git.onelab.eu Git - lxc-userspace.git/blob

1 #!/usr/bin/python

2

3 import sys

4 import os

5 import setns

6

7 from argparse import ArgumentParser

8

9 drop_capabilities='cap_sys_admin,cap_sys_boot,cap_sys_module'

10

11 # can set to True here, but also use the -d option

12 debug = False

13

14 def getarch(f):

15 output = os.popen('readelf -h %s 2>&1'%f).readlines()

16 classlines = [x for x in output if ('Class' in x.split(':')[0])]

17 line = classlines[0]

18 c = line.split(':')[1]

19 if ('ELF64' in c):

20 return 'x86_64'

21 elif ('ELF32' in c):

22 return 'i686'

23 else:

24 raise Exception('Could not determine architecture')

25

26 def umount(fs_dir, opts=''):

27 output = os.popen('/bin/umount %s %s 2>&1'%(opts, fs_dir)).read()

28 return ('device is busy' not in output)

29

30 def main ():

31 parser = ArgumentParser()

32 parser.add_argument("-n", "--nonet",

33 action="store_true", dest="netns", default=False,

34 help="Don't enter network namespace")

35 parser.add_argument("-m", "--nomnt",

36 action="store_true", dest="mntns", default=False,

37 help="Don't enter mount namespace")

38 parser.add_argument("-p", "--nopid",

39 action="store_true", dest="pidns", default=False,

40 help="Don't enter pid namespace")

41 parser.add_argument("-r", "--root",

42 action="store_true", dest="root", default=False,

43 help="Enter as root: be careful")

44 parser.add_argument("-i","--internal",

45 action="store_true", dest="internal", default=False,

46 help="does *not* prepend '-- -c' to arguments - or invoke lxcsu-internal")

47 parser.add_argument("-d","--debug",

48 action='store_true', dest='debug', default=False,

49 help="debug option")

50 parser.add_argument("-s","--nosliceuid",

51 action='store_true', dest="nosliceuid", default=False,

52 help="do not change to slice uid inside of slice")

53 parser.add_argument("-o","--noslicehome",

54 action='store_true', dest="noslicehome", default=False,

55 help="do not change to slice home directory inside of slice")

56

57 if os.path.exists("/etc/lxcsu_default"):

58 defaults = parser.parse_args(file("/etc/lxcsu_default","r").read().split())

59 parser.set_defaults(**defaults.__dict__)

60

61 parser.add_argument ("slice_name")

62 parser.add_argument ("command_to_run",nargs="*")

63

64 args = parser.parse_args()

65 slice_name=args.slice_name

66

67 # unless we run the symlink 'lxcsu-internal', or we specify the -i option, prepend '--' '-c'

68 if sys.argv[0].find('internal')>=0: args.internal=True

69

70 if len(args.command_to_run)>0 and (args.command_to_run[0] == "/sbin/service"):

71 # A quick hack to support nodemanager interfaces.py when restarting

72 # networking in a slice.

73 args.nosliceuid = True

74

75 # plain lxcsu

76 if not args.internal:

77 # no command given: enter interactive shell

78 if not args.command_to_run: args.command_to_run=['/bin/sh']

79 args.command_to_run = [ '-c' ] + [" ".join(args.command_to_run)]

80

81 # support for either setting debug at the top of this file, or on the command-line

82 if args.debug:

83 global debug

84 debug=True

85

86 try:

87 cmd = '/usr/bin/virsh --connect lxc:/// domid %s'%slice_name

88 pidnum = int(os.popen(cmd).read().rstrip())

89 except:

90 print "Error finding slice %s"%slice_name

91 exit(1)

92

93 pid = '%s'%pidnum

94 if debug: print "Found pidnum",pidnum

95 cmdline = open('/proc/%s/cmdline'%pidnum).read().rstrip('\n\x00')

96 arch = getarch('/proc/%s/exe'%pid)

97

98 if (not pid):

99 print "Not started: %s"%slice_name

100 exit(1)

101

102 if arch is None:

103 arch = 'x86_64'

104

105 # Set sysctls specific to slice

106 sysctls = []

107 sysctl_dir = '/etc/planetlab/vsys-attributes/%s'%slice_name

108 if (os.access(sysctl_dir,0)):

109 entries = os.listdir(sysctl_dir)

110 for e in entries:

111 prefix = 'vsys_sysctl.'

112 if (e.startswith(prefix)):

113 sysctl_file = '/'.join([sysctl_dir,e])

114 sysctl_name = e[len(prefix):]

115 sysctl_val = open(sysctl_file).read()

116 sysctls.append((sysctl_file, sysctl_name, sysctl_val))

117

118 # Enter cgroups

119 try:

120 for subsystem in ['cpuset','memory','blkio']:

121 open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))

122

123 except Exception,e:

124 if debug: print e

125 print "Error assigning resources: %s"%slice_name

126 exit(1)

127

128 try:

129 open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))

130 except Exception,e:

131 if debug: print e

132 print "Error assigning cpuacct: %s" % slice_name

133 exit(1)

134

135 # If the slice is frozen, then we'll get an EBUSY when trying to write to the task

136 # list for the freezer cgroup. Since the user couldn't do anything anyway, it's best

137 # in this case to error out the shell. (an alternative would be to un-freeze it,

138 # add the task, and re-freeze it)

139 try:

140 f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')

141 f.write(str(os.getpid()))

142 # note: we need to call f.close() explicitly, or we'll get an exception in

143 # the object destructor, which will not be caught

144 f.close()

145 except Exception,e:

146 if debug: print e

147 print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name

148 exit(1)

149

150 setns.chcontext('/proc/%s/ns/uts'%pid)

151 setns.chcontext('/proc/%s/ns/ipc'%pid)

152

153 if (not args.pidns):

154 setns.chcontext('/proc/%s/ns/pid'%pid)

155

156 if (not args.netns):

157 setns.chcontext('/proc/%s/ns/net'%pid)

158

159 if (not args.mntns):

160 setns.chcontext('/proc/%s/ns/mnt'%pid)

161

162 proc_mounted = False

163 if (not os.access('/proc/self',0)):

164 proc_mounted = True

165 setns.proc_mount()

166

167 for (sysctl_file, sysctl_name, sysctl_val) in sysctls:

168 for fn in ["/sbin/sysctl", "/usr/sbin/sysctl", "/bin/sysctl", "/usr/bin/sysctl"]:

169 if os.path.exists(fn):

170 os.system('%s -w %s=%s >/dev/null 2>&1'%(fn, sysctl_name,sysctl_val))

171 break

172 else:

173 print "Error: image does not have a sysctl binary"

174

175 # cgroups is not yet LXC-safe, so we need to use the coarse grained access control

176 # strategy of unmounting the filesystem

177

178 umount_result = True

179 for subsystem in ['cpuset','cpu,cpuacct','memory','devices','freezer','net_cls','blkio','perf_event','systemd']:

180 fs_path = '/sys/fs/cgroup/%s'%subsystem

181 if (not umount(fs_path,'-l')):

182 pass

183 # Leaving these comments for historical reference

184 #print "Error disabling cgroup access"

185 #exit(1) - Don't need this because failure here implies failure in the call to umount /sys/fs/cgroup

186

187 if (not umount('/sys/fs/cgroup')):

188 print "Error disabling cgroup access"

189 exit(1)

190

191 pid = os.fork()

192

193 # capsh has a --user option starting with f14

194 # so if only for f12 we need to fake this one

195 #

196 # capsh.c does essentially the following when invoked with --user:

197 # pwd = getpwnam(user); ...

198 # ngroups = MAX_GROUPS;

199 # status = getgrouplist(user, pwd->pw_gid, groups, &ngroups); ...

200 # status = setgroups(ngroups, groups); ...

201 # status = setgid(pwd->pw_gid); ...

202 # status = setuid(pwd->pw_uid); ...

203 # however we cannot simulate that ourselves because if we did in this process then

204 # capsh could not be allowed to mess with caps any more

205

206 def getuid (slicename):

207 import pwd

208 try:

209 return pwd.getpwnam(slicename).pw_uid

210 except:

211 return

212

213 if (pid == 0):

214 cap_arg = '--drop='+drop_capabilities

215

216 if (not args.root):

217 if (args.nosliceuid):

218 # we still want to drop capabilities, but don't want to switch UIDs

219 exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--','--login',]+args.command_to_run

220 else:

221 uid = getuid (slice_name)

222 if not uid:

223 print "lxcsu could not spot %s in /etc/passwd - exiting"%slice_name

224 exit(1)

225 exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--uid=%s'%uid,'--','--login',]+args.command_to_run

226 # once we can drop f12, it would be nicer to instead go for

227 # exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--user=%s'%slice_name,'--','--login',]+args.command_to_run

228 else:

229 exec_args = [arch,'/usr/sbin/capsh','--','--login']+args.command_to_run

230

231 os.environ['SHELL'] = '/bin/sh'

232 if os.path.exists('/etc/planetlab/lib/bind_public.so'):

233 os.environ['LD_PRELOAD'] = '/etc/planetlab/lib/bind_public.so'

234 if not args.noslicehome:

235 os.environ['HOME'] = '/home/%s'%slice_name

236 os.chdir("/home/%s"%(slice_name))

237 if debug: print 'lxcsu:execv:','/usr/bin/setarch',exec_args

238 os.execv('/usr/bin/setarch',exec_args)

239 else:

240 setns.proc_umount()

241 _,status = os.waitpid(pid,0)

242 exit(os.WEXITSTATUS(status))

243

244 if __name__ == '__main__':

245 main()