allow privileged IMP to linger during flux-imp run to support signal forwarding

src/imp/run.c

@@ -51,6 +51,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <pwd.h>
 #include <signal.h>
 
@@ -61,6 +62,7 @@
 #include "imp_state.h"
 #include "impcmd.h"
 #include "privsep.h"
+#include "signals.h"
 
 extern char **environ;
 
@@ -142,7 +144,8 @@ static struct kv *get_run_env (struct kv *kv, const cf_t *allowed_env)
 }
 
 static void __attribute__((noreturn))
-imp_run (const char *name,
+imp_run (struct imp_state *imp,
+         const char *name,
          const cf_t *run_cf,
          struct kv *kv_env)
 {
@@ -151,6 +154,8 @@ imp_run (const char *name,
     char **env;
     const char *args[2];
     int exit_code;
+    int status;
+    pid_t child;
 
     if (!(path = cf_string (cf_get_in (run_cf, "path")))
         || path[0] != '/')
@@ -160,7 +165,7 @@ imp_run (const char *name,
         imp_die (1, "run %s: relative path not allowed", name);
 
     /*  Get passwd entry for current user to set HOME and USER */
-    if (!(pwd = getpwuid (getuid ())))
+    if (!(pwd = getpwuid (geteuid ())))
         imp_die (1, "run: failed to find target user");
 
     /*  Set HOME and USER */
@@ -181,20 +186,55 @@ imp_run (const char *name,
     if (chdir ("/") < 0)
         imp_die (1, "run: failed to chdir to /");
 
-    args[0] = path;
-    args[1] = NULL;
+    /* Block signals so parent isn't terminated
+     */
+    imp_sigblock_all ();
+
+    if ((child = fork ()) < 0)
+        imp_die (1, "run: fork: %s", strerror (errno));
+
+    imp_set_signal_child (child);
+
+    if (child == 0) {
+        /* unblock all signals */
+        imp_sigunblock_all ();
+
+        if (setuid (geteuid()) < 0
+            || setgid (getegid()) < 0)
+            imp_die (1, "setuid: %s", strerror (errno));
+
+        args[0] = path;
+        args[1] = NULL;
 #if CODE_COVERAGE_ENABLED
-    __gcov_dump ();
-    __gcov_reset ();
+        __gcov_dump ();
+        __gcov_reset ();
 #endif
-    execve (path, (char **) args, env);
+        execve (path, (char **) args, env);
 
-    if (errno == EPERM || errno == EACCES)
-        exit_code = 126;
-    else
-        exit_code = 127;
+        if (errno == EPERM || errno == EACCES)
+            exit_code = 126;
+        else
+            exit_code = 127;
+        imp_die (exit_code, "%s: %s", path, strerror (errno));
+    }
+
+    /* Parent:
+     */
+    imp_setup_signal_forwarding (imp);
 
-    imp_die (exit_code, "%s: %s", path, strerror (errno));
+    /* Parent: wait for child to exit */
+    while (waitpid (child, &status, 0) != child) {
+        if (errno != EINTR)
+            imp_die (1, "waitpid: %s", strerror (errno));
+    }
+
+    /* Exit with status of the child process */
+    if (WIFEXITED (status))
+        exit (WEXITSTATUS (status));
+    else if (WIFSIGNALED (status))
+        imp_raise (WTERMSIG (status));
+    else
+        exit (1);
 }
 
 
@@ -235,11 +275,7 @@ int imp_run_privileged (struct imp_state *imp,
     if (!kv_env)
         imp_die (1, "run: error processing command environment");
 
-    if (setuid (geteuid()) < 0
-        || setgid (getegid()) < 0)
-        imp_die (1, "setuid: %s", strerror (errno));
-
-    imp_run (name, cf_run, kv_env);
+    imp_run (imp, name, cf_run, kv_env);
 
     return 0;
 }
@@ -338,7 +374,7 @@ int imp_run_unprivileged (struct imp_state *imp, struct kv *kv)
         imp_die (1, "run: permission denied");
 
     kv_env = get_run_env (kv, cf_get_in (cf_run, "allowed-environment"));
-    imp_run (imp->argv[2], cf_run, kv_env);
+    imp_run (imp, imp->argv[2], cf_run, kv_env);
 
     return 0;
 }

t/t2002-imp-run.t

@@ -10,6 +10,8 @@ Basic flux-imp run functionality and corner case handing tests
 test -n "$FLUX_TESTS_LOGFILE" && set -- "$@" --logfile
 . `dirname $0`/sharness.sh
 
+test "$chain_lint" = "t" || test_set_prereq NO_CHAIN_LINT
+
 flux_imp=${SHARNESS_BUILD_DIRECTORY}/src/imp/flux-imp
 sign=${SHARNESS_BUILD_DIRECTORY}/t/src/sign
 
@@ -49,6 +51,10 @@ test_expect_success 'create configs for flux-imp exec and signer' '
 	path = "$TESTDIR/test.sh"
 	[run.allowednotset]
 	path = "$TESTDIR/test.sh"
+	[run.sleep]
+	allowed-users = [ "$(whoami)" ]
+	allowed-environment = [ "TEST_*", "EXACT_MATCH" ]
+	path = "$TESTDIR/sleep.sh"
 	EOF
 '
 test_expect_success 'create test shell scripts' '
@@ -61,12 +67,20 @@ test_expect_success 'create test shell scripts' '
 	env
 	EOF
 	chmod +x $TESTDIR/test.sh &&
+	cat <<-EOF >$TESTDIR/sleep.sh &&
+	#!/bin/sh
+	echo \$PPID >$TESTDIR/sleep.pid
+	sleep 30
+	EOF
+	cat $TESTDIR/sleep.sh &&
+	chmod +x $TESTDIR/sleep.sh &&
 	touch $TESTDIR/noexec.sh &&
 	chmod 600 $TESTDIR/noexec.sh
 '
 test_expect_success SUDO 'set appropriate permissions for sudo based tests' '
 	$SUDO chown root.root $TESTDIR $TESTDIR/* &&
 	$SUDO chmod 755 $TESTDIR $TESTDIR/test.sh &&
+	$SUDO chmod 755 $TESTDIR $TESTDIR/sleep.sh &&
 	$SUDO chmod 644 $TESTDIR/test.toml
 '
 
@@ -158,6 +172,26 @@ test_expect_success SUDO 'flux-imp run allows FLUX_JOB_ID and FLUX_JOB_USERID' '
 	grep ^FLUX_JOB_ID=1234 sudo-run-test-uid-jobid.out &&
 	grep ^FLUX_JOB_USERID=$(id -u) sudo-run-test-uid-jobid.out
 '
+
+wait_for_file() {
+        count=0 &&
+        while ! test -f $1; do
+            sleep 0.1
+            count=$((count+1))
+            test $count -gt 20 && break
+        done
+	test -f $1
+}
+test_expect_success SUDO,NO_CHAIN_LINT 'flux-imp run: setuid IMP lingers' '
+	$SUDO $flux_imp run sleep &
+	imp_pid=$! &&
+	wait_for_file $TESTDIR/sleep.pid &&
+	test_when_finished "$SUDO rm -f $pidfile" &&
+	pid=$(cat $TESTDIR/sleep.pid) &&
+	test $(ps --no-header -o comm -p ${pid}) = "flux-imp" &&
+	kill -TERM $pid &&
+	test_expect_code 143 wait $imp_pid
+'
 test_expect_success SUDO 'flux-imp run will not run file with bad ownership' '
 	$SUDO chown $USER $TESTDIR/test.sh &&
 	test_must_fail $SUDO $flux_imp run test &&