MFp4 @229477:

The gethostname(3) function won't work in capability mode, because reading
kern.hostname sysctl is not permitted there.  Cache hostname early and use
cached value later.

Reviewed by:	brooks
Sponsored by:	The FreeBSD Foundation

1 files changed, 11 insertions, 4 deletions

diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index fa9a49b..0380020 100644
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -91,6 +91,8 @@ int log_perror = 1;
 int privfd;
 int nullfd = -1;
 
+char hostname[_POSIX_HOST_NAME_MAX + 1];
+
 struct iaddr iaddr_broadcast = { 4, { 255, 255, 255, 255 } };
 struct in_addr inaddr_any, inaddr_broadcast;
 
@@ -446,6 +448,13 @@ main(int argc, char *argv[])
 			error("no such user: nobody");
 	}
 
+	/*
+	 * Obtain hostname before entering capability mode - it won't be
+	 * possible then, as reading kern.hostname is not permitted.
+	 */
+	if (gethostname(hostname, sizeof(hostname)) < 0)
+		hostname[0] = '\0';
+
 	if (pipe(pipe_fd) == -1)
 		error("pipe");
 
@@ -1525,9 +1534,8 @@ make_discover(struct interface_info *ip, struct client_lease *lease)
 		}
 
 	/* send host name if not set via config file. */
-	char hostname[_POSIX_HOST_NAME_MAX+1];
 	if (!options[DHO_HOST_NAME]) {
-		if (gethostname(hostname, sizeof(hostname)) == 0) {
+		if (hostname[0] != '\0') {
 			size_t len;
 			char* posDot = strchr(hostname, '.');
 			if (posDot != NULL)
@@ -1649,9 +1657,8 @@ make_request(struct interface_info *ip, struct client_lease * lease)
 		}
 
 	/* send host name if not set via config file. */
-	char hostname[_POSIX_HOST_NAME_MAX+1];
 	if (!options[DHO_HOST_NAME]) {
-		if (gethostname(hostname, sizeof(hostname)) == 0) {
+		if (hostname[0] != '\0') {
 			size_t len;
 			char* posDot = strchr(hostname, '.');
 			if (posDot != NULL)