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Use a dbus service name as its app_id #921

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Use a dbus service name as its app_id #921

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50 changes: 47 additions & 3 deletions src/xdp-utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -189,6 +189,40 @@ _xdp_parse_app_id_from_unit_name (const char *unit)

return g_steal_pointer (&app_id);
}

char *
_xdp_parse_app_id_from_dbus_name (const char *unit)
{
g_autoptr(GRegex) regex = NULL;
g_autoptr(GMatchInfo) match = NULL;
g_autoptr(GError) error = NULL;
g_autofree char *app_id = NULL;

g_assert (g_str_has_prefix (unit, "dbus-"));

// Parses a unit name such as dbus-:1.2-org.kde.kdeconnect@7.service
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@smcv smcv Nov 29, 2022 •
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This naming convention for systemd units is specific to dbus-broker.

On systems that have systemd activation available, the reference implementation (dbus-daemon) does not guarantee that activated services are in any sort of systemd service or scope: D-Bus services with SystemdService=foo.service are run as foo.service (probably also true for dbus-broker), and D-Bus services without SystemdService are run via "traditional activation", mechanically the same as what happens on non-systemd systems like *BSD or Devuan, so they end up as child processes in dbus.service (this behaviour is unlike dbus-broker).

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Having said that, if a unit name matches this pattern then you can probably be quite confident that it's named according to how dbus-broker does it.

regex = g_regex_new ("^dbus-:[[:digit:]]+\\.[[:digit:]]+-"
"(.+?\\..+?\\..+?)(?:[@\\-][[:alnum:]]*)\\.service$",
0, 0, &error);
g_assert (error == NULL);
if (g_regex_match (regex, unit, 0, &match))
{
const char *escaped_app_id;
/* Unescape the unit name which may have \x hex codes in it, e.g.
* "app-gnome-org.gnome.Evolution\x2dalarm\x2dnotify-2437.scope"
*/
escaped_app_id = g_match_info_fetch (match, 1);
if (cunescape (escaped_app_id, UNESCAPE_RELAX, &app_id) < 0)
app_id = g_strdup ("");
}
else
{
g_warning("Failed to parse dbus name %s", unit);
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@smcv smcv Nov 29, 2022 •
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This will warn on some entirely legitimate unit names. There is a weak convention that a D-Bus service with Name=com.example.Whatever often has SystemdService=dbus-com.example.Whatever.service, which starts with dbus- but does not match dbus-broker's pattern.

I don't know of any concrete examples of user services (session bus services) doing this, but systemd's own dbus-org.freedesktop.login1.service and friends use this pattern for their system services (system bus services).

app_id = g_strdup ("");
}

return g_steal_pointer (&app_id);
}
#endif /* HAVE_LIBSYSTEMD */

void
Expand All @@ -206,13 +240,23 @@ set_appid_from_pid (XdpAppInfo *app_info, pid_t pid)
* fetching our own systemd units or the unit might not be started by the
* desktop environment (e.g. it's a script run from terminal).
*/
if (res == -ENODATA || res < 0 || !unit || !g_str_has_prefix (unit, "app-"))
if (res == -ENODATA || res < 0 || !unit)
{
app_info->id = g_strdup ("");
return;
}

app_info->id = _xdp_parse_app_id_from_unit_name (unit);
if (g_str_has_prefix (unit, "app-"))
{
app_info->id = _xdp_parse_app_id_from_unit_name (unit);
}
else if (g_str_has_prefix (unit, "dbus-"))
{
app_info->id = _xdp_parse_app_id_from_dbus_name (unit);
}
else
{
app_info->id = g_strdup ("");
}
g_debug ("Assigning app ID \"%s\" to pid %ld which has unit \"%s\"",
app_info->id, (long) pid, unit);

Expand Down