[PATCH 6/7] cifs.upcall: use ip address passed by kernel to get server's hostname

Instead of using the hostname given by the upcall to get the server's
principal, take the IP address given in the upcall and reverse resolve
it to a hostname.

Signed-off-by: Jeff Layton <[email protected]>
---
 client/cifs.upcall.c |   68 +++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/client/cifs.upcall.c b/client/cifs.upcall.c
index 38be876..1e58503 100644
--- a/client/cifs.upcall.c
+++ b/client/cifs.upcall.c
@@ -150,15 +150,15 @@ handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
 #define DKD_HAVE_HOSTNAME	0x1
 #define DKD_HAVE_VERSION	0x2
 #define DKD_HAVE_SEC		0x4
-#define DKD_HAVE_IPV4		0x8
-#define DKD_HAVE_IPV6		0x10
-#define DKD_HAVE_UID		0x20
-#define DKD_HAVE_PID		0x40
-#define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
+#define DKD_HAVE_IP		0x8
+#define DKD_HAVE_UID		0x10
+#define DKD_HAVE_PID		0x20
+#define DKD_MUSTHAVE_SET (DKD_HAVE_IP|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 
 static struct decoded_args {
 	int		ver;
 	char		*hostname;
+	char		*ip;
 	uid_t		uid;
 	pid_t		pid;
 	sectype_t	sec;
@@ -167,6 +167,7 @@ static struct decoded_args {
 static unsigned int
 decode_key_description(const char *desc, struct decoded_args *arg)
 {
+	int len;
 	int retval = 0;
 	char *pos;
 	const char *tkn = desc;
@@ -174,7 +175,6 @@ decode_key_description(const char *desc, struct decoded_args *arg)
 	do {
 		pos = index(tkn, ';');
 		if (strncmp(tkn, "host=", 5) == 0) {
-			int len;
 
 			if (pos == NULL)
 				len = strlen(tkn);
@@ -186,10 +186,18 @@ decode_key_description(const char *desc, struct decoded_args *arg)
 			arg->hostname = SMB_XMALLOC_ARRAY(char, len);
 			strlcpy(arg->hostname, tkn + 5, len);
 			retval |= DKD_HAVE_HOSTNAME;
-		} else if (strncmp(tkn, "ipv4=", 5) == 0) {
-			/* BB: do we need it if we have hostname already? */
-		} else if (strncmp(tkn, "ipv6=", 5) == 0) {
-			/* BB: do we need it if we have hostname already? */
+		} else if (!strncmp(tkn, "ip4=", 4) ||
+			   !strncmp(tkn, "ip6=", 4)) {
+			if (pos == NULL)
+				len = strlen(tkn);
+			else
+				len = pos - tkn;
+
+			len -= 3;
+			SAFE_FREE(arg->ip);
+			arg->ip = SMB_XMALLOC_ARRAY(char, len);
+			strlcpy(arg->ip, tkn + 4, len);
+			retval |= DKD_HAVE_IP;
 		} else if (strncmp(tkn, "pid=", 4) == 0) {
 			errno = 0;
 			arg->pid = strtol(tkn + 4, NULL, 0);
@@ -288,6 +296,35 @@ cifs_resolver(const key_serial_t key, const char *key_descr)
 	return 0;
 }
 
+static int
+ip_to_fqdn(const char *ipaddr, char *host, size_t hostlen)
+{
+	int rc;
+	struct addrinfo hints = { .ai_flags = AI_NUMERICHOST };
+	struct addrinfo *res;
+
+	rc = getaddrinfo(ipaddr, NULL, &hints, &res);
+	if (rc) {
+		syslog(LOG_DEBUG, "%s: failed to resolve %s to ipaddr: %s",
+			__func__, ipaddr,
+			rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
+		return rc;
+	}
+
+	rc = getnameinfo(res->ai_addr, res->ai_addrlen, host, hostlen,
+			 NULL, 0, NI_NAMEREQD);
+	freeaddrinfo(res);
+	if (rc) {
+		syslog(LOG_DEBUG, "%s: failed to resolve %s to fqdn: %s",
+			__func__, ipaddr,
+			rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
+		return rc;
+	}
+
+	syslog(LOG_DEBUG, "%s: resolved %s to %s", __func__, ipaddr, host);
+	return 0;
+}
+
 static void
 usage(void)
 {
@@ -306,6 +343,7 @@ int main(const int argc, char *const argv[])
 	long rc = 1;
 	int c;
 	char *buf, *princ, *ccname = NULL;
+	char hostbuf[NI_MAXHOST];
 	struct decoded_args arg = { };
 	const char *oid;
 
@@ -383,12 +421,18 @@ int main(const int argc, char *const argv[])
 		}
 	}
 
+	if (have & DKD_HAVE_IP) {
+		rc = ip_to_fqdn(arg.ip, hostbuf, sizeof(hostbuf));
+		if (rc)
+			goto out;
+	}
+
 	// do mech specific authorization
 	switch (arg.sec) {
 	case MS_KRB5:
 	case KRB5:
 		/* for "cifs/" service name + terminating 0 */
-		datalen = strlen(arg.hostname) + 5 + 1;
+		datalen = strnlen(hostbuf, sizeof(hostbuf)) + 5 + 1;
 		princ = SMB_XMALLOC_ARRAY(char, datalen);
 		if (!princ) {
 			rc = 1;
@@ -405,7 +449,7 @@ int main(const int argc, char *const argv[])
 		 * getting a host/ principal if that doesn't work.
 		 */
 		strlcpy(princ, "cifs/", datalen);
-		strlcpy(princ + 5, arg.hostname, datalen - 5);
+		strlcpy(princ + 5, hostbuf, datalen - 5);
 		rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
 		if (rc) {
 			memcpy(princ, "host/", 5);
-- 
1.6.0.6