src/klish-plugin-infix: new symbol shell@infix with user tracking

This patch adds a new klish symbol, shell@infix, which performs proper
droprivs before calling the configured shell.

Fix #298: track user id so shell command gets correct user

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

package/klish-plugin-infix/klish-plugin-infix.mk

@@ -29,6 +29,12 @@ else
 KLISH_PLUGIN_INFIX_CONF_OPTS += --disable-shell
 endif
 
+ifeq ($(BR2_PACKAGE_BASH),y)
+KLISH_PLUGIN_INFIX_CONF_OPTS += --with-shell=/bin/bash
+else
+KLISH_PLUGIN_INFIX_CONF_OPTS += --with-shell=/bin/sh
+endif
+
 define KLISH_PLUGIN_INFIX_INSTALL_DOC
 	$(INSTALL) -t $(TARGET_DIR)/usr/share/infix/cli -D -m 0644 \
 		$(wildcard $(BR2_EXTERNAL_INFIX_PATH)/doc/cli/*.md)

src/klish-plugin-infix/configure.ac

@@ -2,7 +2,7 @@ AC_PREREQ(2.61)
 AC_INIT([klish-plugin-infix], [1.0.0],
 	[https://github.com/kernelkit/infix/issues])
 AM_INIT_AUTOMAKE(1.11 foreign subdir-objects)
-AM_SILENT_RULES(yes)
+AM_SILENT_RULES(no)
 
 LT_INIT
 
@@ -26,6 +26,10 @@ AC_ARG_ENABLE(shell,
         AS_HELP_STRING([--enable-shell], [Enable shell access from CLI]),,[
 	enable_shell=no])
 
+AC_ARG_WITH(shell,
+        AS_HELP_STRING([--with-shell=shell], [Path to shell to use, default: /bin/sh]),
+	[shell=$withval], [shell=yes])
+
 # Check for pkg-config first, warn if it's not installed
 PKG_PROG_PKG_CONFIG
 
@@ -37,6 +41,12 @@ AC_CHECK_LIB([klish], [kplugin_new],, AC_MSG_ERROR([Klish not found]))
 AM_CONDITIONAL(CONTAINERS,   [test "x$enable_containers" != "xno"])
 AM_CONDITIONAL(SHELL,        [test "x$enable_shell" != "xno"])
 
+AS_IF([test "x$with_shell" != "xno"], [
+	AS_IF([test "x$shell" = "xyes"], [shell=/bin/sh])
+	with_shell=$shell
+	AC_DEFINE_UNQUOTED(SHELL, "$shell", [Default: /bin/sh])],[
+	AC_DEFINE_UNQUOTED(SHELL, "/bin/sh")])
+
 test "x$prefix" = xNONE && prefix=$ac_default_prefix
 test "x$exec_prefix" = xNONE && exec_prefix='${prefix}'
 
@@ -47,3 +57,32 @@ KLISHCONFDIR=`eval echo $sysconfdir/klish`
 AC_SUBST(KLISHCONFDIR)
 
 AC_OUTPUT
+
+cat <<EOF
+
+------------------ Summary ------------------
+ $PACKAGE_NAME version $PACKAGE_VERSION
+  Prefix................: $prefix
+  Exec prefix...........: $eprefix
+  Sysconfdir............: `eval echo $sysconfdir`
+  Localstatedir.........: `eval echo $localstatedir`
+  Default fstab.........: `eval echo $fstab`
+  System environment....: ${sysconfig_path:-${sysconfig}}
+  C Compiler............: $CC $CFLAGS $CPPFLAGS $LDFLAGS $LIBS
+  Linker................: $LD $LLDP_LDFLAGS $LLDP_BIN_LDFLAGS $LDFLAGS $LIBS
+
+Optional features:
+  Container support ....: $enable_containers
+  Allow shell access ...: $enable_shell
+  Shell to use .........: $with_shell
+
+------------- Compiler version --------------
+$($CC --version || true)
+-------------- Linker version ---------------
+$($LD --version || true)
+---------------------------------------------
+
+Check the above options and compile with:
+ ${MAKE-make}
+
+EOF

src/klish-plugin-infix/src/infix.c

@@ -1,6 +1,7 @@
 #include <assert.h>
 #include <dirent.h>
 #include <errno.h>
+#include <pwd.h>
 #include <stdio.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -14,6 +15,7 @@
 #include <sysrepo/values.h>
 
 #include <klish/kplugin.h>
+#include <klish/ksession.h>
 #include <klish/kcontext.h>
 
 #include <libyang/libyang.h>
@@ -527,6 +529,53 @@ err:
 	return -1;
 }
 
+int infix_shell(kcontext_t *ctx)
+{
+	const char *user = "root";
+	ksession_t *session;
+	pid_t pid;
+	int rc;
+
+	session = kcontext_session(ctx);
+	if (session) {
+		user = ksession_user(session);
+		if (!user)
+			user = "root";
+	}
+
+	pid = fork();
+	if (pid == -1)
+		return -1;
+
+	if (!pid) {
+		struct passwd *pw;
+		char *args[] = {
+			"env", "CLISH=yes",
+			SHELL, "-il",
+			NULL
+		};
+
+		pw = getpwnam(user);
+		if (setgid(pw->pw_gid) || setuid(pw->pw_uid)) {
+			fprintf(stderr, "Aborting, failed dropping privileges to (UID:%d GID:%d): %s\n",
+				pw->pw_uid, pw->pw_gid, strerror(errno));
+			_exit(1);
+		}
+
+		_exit(execvp(args[0], args));
+	}
+
+	while (waitpid(pid, &rc, 0) != pid)
+		;
+
+	if (WIFEXITED(rc))
+		rc = WEXITSTATUS(rc);
+	else if (WIFSIGNALED(rc))
+		rc = -2;
+
+	return rc;
+}
+
 int infix_rpc(kcontext_t *ctx)
 {
 	kpargv_pargs_node_t *iter;
@@ -612,6 +661,7 @@ int kplugin_infix_init(kcontext_t *ctx)
 	kplugin_add_syms(plugin, ksym_new("erase", infix_erase));
 	kplugin_add_syms(plugin, ksym_new("files", infix_files));
 	kplugin_add_syms(plugin, ksym_new("ifaces", infix_ifaces));
+	kplugin_add_syms(plugin, ksym_new("shell", infix_shell));
 	kplugin_add_syms(plugin, ksym_new("rpc", infix_rpc));
 
 	return 0;

src/klish-plugin-infix/xml/shell.xml

@@ -7,7 +7,7 @@
   <VIEW name="main">
 
     <COMMAND name="shell" help="Enter system shell">
-      <ACTION sym="script" in="tty" out="tty" interrupt="true">/usr/bin/env CLISH=yes bash -l</ACTION>
+      <ACTION sym="shell@infix" in="tty" out="tty" interrupt="true" />
     </COMMAND>
 
   </VIEW>