
for (pp = p->list; pp; pp = pp->next) {
if (VIR_STRDUP(shargv[i++], pp->str) < 0)
goto error;
}
} else if (p->type == VIR_CONF_STRING) {
if (VIR_STRDUP(shargv[i++], p->str) < 0)
goto error;
}
shargv[i] = NULL;
*retshargvlen = i;
*retshargv = shargv;
return 0;
error:
*retshargv = NULL;
*retshargvlen = 0;
virStringFreeList(shargv);
return -1;
}
static char *progname;
/*
* Print usage
*/
static void
usage(void)
{
fprintf(stdout,
_("\n"
"Usage:\n"
" %s [option]\n\n"
"Options:\n"
" -h | --help Display program help\n"
" -V | --version Display program version\n"
" -c CMD Run CMD via shell\n"
"\n"
"libvirt login shell\n"),
progname);
return;
}
/* Display version information. */
static void
show_version(void)
{
printf("%s (%s) %s\n", progname, PACKAGE_NAME, PACKAGE_VERSION);
}
int
main(int argc, char **argv)
{
virConfPtr conf = NULL;
const char *login_shell_path = conf_file;
pid_t cpid = -1;
int ret = EXIT_CANCELED;
int status;
uid_t uid = getuid();
gid_t gid = getgid();
char *name = NULL;
char **shargv = NULL;
size_t shargvlen = 0;
char *shcmd = NULL;
virSecurityModelPtr secmodel = NULL;
virSecurityLabelPtr seclabel = NULL;
virDomainPtr dom = NULL;
virConnectPtr conn = NULL;
char *homedir = NULL;
int arg;
int longindex = -1;
int ngroups;
gid_t *groups = NULL;
ssize_t nfdlist = 0;
int *fdlist = NULL;
int openmax;
size_t i;
const char *cmdstr = NULL;
char *tmp;
char *term = NULL;
virErrorPtr saved_err = NULL;
bool autoshell = false;
struct option opt[] = {
{"help", no_argument, NULL, 'h'},
{"version", optional_argument, NULL, 'V'},
{NULL, 0, NULL, 0}
};
if (virInitialize() < 0) {
fprintf(stderr, _("Failed to initialize libvirt error handling"));
return EXIT_CANCELED;
}
virSetErrorFunc(NULL, NULL);
virSetErrorLogPriorityFunc(NULL);
progname = argv[0];
if (virGettextInitialize() < 0)
return ret;
while ((arg = getopt_long(argc, argv, "hVc:", opt, &longindex)) != -1) {
switch (arg) {
case 'h':
usage();
exit(EXIT_SUCCESS);
case 'V':
show_version();
exit(EXIT_SUCCESS);
case 'c':
cmdstr = optarg;
break;
case '?':
default:
usage();
exit(EXIT_CANCELED);
}
}
if (argc > optind) {
virReportSystemError(EINVAL, _("%s takes no options"), progname);
goto cleanup;
}
if (uid == 0) {
virReportSystemError(EPERM, _("%s must be run by non root users"),
progname);
goto cleanup;
}
name = virGetUserName(uid);
if (!name)
goto cleanup;
homedir = virGetUserDirectoryByUID(uid);
if (!homedir)
goto cleanup;
if (!(conf = virConfReadFile(login_shell_path, 0)))
goto cleanup;
if ((ngroups = virGetGroupList(uid, gid, &groups)) < 0)
goto cleanup;
if (virLoginShellAllowedUser(conf, name, groups) < 0)
goto cleanup;
if (virLoginShellGetShellArgv(conf, &shargv, &shargvlen) < 0)
goto cleanup;
if (virLoginShellGetAutoShell(conf, &autoshell) < 0)
goto cleanup;
conn = virConnectOpen("lxc:///");
if (!conn)
goto cleanup;
dom = virDomainLookupByName(conn, name);
if (!dom)
goto cleanup;
if (!virDomainIsActive(dom) && virDomainCreate(dom) < 0) {
virErrorPtr last_error;
last_error = virGetLastError();
if (last_error->code != VIR_ERR_OPERATION_INVALID) {
virReportSystemError(last_error->code,
_("Can't create %s container: %s"),
name, last_error->message);
goto cleanup;
}
}
openmax = sysconf(_SC_OPEN_MAX);
if (openmax < 0) {
virReportSystemError(errno, "%s",
_("sysconf(_SC_OPEN_MAX) failed"));
goto cleanup;
}
if ((nfdlist = virDomainLxcOpenNamespace(dom, &fdlist, 0)) < 0)
goto cleanup;
if (VIR_ALLOC(secmodel) < 0)
goto cleanup;
if (VIR_ALLOC(seclabel) < 0)
goto cleanup;
if (virNodeGetSecurityModel(conn, secmodel) < 0)
goto cleanup;
if (virDomainGetSecurityLabel(dom, seclabel) < 0)
goto cleanup;
if (virSetUIDGID(0, 0, NULL, 0) < 0)
goto cleanup;
if (virDomainLxcEnterSecurityLabel(secmodel, seclabel, NULL, 0) < 0)
goto cleanup;
if (nfdlist > 0 &&
virDomainLxcEnterNamespace(dom, nfdlist, fdlist, NULL, NULL, 0) < 0)
goto cleanup;
if (virSetUIDGID(uid, gid, groups, ngroups) < 0)
goto cleanup;
if (chdir(homedir) < 0) {
virReportSystemError(errno, _("Unable to chdir(%s)"), homedir);
goto cleanup;
}
if (autoshell) {
tmp = virGetUserShell(uid);
if (tmp) {
virStringFreeList(shargv);
shargvlen = 1;
if (VIR_ALLOC_N(shargv[0], shargvlen + 1) < 0) {
VIR_FREE(tmp);
goto cleanup;
}
shargv[0] = tmp;
shargv[1] = NULL;
}
}
if (cmdstr) {
if (VIR_REALLOC_N(shargv, shargvlen + 3) < 0)
goto cleanup;
if (VIR_STRDUP(shargv[shargvlen++], "-c") < 0)
goto cleanup;
if (VIR_STRDUP(shargv[shargvlen++], cmdstr) < 0)
goto cleanup;
shargv[shargvlen] = NULL;
}
/* We need to modify the first elementin shargv
* so that it has the relative filename and has
* a leading '-' to indicate it is a login shell
*/
shcmd = shargv[0];
if (shcmd[0] != '/') {
virReportSystemError(errno,
_("Shell '%s' should have absolute path"),
shcmd);
goto cleanup;
}
tmp = strrchr(shcmd, '/');
if (VIR_STRDUP(shargv[0], tmp) < 0)
goto cleanup;
shargv[0][0] = '-';
/* We're duping the string because the clearenv()
* call will shortly release the pointer we get
* back from virGetEnvAllowSUID() right here */
if (VIR_STRDUP(term, virGetEnvAllowSUID("TERM")) < 0)
goto cleanup;
/* A fork is required to create new process in correct pid namespace. */
if ((cpid = virFork()) < 0)
goto cleanup;
if (cpid == 0) {
int tmpfd;
for (i = 3; i < openmax; i++) {
tmpfd = i;
VIR_MASS_CLOSE(tmpfd);
}
clearenv();
setenv("PATH", "/bin:/usr/bin", 1);
setenv("SHELL", shcmd, 1);
setenv("USER", name, 1);
setenv("LOGNAME", name, 1);
setenv("HOME", homedir, 1);
if (term)
setenv("TERM", term, 1);
if (execv(shcmd, (char *const*) shargv) < 0) {
virReportSystemError(errno, _("Unable to exec shell %s"),
shcmd);
virDispatchError(NULL);
return errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE;
}
}
/* At this point, the parent is now waiting for the child to exit,
* but as that may take a long time, we release resources now. */
cleanup:
saved_err = virSaveLastError();
if (nfdlist > 0)
for (i = 0; i < nfdlist; i++)
VIR_FORCE_CLOSE(fdlist[i]);
VIR_FREE(fdlist);
virConfFree(conf);
if (dom)
virDomainFree(dom);
if (conn)
virConnectClose(conn);
virStringFreeList(shargv);
VIR_FREE(shcmd);
VIR_FREE(term);
VIR_FREE(name);
VIR_FREE(homedir);
VIR_FREE(seclabel);
VIR_FREE(secmodel);
VIR_FREE(groups);
if (virProcessWait(cpid, &status, true) == 0)
virProcessExitWithStatus(status);
if (saved_err) {
virSetError(saved_err);
virDispatchError(NULL);
}
return ret;
}
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