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core/load-fragment: modernize config_parse_exec

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Mike Yuan 2024-04-11 03:21:41 +08:00
parent 5152b8459a
commit 21b366121f
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GPG key ID: 417471C0A40F58B3
1 changed files with 52 additions and 74 deletions
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126
src/core/load-fragment.c
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@ -856,9 +856,7 @@ int config_parse_exec(
void *userdata) {
ExecCommand **e = ASSERT_PTR(data);
const Unit *u = userdata;
const char *p;
bool semicolon;
const Unit *u = ASSERT_PTR(userdata);
int r;
assert(filename);
@ -873,15 +871,11 @@ int config_parse_exec(
return 0;
}
p = rvalue;
const char *p = rvalue;
bool semicolon;
do {
_cleanup_free_ char *path = NULL, *firstword = NULL;
ExecCommandFlags flags = 0;
bool ignore = false, separate_argv0 = false;
_cleanup_free_ ExecCommand *nce = NULL;
_cleanup_strv_free_ char **n = NULL;
size_t nlen = 0;
const char *f;
semicolon = false;
@ -895,25 +889,30 @@ int config_parse_exec(
continue;
}
f = firstword;
for (;;) {
/* We accept an absolute path as first argument. If it's prefixed with - and the path doesn't
* exist, we ignore it instead of erroring out; if it's prefixed with @, we allow overriding of
* argv[0]; if it's prefixed with :, we will not do environment variable substitution;
* if it's prefixed with +, it will be run with full privileges and no sandboxing; if
* it's prefixed with '!' we apply sandboxing, but do not change user/group credentials; if
* it's prefixed with '!!', then we apply user/group credentials if the kernel supports ambient
* capabilities -- if it doesn't we don't apply the credentials themselves, but do apply most
* other sandboxing, with some special exceptions for changing UID.
*
* The idea is that '!!' may be used to write services that can take benefit of systemd's
* UID/GID dropping if the kernel supports ambient creds, but provide an automatic fallback to
* privilege dropping within the daemon if the kernel does not offer that. */
const char *f = firstword;
bool ignore, separate_argv0 = false;
ExecCommandFlags flags = 0;
if (*f == '-' && !(flags & EXEC_COMMAND_IGNORE_FAILURE)) {
for (;; f++) {
/* We accept an absolute path as first argument. Valid prefixes and their effect:
*
* "-": Ignore if the path doesn't exist
* "@": Allow overridding argv[0] (supplied as a separate argument)
* ":": Disable environment variable substitution
* "+": Run with full privileges and no sandboxing
* "!": Apply sandboxing except for user/group credentials
* "!!": Apply user/group credentials if the kernel supports ambient capabilities -
* if it doesn't we don't apply the credentials themselves, but do apply
* most other sandboxing, with some special exceptions for changing UID.
*
* The idea is that '!!' may be used to write services that can take benefit of
* systemd's UID/GID dropping if the kernel supports ambient creds, but provide
* an automatic fallback to privilege dropping within the daemon if the kernel
* does not offer that. */
if (*f == '-' && !(flags & EXEC_COMMAND_IGNORE_FAILURE))
flags |= EXEC_COMMAND_IGNORE_FAILURE;
ignore = true;
} else if (*f == '@' && !separate_argv0)
else if (*f == '@' && !separate_argv0)
separate_argv0 = true;
else if (*f == ':' && !(flags & EXEC_COMMAND_NO_ENV_EXPAND))
flags |= EXEC_COMMAND_NO_ENV_EXPAND;
@ -926,9 +925,10 @@ int config_parse_exec(
flags |= EXEC_COMMAND_AMBIENT_MAGIC;
} else
break;
f++;
}
ignore = FLAGS_SET(flags, EXEC_COMMAND_IGNORE_FAILURE);
r = unit_path_printf(u, f, &path);
if (r < 0) {
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, r,
@ -938,19 +938,18 @@ int config_parse_exec(
}
if (isempty(path)) {
/* First word is either "-" or "@" with no command. */
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, 0,
"Empty path in command line%s: '%s'",
"Empty path in command line%s: %s",
ignore ? ", ignoring" : "", rvalue);
return ignore ? 0 : -ENOEXEC;
}
if (!string_is_safe(path)) {
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, 0,
"Executable name contains special characters%s: %s",
"Executable path contains special characters%s: %s",
ignore ? ", ignoring" : "", path);
return ignore ? 0 : -ENOEXEC;
}
if (endswith(path, "/")) {
if (path_implies_directory(path)) {
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, 0,
"Executable path specifies a directory%s: %s",
ignore ? ", ignoring" : "", path);
@ -964,92 +963,71 @@ int config_parse_exec(
return ignore ? 0 : -ENOEXEC;
}
if (!separate_argv0) {
char *w = NULL;
_cleanup_strv_free_ char **args = NULL;
if (!GREEDY_REALLOC0(n, nlen + 2))
if (!separate_argv0)
if (strv_extend(&args, path) < 0)
return log_oom();
w = strdup(path);
if (!w)
return log_oom();
n[nlen++] = w;
n[nlen] = NULL;
}
path_simplify(path);
while (!isempty(p)) {
_cleanup_free_ char *word = NULL, *resolved = NULL;
/* Check explicitly for an unquoted semicolon as
* command separator token. */
/* Check explicitly for an unquoted semicolon as command separator token. */
if (p[0] == ';' && (!p[1] || strchr(WHITESPACE, p[1]))) {
p++;
p += strspn(p, WHITESPACE);
p = skip_leading_chars(p, /* bad = */ NULL);
semicolon = true;
break;
}
/* Check for \; explicitly, to not confuse it with \\; or "\;" or "\\;" etc.
* extract_first_word() would return the same for all of those. */
* extract_first_word() would return the same for all of those. */
if (p[0] == '\\' && p[1] == ';' && (!p[2] || strchr(WHITESPACE, p[2]))) {
char *w;
p += 2;
p += strspn(p, WHITESPACE);
p = skip_leading_chars(p, /* bad = */ NULL);
if (!GREEDY_REALLOC0(n, nlen + 2))
if (strv_extend(&args, ";") < 0)
return log_oom();
w = strdup(";");
if (!w)
return log_oom();
n[nlen++] = w;
n[nlen] = NULL;
continue;
}
r = extract_first_word_and_warn(&p, &word, NULL, EXTRACT_UNQUOTE|EXTRACT_CUNESCAPE, unit, filename, line, rvalue);
if (r == 0)
break;
if (r < 0)
return ignore ? 0 : -ENOEXEC;
if (r == 0)
break;
r = unit_full_printf(u, word, &resolved);
if (r < 0) {
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, r,
"Failed to resolve unit specifiers in %s%s: %m",
"Failed to resolve unit specifiers in '%s'%s: %m",
word, ignore ? ", ignoring" : "");
return ignore ? 0 : -ENOEXEC;
}
if (!GREEDY_REALLOC(n, nlen + 2))
if (strv_consume(&args, TAKE_PTR(resolved)) < 0)
return log_oom();
n[nlen++] = TAKE_PTR(resolved);
n[nlen] = NULL;
}
if (!n || !n[0]) {
if (strv_isempty(args)) {
log_syntax(unit, ignore ? LOG_WARNING : LOG_ERR, filename, line, 0,
"Empty executable name or zeroeth argument%s: %s",
ignore ? ", ignoring" : "", rvalue);
return ignore ? 0 : -ENOEXEC;
}
nce = new0(ExecCommand, 1);
if (!nce)
ExecCommand *nec = new(ExecCommand, 1);
if (!nec)
return log_oom();
nce->argv = TAKE_PTR(n);
nce->path = TAKE_PTR(path);
nce->flags = flags;
*nec = (ExecCommand) {
.path = path_simplify(TAKE_PTR(path)),
.argv = TAKE_PTR(args),
.flags = flags,
};
exec_command_append_list(e, nce);
/* Do not _cleanup_free_ these. */
nce = NULL;
exec_command_append_list(e, nec);
rvalue = p;
} while (semicolon);