xdg-autostart-generator: Add a generator for XDG autostart files

This generator can be used by desktop environments to launch autostart
applications and services. The feature is an opt-in, triggered by
xdg-desktop-autostart.target being activated.

Also included is the new binary xdg-autostart-condition. This binary is
used as an ExecCondition to test the OnlyShowIn and NotShowIn XDG
desktop file keys. These need to be evaluated against the
XDG_CURRENT_DESKTOP environment variable which may not be known at
generation time.

Co-authored-by: Henri Chain <henri.chain@enioka.com>

1 files changed, 618 insertions, 0 deletions

diff --git a/src/xdg-autostart-generator/xdg-autostart-service.c b/src/xdg-autostart-generator/xdg-autostart-service.c
new file mode 100644
index 00000000000..9ff80c5bb04
--- /dev/null
+++ b/src/xdg-autostart-generator/xdg-autostart-service.c
@@ -0,0 +1,618 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "xdg-autostart-service.h"
+
+#include "conf-parser.h"
+#include "escape.h"
+#include "unit-name.h"
+#include "path-util.h"
+#include "fd-util.h"
+#include "generator.h"
+#include "log.h"
+#include "specifier.h"
+#include "string-util.h"
+#include "nulstr-util.h"
+#include "strv.h"
+
+XdgAutostartService* xdg_autostart_service_free(XdgAutostartService *s) {
+        if (!s)
+                return NULL;
+
+        free(s->name);
+        free(s->path);
+        free(s->description);
+
+        free(s->type);
+        free(s->exec_string);
+
+        strv_free(s->only_show_in);
+        strv_free(s->not_show_in);
+
+        free(s->try_exec);
+        free(s->autostart_condition);
+        free(s->kde_autostart_condition);
+
+        free(s->gnome_autostart_phase);
+
+        return mfree(s);
+}
+
+char *xdg_autostart_service_translate_name(const char *name) {
+        _cleanup_free_ char *c = NULL, *escaped = NULL;
+        char *res;
+
+        c = strdup(name);
+        if (!c)
+                return NULL;
+
+        res = endswith(c, ".desktop");
+        if (res)
+                *res = '\0';
+
+        escaped = unit_name_escape(c);
+        if (!escaped)
+                return NULL;
+
+        return strjoin("app-", escaped, "-autostart.service");
+}
+
+static int xdg_config_parse_bool(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        bool *b = data;
+        const char *value;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        if (streq(rvalue, "true"))
+                *b = true;
+        else if (streq(rvalue, "false"))
+                *b = false;
+        else
+                return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL), "Invalid value for boolean: %s", value);
+
+        return 0;
+}
+
+/* Unescapes the string in-place, returns non-zero status on error. */
+static int xdg_unescape_string(
+                const char *unit,
+                const char *filename,
+                int line,
+                char *str) {
+
+        char *in;
+        char *out;
+
+        assert(str);
+
+        in = out = str;
+
+        for (; *in; in++, out++) {
+                if (*in == '\\') {
+                        /* Move forward, and ensure it is a valid escape. */
+                        in++;
+
+                        switch (*in) {
+                                case 's':
+                                        *out = ' ';
+                                        break;
+                                case 'n':
+                                        *out = '\n';
+                                        break;
+                                case 't':
+                                        *out = '\t';
+                                        break;
+                                case 'r':
+                                        *out = '\r';
+                                        break;
+                                case '\\':
+                                        *out = '\\';
+                                        break;
+                                case ';':
+                                        /* Technically only permitted for strv. */
+                                        *out = ';';
+                                        break;
+                                default:
+                                        return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL), "Undefined escape sequence \\%c.", *in);
+                        }
+
+                        continue;
+                }
+
+                *out = *in;
+        }
+        *out = '\0';
+
+        return 0;
+}
+
+/* Note: We do not bother with unescaping the strings, hence the _raw postfix. */
+static int xdg_config_parse_string(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        _cleanup_free_ char *res = NULL;
+        char **out = data;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        /* XDG does not allow duplicate definitions. */
+        if (*out) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Key %s was defined multiple times, ignoring.", lvalue);
+                return 0;
+        }
+
+        res = strdup(rvalue);
+        if (!res)
+                return log_oom();
+
+        r = xdg_unescape_string(unit, filename, line, res);
+        if (r < 0)
+                return r;
+
+        *out = TAKE_PTR(res);
+        return 0;
+}
+
+static int xdg_config_parse_strv(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        char ***sv = data;
+        const char *start;
+        const char *end;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        /* XDG does not allow duplicate definitions. */
+        if (*sv) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Key %s was defined multiple times, ignoring.", lvalue);
+                return 0;
+        }
+
+        *sv = strv_new(NULL);
+        if (!*sv)
+                return log_oom();
+
+        /* We cannot use strv_split because it does not handle escaping correctly. */
+        start = rvalue;
+
+        for (end = start; *end; end++) {
+                if (*end == '\\') {
+                        /* Move forward, and ensure it is a valid escape. */
+                        end++;
+                        if (strchr("sntr\\;", *end) == NULL) {
+                                log_syntax(unit, LOG_ERR, filename, line, 0, "Undefined escape sequence \\%c.", *end);
+                                return 0;
+                        }
+                        continue;
+                }
+
+                if (*end == ';') {
+                        _cleanup_free_ char *copy = NULL;
+
+                        copy = strndup(start, end - start);
+                        if (!copy)
+                                return log_oom();
+                        r = xdg_unescape_string(unit, filename, line, copy);
+                        if (r < 0)
+                                return r;
+                        r = strv_consume(sv, TAKE_PTR(copy));
+                        if (r < 0)
+                                return log_oom();
+
+                        start = end + 1;
+                }
+        }
+
+        /* Any trailing entry should be ignored if it is empty. */
+        if (end > start) {
+                r = strv_extend(sv, start);
+                if (r < 0)
+                        return log_oom();
+        }
+
+        return 0;
+}
+
+static int xdg_config_item_table_lookup(
+                const void *table,
+                const char *section,
+                const char *lvalue,
+                ConfigParserCallback *func,
+                int *ltype,
+                void **data,
+                void *userdata) {
+
+        assert(lvalue);
+
+        /* Ignore any keys with [] as those are translations. */
+        if (strchr(lvalue, '[')) {
+                *func = NULL;
+                *ltype = 0;
+                *data = NULL;
+                return 1;
+        }
+
+        return config_item_table_lookup(table, section, lvalue, func, ltype, data, userdata);
+}
+
+XdgAutostartService *xdg_autostart_service_parse_desktop(const char *path) {
+        _cleanup_(xdg_autostart_service_freep) XdgAutostartService *service = NULL;
+        int r;
+
+        service = new0(XdgAutostartService, 1);
+        if (!service)
+                return NULL;
+
+        service->path = strdup(path);
+        if (!service->path)
+                return NULL;
+
+        const ConfigTableItem items[] = {
+                { "Desktop Entry", "Name",                      xdg_config_parse_string, 0, &service->description},
+                { "Desktop Entry", "Exec",                      xdg_config_parse_string, 0, &service->exec_string},
+                { "Desktop Entry", "TryExec",                   xdg_config_parse_string, 0, &service->try_exec},
+                { "Desktop Entry", "Type",                      xdg_config_parse_string, 0, &service->type},
+                { "Desktop Entry", "OnlyShowIn",                xdg_config_parse_strv, 0,   &service->only_show_in},
+                { "Desktop Entry", "NotShowIn",                 xdg_config_parse_strv, 0,   &service->not_show_in},
+                { "Desktop Entry", "Hidden",                    xdg_config_parse_bool, 0,   &service->hidden},
+                { "Desktop Entry", "AutostartCondition",        xdg_config_parse_string, 0, &service->autostart_condition},
+                { "Desktop Entry", "X-KDE-autostart-condition", xdg_config_parse_string, 0, &service->kde_autostart_condition},
+                { "Desktop Entry", "X-GNOME-Autostart-Phase",   xdg_config_parse_string, 0, &service->gnome_autostart_phase},
+                { "Desktop Entry", "X-systemd-skip",            xdg_config_parse_bool, 0,   &service->systemd_skip},
+
+                /* Common entries that we do not use currently. */
+                { "Desktop Entry", "Categories", NULL, 0, NULL},
+                { "Desktop Entry", "Comment", NULL, 0, NULL},
+                { "Desktop Entry", "Encoding", NULL, 0, NULL},
+                { "Desktop Entry", "GenericName", NULL, 0, NULL},
+                { "Desktop Entry", "Icon", NULL, 0, NULL},
+                { "Desktop Entry", "Keywords", NULL, 0, NULL},
+                { "Desktop Entry", "NoDisplay", NULL, 0, NULL},
+                { "Desktop Entry", "StartupNotify", NULL, 0, NULL},
+                { "Desktop Entry", "Terminal", NULL, 0, NULL},
+                { "Desktop Entry", "Version", NULL, 0, NULL},
+                {}
+        };
+
+        r = config_parse(NULL, service->path, NULL,
+                         "Desktop Entry\0",
+                         xdg_config_item_table_lookup, items,
+                         CONFIG_PARSE_WARN, service);
+        /* If parsing failed, only hide the file so it will still mask others. */
+        if (r < 0) {
+                log_warning_errno(r, "Failed to parse %s, ignoring it", service->path);
+                service->hidden = true;
+        }
+
+        return TAKE_PTR(service);
+}
+
+int xdg_autostart_format_exec_start(
+                const char *exec,
+                char **ret_exec_start) {
+
+        _cleanup_strv_free_ char **exec_split = NULL;
+        char *res;
+        size_t n, i;
+        bool first_arg;
+        int r;
+
+        /*
+         * Unfortunately, there is a mismatch between systemd's idea of $PATH
+         * and XDGs. i.e. we need to ensure that we have an absolute path to
+         * support cases where $PATH has been modified from the default set.
+         *
+         * Note that this is only needed for development environments though;
+         * so while it is important, this should have no effect in production
+         * environments.
+         *
+         * To be compliant with the XDG specification, we also need to strip
+         * certain parameters and such. Doing so properly makes parsing the
+         * command line unavoidable.
+         *
+         * NOTE: Technically, XDG only specifies " as quotes, while this also
+         *       accepts '.
+         */
+        exec_split = strv_split_full(exec, WHITESPACE, SPLIT_QUOTES | SPLIT_RELAX);
+        if (!exec_split)
+                return -ENOMEM;
+
+        if (strv_isempty(exec_split))
+                return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Exec line is empty");
+
+        first_arg = true;
+        for (i = n = 0; exec_split[i]; i++) {
+                _cleanup_free_ char *c = NULL, *raw = NULL, *p = NULL, *escaped = NULL, *quoted = NULL;
+
+                r = cunescape(exec_split[i], 0, &c);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to unescape '%s': %m", exec_split[i]);
+
+                if (first_arg) {
+                        _cleanup_free_ char *executable = NULL;
+
+                        /* This is the executable, find it in $PATH */
+                        first_arg = false;
+                        r = find_binary(c, &executable);
+                        if (r < 0)
+                                return log_info_errno(r, "Exec binary '%s' does not exist: %m", c);
+
+                        escaped = cescape(executable);
+                        if (!escaped)
+                                return log_oom();
+
+                        free(exec_split[n]);
+                        exec_split[n++] = TAKE_PTR(escaped);
+                        continue;
+                }
+
+                /*
+                 * Remove any standardised XDG fields; we assume they never appear as
+                 * part of another argument as that just does not make any sense as
+                 * they can be empty (GLib will e.g. turn "%f" into an empty argument).
+                 * Other implementations may handle this differently.
+                 */
+                if (STR_IN_SET(c,
+                               "%f", "%F",
+                               "%u", "%U",
+                               "%d", "%D",
+                               "%n", "%N",
+                               "%i", /* Location of icon, could be implemented. */
+                               "%c", /* Translated application name, could be implemented. */
+                               "%k", /* Location of desktop file, could be implemented. */
+                               "%v",
+                               "%m"
+                               ))
+                        continue;
+
+                /*
+                 * %% -> % and then % -> %% means that we correctly quote any %
+                 * and also quote any left over (and invalid) % specifier from
+                 * the desktop file.
+                 */
+                raw = strreplace(c, "%%", "%");
+                if (!raw)
+                        return log_oom();
+                p = strreplace(raw, "%", "%%");
+                if (!p)
+                        return log_oom();
+                escaped = cescape(p);
+                if (!escaped)
+                        return log_oom();
+
+                quoted = strjoin("\"", escaped, "\"");
+                if (!quoted)
+                        return log_oom();
+
+                free(exec_split[n]);
+                exec_split[n++] = TAKE_PTR(quoted);
+        }
+        for (; exec_split[n]; n++)
+                exec_split[n] = mfree(exec_split[n]);
+
+        res = strv_join(exec_split, " ");
+        if (!res)
+                return log_oom();
+
+        *ret_exec_start = res;
+        return 0;
+}
+
+static int xdg_autostart_generate_desktop_condition(
+                FILE *f,
+                const char *test_binary,
+                const char *condition) {
+
+        int r;
+
+        /* Generate an ExecCondition for GNOME autostart condition */
+        if (!isempty(condition)) {
+                _cleanup_free_ char *gnome_autostart_condition_path = NULL, *e_autostart_condition = NULL;
+
+                r = find_binary(test_binary, &gnome_autostart_condition_path);
+                if (r < 0) {
+                        log_full_errno(r == -ENOENT ? LOG_INFO : LOG_WARNING, r,
+                                       "%s not found: %m", test_binary);
+                        fprintf(f, "# ExecCondition using %s skipped due to missing binary.\n", test_binary);
+                        return r;
+                }
+
+                e_autostart_condition = cescape(condition);
+                if (!e_autostart_condition)
+                        return log_oom();
+
+                fprintf(f,
+                         "ExecCondition=%s --condition \"%s\"\n",
+                         gnome_autostart_condition_path,
+                         e_autostart_condition);
+        }
+
+        return 0;
+}
+
+int xdg_autostart_service_generate_unit(
+                XdgAutostartService *service,
+                const char *dest) {
+
+        _cleanup_free_ char *path_escaped = NULL, *exec_start = NULL, *unit = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        int r;
+
+        assert(service);
+
+        /* Nothing to do for hidden services. */
+        if (service->hidden) {
+                log_info("Not generating service for XDG autostart %s, it is hidden.", service->name);
+                return 0;
+        }
+
+        if (service->systemd_skip) {
+                log_info("Not generating service for XDG autostart %s, should be skipped by generator.", service->name);
+                return 0;
+        }
+
+        /* Nothing to do if type is not Application. */
+        if (!streq_ptr(service->type, "Application")) {
+                log_info("Not generating service for XDG autostart %s, it is hidden.", service->name);
+                return 0;
+        }
+
+        if (!service->exec_string) {
+                log_warning("Not generating service for XDG autostart %s, it is has no Exec= line.", service->name);
+                return 0;
+        }
+
+        /*
+         * The TryExec key cannot be checked properly from the systemd unit,
+         * it is trivial to check using find_binary though.
+         */
+        if (service->try_exec) {
+                r = find_binary(service->try_exec, NULL);
+                if (r < 0) {
+                        log_full_errno(r == -ENOENT ? LOG_INFO : LOG_WARNING, r,
+                                       "Not generating service for XDG autostart %s, could not find TryExec= binary %s: %m",
+                                       service->name, service->try_exec);
+                        return 0;
+                }
+        }
+
+        r = xdg_autostart_format_exec_start(service->exec_string, &exec_start);
+        if (r < 0) {
+                log_warning_errno(r,
+                                  "Not generating service for XDG autostart %s, error parsing Exec= line: %m",
+                                  service->name);
+                return 0;
+        }
+
+        if (streq_ptr(service->gnome_autostart_phase, "EarlyInitialization")) {
+                log_info("Not generating service for XDG autostart %s, EarlyInitialization needs to be handled separately.",
+                         service->name);
+                return 0;
+        }
+
+        path_escaped = specifier_escape(service->path);
+        if (!path_escaped)
+                return log_oom();
+
+        unit = path_join(dest, service->name);
+        if (!unit)
+                return log_oom();
+
+        f = fopen(unit, "wxe");
+        if (!f)
+                return log_error_errno(errno, "Failed to create unit file %s: %m", unit);
+
+        fprintf(f,
+                "# Automatically generated by systemd-xdg-autostart-generator\n\n"
+                "[Unit]\n"
+                "Documentation=man:systemd-xdg-autostart-generator(8)\n"
+                "SourcePath=%s\n"
+                "PartOf=graphical-session.target\n\n",
+                path_escaped);
+
+        if (service->description) {
+                _cleanup_free_ char *t = NULL;
+
+                t = specifier_escape(service->description);
+                if (!t)
+                        return log_oom();
+
+                fprintf(f, "Description=%s\n", t);
+        }
+
+        /* Only start after the session is ready.
+         * XXX: GNOME has an autostart order which we may want to support.
+         *      It is not clear how this can be implemented reliably, which
+         *      is why it is skipped for now. */
+        fprintf(f,
+                "After=graphical-session.target\n");
+
+        fprintf(f,
+                "\n[Service]\n"
+                "Type=simple\n"
+                "ExecStart=:%s\n"
+                "Restart=no\n"
+                "TimeoutSec=5s\n"
+                "Slice=app.slice\n",
+                exec_start);
+
+        /* Generate an ExecCondition to check $XDG_CURRENT_DESKTOP */
+        if (!strv_isempty(service->only_show_in) || !strv_isempty(service->not_show_in)) {
+                _cleanup_free_ char *only_show_in = NULL, *not_show_in = NULL, *e_only_show_in = NULL, *e_not_show_in = NULL;
+
+                only_show_in = strv_join(service->only_show_in, ":");
+                not_show_in = strv_join(service->not_show_in, ":");
+                if (!only_show_in || !not_show_in)
+                        return log_oom();
+
+                e_only_show_in = cescape(only_show_in);
+                e_not_show_in = cescape(not_show_in);
+                if (!e_only_show_in || !e_not_show_in)
+                        return log_oom();
+
+                /* Just assume the values are reasonably sane */
+                fprintf(f,
+                        "ExecCondition=" ROOTLIBEXECDIR "/systemd-xdg-autostart-condition \"%s\" \"%s\"\n",
+                        e_only_show_in,
+                        e_not_show_in);
+        }
+
+        r = xdg_autostart_generate_desktop_condition(f,
+                                                     "gnome-systemd-autostart-condition",
+                                                     service->autostart_condition);
+        if (r < 0)
+                return r;
+
+        r = xdg_autostart_generate_desktop_condition(f,
+                                                     "kde-systemd-start-condition",
+                                                     service->kde_autostart_condition);
+        if (r < 0)
+                return r;
+
+        (void) generator_add_symlink(dest, "xdg-desktop-autostart.target", "wants", service->name);
+
+        return 0;
+}