Easier to use ipa_gethostfqdn()

ipa_gethostfqdn() now returns a pointer to a statically allocated buffer
or NULL in case of an error. The caller no longer has to supply a
correctly allocated buffer.

Rename IPA_HOST_HOST to_LEN IPA_HOST_FQDN_LEN and use IPA_HOST_FQDN_LEN
wherever code copies a hostname supplied from ipa_gethostfqdn().

Clarify that MAXHOSTNAMELEN and MAXHOSTFQDNLEN are different things.

Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>

client/ipa-join.c

@@ -1445,7 +1445,6 @@ main(int argc, const char **argv) {
     static const char *keytab = NULL;
     static const char *bindpw = NULL;
     static const char *basedn = NULL;
-    char fqdn[IPA_HOST_NAME_LEN];
     int quiet = 0;
     int unenroll = 0;
     int force = 0;
@@ -1498,12 +1497,12 @@ main(int argc, const char **argv) {
 
     /* auto-detect and verify hostname */
     if (!hostname) {
-        if (ipa_gethostname(fqdn) != 0) {
+        hostname = ipa_gethostfqdn();
+        if (hostname == NULL) {
             if (!quiet)
                 fprintf(stderr, _("Cannot get host's FQDN!\n"));
             exit(22);
         }
-        hostname = fqdn;
     }
     if (NULL == strstr(hostname, ".")) {
         if (!quiet) {

daemons/ipa-kdb/ipa_kdb.c

@@ -53,7 +53,7 @@ static void ipadb_context_free(krb5_context kcontext,
         free((*ctx)->base);
         free((*ctx)->realm_base);
         free((*ctx)->accounts_base);
-        free((*ctx)->kdc_hostname);
+        /* kdc_hostname is a pointer to a static char[] */
         /* ldap free lcontext */
         if ((*ctx)->lcontext) {
             ldap_unbind_ext_s((*ctx)->lcontext, NULL, NULL);
@@ -536,7 +536,6 @@ static krb5_error_code ipadb_init_module(krb5_context kcontext,
 {
     struct ipadb_context *ipactx;
     krb5_error_code kerr;
-    char hostname[IPA_HOST_NAME_LEN];
     int ret;
     int i;
 
@@ -604,14 +603,9 @@ static krb5_error_code ipadb_init_module(krb5_context kcontext,
         goto fail;
     }
 
-    ret = ipa_gethostfqdn(hostname);
+    ipactx->kdc_hostname = ipa_gethostfqdn();
-    if (ret != 0) {
-        ret = errno;
-        goto fail;
-    }
-    ipactx->kdc_hostname = strdup(hostname);
     if (!ipactx->kdc_hostname) {
-        ret = ENOMEM;
+        ret = errno;
         goto fail;
     }
 

daemons/ipa-kdb/ipa_kdb.h

@@ -49,10 +49,6 @@
 #include "ipa_krb5.h"
 #include "ipa_pwd.h"
 
-#ifndef MAXHOSTNAMELEN
-#define MAXHOSTNAMELEN 64
-#endif
-
 /* easier to copy the defines here than to mess with kadm5/admin.h
  * for now */
 #define KMASK_PRINCIPAL         0x000001
@@ -119,7 +115,7 @@ struct ipadb_context {
     char *realm;
     char *realm_base;
     char *accounts_base;
-    char *kdc_hostname;
+    const char *kdc_hostname;
     LDAP *lcontext;
     krb5_context kcontext;
     bool override_restrictions;

daemons/ipa-kdb/ipa_kdb_mspac.c

@@ -22,6 +22,7 @@
 
 #include "config.h"
 
+#include "ipa_hostname.h"
 #include "ipa_kdb.h"
 #include "ipa_mspac.h"
 #include <talloc.h>
@@ -2351,12 +2352,10 @@ done:
 
 static char *get_server_netbios_name(struct ipadb_context *ipactx)
 {
-    char hostname[MAXHOSTNAMELEN + 1]; /* NOTE: this is 64, too little ? */
+    char hostname[IPA_HOST_FQDN_LEN]; /* NOTE: long enough for DNS name */
     char *p;
 
-    strncpy(hostname, ipactx->kdc_hostname, MAXHOSTNAMELEN);
+    strncpy(hostname, ipactx->kdc_hostname, IPA_HOST_FQDN_LEN);
-    /* May miss termination */
-    hostname[MAXHOSTNAMELEN] = '\0';
     for (p = hostname; *p; p++) {
         if (*p == '.') {
             *p = 0;

daemons/ipa-otpd/main.c

@@ -213,7 +213,8 @@ static krb5_error_code setup_ldap(const char *uri, krb5_boolean bind,
 
 int main(int argc, char **argv)
 {
-    char hostname[IPA_HOST_NAME_LEN];
+    const char *hostname;
+    char fqdn[IPA_HOST_FQDN_LEN];
     krb5_error_code retval;
     krb5_data hndata;
     verto_ev *sig;
@@ -228,10 +229,12 @@ int main(int argc, char **argv)
     memset(&ctx, 0, sizeof(ctx));
     ctx.exitstatus = 1;
 
-    if (ipa_gethostfqdn(hostname) < 0) {
+    hostname = ipa_gethostfqdn();
+    if (hostname == NULL) {
         otpd_log_err(errno, "Unable to get hostname");
         goto error;
     }
+    strncpy(fqdn, hostname, IPA_HOST_FQDN_LEN);
 
     retval = krb5_init_context(&ctx.kctx);
     if (retval != 0) {
@@ -253,7 +256,7 @@ int main(int argc, char **argv)
     }
 
     /* Set NAS-Identifier. */
-    hndata.data = hostname;
+    hndata.data = fqdn;
     hndata.length = strlen(hndata.data);
     retval = krad_attrset_add(ctx.attrs, krad_attr_name2num("NAS-Identifier"),
                               &hndata);

daemons/ipa-sam/ipa_sam.c

@@ -4441,8 +4441,7 @@ static char *sec_key(TALLOC_CTX *mem_ctx, const char *d)
 
 static NTSTATUS save_sid_to_secret(struct ipasam_private *ipasam_state)
 {
-	char hostname[IPA_HOST_NAME_LEN];
+	const char *hostname;
-	int ret;
 	char *p;
 	TALLOC_CTX *tmp_ctx;
 	NTSTATUS status = NT_STATUS_UNSUCCESSFUL;
@@ -4467,8 +4466,8 @@ static NTSTATUS save_sid_to_secret(struct ipasam_private *ipasam_state)
 		goto done;
 	}
 
-	ret = ipa_gethostfqdn(hostname);
+	hostname = ipa_gethostfqdn();
-	if (ret == -1) {
+	if (hostname == NULL) {
 		DEBUG(1, ("ipa_gethostfqdn failed.\n"));
 		status = NT_STATUS_UNSUCCESSFUL;
 		goto done;
@@ -4721,10 +4720,9 @@ static int bind_callback(LDAP *ldap_struct, struct smbldap_state *ldap_state, vo
 static NTSTATUS ipasam_generate_principals(struct ipasam_private *ipasam_state) {
 
 	krb5_error_code rc;
-	int ret;
 	krb5_context context;
 	NTSTATUS status = NT_STATUS_UNSUCCESSFUL;
-	char hostname[IPA_HOST_NAME_LEN];
+	const char *hostname;
 	char *default_realm = NULL;
 
 	if (!ipasam_state) {
@@ -4736,8 +4734,8 @@ static NTSTATUS ipasam_generate_principals(struct ipasam_private *ipasam_state)
 		return status;
 	}
 
-	ret = ipa_gethostfqdn(hostname);
+	hostname = ipa_gethostfqdn();
-	if (ret == -1) {
+	if (hostname == NULL) {
 		DEBUG(1, ("ipa_gethostfqdn failed.\n"));
 		goto done;
 	}

daemons/ipa-slapi-plugins/ipa-cldap/ipa_cldap.h

@@ -61,10 +61,6 @@
 #define MAX_DG_SIZE 4096
 #define NETBIOS_NAME_MAX 15
 
-#ifndef MAXHOSTNAMELEN
-#define MAXHOSTNAMELEN 64
-#endif
-
 struct ipa_cldap_ctx {
     Slapi_ComponentId *plugin_id;
     pthread_t tid;

daemons/ipa-slapi-plugins/ipa-cldap/ipa_cldap_netlogon.c

@@ -157,7 +157,7 @@ char *make_netbios_name(TALLOC_CTX *mem_ctx, const char *s)
 #define NETLOGON_SAM_LOGON_RESPONSE_EX_pusher \
             (ndr_push_flags_fn_t)ndr_push_NETLOGON_SAM_LOGON_RESPONSE_EX_with_flags
 
-static int ipa_cldap_encode_netlogon(char *fq_hostname, char *domain,
+static int ipa_cldap_encode_netlogon(const char *fq_hostname, char *domain,
                                      char *guid, char *sid, char *name,
                                      uint32_t ntver, struct berval *reply)
 {
@@ -237,7 +237,7 @@ int ipa_cldap_netlogon(struct ipa_cldap_ctx *ctx,
                        struct ipa_cldap_req *req,
                        struct berval *reply)
 {
-    char hostname[IPA_HOST_NAME_LEN];
+    const char *hostname;
     char *domain = NULL;
     char *our_domain = NULL;
     char *guid = NULL;
@@ -322,8 +322,8 @@ int ipa_cldap_netlogon(struct ipa_cldap_ctx *ctx,
         goto done;
     }
 
-    ret = ipa_gethostfqdn(hostname);
+    hostname = ipa_gethostfqdn();
-    if (ret == -1) {
+	if (hostname == NULL) {
         ret = errno;
         goto done;
     }

ipalib/constants.py

@@ -313,7 +313,10 @@ RA_AGENT_PROFILE = 'caSubsystemCert'
 CA_DBUS_TIMEOUT = 120
 
 # Maximum hostname length in Linux
+# It's the max length of uname's nodename and return value of gethostname().
 MAXHOSTNAMELEN = 64
+# DNS name is 255 octets, effectively 253 ASCII characters.
+MAXHOSTFQDNLEN = 253
 
 # regexp definitions
 PATTERN_GROUPUSER_NAME = (

ipapython/fqdn.py

@@ -9,6 +9,9 @@ import socket
 def gethostfqdn():
     """Get the fully qualified domain name of current host from glibc
 
+    This function may return an FQDN with up to MAXHOSTFQDNLEN characters
+    (253). The effective hostname is still limited to MAXHOSTNAMELEN (64).
+
     :return: FQDN as str
     """
     hostname = socket.gethostname()
@@ -26,4 +29,5 @@ def gethostfqdn():
         flags=socket.AI_CANONNAME | socket.AI_ADDRCONFIG
     )
     # first addrinfo struct, fourth field is canonical name
+    # getaddrinfo() either raises an exception or returns at least one entry
     return gai[0][3]

util/ipa_hostname.c

@@ -7,37 +7,25 @@
 #define _GNU_SOURCE
 #endif
 
-#include <netdb.h>
 #include <errno.h>
+#include <netdb.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <unistd.h>
 
 #include "ipa_hostname.h"
 
-int
-ipa_gethostname(char *name)
-{
-    int ret;
-
-    ret = gethostname(name, IPA_HOST_NAME_LEN - 1);
-
-    /* Make double sure it is terminated */
-    name[IPA_HOST_NAME_LEN - 1] = '\0';
-
-    return ret;
-}
-
 static int
 _get_fqdn(char *fqdn)
 {
-    char hostname[IPA_HOST_NAME_LEN];
+    char hostname[IPA_HOST_FQDN_LEN];
     char *canonname = NULL;
     struct addrinfo hints;
     struct addrinfo *ai = NULL;
     int r;
 
-    r = ipa_gethostname(hostname);
+    r = gethostname(hostname, IPA_HOST_FQDN_LEN - 1);
     if (r != 0) {
         goto error;
     }
@@ -69,7 +57,7 @@ _get_fqdn(char *fqdn)
         errno = ENOENT;
         goto error;
     }
-    if (strlen(canonname) >= IPA_HOST_NAME_LEN) {
+    if (strlen(canonname) > (IPA_HOST_FQDN_LEN - 1)) {
         errno = ENAMETOOLONG;
         goto error;
     }
@@ -82,30 +70,29 @@ _get_fqdn(char *fqdn)
     }
 #endif
 
-    strcpy(fqdn, canonname);
+    strncpy(fqdn, canonname, IPA_HOST_FQDN_LEN);
     /* Make double sure it is terminated */
-    fqdn[IPA_HOST_NAME_LEN - 1] = '\0';
+    fqdn[IPA_HOST_FQDN_LEN - 1] = '\0';
     freeaddrinfo(ai);
     return 0;
 
   error:
-    fqdn[0] = '\0';
     if (ai != NULL) {
         freeaddrinfo(ai);
     }
     return -1;
 }
 
-int ipa_gethostfqdn(char *name)
-{
-    static char cached_fqdn[IPA_HOST_NAME_LEN] = {0};
 
-    if (!cached_fqdn) {
+const char* ipa_gethostfqdn()
+{
+    static char cached_fqdn[IPA_HOST_FQDN_LEN] = {0};
+
+    if (*cached_fqdn == '\0') {
         int res = _get_fqdn(cached_fqdn);
         if (res != 0) {
-            return -1;
+            return NULL;
         }
     }
-    strcpy(name, cached_fqdn);
+    return (const char*)cached_fqdn;
-    return 0;
 }

util/ipa_hostname.h

@@ -2,18 +2,14 @@
  * Copyright (C) 2020  FreeIPA Contributors see COPYING for license
  */
 
-#include <limits.h>
+/* FQDN host name length including trailing NULL byte
-#include <unistd.h>
-
-/*
- * host name length including NULL byte
  *
- * NOTE: length hardcoded in kernel
+ * This may be longer than HOST_NAME_MAX. The hostname (effectively uname()'s
+ * node name) is limited to 64 characters on Linux. ipa_gethostfqdn() returns
+ * a FQDN from NSS which can be up to 255 octets including NULL byte.
+ * Effectively the FQDN is 253 ASCII characters.
  */
-#define IPA_HOST_NAME_LEN (HOST_NAME_MAX + 1)
+#define IPA_HOST_FQDN_LEN 255
 
-int
+const char*
-ipa_gethostname(char *name);
+ipa_gethostfqdn(void);
-
-int
-ipa_gethostfqdn(char *name);