The behaviour mimics chroot.
Possibly it would have been nicer to to query the password database in
the new namepace and run the shell of the user there, but it's hard to
do correctly. getpwuid() might need to load nss plugins, and the arch
in the new namespace might be different (in case of NEWNS mounts), or
the hostname might be different, etc. So in general it's not possible
to do it reliably.
Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@xxxxxxxxx>
---
include/exec_shell.h | 1 +
lib/Makemodule.am | 3 ++-
lib/exec_shell.c | 19 +++++++++++++++++++
sys-utils/Makemodule.am | 1 +
sys-utils/nsenter.1 | 5 ++++-
sys-utils/nsenter.c | 13 +++++++------
sys-utils/unshare.c | 9 +++++----
7 files changed, 39 insertions(+), 12 deletions(-)
create mode 100644 include/exec_shell.h
create mode 100644 lib/exec_shell.c
diff --git a/include/exec_shell.h b/include/exec_shell.h
new file mode 100644
index 0000000..a2aa757
--- /dev/null
+++ b/include/exec_shell.h
@@ -0,0 +1 @@
+extern void __attribute__((__noreturn__)) exec_shell(void);
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 81e20b1..74b6bc1 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -24,7 +24,8 @@ libcommon_la_SOURCES = \
lib/tt.c \
lib/wholedisk.c \
lib/ttyutils.c \
- lib/xgetpass.c
+ lib/xgetpass.c \
+ lib/exec_shell.c
if LINUX
libcommon_la_SOURCES += \
diff --git a/lib/exec_shell.c b/lib/exec_shell.c
new file mode 100644
index 0000000..cfd7801
--- /dev/null
+++ b/lib/exec_shell.c
@@ -0,0 +1,19 @@
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "nls.h"
+#include "c.h"
+
+#include "exec_shell.h"
+
+#define DEFAULT_SHELL "/bin/sh"
+
+void __attribute__((__noreturn__)) exec_shell(void) {
+ const char *shell = getenv("SHELL");
+ if (!shell)
+ shell = DEFAULT_SHELL;
+ execl(shell, basename(shell), "-i", NULL);
+ err(EXIT_FAILURE, _("exec %s failed"), shell);
+}
diff --git a/sys-utils/Makemodule.am b/sys-utils/Makemodule.am
index 86c529e..c214b92 100644
--- a/sys-utils/Makemodule.am
+++ b/sys-utils/Makemodule.am
@@ -287,6 +287,7 @@ if BUILD_UNSHARE
usrbin_exec_PROGRAMS += unshare
dist_man_MANS += sys-utils/unshare.1
unshare_SOURCES = sys-utils/unshare.c
+unshare_LDADD = $(LDADD) libcommon.la
endif
if BUILD_NSENTER
diff --git a/sys-utils/nsenter.1 b/sys-utils/nsenter.1
index ea3c1b0..4a6a34d 100644
--- a/sys-utils/nsenter.1
+++ b/sys-utils/nsenter.1
@@ -4,7 +4,7 @@ nsenter \- run program with namespaces of other processes
.SH SYNOPSIS
.B nsenter
.RI [ options ]
-program
+.RI [ program ]
.RI [ arguments ]
.SH DESCRIPTION
Enters the contexts of one or more other processes and then executes specified
@@ -50,6 +50,9 @@ flag).
See the
.BR clone (2)
for exact semantics of the flags.
+.TP
+If program is not given, run ``${SHELL} \fB\-i\fR'' (default: /bin\:/sh).
+
.SH OPTIONS
Argument with square brakets, such as [\fIfile\fR], means optional argument.
Command line syntax to specify optional argument \-\-mount=/path\:/to\:/file.
diff --git a/sys-utils/nsenter.c b/sys-utils/nsenter.c
index 3df4338..ea2c5b1 100644
--- a/sys-utils/nsenter.c
+++ b/sys-utils/nsenter.c
@@ -17,8 +17,6 @@
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
-#include <sys/types.h>
-#include <sys/wait.h>
#include <dirent.h>
#include <errno.h>
#include <getopt.h>
@@ -28,12 +26,15 @@
#include <stdbool.h>
#include <unistd.h>
#include <assert.h>
+#include <sys/types.h>
+#include <sys/wait.h>
#include "strutils.h"
#include "nls.h"
#include "c.h"
#include "closestream.h"
#include "namespace.h"
+#include "exec_shell.h"
static struct namespace_file {
int nstype;
@@ -253,9 +254,6 @@ int main(int argc, char *argv[])
}
}
- if (optind >= argc)
- usage(EXIT_FAILURE);
-
/*
* Open remaining namespace and directory descriptors.
*/
@@ -317,7 +315,10 @@ int main(int argc, char *argv[])
if (do_fork == 1)
continue_as_child();
- execvp(argv[optind], argv + optind);
+ if (optind < argc)
+ execvp(argv[optind], argv + optind);
+ else
+ exec_shell();
err(EXIT_FAILURE, _("failed to execute %s"), argv[optind]);
}
diff --git a/sys-utils/unshare.c b/sys-utils/unshare.c
index 62d2fcb..52a76e8 100644
--- a/sys-utils/unshare.c
+++ b/sys-utils/unshare.c
@@ -29,6 +29,7 @@
#include "c.h"
#include "closestream.h"
#include "namespace.h"
+#include "exec_shell.h"
static void usage(int status)
{
@@ -107,13 +108,13 @@ int main(int argc, char *argv[])
}
}
- if(optind >= argc)
- usage(EXIT_FAILURE);
-
if(-1 == unshare(unshare_flags))
err(EXIT_FAILURE, _("unshare failed"));
- execvp(argv[optind], argv + optind);
+ if (optind < argc)
+ execvp(argv[optind], argv + optind);
+ else
+ exec_shell();
err(EXIT_FAILURE, _("failed to execute %s"), argv[optind]);
}
--
1.8.1
--
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