···
+
(* From Obuilder see License file at end of document *)
+
let ( / ) = Eio.Path.( / )
+
let ( // ) = Filename.concat
+
type config = { fast_sync : bool }
+
let ch = Unix.open_process_in "uname -m" in
+
let arch = input_line ch in
+
match Unix.close_process_in ch with
+
| Unix.WEXITED 0 -> String.trim arch
+
| _ -> failwith "Failed to get arch with 'uname -m'"
+
match get_machine () with
+
| "x86_64" -> [ "SCMP_ARCH_X86_64"; "SCMP_ARCH_X86"; "SCMP_ARCH_X32" ]
+
| "aarch64" -> [ "SCMP_ARCH_AARCH64"; "SCMP_ARCH_ARM" ]
+
let secret_file id = "secret-" ^ string_of_int id
+
module Json_config = struct
+
let mount ?(options = []) ~ty ~src dst =
+
("destination", `String dst);
+
("source", `String src);
+
("options", `List (List.map (fun x -> `String x) options));
+
let strings xs = `List (List.map (fun x -> `String x) xs)
+
let namespace x = `Assoc [ ("type", `String x) ]
+
(* This is a subset of the capabilities that Docker uses by default.
+
These control what root can do in the container.
+
If the init process is non-root, permitted, effective and ambient sets are cleared.
+
See capabilities(7) for full details. *)
+
let default_linux_caps =
+
(* Make arbitrary changes to file UIDs and GIDs *)
+
(* Bypass file read, write, and execute permission checks. *)
+
(* Set SUID/SGID bits. *)
+
(* Bypass permission checks. *)
+
(* Create special files using mknod. *)
+
(* Make arbitrary manipulations of process GIDs. *)
+
(* Make arbitrary manipulations of process UIDs. *)
+
(* Set arbitrary capabilities on a file. *)
+
(* Add any capability from bounding set to inheritable set. *)
+
(* Bypass permission checks for sending signals. *)
+
(* Write records to kernel auditing log. *)
+
(* Allowed by Docker, but disabled here (because we use host networking):
+
"CAP_NET_RAW"; (* Use RAW and PACKET sockets / bind to any address *)
+
"CAP_NET_BIND_SERVICE"; (* Bind a socket to Internet domain privileged ports. *)
+
let seccomp_syscalls ~fast_sync =
+
(* Sync calls are pointless for the builder, because if the computer crashes then we'll
+
just throw the build dir away and start again. And btrfs sync is really slow.
+
Based on https://bblank.thinkmo.de/using-seccomp-to-filter-sync-operations.html
+
Note: requires runc >= v1.0.0-rc92. *)
+
("action", `String "SCMP_ACT_ERRNO");
+
(* Return error "success" *)
+
("defaultAction", `String "SCMP_ACT_ALLOW");
+
("syscalls", `List (seccomp_syscalls ~fast_sync:true));
+
entrypoint : string option;
+
let make { cwd; argv; hostname; network; user; env; entrypoint } ~config_dir
+
~results_dir : Yojson.Safe.t =
+
assert (entrypoint = None);
+
`Assoc [ ("uid", `Int uid); ("gid", `Int gid) ]
+
Fmt.failwith "Unsupported network configuration %a"
+
let namespaces = network_ns @ [ "pid"; "ipc"; "uts"; "mount" ] in
+
("ociVersion", `String "1.0.1-dev");
+
("terminal", `Bool false);
+
("args", strings argv);
+
("bounding", strings default_linux_caps);
+
(* Limits capabilities gained on execve. *)
+
("effective", strings default_linux_caps);
+
(* Checked by kernel to decide access *)
+
("inheritable", strings default_linux_caps);
+
(* Preserved across an execve (if root, or cap in ambient set) *)
+
("permitted", strings default_linux_caps);
+
(* Limiting superset for the effective capabilities *)
+
("type", `String "RLIMIT_NOFILE");
+
("noNewPrivileges", `Bool false);
+
("path", `String (results_dir // "rootfs"));
+
("readonly", `Bool false);
+
("hostname", `String hostname);
+
[ (* TODO: copy to others? *) "nosuid"; "noexec"; "nodev" ]
+
:: mount "/dev" ~ty:"tmpfs" ~src:"tmpfs"
+
~options:[ "nosuid"; "strictatime"; "mode=755"; "size=65536k" ]
+
:: mount "/dev/pts" ~ty:"devpts" ~src:"devpts"
+
(* This is how Docker does it. runc's default is a bit different. *)
+
~ty:"sysfs" ~src:"sysfs"
+
~options:[ "nosuid"; "noexec"; "nodev"; "ro" ]
+
:: mount "/sys/fs/cgroup" ~ty:"cgroup" ~src:"cgroup"
+
~options:[ "ro"; "nosuid"; "noexec"; "nodev" ]
+
:: mount "/dev/shm" ~ty:"tmpfs" ~src:"shm"
+
[ "nosuid"; "noexec"; "nodev"; "mode=1777"; "size=65536k" ]
+
:: mount "/dev/mqueue" ~ty:"mqueue" ~src:"mqueue"
+
~options:[ "nosuid"; "noexec"; "nodev" ]
+
:: mount "/etc/hosts" ~ty:"bind" ~src:(config_dir // "hosts")
+
~options:[ "ro"; "rbind"; "rprivate" ]
+
(if network = [ "host" ] then
+
mount "/etc/resolv.conf" ~ty:"bind" ~src:"/etc/resolv.conf"
+
~options:[ "ro"; "rbind"; "rprivate" ];
+
("namespaces", `List (List.map namespace namespaces));
+
("seccomp", seccomp_policy);
+
let spawn ~sw fs proc config dir =
+
let tmp = Filename.temp_dir ~perms:0o700 "shelter-run-" "" in
+
let eio_tmp = Eio.Path.(fs / tmp) in
+
let json_config = Json_config.make config ~config_dir:tmp ~results_dir:dir in
+
Eio.Path.save ~create:(`If_missing 0o644) (eio_tmp / "config.json")
+
(Yojson.Safe.pretty_to_string json_config ^ "\n");
+
Eio.Path.save ~create:(`If_missing 0o644) (eio_tmp / "hosts")
+
"127.0.0.1 localhost builder";
+
let id = string_of_int !next_id in
+
let cmd = [ "runc"; "--root"; "runc"; "run"; id ] in
+
Eio.Process.spawn ~sw proc ~cwd:eio_tmp cmd
+
Version 2.0, January 2004
+
https://www.apache.org/licenses/
+
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END OF TERMS AND CONDITIONS
+
Copyright 2020 Thomas Leonard
+
Licensed under the Apache License, Version 2.0 (the "License");
+
you may not use this file except in compliance with the License.
+
You may obtain a copy of the License at
+
https://www.apache.org/licenses/LICENSE-2.0
+
Unless required by applicable law or agreed to in writing, software
+
distributed under the License is distributed on an "AS IS" BASIS,
+
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
See the License for the specific language governing permissions and
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limitations under the License. *)
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