Unify usage of function gethostname

man gethostanme says:
NOTES
   SUSv2  guarantees  that  "Host  names  are  limited  to   255   bytes".
   POSIX.1-2001 guarantees that "Host names (not including the terminating
   null  byte)  are  limited   to   HOST_NAME_MAX   bytes".    On   Linux,
   HOST_NAME_MAX  is  defined  with the value 64, which has been the limit
   since Linux 1.0 (earlier kernels imposed a limit of 8 bytes).

Reviewed-by: Pavel Březina <pbrezina@redhat.com>
(cherry picked from commit bf6f1b3d49e17b1adf0448c0b06e94b1e52ddffd)

4 files changed, 10 insertions, 9 deletions

diff --git a/src/providers/data_provider_fo.c b/src/providers/data_provider_fo.c
index 526ae58f1..7e2e50e6f 100644
--- a/src/providers/data_provider_fo.c
+++ b/src/providers/data_provider_fo.c
@@ -258,7 +258,7 @@ errno_t be_fo_set_dns_srv_lookup_plugin(struct be_ctx *be_ctx,
                                         const char *hostname)
 {
     struct fo_resolve_srv_dns_ctx *srv_ctx = NULL;
-    char resolved_hostname[HOST_NAME_MAX];
+    char resolved_hostname[HOST_NAME_MAX + 1];
     errno_t ret;
 
     if (hostname == NULL) {
@@ -269,7 +269,7 @@ errno_t be_fo_set_dns_srv_lookup_plugin(struct be_ctx *be_ctx,
                   "gethostname() failed: [%d]: %s\n", ret, strerror(ret));
             return ret;
         }
-        resolved_hostname[HOST_NAME_MAX-1] = '\0';
+        resolved_hostname[HOST_NAME_MAX] = '\0';
         hostname = resolved_hostname;
     }
 
diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index 34f23ec80..96404c4c8 100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -229,14 +229,14 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
             full_princ = talloc_strdup(memctx, princ_str);
         }
     } else {
-        char hostname[512];
+        char hostname[HOST_NAME_MAX + 1];
 
-        ret = gethostname(hostname, 511);
+        ret = gethostname(hostname, HOST_NAME_MAX);
         if (ret == -1) {
             krberr = KRB5KRB_ERR_GENERIC;
             goto done;
         }
-        hostname[511] = '\0';
+        hostname[HOST_NAME_MAX] = '\0';
 
         DEBUG(SSSDBG_TRACE_LIBS, "got hostname: [%s]\n", hostname);
 
diff --git a/src/providers/ldap/sdap_access.c b/src/providers/ldap/sdap_access.c
index 4e1709028..486a08c85 100644
--- a/src/providers/ldap/sdap_access.c
+++ b/src/providers/ldap/sdap_access.c
@@ -1067,7 +1067,7 @@ static errno_t sdap_access_host(struct ldb_message *user_entry)
     struct ldb_message_element *el;
     unsigned int i;
     char *host;
-    char hostname[HOST_NAME_MAX+1];
+    char hostname[HOST_NAME_MAX + 1];
 
     el = ldb_msg_find_element(user_entry, SYSDB_AUTHORIZED_HOST);
     if (!el || el->num_values == 0) {
@@ -1075,11 +1075,12 @@ static errno_t sdap_access_host(struct ldb_message *user_entry)
         return ERR_ACCESS_DENIED;
     }
 
-    if (gethostname(hostname, sizeof(hostname)) == -1) {
+    if (gethostname(hostname, HOST_NAME_MAX) == -1) {
         DEBUG(SSSDBG_CRIT_FAILURE,
               "Unable to get system hostname. Access denied\n");
         return ERR_ACCESS_DENIED;
     }
+    hostname[HOST_NAME_MAX] = '\0';
 
     /* FIXME: PADL's pam_ldap also calls gethostbyname() on the hostname
      *        in some attempt to get aliases and/or FQDN for the machine.
diff --git a/src/resolv/async_resolv_utils.c b/src/resolv/async_resolv_utils.c
index b24ae603f..c5ae5f9d4 100644
--- a/src/resolv/async_resolv_utils.c
+++ b/src/resolv/async_resolv_utils.c
@@ -44,7 +44,7 @@ resolv_get_domain_send(TALLOC_CTX *mem_ctx,
     struct resolv_get_domain_state *state = NULL;
     struct tevent_req *req = NULL;
     struct tevent_req *subreq = NULL;
-    char system_hostname[HOST_NAME_MAX];
+    char system_hostname[HOST_NAME_MAX + 1];
     errno_t ret;
 
     req = tevent_req_create(mem_ctx, &state,
@@ -63,7 +63,7 @@ resolv_get_domain_send(TALLOC_CTX *mem_ctx,
                                         ret, strerror(ret));
             goto immediately;
         }
-        system_hostname[HOST_NAME_MAX-1] = '\0';
+        system_hostname[HOST_NAME_MAX] = '\0';
         hostname = system_hostname;
     }