Merge 4c9769353e into c946b13575

Similar how we do this as various places: if SIZE_MAX is specified as
size determine the size automatically via strlen().

docs/OSC-CONTEXT.md

@@ -0,0 +1,283 @@
+---
+title: OSC 300819: Hierarchial Context Signalling
+category: Interfaces
+layout: default
+SPDX-License-Identifier: LGPL-2.1-or-later
+---
+
+# OSC 300819: Hierarchial Context Signalling
+
+A terminal connects a user with programs. Control of the program side of
+terminals is typically passed around to various different components while the
+user is active: a shell might pass control to a process it invokes. If that
+process is `run0` then primary control is passed to the privileged session of
+the target user. If `systemd-nspawn` is invoked to start a container primary
+controls is passed to that container, and so on.
+
+A terminal emulator might be interested to know which component is currently is
+in primary control of the program side of a terminal. OSC 3000910 is a
+mechanism to inform it about such contexts. Each component taking over control
+can inform the terminal emulators that a new context begins now, and then use
+the terminal or pass control down to further apps, which can introduce
+contexts. Each context may carry various discriptive metadata fields.
+
+## Status
+
+This OS is invented by systemd. Currently, no terminal application is known
+that consumes these sequences.
+
+## Usecases
+
+Terminal emulators can use hierarchial context information:
+
+1. To introduce markers/bookmarks in the output that the user can jump between.
+
+2. To visually identify output from different contexts. For example the
+   background can be tinted in a reddish tone when privileges are acquired, and
+   similar.
+
+3. Meta information on specific output can be shown in a tooltip or similar
+
+4. Programs (and all subcontexts) can be killed by right-clicking on the output
+   they generate.
+
+5. Failed commands or aborted sessions can be marked requesting use attention.
+
+## Context Types
+
+There are various types of contexts defined by this specification:
+
+1. `boot` → a booted system initiates this context early at boot. (systemd's
+   PID 1 generates this on `/dev/console`.)
+
+2. `container` → a container managed initialized an interactive connection to a
+   container. (`systemd-nspawn` generates this when interactively invoking a
+   container. `machinectl login`, `machinectl shell` do this too.)
+
+3. `vm` → a VMM initialized a terminal connection to VM. (`systemd-vmspawn`
+   generates this when interactively invoking a VM, as one example.)
+
+4. `elevate` → when the user interactively acquired higher privileges. (`run0`
+   initiates a context of this type whenever the user invokes it to acquire
+   root privileges.)
+
+5. `chpriv` → similar, but when the user acquired *different* privileges, not
+   necessarily higher ones. (`run0` initiates a context of this type whenever
+   the user invokes it to acquire non-root privileges of another user.)
+
+5. `subcontext` → similar, but the source and target privileges where
+   identical. (`run0` initiates a context of this type whenever the user
+   invokes it to acquire privileges of the user itself.)
+
+6. `remote` → a user invoked a tool such as `ssh` to connect to a remote
+   system.
+
+7. `shell` → an interactive terminal shell initiates this context
+
+8. `command` → a shell interactively invokes a new program.
+
+9. `app` → an interactive program may initiate this context.
+
+10. `service` → the service manager invokes an interactive service on the terminal
+
+11. `session` → a login session of the user is initialized.
+
+## Semantics
+
+Contexts in the sense of OSC 300819 are hierarchial, and describe a tree
+structure: whenever a new context is opened it becomes the new active context,
+and the previously active context becomes its parent (if there is one). Only
+one context is currently active, but previously opened contexts remain valid in
+the background. Any other data written or read should be considered associated
+with the currently active context.
+
+Each context carries an identifier, chosen by the component opening the
+context. The identifier can chosen freely, but must not be longer than 64
+characters. The characters may be in the 32…126 byte range. Identifiers should universally
+unique, for example randomly generated. A freshly generated UUID would work
+well for this, but this could also be something like the Linux boot ID combined
+with the 64bit inode number of Linux pidfds, or something hashed from it.
+
+Fundamentally, there are two OSC 300819 commands defined:
+
+1. OSC "`300819;S`" (the *start sequence*) → this initiates, updates or indicates a return to a
+   context. It carries a context identifier, and typically some metadata. This
+   may be send to first initiate a context. If sent again for the a context ID
+   that was initiated already this indicates an update of the existing
+   context. In this case, any previously set metadata fields for the context
+   are flushed out, reset to their defaults, and then reinitialized from the
+   newly supplied data. Also, in this case any subcontects of the contexts are
+   implicitly terminated.
+
+2. OSC "`300819;X`" (the *end sequence*)→ this terminates a context. It carries a context
+   identifier to close, initiated before with OSC `300819;S`. It may also carry
+   additional metadata.
+
+## General Syntax
+
+This builds on ECMA-48, and reuses the OSC and ST concepts introduced there.
+
+For sequences following this specification it is recommended to encode OSC as
+0x1B 0x5D, and ST as 0x1B 0x5C.
+
+ECMA-48 only allows characters from the range 0x20…0x7e (i.e. 32…126) inside
+OSC sequences. Hence, any fields that shall contain characters outside of this
+range require escaping. All textual fields must be encoded in UTF-8, which
+then must be escaped.
+
+Escaping shall be applied by taking the byte values of the characters to
+escape, and formatting them as lower-case hexadecimal prefixed with
+`\x`. Example: `Schöpfgefäß` becomes `Sch\xc3\xb6pfgef\xc3\xa4\xc3\x9f`.
+
+The start sequence begins with OSC, followed by the character `S`, followed by
+the context ID. This is then followed by any number of metadata fields,
+including none. Metadata fields begin with a semicolon (`;`) and end in a
+character identifiying the type of field. The sequence ends in ST.
+
+The end sequence begins with OSC, followed by the character `X`, followed by
+the context ID, and a series of metadata fields in the the syntax as for the
+start sequence.
+
+## Metadata Fields
+
+The following fields are currently defined:
+
+| Suffix | Context Types | Description                                                                                                 |
+|--------|---------------|-------------------------------------------------------------------------------------------------------------|
+| `u`    | *all*         | UNIX user name the process issuing the sequence runs as                                                     |
+| `h`    | *all*         | UNIX host name of the system the process issuing the sequence runs on                                       |
+| `m`    | *all*         | The machine ID (i.e. `/etc/machine-id`) of the system the process issuing the sequence runs on              |
+| `b`    | *all*         | The boot ID (i.e. `/proc/sys/kernel/random/boot_id`) of the system the process issuing the sequence runs on |
+| `p`    | *all*         | The numeric PID of the process issuing the sequence, in decimal notation                                    |
+| `P`    | *all*         | The 64bit inode number of the pidfd of the process issuing the sequence, in decimal notation                |
+| `c`    | *all*         | The process name (i.e. `/proc/$PID/comm`, `PR_GET_NAME`) of the process issuing the sequence                |
+| `v`    | `vm`          | The name of the VM being invoked                                                                            |
+| `C`    | `container`   | The name of the container being invoked                                                                     |
+| `U`    | `elevate`, `chpriv`, `vm`, `container`, `remote` | Target UNIX user name                                                    |
+| `H`    | `remote`      | Target UNIX, DNS host name, or IP address                                                                   |
+
+All fields are optional, including the context type. However, it is generally
+recommended to always include the first 7 fields listed above, to make it easy
+to pinpoint the origin of a context in a race-free fashion without any
+ambiguities.
+
+## Examples
+
+1. A new container `foobar` has been invoked by user `lennart` on host `zeta`:
+   `OSC "300819;Sbed86fab93af4328bbed0a1224af6d40;lennartu;zetah;3deb5353d3ba43d08201c136a47ead7bm;d4a3d0fdf2e24fdea6d971ce73f4fbf2b;1062862p;1063162P;foobarc;containert" ST`
+
+2. A context ends: `OSC "300819;Xbed86fab93af4328bbed0a1224af6d40" ST`
+
+## Syntax in ABNF
+
+```abnf
+OSC          = %x1B %x5D
+ST           = %x1B %x5C
+
+DECIMAL      = "0"-"9"
+HEX          = "0"-"9" / "A"-"F" / "a-f"
+ID128        = 32*36(HEX / "-")
+UINT64       = 1*20DECIMAL
+ESCAPED      = "\x" HEX HEX
+SAFE         = %x20-3a / %x3c-5b / %x5d-7e / ESCAPED
+
+CTXID        = 1*64SAFE
+
+USER         = 1*255SAFE "u"
+HOSTNAME     = 1*255SAFE "h"
+MACHINEID    = 1D128 "m"
+BOOTID       = ID128 "b"
+PID          = UINT64 "p"
+PIDFDID      = UINT64 "P"
+COMM         = 1*255SAFE "c"
+
+TYPE         = ("service" / "session" / "shell" / "command" / "vm" / "container" / "elevate" / "chpriv"  / "subcontext" / "remote" / "boot" / "app") "t"
+
+SESSIONID    = 1*255SAFE "s"
+CWD          = 1*255SAFE "d"
+CMDLINE      = *255SAFE "L"
+VMNAME       = 1*255SAFE "v"
+CONTAINERNAME= 1*255SAFE "C"
+TARGETUSER   = 1*255SAFE "U"
+TARGETHOST   = 1*255SAFE "H"
+APPID        = 1*255SAFE "A"
+
+STARTFIELD   = (USER / HOSTNAME / MACHINEID / BOOTID / PID / PIDFDID / COMM / TYPE / SESSIONID / CWD / CMDLINE / VMNAME / CONTAINERNAME / TARGETUSER / TARGETHOST / APPID)
+STARTSEQ     = OSC "300819;" CTXID "S" *(";" STARTFIELD) ST
+
+EXIT         = "success" / "failure" / "crash" / "interrupt"
+STATUS       = UINT64
+SIGNAL       = "SIGBUS" / "SIGTRAP" / "SIGABRT" / "SIGSEGV" / …
+
+ENDFIELD     = (EXIT / STATUS / SIGNAL)
+ENDSEQ       = OSC "300819;" CTXID "X" *(";" ENDFIELD) ST
+```
+
+## Known OSC Prefixes
+
+Here's a list of OSC prefixes used by the various sequences currently in public
+use in various terminal emulators. It's not going to be complete, but I tried
+to do some reasonably thorough research to avoid conflicts with the new OSC
+sequence defined above.
+
+| OSC Prefix      | Purpose                                                    |
+|----------------:|------------------------------------------------------------|
+|     `OSC "0;…"` | Icon name + window title                                   |
+|     `OSC "1;…"` | Icon name                                                  |
+|     `OSC "2;…"` | Window title                                               |
+|     `OSC "3;…"` | X11 property                                               |
+|     `OSC "4;…"` | Palette                                                    |
+|     `OSC "5;…"` | Special palette                                            |
+|     `OSC "6;…"` | Disable special color                                      |
+|     `OSC "7;…"` | Report cwd                                                 |
+|     `OSC "8;…"` | Hyperlink                                                  |
+|     `OSC "9;…"` | Progress bar (conemu) [conflict: also growl notifications] |
+|    `OSC "10;…"` | Change colors                                              |
+|    `OSC "11;…"` | "                                                          |
+|    `OSC "12;…"` | "                                                          |
+|    `OSC "13;…"` | "                                                          |
+|    `OSC "14;…"` | "                                                          |
+|    `OSC "15;…"` | "                                                          |
+|    `OSC "16;…"` | "                                                          |
+|    `OSC "17;…"` | "                                                          |
+|    `OSC "18;…"` | "                                                          |
+|    `OSC "19;…"` | "                                                          |
+|    `OSC "21;…"` | Query colors (kitty)                                       |
+|    `OSC "22;…"` | Cursor shape                                               |
+|    `OSC "46;…"` | Log file                                                   |
+|    `OSC "50;…"` | Set font                                                   |
+|    `OSC "51;…"` | Emacs shell                                                |
+|    `OSC "52;…"` | Manipulate selection data (aka clipboard)                  |
+|    `OSC "60;…"` | Query allowed                                              |
+|    `OSC "61;…"` | Query disallowed                                           |
+|    `OSC "99;…"` | Notifications (kitty)                                      |
+|   `OSC "104;…"` | Reset color                                                |
+|   `OSC "105;…"` | Enable/disable special color                               |
+|   `OSC "110;…"` | Reset colors                                               |
+|   `OSC "111;…"` | "                                                          |
+|   `OSC "112;…"` | "                                                          |
+|   `OSC "113;…"` | "                                                          |
+|   `OSC "114;…"` | "                                                          |
+|   `OSC "115;…"` | "                                                          |
+|   `OSC "116;…"` | "                                                          |
+|   `OSC "117;…"` | "                                                          |
+|   `OSC "118;…"` | "                                                          |
+|   `OSC "119;…"` | "                                                          |
+|   `OSC "133;…"` | Prompt/command begin/command end (finalterm/iterm2)        |
+|   `OSC "440;…"` | Audio (mintty)                                             |
+|   `OSC "633;…"` | vscode action (Windows Terminal)                           |
+|   `OSC "666;…"` | "termprop" (vte)                                           |
+|   `OSC "701;…"` | Locale (mintty)                                            |
+|   `OSC "777;…"` | Notification (rxvt)                                        |
+|  `OSC "7704;…"` | ANSI colors (mintty)                                       |
+|  `OSC "7750;…"` | Emoji style (mintty)                                       |
+|  `OSC "7770;…"` | Font size (mintty)                                         |
+|  `OSC "7771;…"` | Glyph coverage (mintty)                                    |
+|  `OSC "7721:…"` | Copy window title (mintty)                                 |
+|  `OSC "7777;…"` | Window size (mintty)                                       |
+|  `OSC "9001;…"` | Action (Windows Terminal)                                  |
+|  `OSC "1337;…"` | iterm2 multiplex seeuqnece                                 |
+|  `OSC "5522;…"` | Clipboard (kitty)                                          |
+| `OSC "30001;…"` | Push color onto stack (kitty)                              |
+| `OSC "30101;…"` | Pop color from stack (kitty)                               |
+| `OSC "77119;…"` | Wide chars (mintty)                                        |

src/basic/escape.c

@@ -365,6 +365,8 @@ char* xescape_full(const char *s, const char *bad, size_t console_width, XEscape
         char *ans, *t, *prev, *prev2;
         const char *f;
 
+        assert(s);
+
         /* Escapes all chars in bad, in addition to \ and all special chars, in \xFF style escaping. May be
          * reversed with cunescape(). If XESCAPE_8_BIT is specified, characters >= 127 are let through
          * unchanged. This corresponds to non-ASCII printable characters in pre-unicode encodings.
@@ -397,7 +399,7 @@ char* xescape_full(const char *s, const char *bad, size_t console_width, XEscape
 
                 if ((unsigned char) *f < ' ' ||
                     (!FLAGS_SET(flags, XESCAPE_8_BIT) && (unsigned char) *f >= 127) ||
-                    *f == '\\' || strchr(bad, *f)) {
+                    *f == '\\' || (bad && strchr(bad, *f))) {
                         if ((size_t) (t - ans) + 4 + 3 * force_ellipsis > console_width)
                                 break;
 

src/basic/hexdecoct.c

@@ -866,6 +866,9 @@ void hexdump(FILE *f, const void *p, size_t s) {
 
         assert(b || s == 0);
 
+        if (s == SIZE_MAX)
+                s = strlen(p);
+
         if (!f)
                 f = stdout;
 

src/basic/process-util.c

@@ -3,6 +3,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
+#include <linux/magic.h>
 #include <linux/oom.h>
 #include <pthread.h>
 #include <spawn.h>
@@ -11,6 +12,9 @@
 #include <stdlib.h>
 #include <sys/mount.h>
 #include <sys/personality.h>
+#if HAVE_PIDFD_OPEN
+#include <sys/pidfd.h>
+#endif
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -40,6 +44,7 @@
 #include "log.h"
 #include "macro.h"
 #include "memory-util.h"
+#include "missing_magic.h"
 #include "missing_sched.h"
 #include "missing_syscall.h"
 #include "missing_threads.h"
@@ -2289,3 +2294,42 @@ _noreturn_ void report_errno_and_exit(int errno_fd, int error) {
 
         _exit(EXIT_FAILURE);
 }
+
+int getpidfdid_cached(uint64_t *ret) {
+        static uint64_t cached = 0;
+        static int initialized = 0;
+        int r;
+
+        assert(ret);
+
+        if (initialized > 0) {
+                *ret = cached;
+                return 0;
+        }
+        if (initialized < 0)
+                return initialized;
+
+        _cleanup_close_ int fd = pidfd_open(getpid_cached(), 0);
+        if (fd < 0) {
+                if (ERRNO_IS_NOT_SUPPORTED(errno))
+                        return (initialized = -EOPNOTSUPP);
+
+                return -errno;
+        }
+
+        r = fd_is_fs_type(fd, PID_FS_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return (initialized = -EOPNOTSUPP);
+
+        struct stat st;
+        if (fstat(fd, &st) < 0)
+                return -errno;
+        if (st.st_ino == 0)
+                return (initialized = -EOPNOTSUPP);
+
+        *ret = cached = st.st_ino;
+        initialized = 1;
+        return 0;
+}

src/basic/process-util.h

@@ -275,3 +275,5 @@ int proc_dir_read(DIR *d, pid_t *ret);
 int proc_dir_read_pidref(DIR *d, PidRef *ret);
 
 _noreturn_ void report_errno_and_exit(int errno_fd, int error);
+
+int getpidfdid_cached(uint64_t *ret);

src/basic/random-util.c

@@ -42,6 +42,7 @@ static void fallback_random_bytes(void *p, size_t n) {
                 uint64_t call_id, block_id;
                 usec_t stamp_mono, stamp_real;
                 pid_t pid, tid;
+                uint64_t pidfdid;
                 uint8_t auxval[16];
         } state = {
                 /* Arbitrary domain separation to prevent other usage of AT_RANDOM from clashing. */
@@ -57,6 +58,8 @@ static void fallback_random_bytes(void *p, size_t n) {
         memcpy(state.auxval, ULONG_TO_PTR(getauxval(AT_RANDOM)), sizeof(state.auxval));
 #endif
 
+        (void) getpidfdid_cached(&state.pidfdid);
+
         while (n > 0) {
                 struct sha256_ctx ctx;
 

src/core/main.c

@@ -45,6 +45,7 @@
 #include "efivars.h"
 #include "emergency-action.h"
 #include "env-util.h"
+#include "escape.h"
 #include "exit-status.h"
 #include "fd-util.h"
 #include "fdset.h"
@@ -57,6 +58,7 @@
 #include "ima-setup.h"
 #include "import-creds.h"
 #include "initrd-util.h"
+#include "io-util.h"
 #include "ipe-setup.h"
 #include "killall.h"
 #include "kmod-setup.h"
@@ -73,6 +75,7 @@
 #include "mount-setup.h"
 #include "mount-util.h"
 #include "os-util.h"
+#include "osc-context.h"
 #include "pager.h"
 #include "parse-argument.h"
 #include "parse-util.h"
@@ -2380,6 +2383,38 @@ static void log_execution_mode(bool *ret_first_boot) {
         *ret_first_boot = first_boot;
 }
 
+static int write_boot_or_shutdown_osc(bool boot) {
+        int r;
+
+        if (getenv_terminal_is_dumb())
+                return 0;
+
+        const char *type = boot ? "boot" : "shutdown";
+
+        _cleanup_close_ int fd = open_terminal("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return log_debug_errno(fd, "Failed to open /dev/console to print %s OSC, ignoring: %m", type);
+
+        _cleanup_free_ char *seq = NULL;
+        if (boot)
+                r = osc_context_open_boot(&seq);
+        else
+                r = osc_context_close(SD_ID128_ALLF, &seq);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to acquire %s OSC sequence, ignoring: %m", type);
+
+        r = loop_write(fd, seq, strlen(seq));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to write %s OSC sequence, ignoring: %m", type);
+
+        if (DEBUG_LOGGING) {
+                _cleanup_free_ char *h = cescape(seq);
+                log_debug("OSC sequence for %s successfully written: %s", type, strna(h));
+        }
+
+        return 0;
+}
+
 static int initialize_runtime(
                 bool skip_setup,
                 bool first_boot,
@@ -2438,6 +2473,8 @@ static int initialize_runtime(
 
                         write_container_id();
 
+                        (void) write_boot_or_shutdown_osc(/* boot= */ true);
+
                         /* Copy os-release to the propagate directory, so that we update it for services running
                          * under RootDirectory=/RootImage= when we do a soft reboot. */
                         r = setup_os_release(RUNTIME_SCOPE_SYSTEM);
@@ -3427,6 +3464,8 @@ finish:
         }
 #endif
 
+        (void) write_boot_or_shutdown_osc(/* boot= */ false);
+
         if (r < 0)
                 (void) sd_notifyf(/* unset_environment= */ false,
                                   "ERRNO=%i", -r);

src/machine/machinectl.c

@@ -45,6 +45,7 @@
 #include "main-func.h"
 #include "mkdir.h"
 #include "nulstr-util.h"
+#include "osc-context.h"
 #include "pager.h"
 #include "parse-argument.h"
 #include "parse-util.h"
@@ -1227,6 +1228,13 @@ static int process_forward(sd_event *event, PTYForward **forward, int master, PT
                         log_info("Connected to machine %s. Press ^] three times within 1s to exit session.", name);
         }
 
+        _cleanup_(osc_context_closep) sd_id128_t osc_context_id = SD_ID128_NULL;
+        if (!terminal_is_dumb()) {
+                r = osc_context_open_container(name, /* ret_seq= */ NULL, &osc_context_id);
+                if (r < 0)
+                        return r;
+        }
+
         r = sd_event_set_signal_exit(event, true);
         if (r < 0)
                 return log_error_errno(r, "Failed to enable SIGINT/SITERM handling: %m");

src/nspawn/nspawn.c

@@ -84,6 +84,7 @@
 #include "nsresource.h"
 #include "nulstr-util.h"
 #include "os-util.h"
+#include "osc-context.h"
 #include "pager.h"
 #include "parse-argument.h"
 #include "parse-util.h"
@@ -5685,6 +5686,13 @@ static int run_container(
                 (void) expose_port_execute(rtnl, &expose_args->fw_ctx, arg_expose_ports, AF_INET6, &expose_args->address6);
         }
 
+        _cleanup_(osc_context_closep) sd_id128_t osc_context_id = SD_ID128_NULL;
+        if (IN_SET(arg_console_mode, CONSOLE_INTERACTIVE, CONSOLE_READ_ONLY) && !terminal_is_dumb()) {
+                r = osc_context_open_container(arg_machine, /* ret_seq= */ NULL, &osc_context_id);
+                if (r < 0)
+                        return r;
+        }
+
         if (arg_console_mode != CONSOLE_PIPE) {
                 _cleanup_close_ int fd = -EBADF;
                 PTYForwardFlags flags = 0;

src/run/run.c

@@ -30,6 +30,7 @@
 #include "fs-util.h"
 #include "hostname-util.h"
 #include "main-func.h"
+#include "osc-context.h"
 #include "parse-argument.h"
 #include "parse-util.h"
 #include "path-util.h"
@@ -2041,6 +2042,7 @@ static int start_transient_service(sd_bus *bus) {
                         return r;
         }
 
+        _cleanup_(osc_context_closep) sd_id128_t osc_context_id = SD_ID128_NULL;
         if (arg_wait || arg_stdio != ARG_STDIO_NONE) {
                 _cleanup_(run_context_done) RunContext c = {
                         .cpu_usage_nsec = NSEC_INFINITY,
@@ -2067,6 +2069,12 @@ static int start_transient_service(sd_bus *bus) {
                         return log_oom();
 
                 if (pty_fd >= 0) {
+                        if (!terminal_is_dumb() && arg_exec_user) {
+                                r = osc_context_open_chpriv(arg_exec_user, /* ret_seq= */ NULL, &osc_context_id);
+                                if (r < 0)
+                                        return r;
+                        }
+
                         (void) sd_event_set_signal_exit(c.event, true);
 
                         if (!arg_quiet)

src/shared/meson.build

@@ -132,6 +132,7 @@ shared_sources = files(
         'open-file.c',
         'openssl-util.c',
         'output-mode.c',
+        'osc-context.c',
         'pager.c',
         'parse-argument.c',
         'parse-helpers.c',

src/shared/osc-context.c

@@ -0,0 +1,275 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#if HAVE_SYS_AUXV_H
+#  include <sys/auxv.h>
+#endif
+
+#include "escape.h"
+#include "hostname-util.h"
+#include "osc-context.h"
+#include "process-util.h"
+#include "string-util.h"
+#include "terminal-util.h"
+#include "user-util.h"
+
+/* This currently generates open sequences for OSC 300819 types "boot", "container", "vm", "elevate",
+ * "chpriv", "subcontext". */
+
+/* TODO:
+ *
+ *  → "service" (from the service manager)
+ *  → "session" (from pam_systemd?)
+ *  → "shell", "command" (from a bash profile drop-in?)
+ *
+ * Not generated by systemd: "remote" (would have to be generated from the SSH client), "app".
+ */
+
+static int strextend_escaped(char **s, const char *prefix, const char *value, const char *suffix) {
+        assert(s);
+        assert(value);
+
+        if (!strextend(s, prefix))
+                return -ENOMEM;
+
+        _cleanup_free_ char *e = xescape(value, ";\\");
+        if (!e)
+                return -ENOMEM;
+
+        if (!strextend(s, e))
+                return -ENOMEM;
+
+        if (!strextend(s, suffix))
+                return -ENOMEM;
+
+        return 0;
+}
+
+static int osc_append_identity(char **s) {
+        int r;
+
+        assert(s);
+
+        _cleanup_free_ char *u = getusername_malloc();
+        if (u) {
+                r = strextend_escaped(s, ";", u, "u");
+                if (r < 0)
+                        return r;
+        }
+
+        _cleanup_free_ char *h = gethostname_malloc();
+        if (h) {
+                r = strextend_escaped(s, ";", h, "h");
+                if (r < 0)
+                        return r;
+        }
+
+        sd_id128_t id;
+        if (sd_id128_get_machine(&id) >= 0) {
+                r = strextendf(s, ";" SD_ID128_FORMAT_STR "m", SD_ID128_FORMAT_VAL(id));
+                if (r < 0)
+                        return r;
+        }
+
+        if (sd_id128_get_boot(&id) >= 0) {
+                r = strextendf(s, ";" SD_ID128_FORMAT_STR "b", SD_ID128_FORMAT_VAL(id));
+                if (r < 0)
+                        return r;
+        }
+
+        r = strextendf(s, ";" PID_FMT "p", getpid_cached());
+        if (r < 0)
+                return r;
+
+        uint64_t pidfdid;
+        r = getpidfdid_cached(&pidfdid);
+        if (r >= 0) {
+                r = strextendf(s, ";%" PRIu64 "P", pidfdid);
+                if (r < 0)
+                        return r;
+        }
+
+        r = strextend_escaped(s, ";", program_invocation_short_name, "c");
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static void osc_context_default_id(sd_id128_t *ret_id) {
+
+        /* Usually we only want one context ID per tool. Since we don't want to store the ID let's just hash
+         * one from process credentials */
+
+        struct {
+                uint64_t pidfdid;
+                uint8_t auxval[16];
+                pid_t pid;
+        } data = {
+                .pid = getpid_cached(),
+        };
+
+        assert(ret_id);
+
+        (void) getpidfdid_cached(&data.pidfdid);
+
+        memcpy(data.auxval, ULONG_TO_PTR(getauxval(AT_RANDOM)), sizeof(data.auxval));
+
+        ret_id->qwords[0] = siphash24(&data, sizeof(data), SD_ID128_MAKE(3f,8c,ee,e1,fd,35,41,ec,b8,b1,90,d4,59,e2,ae,5b).bytes);
+        ret_id->qwords[1] = siphash24(&data, sizeof(data), SD_ID128_MAKE(c6,41,ec,1b,d8,85,48,c0,8e,11,d7,e1,e1,fa,9e,03).bytes);
+}
+
+static int osc_context_intro(char **ret_seq, sd_id128_t *ret_context_id) {
+        int r;
+
+        assert(ret_seq);
+
+        /* If the user passed us a buffer for the context ID generate a randomized one, since we have a place
+         * to store it. The user should pass the ID back to osc_context_close() later on. if the user did not
+         * pass us a buffer, we'll use a session ID hashed from process properties that remain stable as long
+         * our process exists. It hence also remains stable across reexec and similar. */
+        sd_id128_t id;
+        if (ret_context_id) {
+                r = sd_id128_randomize(&id);
+                if (r < 0)
+                        return r;
+        } else
+                osc_context_default_id(&id);
+
+        _cleanup_free_ char *seq = NULL;
+        if (asprintf(&seq, ANSI_OSC "300819;S" SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(id)) < 0)
+                return -ENOMEM;
+
+        r = osc_append_identity(&seq);
+        if (r < 0)
+                return r;
+
+        if (ret_context_id)
+                *ret_context_id = id;
+
+        *ret_seq = TAKE_PTR(seq);
+        return 0;
+}
+
+static int osc_context_outro(char *_seq, sd_id128_t id, char **ret_seq, sd_id128_t *ret_context_id) {
+        _cleanup_free_ char *seq = TAKE_PTR(_seq); /* We take possession of the string no matter what */
+
+        if (ret_seq)
+                *ret_seq = TAKE_PTR(seq);
+        else {
+                fputs(seq, stdout);
+                fflush(stdout);
+        }
+
+        if (ret_context_id)
+                *ret_context_id = id;
+
+        return 0;
+}
+
+int osc_context_open_boot(char **ret_seq) {
+        int r;
+
+        _cleanup_free_ char *seq = NULL;
+        sd_id128_t id;
+        r = osc_context_intro(&seq, /* ret_context_id= */ NULL);
+        if (r < 0)
+                return r;
+
+        if (!strextend(&seq, ";" "boot" "t" ANSI_ST))
+                return -ENOMEM;
+
+        return osc_context_outro(TAKE_PTR(seq), id, ret_seq, /* ret_context_id= */ NULL);
+}
+
+int osc_context_open_container(const char *name, char **ret_seq, sd_id128_t *ret_context_id) {
+        int r;
+
+        _cleanup_free_ char *seq = NULL;
+        sd_id128_t id;
+        r = osc_context_intro(&seq, ret_context_id ?: &id);
+        if (r < 0)
+                return r;
+
+        if (name) {
+                r = strextend_escaped(&seq, ";", name, "C");
+                if (r < 0)
+                        return r;
+        }
+
+        if (!strextend(&seq, ";" "container" "t" ANSI_ST))
+                return -ENOMEM;
+
+        return osc_context_outro(TAKE_PTR(seq), id, ret_seq, ret_context_id);
+}
+
+int osc_context_open_vm(const char *name, char **ret_seq, sd_id128_t *ret_context_id) {
+        int r;
+
+        assert(name);
+
+        _cleanup_free_ char *seq = NULL;
+        sd_id128_t id;
+        r = osc_context_intro(&seq, ret_context_id ?: &id);
+        if (r < 0)
+                return r;
+
+        r = strextend_escaped(&seq, ";", name, "v");
+        if (r < 0)
+                return r;
+
+        if (!strextend(&seq, ";" "vm" "t" ANSI_ST))
+                return r;
+
+        return osc_context_outro(TAKE_PTR(seq), id, ret_seq, ret_context_id);
+}
+
+int osc_context_open_chpriv(const char *target_user, char **ret_seq, sd_id128_t *ret_context_id) {
+        int r;
+
+        assert(target_user);
+
+        _cleanup_free_ char *seq = NULL;
+        sd_id128_t id;
+        r = osc_context_intro(&seq, ret_context_id ?: &id);
+        if (r < 0)
+                return r;
+
+        if (STR_IN_SET(target_user, "root", "0")) {
+                if (!strextend(&seq, ";" "elevate" "t" ANSI_ST))
+                        return -ENOMEM;
+        } else if (is_this_me(target_user) > 0) {
+                if (!strextend(&seq, ";" "subcontext" "t" ANSI_ST))
+                        return -ENOMEM;
+        } else {
+                r = strextend_escaped(&seq, ";", target_user, "U");
+                if (r < 0)
+                        return r;
+
+                if (!strextend(&seq, ";" "chpriv" "t" ANSI_ST))
+                        return -ENOMEM;
+        }
+
+        return osc_context_outro(TAKE_PTR(seq), id, ret_seq, ret_context_id);
+}
+
+int osc_context_close(sd_id128_t id, char **ret_seq) {
+
+        if (sd_id128_is_null(id)) /* nil uuid: no session opened */
+                return 0;
+
+        if (sd_id128_is_allf(id)) /* max uuid: default session opened */
+                osc_context_default_id(&id);
+
+        _cleanup_free_ char *seq = NULL;
+        if (asprintf(&seq, ANSI_OSC "300819;X" SD_ID128_FORMAT_STR ANSI_ST, SD_ID128_FORMAT_VAL(id)) < 0)
+                return -ENOMEM;
+
+        if (ret_seq)
+                *ret_seq = TAKE_PTR(seq);
+        else {
+                fputs(seq, stdout);
+                fflush(stdout);
+        }
+
+        return 0;
+}

src/shared/osc-context.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-id128.h"
+
+int osc_context_open_boot(char **ret_seq);
+int osc_context_open_container(const char *name, char **ret_seq, sd_id128_t *ret_context_id);
+int osc_context_open_vm(const char *name, char **ret_seq, sd_id128_t *ret_context_id);
+int osc_context_open_chpriv(const char *target_user, char **ret_seq, sd_id128_t *ret_context_id);
+int osc_context_close(sd_id128_t id, char **ret_seq);
+
+static inline void osc_context_closep(sd_id128_t *context_id) {
+        (void) osc_context_close(*context_id, NULL);
+}

src/test/meson.build

@@ -137,6 +137,7 @@ simple_tests += files(
         'test-open-file.c',
         'test-ordered-set.c',
         'test-os-util.c',
+        'test-osc-context.c',
         'test-parse-argument.c',
         'test-parse-helpers.c',
         'test-path-lookup.c',

src/test/test-osc-context.c

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "hexdecoct.h"
+#include "osc-context.h"
+#include "tests.h"
+
+#include "escape.h"
+
+TEST(osc) {
+        _cleanup_free_ char *seq = NULL;
+
+        log_info("boot");
+        assert_se(osc_context_open_boot(&seq) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        assert_se(osc_context_close(SD_ID128_ALLF, &seq) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        log_info("container");
+        sd_id128_t id;
+        assert_se(osc_context_open_container("foobar", &seq, &id) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        assert_se(osc_context_close(id, &seq) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        log_info("vm");
+        assert_se(osc_context_open_vm("foobar", &seq, &id) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        assert_se(osc_context_close(id, &seq) >= 0);
+        hexdump(/* f = */ NULL, seq, SIZE_MAX);
+        seq = mfree(seq);
+
+        printf("%s\n", xescape("Schöpfgefäß", NULL));
+}
+
+static int intro(void) {
+        log_show_color(true);
+        return EXIT_SUCCESS;
+}
+
+DEFINE_TEST_MAIN_WITH_INTRO(LOG_INFO, intro);

src/test/test-process-util.c

@@ -994,6 +994,21 @@ TEST(pid_get_start_time) {
         ASSERT_GE(start_time2, start_time);
 }
 
+TEST(getpidfdid_cached) {
+        int r;
+
+        log_info("pid=" PID_FMT, getpid_cached());
+
+        uint64_t id;
+        r = getpidfdid_cached(&id);
+        if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
+                log_info("pidfdid not supported");
+        else {
+                assert(r >= 0);
+                log_info("pidfdid=%" PRIu64, id);
+        }
+}
+
 static int intro(void) {
         log_show_color(true);
         return EXIT_SUCCESS;

src/vmspawn/vmspawn.c

@@ -47,6 +47,7 @@
 #include "main-func.h"
 #include "mkdir.h"
 #include "netif-util.h"
+#include "osc-context.h"
 #include "pager.h"
 #include "parse-argument.h"
 #include "parse-util.h"
@@ -2189,8 +2190,15 @@ static int run_virtual_machine(int kvm_device_fd, int vhost_device_fd) {
         /* Exit when the child exits */
         (void) event_add_child_pidref(event, NULL, &child_pidref, WEXITED, on_child_exit, NULL);
 
+        _cleanup_(osc_context_closep) sd_id128_t osc_context_id = SD_ID128_NULL;
         _cleanup_(pty_forward_freep) PTYForward *forward = NULL;
         if (master >= 0) {
+                if (!terminal_is_dumb()) {
+                        r = osc_context_open_vm(arg_machine, /* ret_seq= */ NULL, &osc_context_id);
+                        if (r < 0)
+                                return r;
+                }
+
                 r = pty_forward_new(event, master, ptyfwd_flags, &forward);
                 if (r < 0)
                         return log_error_errno(r, "Failed to create PTY forwarder: %m");