Port the systemd hostname_is_valid() function to perform hostname
validation and inform the user about a invalid hostname.
Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
---
common/misc.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)
diff --git a/common/misc.c b/common/misc.c
index e266f0951ee9..dc498ad0b318 100644
--- a/common/misc.c
+++ b/common/misc.c
@@ -13,6 +13,7 @@
#include <led.h>
#include <of.h>
#include <restart.h>
+#include <string.h>
#include <linux/stringify.h>
int errno;
@@ -146,6 +147,67 @@ static char *hostname;
static char *serial_number;
static char *of_machine_compatible;
+/* Note that HOST_NAME_MAX is 64 on Linux */
+#define BAREBOX_HOST_NAME_MAX 64
+
+static bool barebox_valid_ldh_char(char c)
+{
+ /* "LDH" -> "Letters, digits, hyphens", as per RFC 5890, Section 2.3.1 */
+ return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+ (c >= '0' && c <= '9') || c == '-';
+}
+
+static bool barebox_hostname_is_valid(const char *s)
+{
+ unsigned int n_dots = 0;
+ const char *p;
+ bool dot, hyphen;
+
+ /*
+ * Check if s looks like a valid hostname or FQDN. This does not do full
+ * DNS validation, but only checks if the name is composed of allowed
+ * characters and the length is not above the maximum allowed by Linux.
+ * Doesn't accept empty hostnames, hostnames with leading dots, and
+ * hostnames with multiple dots in a sequence. Doesn't allow hyphens at
+ * the beginning or end of label.
+ */
+ if (isempty(s))
+ return false;
+
+ for (p = s, dot = hyphen = true; *p; p++) {
+ if (*p == '.') {
+ if (dot || hyphen)
+ return false;
+
+ dot = true;
+ hyphen = false;
+ n_dots++;
+
+ } else if (*p == '-') {
+ if (dot)
+ return false;
+
+ dot = false;
+ hyphen = true;
+
+ } else {
+ if (!barebox_valid_ldh_char(*p))
+ return false;
+
+ dot = false;
+ hyphen = false;
+ }
+ }
+
+ if (dot || hyphen)
+ return false;
+
+ if (p - s > BAREBOX_HOST_NAME_MAX)
+ return false;
+
+ return true;
+}
+
/*
* The hostname is supposed to be the shortname of a board. It should
* contain only lowercase letters, numbers, '-', '_'. No whitespaces
@@ -156,6 +218,10 @@ void barebox_set_hostname(const char *__hostname)
globalvar_add_simple_string("hostname", &hostname);
free(hostname);
+
+ if (!barebox_hostname_is_valid(__hostname))
+ pr_warn("Hostname is not valid, please fix it\n");
+
hostname = xstrdup(__hostname);
}
--
2.39.2
