Oh god, well this was terrible

docker/admin/install.bash

@@ -53,6 +53,7 @@ sudo
 tmux
 terraform
 unzip
+uuid-runtime
 vim
 wget
 yarn

docker/runtime/install.bash

@@ -59,6 +59,7 @@ strace
 sudo
 tmux
 tree
+uuid-runtime
 vim
 
 "

system/res/docker-exec.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+
+import argparse
+import signal
+import subprocess
+import sys
+import uuid
+
+class Parser(argparse.ArgumentParser):
+    def format_help(self):
+        return """
+Usage:  docker-exec.bash [OPTIONS] CONTAINER COMMAND [ARG...]
+
+Run a command in a running container
+
+Options:
+  -i, --interactive   Keep STDIN open even if not attached
+  -t, --tty           Allocate a pseudo-TTY
+  -u, --user string   Username or UID (format: <name|uid>:[<group|gid>])
+"""
+
+parser = Parser()
+parser.add_argument("-i", "--interactive", action="store_true")
+parser.add_argument("-t", "--tty", action="store_true")
+parser.add_argument("-u", "--user", type=str)
+parser.add_argument("container", type=str)
+parser.add_argument("arg", type=str, nargs="*")
+
+args = parser.parse_args()
+
+pidfiles = "/var/run/riju/pidfiles"
+pidfile = pidfiles + "/" + str(uuid.uuid4()).replace("-", "")
+print(pidfile)
+
+# We have to use 'kill -9' here, otherwise runuser intercepts the
+# signal and takes its sweet time cleaning up.
+def cleanup(*ignored_args):
+    subprocess.run([
+        "docker",
+        "exec",
+        args.container,
+        "bash",
+        "-c",
+        f"""
+set -euo pipefail
+if [[ -f '{pidfile}' ]]; then
+    kill -9 -$(< '{pidfile}')
+    rm -f '{pidfile}'
+fi
+        """
+    ])
+
+signal.signal(signal.SIGINT, cleanup)
+signal.signal(signal.SIGTERM, cleanup)
+
+exec_args = []
+
+if args.interactive:
+    exec_args.append("-i")
+if args.tty:
+    exec_args.append("-t")
+
+runuser_args = []
+
+if args.user:
+    runuser_args = ["runuser", "-u", args.user, "--"]
+
+subprocess.run([
+    "docker",
+    "exec",
+    *exec_args,
+    args.container,
+    "bash",
+    "-c",
+    f"""
+set -euo pipefail
+umask 077
+mkdir -p '{pidfiles}'
+echo "$$" > '{pidfile}'
+exec "$@"
+    """,
+    "--",
+    *runuser_args,
+    *args.arg,
+])

system/src/riju-system-privileged.c

@@ -134,11 +134,11 @@ void exec(char *uuid, int argc, char **cmdline, bool pty)
   if (asprintf(&container, "riju-session-%s", uuid) < 0)
     die("asprintf failed");
   char *argvPrefix[] = {
-    "docker",
+    "./system/res/docker-exec.py",
-    "exec",
     "--user", "riju",
     pty ? "-it" : "-i",
     container,
+    "--",
   };
   char **argv = malloc(sizeof(argvPrefix) + (argc + 1) * sizeof(char *));
   if (argv == NULL)