dhcp: dhclient: set type 0 for printable client IDs

The documentation for the ipv4.dhcp-client-id property says:

 If the property is not a hex string it is considered as a
 non-hardware-address client ID and the 'type' field is set to 0.

However, currently we set the client-id without the leading zero byte
in the dhclient configuration and thus dhclient sends the first string
character as type and the remainder as client-id content. Looking
through git history, the dhclient plugin has always behaved this way
even if the intent was clearly that string client-id had to be zero
padded (this is evident by looking at
nm_dhcp_utils_client_id_string_to_bytes()). The internal plugin
instead sends the correct client-id with zero type.

Change the dhclient plugin to honor the documented behavior and add
the leading zero byte when the client-id is a string.

This commit introduces a change in behavior for users that have
dhcp=dhclient and have a plain string (not hexadecimal) set in
ipv4.dhcp-client-id, as NM will send a different client-id possibly
changing the IP address returned by the server.

https://bugzilla.gnome.org/show_bug.cgi?id=793957

NEWS

@@ -1,3 +1,14 @@
+=============================================
+NetworkManager-1.?? (not released yet)
+Overview of changes since NetworkManager-1.10
+=============================================
+
+* A non-hexadecimal DHCPv4 client-id is now properly passed to
+  dhclient with the first byte (type) set to zero, as stated in the
+  documentation. This represents a change in behavior since previous
+  versions where the first character of the string was used as
+  type. The internal client is not affected by the change.
+
 ============================================
 NetworkManager-1.10
 Overview of changes since NetworkManager-1.8

src/dhcp/nm-dhcp-dhclient-utils.c

@@ -138,8 +138,9 @@ add_ip4_config (GString *str, GBytes *client_id, const char *hostname, gboolean
 				g_string_append_printf (str, "%02x", (guint8) p[i]);
 			}
 		} else {
-			/* Printable; just add to the line minus the 'type' */
+			/* Printable; just add to the line with type 0 */
 			g_string_append_c (str, '"');
+			g_string_append (str, "\\x00");
 			g_string_append_len (str, p + 1, l - 1);
 			g_string_append_c (str, '"');
 		}
@@ -177,31 +178,60 @@ read_client_id (const char *str)
 {
 	gs_free char *s = NULL;
 	char *p;
+	int i = 0, j = 0;
 
 	nm_assert (!strncmp (str, CLIENTID_TAG, NM_STRLEN (CLIENTID_TAG)));
-
 	str += NM_STRLEN (CLIENTID_TAG);
+
+	if (!g_ascii_isspace (*str))
+		return NULL;
 	while (g_ascii_isspace (*str))
 		str++;
 
 	if (*str == '"') {
+		/* Parse string literal with escape sequences */
 		s = g_strdup (str + 1);
 		p = strrchr (s, '"');
 		if (p)
 			*p = '\0';
 		else
 			return NULL;
-	} else
-		s = g_strdup (str);
 
+		if (!s[0])
+			return NULL;
+
+		while (s[i]) {
+			if (   s[i] == '\\'
+			    && s[i + 1] == 'x'
+			    && g_ascii_isxdigit (s[i + 2])
+			    && g_ascii_isxdigit (s[i + 3])) {
+				s[j++] =  (g_ascii_xdigit_value (s[i + 2]) << 4)
+				         + g_ascii_xdigit_value (s[i + 3]);
+				i += 4;
+				continue;
+			}
+			if (   s[i] == '\\'
+			    && s[i + 1] >= '0' && s[i + 1] <= '7'
+			    && s[1 + 2] >= '0' && s[i + 2] <= '7'
+			    && s[1 + 3] >= '0' && s[i + 3] <= '7') {
+				s[j++] =    ((s[i + 1] - '0') << 6)
+				          + ((s[i + 2] - '0') << 3)
+				          + ( s[i + 3] - '0');
+				i += 4;
+				continue;
+			}
+			s[j++] = s[i++];
+		}
+		return g_bytes_new_take (g_steal_pointer (&s), j);
+	}
+
+	/* Otherwise, try to read a hexadecimal sequence */
+	s = g_strdup (str);
 	g_strchomp (s);
 	if (s[strlen (s) - 1] == ';')
 		s[strlen (s) - 1] = '\0';
 
-	if (!s[0])
+	return nm_utils_hexstr2bin (s);
-		return NULL;
-
-	return nm_dhcp_utils_client_id_string_to_bytes (s);
 }
 
 GBytes *

src/dhcp/tests/test-dhcp-dhclient.c

@@ -154,7 +154,7 @@ test_override_client_id (void)
 static const char *quote_client_id_expected = \
 	"# Created by NetworkManager\n"
 	"\n"
-	"send dhcp-client-identifier \"1234\"; # added by NetworkManager\n"
+	"send dhcp-client-identifier \"\\x00abcd\"; # added by NetworkManager\n"
 	"\n"
 	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
 	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
@@ -172,7 +172,36 @@ test_quote_client_id (void)
 {
 	test_config (NULL, quote_client_id_expected,
 	             AF_INET, NULL, 0, FALSE,
-	             "1234",
+	             "abcd",
+	             NULL,
+	             "eth0",
+	             NULL);
+}
+
+/*****************************************************************************/
+
+static const char *hex_zero_client_id_expected = \
+	"# Created by NetworkManager\n"
+	"\n"
+	"send dhcp-client-identifier 00:11:22:33; # added by NetworkManager\n"
+	"\n"
+	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
+	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
+	"option wpad code 252 = string;\n"
+	"\n"
+	"also request rfc3442-classless-static-routes;\n"
+	"also request ms-classless-static-routes;\n"
+	"also request static-routes;\n"
+	"also request wpad;\n"
+	"also request ntp-servers;\n"
+	"\n";
+
+static void
+test_hex_zero_client_id (void)
+{
+	test_config (NULL, hex_zero_client_id_expected,
+	             AF_INET, NULL, 0, FALSE,
+	             "00:11:22:33",
 	             NULL,
 	             "eth0",
 	             NULL);
@@ -183,7 +212,7 @@ test_quote_client_id (void)
 static const char *ascii_client_id_expected = \
 	"# Created by NetworkManager\n"
 	"\n"
-	"send dhcp-client-identifier \"qb:cd:ef:12:34:56\"; # added by NetworkManager\n"
+	"send dhcp-client-identifier \"\\x00qb:cd:ef:12:34:56\"; # added by NetworkManager\n"
 	"\n"
 	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
 	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
@@ -239,13 +268,13 @@ test_hex_single_client_id (void)
 /*****************************************************************************/
 
 static const char *existing_hex_client_id_orig = \
-	"send dhcp-client-identifier 00:30:04:20:7A:08;\n";
+	"send dhcp-client-identifier 10:30:04:20:7A:08;\n";
 
 static const char *existing_hex_client_id_expected = \
 	"# Created by NetworkManager\n"
 	"# Merged from /path/to/dhclient.conf\n"
 	"\n"
-	"send dhcp-client-identifier 00:30:04:20:7A:08;\n"
+	"send dhcp-client-identifier 10:30:04:20:7A:08;\n"
 	"\n"
 	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
 	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
@@ -262,7 +291,7 @@ static void
 test_existing_hex_client_id (void)
 {
 	gs_unref_bytes GBytes *new_client_id = NULL;
-	const guint8 bytes[] = { 0x00, 0x30, 0x04,0x20, 0x7A, 0x08 };
+	const guint8 bytes[] = { 0x10, 0x30, 0x04, 0x20, 0x7A, 0x08 };
 
 	new_client_id = g_bytes_new (bytes, sizeof (bytes));
 	test_config (existing_hex_client_id_orig, existing_hex_client_id_expected,
@@ -275,16 +304,52 @@ test_existing_hex_client_id (void)
 
 /*****************************************************************************/
 
+static const char *existing_escaped_client_id_orig = \
+	"send dhcp-client-identifier \"\\044test\\xfe\";\n";
+
+static const char *existing_escaped_client_id_expected = \
+	"# Created by NetworkManager\n"
+	"# Merged from /path/to/dhclient.conf\n"
+	"\n"
+	"send dhcp-client-identifier \"\\044test\\xfe\";\n"
+	"\n"
+	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
+	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
+	"option wpad code 252 = string;\n"
+	"\n"
+	"also request rfc3442-classless-static-routes;\n"
+	"also request ms-classless-static-routes;\n"
+	"also request static-routes;\n"
+	"also request wpad;\n"
+	"also request ntp-servers;\n"
+	"\n";
+
+static void
+test_existing_escaped_client_id (void)
+{
+	gs_unref_bytes GBytes *new_client_id = NULL;
+
+	new_client_id = g_bytes_new ("$test\xfe", 6);
+	test_config (existing_escaped_client_id_orig, existing_escaped_client_id_expected,
+	             AF_INET, NULL, 0, FALSE,
+	             NULL,
+	             new_client_id,
+	             "eth0",
+	             NULL);
+}
+
+/*****************************************************************************/
+
 #define EACID "qb:cd:ef:12:34:56"
 
 static const char *existing_ascii_client_id_orig = \
-	"send dhcp-client-identifier \"" EACID "\";\n";
+	"send dhcp-client-identifier \"\\x00" EACID "\";\n";
 
 static const char *existing_ascii_client_id_expected = \
 	"# Created by NetworkManager\n"
 	"# Merged from /path/to/dhclient.conf\n"
 	"\n"
-	"send dhcp-client-identifier \"" EACID "\";\n"
+	"send dhcp-client-identifier \"\\x00" EACID "\";\n"
 	"\n"
 	"option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;\n"
 	"option ms-classless-static-routes code 249 = array of unsigned integer 8;\n"
@@ -1036,9 +1101,11 @@ main (int argc, char **argv)
 	g_test_add_func ("/dhcp/dhclient/orig_missing", test_orig_missing);
 	g_test_add_func ("/dhcp/dhclient/override_client_id", test_override_client_id);
 	g_test_add_func ("/dhcp/dhclient/quote_client_id", test_quote_client_id);
+	g_test_add_func ("/dhcp/dhclient/hex_zero_client_id", test_hex_zero_client_id);
 	g_test_add_func ("/dhcp/dhclient/ascii_client_id", test_ascii_client_id);
 	g_test_add_func ("/dhcp/dhclient/hex_single_client_id", test_hex_single_client_id);
 	g_test_add_func ("/dhcp/dhclient/existing-hex-client-id", test_existing_hex_client_id);
+	g_test_add_func ("/dhcp/dhclient/existing-client-id", test_existing_escaped_client_id);
 	g_test_add_func ("/dhcp/dhclient/existing-ascii-client-id", test_existing_ascii_client_id);
 	g_test_add_func ("/dhcp/dhclient/fqdn", test_fqdn);
 	g_test_add_func ("/dhcp/dhclient/fqdn_options_override", test_fqdn_options_override);