load-fragment: allow quoting in command name and document allowed escapes

The handling of the command name and other arguments is unified. This
simplifies things and should make them more predictable for users.
Incidentally, this makes ExecStart handling match the .desktop file
specification, apart for the requirment for an absolute path.

https://bugs.freedesktop.org/show_bug.cgi?id=86171

1 files changed, 63 insertions, 61 deletions

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 7430036f48..e9659ca344 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -547,9 +547,9 @@ int config_parse_exec(const char *unit,
          * overriding of argv[0]. */
         for (;;) {
                 int i;
-                const char *word, *state;
+                const char *word, *state, *reason;
                 size_t l;
-                bool honour_argv0 = false, ignore = false;
+                bool separate_argv0 = false, ignore = false;
 
                 path = NULL;
                 nce = NULL;
@@ -560,28 +560,23 @@ int config_parse_exec(const char *unit,
                 if (rvalue[0] == 0)
                         break;
 
-                for (i = 0; i < 2; i++) {
-                        if (rvalue[0] == '-' && !ignore) {
-                                ignore = true;
-                                rvalue ++;
-                        }
-
-                        if (rvalue[0] == '@' && !honour_argv0) {
-                                honour_argv0 = true;
-                                rvalue ++;
-                        }
-                }
-
-                if (*rvalue != '/') {
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                   "Executable path is not absolute, ignoring: %s", rvalue);
-                        return 0;
-                }
-
                 k = 0;
                 FOREACH_WORD_QUOTED(word, l, rvalue, state) {
-                        if (strneq(word, ";", MAX(l, 1U)))
-                                goto found;
+                        if (k == 0) {
+                                for (i = 0; i < 2; i++) {
+                                        if (*word == '-' && !ignore) {
+                                                ignore = true;
+                                                word ++;
+                                        }
+
+                                        if (*word == '@' && !separate_argv0) {
+                                                separate_argv0 = true;
+                                                word ++;
+                                        }
+                                }
+                        } else
+                                if (strneq(word, ";", MAX(l, 1U)))
+                                        goto found;
 
                         k++;
                 }
@@ -592,60 +587,69 @@ int config_parse_exec(const char *unit,
                 }
 
         found:
-                n = new(char*, k + !honour_argv0);
+                n = new(char*, k + !separate_argv0);
                 if (!n)
                         return log_oom();
 
                 k = 0;
                 FOREACH_WORD_QUOTED(word, l, rvalue, state) {
-                        if (strneq(word, ";", MAX(l, 1U)))
-                                break;
-                        else if (strneq(word, "\\;", MAX(l, 1U))) {
-                                word ++;
-                                l --;
-                        }
+                        char *c;
+                        unsigned skip;
 
-                        if (honour_argv0 && word == rvalue) {
-                                assert(!path);
+                        if (separate_argv0 ? path == NULL : k == 0) {
+                                /* first word, very special */
+                                skip = separate_argv0 + ignore;
 
-                                path = strndup(word, l);
-                                if (!path) {
-                                        r = log_oom();
-                                        goto fail;
-                                }
+                                /* skip special chars in the beginning */
+                                assert(skip < l);
 
-                                if (!utf8_is_valid(path)) {
-                                        log_invalid_utf8(unit, LOG_ERR, filename, line, EINVAL, rvalue);
-                                        r = 0;
-                                        goto fail;
-                                }
+                        } else if (strneq(word, ";", MAX(l, 1U)))
+                                /* new commandline */
+                                break;
 
-                        } else {
-                                char *c;
+                        else
+                                skip = strneq(word, "\\;", MAX(l, 1U));
 
-                                c = n[k++] = cunescape_length(word, l);
-                                if (!c) {
-                                        r = log_oom();
-                                        goto fail;
-                                }
+                        c = cunescape_length(word + skip, l - skip);
+                        if (!c) {
+                                r = log_oom();
+                                goto fail;
+                        }
 
-                                if (!utf8_is_valid(c)) {
-                                        log_invalid_utf8(unit, LOG_ERR, filename, line, EINVAL, rvalue);
-                                        r = 0;
-                                        goto fail;
-                                }
+                        if (!utf8_is_valid(c)) {
+                                log_invalid_utf8(unit, LOG_ERR, filename, line, EINVAL, rvalue);
+                                r = 0;
+                                goto fail;
                         }
+
+                        /* where to stuff this? */
+                        if (separate_argv0 && path == NULL)
+                                path = c;
+                        else
+                                n[k++] = c;
                 }
 
                 n[k] = NULL;
 
-                if (!n[0]) {
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                   "Invalid command line, ignoring: %s", rvalue);
-                        r = 0;
-                        goto fail;
-                }
+                log_debug("path: %s", path ?: n[0]);
+
+                if (!n[0])
+                        reason = "Empty executable name or zeroeth argument";
+                else if (!string_is_safe(path ?: n[0]))
+                        reason = "Executable path contains special characters";
+                else if (!path_is_absolute(path ?: n[0]))
+                        reason = "Executable path is not absolute";
+                else if (endswith(path ?: n[0], "/"))
+                        reason = "Executable path specifies a directory";
+                else
+                        goto ok;
+
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                           "%s, ignoring: %s", reason, rvalue);
+                r = 0;
+                goto fail;
 
+ok:
                 if (!path) {
                         path = strdup(n[0]);
                         if (!path) {
@@ -654,8 +658,6 @@ int config_parse_exec(const char *unit,
                         }
                 }
 
-                assert(path_is_absolute(path));
-
                 nce = new0(ExecCommand, 1);
                 if (!nce) {
                         r = log_oom();