Merge pull request #3356 from OpenDZ/tixxdz/nspawn-quick-v1

nspawn: filesystem uid patching fixes and other minor improvments

6 files changed, 200 insertions, 108 deletions

diff --git a/Makefile.am b/Makefile.am
index 305099ab66..f8e1fac967 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -3016,6 +3016,8 @@ systemd_nspawn_SOURCES = \
 	src/nspawn/nspawn-expose-ports.h \
 	src/nspawn/nspawn-cgroup.c \
 	src/nspawn/nspawn-cgroup.h \
+	src/nspawn/nspawn-seccomp.c \
+	src/nspawn/nspawn-seccomp.h \
 	src/nspawn/nspawn-register.c \
 	src/nspawn/nspawn-register.h \
 	src/nspawn/nspawn-setuid.c \
diff --git a/src/basic/missing.h b/src/basic/missing.h
index 651e414395..2077ada72d 100644
--- a/src/basic/missing.h
+++ b/src/basic/missing.h
@@ -453,6 +453,18 @@ struct btrfs_ioctl_quota_ctl_args {
 #define MQUEUE_MAGIC 0x19800202
 #endif
 
+#ifndef SECURITYFS_MAGIC
+#define SECURITYFS_MAGIC 0x73636673
+#endif
+
+#ifndef TRACEFS_MAGIC
+#define TRACEFS_MAGIC 0x74726163
+#endif
+
+#ifndef BPF_FS_MAGIC
+#define BPF_FS_MAGIC 0xcafe4a11
+#endif
+
 #ifndef MS_MOVE
 #define MS_MOVE 8192
 #endif
diff --git a/src/nspawn/nspawn-patch-uid.c b/src/nspawn/nspawn-patch-uid.c
index c7382d412d..cc79597c95 100644
--- a/src/nspawn/nspawn-patch-uid.c
+++ b/src/nspawn/nspawn-patch-uid.c
@@ -280,7 +280,13 @@ static int patch_fd(int fd, const char *name, const struct stat *st, uid_t shift
         return r > 0 || changed;
 }
 
-static int is_procfs_sysfs_or_suchlike(int fd) {
+/*
+ * Check if the filesystem is fully compatible with user namespaces or
+ * UID/GID patching. Some filesystems in this list can be fully mounted inside
+ * user namespaces, however their inodes may relate to host resources or only
+ * valid in the global user namespace, therefore no patching should be applied.
+ */
+static int is_fs_fully_userns_compatible(int fd) {
         struct statfs sfs;
 
         assert(fd >= 0);
@@ -300,6 +306,9 @@ static int is_procfs_sysfs_or_suchlike(int fd) {
                F_TYPE_EQUAL(sfs.f_type, PSTOREFS_MAGIC) ||
                F_TYPE_EQUAL(sfs.f_type, SELINUX_MAGIC) ||
                F_TYPE_EQUAL(sfs.f_type, SMACK_MAGIC) ||
+               F_TYPE_EQUAL(sfs.f_type, SECURITYFS_MAGIC) ||
+               F_TYPE_EQUAL(sfs.f_type, BPF_FS_MAGIC) ||
+               F_TYPE_EQUAL(sfs.f_type, TRACEFS_MAGIC) ||
                F_TYPE_EQUAL(sfs.f_type, SYSFS_MAGIC);
 }
 
@@ -311,8 +320,8 @@ static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift
 
         /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we
          * probably shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's
-         * stop the recursion when we hit a procfs or sysfs file system. */
-        r = is_procfs_sysfs_or_suchlike(fd);
+         * stop the recursion when we hit procfs, sysfs or some other special file systems. */
+        r = is_fs_fully_userns_compatible(fd);
         if (r < 0)
                 goto finish;
         if (r > 0) {
diff --git a/src/nspawn/nspawn-seccomp.c b/src/nspawn/nspawn-seccomp.c
new file mode 100644
index 0000000000..2d145b68a7
--- /dev/null
+++ b/src/nspawn/nspawn-seccomp.c
@@ -0,0 +1,143 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <linux/netlink.h>
+#include <sys/capability.h>
+#include <sys/types.h>
+
+#ifdef HAVE_SECCOMP
+#include <seccomp.h>
+#endif
+
+#include "log.h"
+
+#ifdef HAVE_SECCOMP
+#include "seccomp-util.h"
+#endif
+
+#include "nspawn-seccomp.h"
+
+#ifdef HAVE_SECCOMP
+
+static int seccomp_add_default_syscall_filter(scmp_filter_ctx ctx,
+                                              uint64_t cap_list_retain) {
+        unsigned i;
+        int r;
+        static const struct {
+                uint64_t capability;
+                int syscall_num;
+        } blacklist[] = {
+                { CAP_SYS_RAWIO,  SCMP_SYS(iopl)              },
+                { CAP_SYS_RAWIO,  SCMP_SYS(ioperm)            },
+                { CAP_SYS_BOOT,   SCMP_SYS(kexec_load)        },
+                { CAP_SYS_ADMIN,  SCMP_SYS(swapon)            },
+                { CAP_SYS_ADMIN,  SCMP_SYS(swapoff)           },
+                { CAP_SYS_ADMIN,  SCMP_SYS(open_by_handle_at) },
+                { CAP_SYS_MODULE, SCMP_SYS(init_module)       },
+                { CAP_SYS_MODULE, SCMP_SYS(finit_module)      },
+                { CAP_SYS_MODULE, SCMP_SYS(delete_module)     },
+                { CAP_SYSLOG,     SCMP_SYS(syslog)            },
+        };
+
+        for (i = 0; i < ELEMENTSOF(blacklist); i++) {
+                if (cap_list_retain & (1ULL << blacklist[i].capability))
+                        continue;
+
+                r = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);
+                if (r == -EFAULT)
+                        continue; /* unknown syscall */
+                if (r < 0) {
+                        log_error_errno(r, "Failed to block syscall: %m");
+                        return r;
+                }
+        }
+
+        return 0;
+}
+
+int setup_seccomp(uint64_t cap_list_retain) {
+        scmp_filter_ctx seccomp;
+        int r;
+
+        seccomp = seccomp_init(SCMP_ACT_ALLOW);
+        if (!seccomp)
+                return log_oom();
+
+        r = seccomp_add_secondary_archs(seccomp);
+        if (r < 0) {
+                log_error_errno(r, "Failed to add secondary archs to seccomp filter: %m");
+                goto finish;
+        }
+
+        r = seccomp_add_default_syscall_filter(seccomp, cap_list_retain);
+        if (r < 0)
+                goto finish;
+
+        /*
+           Audit is broken in containers, much of the userspace audit
+           hookup will fail if running inside a container. We don't
+           care and just turn off creation of audit sockets.
+
+           This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail
+           with EAFNOSUPPORT which audit userspace uses as indication
+           that audit is disabled in the kernel.
+         */
+
+        r = seccomp_rule_add(
+                        seccomp,
+                        SCMP_ACT_ERRNO(EAFNOSUPPORT),
+                        SCMP_SYS(socket),
+                        2,
+                        SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
+                        SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
+        if (r < 0) {
+                log_error_errno(r, "Failed to add audit seccomp rule: %m");
+                goto finish;
+        }
+
+        r = seccomp_attr_set(seccomp, SCMP_FLTATR_CTL_NNP, 0);
+        if (r < 0) {
+                log_error_errno(r, "Failed to unset NO_NEW_PRIVS: %m");
+                goto finish;
+        }
+
+        r = seccomp_load(seccomp);
+        if (r == -EINVAL) {
+                log_debug_errno(r, "Kernel is probably not configured with CONFIG_SECCOMP. Disabling seccomp audit filter: %m");
+                r = 0;
+                goto finish;
+        }
+        if (r < 0) {
+                log_error_errno(r, "Failed to install seccomp audit filter: %m");
+                goto finish;
+        }
+
+finish:
+        seccomp_release(seccomp);
+        return r;
+}
+
+#else
+
+int setup_seccomp(uint64_t cap_list_retain) {
+        return 0;
+}
+
+#endif
diff --git a/src/nspawn/nspawn-seccomp.h b/src/nspawn/nspawn-seccomp.h
new file mode 100644
index 0000000000..5bde16faf9
--- /dev/null
+++ b/src/nspawn/nspawn-seccomp.h
@@ -0,0 +1,24 @@
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/types.h>
+
+int setup_seccomp(uint64_t cap_list_retain);
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index ac11bcea5a..b421c182ce 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -26,9 +26,6 @@
 #include <linux/loop.h>
 #include <pwd.h>
 #include <sched.h>
-#ifdef HAVE_SECCOMP
-#include <seccomp.h>
-#endif
 #ifdef HAVE_SELINUX
 #include <selinux/selinux.h>
 #endif
@@ -82,15 +79,13 @@
 #include "nspawn-settings.h"
 #include "nspawn-setuid.h"
 #include "nspawn-stub-pid1.h"
+#include "nspawn-seccomp.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "process-util.h"
 #include "ptyfwd.h"
 #include "random-util.h"
 #include "rm-rf.h"
-#ifdef HAVE_SECCOMP
-#include "seccomp-util.h"
-#endif
 #include "selinux-util.h"
 #include "signal-util.h"
 #include "socket-util.h"
@@ -136,7 +131,7 @@ static StartMode arg_start_mode = START_PID1;
 static bool arg_ephemeral = false;
 static LinkJournal arg_link_journal = LINK_AUTO;
 static bool arg_link_journal_try = false;
-static uint64_t arg_retain =
+static uint64_t arg_caps_retain =
         (1ULL << CAP_CHOWN) |
         (1ULL << CAP_DAC_OVERRIDE) |
         (1ULL << CAP_DAC_READ_SEARCH) |
@@ -1075,7 +1070,7 @@ static int parse_argv(int argc, char *argv[]) {
         if (mask_all_settings)
                 arg_settings_mask = _SETTINGS_MASK_ALL;
 
-        arg_retain = (arg_retain | plus | (arg_private_network ? 1ULL << CAP_NET_ADMIN : 0)) & ~minus;
+        arg_caps_retain = (arg_caps_retain | plus | (arg_private_network ? 1ULL << CAP_NET_ADMIN : 0)) & ~minus;
 
         r = detect_unified_cgroup_hierarchy();
         if (r < 0)
@@ -1632,7 +1627,7 @@ static int setup_journal(const char *directory) {
 }
 
 static int drop_capabilities(void) {
-        return capability_bounding_set_drop(arg_retain, false);
+        return capability_bounding_set_drop(arg_caps_retain, false);
 }
 
 static int reset_audit_loginuid(void) {
@@ -1667,99 +1662,6 @@ static int reset_audit_loginuid(void) {
         return 0;
 }
 
-static int setup_seccomp(void) {
-
-#ifdef HAVE_SECCOMP
-        static const struct {
-                uint64_t capability;
-                int syscall_num;
-        } blacklist[] = {
-                { CAP_SYS_RAWIO,  SCMP_SYS(iopl)              },
-                { CAP_SYS_RAWIO,  SCMP_SYS(ioperm)            },
-                { CAP_SYS_BOOT,   SCMP_SYS(kexec_load)        },
-                { CAP_SYS_ADMIN,  SCMP_SYS(swapon)            },
-                { CAP_SYS_ADMIN,  SCMP_SYS(swapoff)           },
-                { CAP_SYS_ADMIN,  SCMP_SYS(open_by_handle_at) },
-                { CAP_SYS_MODULE, SCMP_SYS(init_module)       },
-                { CAP_SYS_MODULE, SCMP_SYS(finit_module)      },
-                { CAP_SYS_MODULE, SCMP_SYS(delete_module)     },
-                { CAP_SYSLOG,     SCMP_SYS(syslog)            },
-        };
-
-        scmp_filter_ctx seccomp;
-        unsigned i;
-        int r;
-
-        seccomp = seccomp_init(SCMP_ACT_ALLOW);
-        if (!seccomp)
-                return log_oom();
-
-        r = seccomp_add_secondary_archs(seccomp);
-        if (r < 0) {
-                log_error_errno(r, "Failed to add secondary archs to seccomp filter: %m");
-                goto finish;
-        }
-
-        for (i = 0; i < ELEMENTSOF(blacklist); i++) {
-                if (arg_retain & (1ULL << blacklist[i].capability))
-                        continue;
-
-                r = seccomp_rule_add(seccomp, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);
-                if (r == -EFAULT)
-                        continue; /* unknown syscall */
-                if (r < 0) {
-                        log_error_errno(r, "Failed to block syscall: %m");
-                        goto finish;
-                }
-        }
-
-        /*
-           Audit is broken in containers, much of the userspace audit
-           hookup will fail if running inside a container. We don't
-           care and just turn off creation of audit sockets.
-
-           This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail
-           with EAFNOSUPPORT which audit userspace uses as indication
-           that audit is disabled in the kernel.
-         */
-
-        r = seccomp_rule_add(
-                        seccomp,
-                        SCMP_ACT_ERRNO(EAFNOSUPPORT),
-                        SCMP_SYS(socket),
-                        2,
-                        SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
-                        SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
-        if (r < 0) {
-                log_error_errno(r, "Failed to add audit seccomp rule: %m");
-                goto finish;
-        }
-
-        r = seccomp_attr_set(seccomp, SCMP_FLTATR_CTL_NNP, 0);
-        if (r < 0) {
-                log_error_errno(r, "Failed to unset NO_NEW_PRIVS: %m");
-                goto finish;
-        }
-
-        r = seccomp_load(seccomp);
-        if (r == -EINVAL) {
-                log_debug_errno(r, "Kernel is probably not configured with CONFIG_SECCOMP. Disabling seccomp audit filter: %m");
-                r = 0;
-                goto finish;
-        }
-        if (r < 0) {
-                log_error_errno(r, "Failed to install seccomp audit filter: %m");
-                goto finish;
-        }
-
-finish:
-        seccomp_release(seccomp);
-        return r;
-#else
-        return 0;
-#endif
-
-}
 
 static int setup_propagate(const char *root) {
         const char *p, *q;
@@ -2988,7 +2890,7 @@ static int outer_child(
         if (r < 0)
                 return r;
 
-        r = setup_seccomp();
+        r = setup_seccomp(arg_caps_retain);
         if (r < 0)
                 return r;
 
@@ -3272,9 +3174,9 @@ static int load_settings(void) {
                         if (settings->capability != 0)
                                 log_warning("Ignoring Capability= setting, file %s is not trusted.", p);
                 } else
-                        arg_retain |= plus;
+                        arg_caps_retain |= plus;
 
-                arg_retain &= ~settings->drop_capability;
+                arg_caps_retain &= ~settings->drop_capability;
         }
 
         if ((arg_settings_mask & SETTING_KILL_SIGNAL) == 0 &&