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dhcp-option: refuse control and non-UTF8 characters in string option

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We oftem save parsed DHCP options into a file, or expose them
through DBus or Varlink. In such case, control characters or non-UTF8
characters may cause many kind of unexpected errors. In general, a DHCP
message that have string options with spurious characters is mostly
malformed or broken. Let's refuse them.

This also makes dhcp_option_parse_string() do not free 'ret' argument,
to follow our usual coding style. So, callers now need to free the
pre-exisitng string if necessary.

Fixes #31708.
This commit is contained in:
Yu Watanabe
2024-03-12 01:57:17 +09:00
parent c84a5f5eaf
commit fa3357b9e8
2 changed files with 21 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libsystemd-network/dhcp-option.c
+14 -14
View File
@@ -396,27 +396,27 @@ int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t c
}
int dhcp_option_parse_string(const uint8_t *option, size_t len, char **ret) {
_cleanup_free_ char *string = NULL;
int r;
assert(option);
assert(ret);
if (len <= 0)
*ret = mfree(*ret);
else {
char *string;
/*
* One trailing NUL byte is OK, we don't mind. See:
* https://github.com/systemd/systemd/issues/1337
*/
r = make_cstring((const char *) option, len, MAKE_CSTRING_ALLOW_TRAILING_NUL, &string);
if (r < 0)
return r;
free_and_replace(*ret, string);
if (len <= 0) {
*ret = NULL;
return 0;
}
/* One trailing NUL byte is OK, we don't mind. See:
* https://github.com/systemd/systemd/issues/1337 */
r = make_cstring((const char *) option, len, MAKE_CSTRING_ALLOW_TRAILING_NUL, &string);
if (r < 0)
return r;
if (!string_is_safe(string) || !utf8_is_valid(string))
return -EINVAL;
*ret = TAKE_PTR(string);
return 0;
}
src/libsystemd-network/sd-dhcp-lease.c
+7 -3
View File
@@ -832,12 +832,16 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void
break;
case SD_DHCP_OPTION_ROOT_PATH:
r = dhcp_option_parse_string(option, len, &lease->root_path);
case SD_DHCP_OPTION_ROOT_PATH: {
_cleanup_free_ char *p = NULL;
r = dhcp_option_parse_string(option, len, &p);
if (r < 0)
log_debug_errno(r, "Failed to parse root path, ignoring: %m");
break;
free_and_replace(lease->root_path, p);
break;
}
case SD_DHCP_OPTION_RENEWAL_TIME:
r = lease_parse_be32_seconds(option, len, /* max_as_infinity = */ true, &lease->t1);
if (r < 0)