cifs NTLMv2/NTLMSSP ntlmv2 within ntlmssp autentication code

Attribue Value (AV) pairs or Target Info (TI) pairs are part of
ntlmv2 authentication.
Structure ntlmv2_resp had only definition for two av pairs.
So removed it, and now allocation of av pairs is dynamic.
For servers like Windows 7/2008, av pairs sent by server in
challege packet (type 2 in the ntlmssp exchange/negotiation) can
vary.

Server sends them during ntlmssp negotiation. So when ntlmssp is used
as an authentication mechanism, type 2 challenge packet from server
has this information.  Pluck it and use the entire blob for
authenticaiton purpose.  If user has not specified, extract
(netbios) domain name from the av pairs which is used to calculate
ntlmv2 hash.  Servers like Windows 7 are particular about the AV pair
blob.

Servers like Windows 2003, are not very strict about the contents
of av pair blob used during ntlmv2 authentication.
So when security mechanism such as ntlmv2 is used (not ntlmv2 in ntlmssp),
there is no negotiation and so genereate a minimal blob that gets
used in ntlmv2 authentication as well as gets sent.

Fields tilen and tilbob are session specific.  AV pair values are defined.

To calculate ntlmv2 response we need ti/av pair blob.

For sec mech like ntlmssp, the blob is plucked from type 2 response from
the server.  From this blob, netbios name of the domain is retrieved,
if user has not already provided, to be included in the Target String
as part of ntlmv2 hash calculations.

For sec mech like ntlmv2, create a minimal, two av pair blob.

The allocated blob is freed in case of error.  In case there is no error,
this blob is used in calculating ntlmv2 response (in CalcNTLMv2_response)
and is also copied on the response to the server, and then freed.

The type 3 ntlmssp response is prepared on a buffer,
5 * sizeof of struct _AUTHENTICATE_MESSAGE, an empirical value large
enough to hold _AUTHENTICATE_MESSAGE plus a blob with max possible
10 values as part of ntlmv2 response and lmv2 keys and domain, user,
workstation  names etc.

Also, kerberos gets selected as a default mechanism if server supports it,
over the other security mechanisms.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 115 insertions, 6 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index eed70cae127..730038a1298 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -27,6 +27,7 @@
 #include "md5.h"
 #include "cifs_unicode.h"
 #include "cifsproto.h"
+#include "ntlmssp.h"
 #include <linux/ctype.h>
 #include <linux/random.h>
 
@@ -262,6 +263,87 @@ void calc_lanman_hash(const char *password, const char *cryptkey, bool encrypt,
 }
 #endif /* CIFS_WEAK_PW_HASH */
 
+/* This is just a filler for ntlmv2 type of security mechanisms.
+ * Older servers are not very particular about the contents of av pairs
+ * in the blob and for sec mechs like ntlmv2, there is no negotiation
+ * as in ntlmssp, so unless domain and server  netbios and dns names
+ * are specified, there is no way to obtain name.  In case of ntlmssp,
+ * server provides that info in type 2 challenge packet
+ */
+static int
+build_avpair_blob(struct cifsSesInfo *ses)
+{
+	struct ntlmssp2_name *attrptr;
+
+	ses->tilen = 2 * sizeof(struct ntlmssp2_name);
+	ses->tiblob = kzalloc(ses->tilen, GFP_KERNEL);
+	if (!ses->tiblob) {
+		ses->tilen = 0;
+		cERROR(1, "Challenge target info allocation failure");
+		return -ENOMEM;
+	}
+	attrptr = (struct ntlmssp2_name *) ses->tiblob;
+	attrptr->type = cpu_to_le16(NTLMSSP_DOMAIN_TYPE);
+
+	return 0;
+}
+
+/* Server has provided av pairs/target info in the type 2 challenge
+ * packet and we have plucked it and stored within smb session.
+ * We parse that blob here to find netbios domain name to be used
+ * as part of ntlmv2 authentication (in Target String), if not already
+ * specified on the command line.
+ * If this function returns without any error but without fetching
+ * domain name, authentication may fail against some server but
+ * may not fail against other (those who are not very particular
+ * about target string i.e. for some, just user name might suffice.
+ */
+static int
+find_domain_name(struct cifsSesInfo *ses)
+{
+	unsigned int attrsize;
+	unsigned int type;
+	unsigned int onesize = sizeof(struct ntlmssp2_name);
+	unsigned char *blobptr;
+	unsigned char *blobend;
+	struct ntlmssp2_name *attrptr;
+
+	if (!ses->tilen || !ses->tiblob)
+		return 0;
+
+	blobptr = ses->tiblob;
+	blobend = ses->tiblob + ses->tilen;
+
+	while (blobptr + onesize < blobend) {
+		attrptr = (struct ntlmssp2_name *) blobptr;
+		type = le16_to_cpu(attrptr->type);
+		if (type == NTLMSSP_AV_EOL)
+			break;
+		blobptr += 2; /* advance attr type */
+		attrsize = le16_to_cpu(attrptr->length);
+		blobptr += 2; /* advance attr size */
+		if (blobptr + attrsize > blobend)
+			break;
+		if (type == NTLMSSP_AV_NB_DOMAIN_NAME) {
+			if (!attrsize)
+				break;
+			if (!ses->domainName) {
+				ses->domainName =
+					kmalloc(attrsize + 1, GFP_KERNEL);
+				if (!ses->domainName)
+						return -ENOMEM;
+				cifs_from_ucs2(ses->domainName,
+					(__le16 *)blobptr, attrsize, attrsize,
+					load_nls_default(), false);
+				break;
+			}
+		}
+		blobptr += attrsize; /* advance attr  value */
+	}
+
+	return 0;
+}
+
 static int calc_ntlmv2_hash(struct cifsSesInfo *ses,
 			    const struct nls_table *nls_cp)
 {
@@ -321,7 +403,8 @@ calc_exit_2:
 	return rc;
 }
 
-void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
+int
+setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
 		      const struct nls_table *nls_cp)
 {
 	int rc;
@@ -333,15 +416,29 @@ void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
 	buf->time = cpu_to_le64(cifs_UnixTimeToNT(CURRENT_TIME));
 	get_random_bytes(&buf->client_chal, sizeof(buf->client_chal));
 	buf->reserved2 = 0;
-	buf->names[0].type = cpu_to_le16(NTLMSSP_DOMAIN_TYPE);
-	buf->names[0].length = 0;
-	buf->names[1].type = 0;
-	buf->names[1].length = 0;
+
+	if (ses->server->secType == RawNTLMSSP) {
+		if (!ses->domainName) {
+			rc = find_domain_name(ses);
+			if (rc) {
+				cERROR(1, "error %d finding domain name", rc);
+				goto setup_ntlmv2_rsp_ret;
+			}
+		}
+	} else {
+		rc = build_avpair_blob(ses);
+		if (rc) {
+			cERROR(1, "error %d building av pair blob", rc);
+			return rc;
+		}
+	}
 
 	/* calculate buf->ntlmv2_hash */
 	rc = calc_ntlmv2_hash(ses, nls_cp);
-	if (rc)
+	if (rc) {
 		cERROR(1, "could not get v2 hash rc %d", rc);
+		goto setup_ntlmv2_rsp_ret;
+	}
 	CalcNTLMv2_response(ses, resp_buf);
 
 	/* now calculate the MAC key for NTLMv2 */
@@ -352,6 +449,15 @@ void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
 	memcpy(&ses->server->session_key.data.ntlmv2.resp, resp_buf,
 	       sizeof(struct ntlmv2_resp));
 	ses->server->session_key.len = 16 + sizeof(struct ntlmv2_resp);
+
+	return 0;
+
+setup_ntlmv2_rsp_ret:
+	kfree(ses->tiblob);
+	ses->tiblob = NULL;
+	ses->tilen = 0;
+
+	return rc;
 }
 
 void CalcNTLMv2_response(const struct cifsSesInfo *ses,
@@ -365,6 +471,9 @@ void CalcNTLMv2_response(const struct cifsSesInfo *ses,
 	hmac_md5_update(v2_session_response+8,
 			sizeof(struct ntlmv2_resp) - 8, &context);
 
+	if (ses->tilen)
+		hmac_md5_update(ses->tiblob, ses->tilen, &context);
+
 	hmac_md5_final(v2_session_response, &context);
 /*	cifs_dump_mem("v2_sess_rsp: ", v2_session_response, 32); */
 }