NTLM auth and sign - Define crypto hash functions and create and send keys needed for key exchange

Mark dependency on crypto modules in Kconfig.

Defining per structures sdesc and cifs_secmech which are used to store
crypto hash functions and contexts.  They are stored per smb connection
and used for all auth mechs to genereate hash values and signatures.

Allocate crypto hashing functions, security descriptiors, and respective
contexts when a smb/tcp connection is established.
Release them when a tcp/smb connection is taken down.

md5 and hmac-md5 are two crypto hashing functions that are used
throught the life of an smb/tcp connection by various functions that
calcualte signagure and ntlmv2 hash, HMAC etc.

structure ntlmssp_auth is defined as per smb connection.

ntlmssp_auth holds ciphertext which is genereated by rc4/arc4 encryption of
secondary key, a nonce using ntlmv2 session key and sent in the session key
field of the type 3 message sent by the client during ntlmssp
negotiation/exchange

A key is exchanged with the server if client indicates so in flags in
type 1 messsage and server agrees in flag in type 2 message of ntlmssp
negotiation.  If both client and agree, a key sent by client in
type 3 message of ntlmssp negotiation in the session key field.
The key is a ciphertext generated off of secondary key, a nonce, using
ntlmv2 hash via rc4/arc4.

Signing works for ntlmssp in this patch. The sequence number within
the server structure needs to be zero until session is established
i.e. till type 3 packet of ntlmssp exchange of a to be very first
smb session on that smb connection is sent.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 113 insertions, 0 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 987b479d55dd..eaa2327ee7af 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -541,6 +541,119 @@ setup_ntlmv2_rsp_ret:
         return rc;
 }
 
+int
+calc_seckey(struct cifsSesInfo *ses)
+{
+        int rc;
+        struct crypto_blkcipher *tfm_arc4;
+        struct scatterlist sgin, sgout;
+        struct blkcipher_desc desc;
+        unsigned char sec_key[CIFS_SESS_KEY_SIZE]; /* a nonce */
+
+        get_random_bytes(sec_key, CIFS_SESS_KEY_SIZE);
+
+        tfm_arc4 = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
+        if (!tfm_arc4 || IS_ERR(tfm_arc4)) {
+                cERROR(1, "could not allocate crypto API arc4\n");
+                return PTR_ERR(tfm_arc4);
+        }
+
+        desc.tfm = tfm_arc4;
+
+        crypto_blkcipher_setkey(tfm_arc4, ses->auth_key.response,
+                                        CIFS_SESS_KEY_SIZE);
+
+        sg_init_one(&sgin, sec_key, CIFS_SESS_KEY_SIZE);
+        sg_init_one(&sgout, ses->ntlmssp.ciphertext, CIFS_CPHTXT_SIZE);
+
+        rc = crypto_blkcipher_encrypt(&desc, &sgout, &sgin, CIFS_CPHTXT_SIZE);
+        if (rc) {
+                cERROR(1, "could not encrypt session key rc: %d\n", rc);
+                crypto_free_blkcipher(tfm_arc4);
+                return rc;
+        }
+
+        /* make secondary_key/nonce as session key */
+        memcpy(ses->auth_key.response, sec_key, CIFS_SESS_KEY_SIZE);
+        /* and make len as that of session key only */
+        ses->auth_key.len = CIFS_SESS_KEY_SIZE;
+
+        crypto_free_blkcipher(tfm_arc4);
+
+        return 0;
+}
+
+void
+cifs_crypto_shash_release(struct TCP_Server_Info *server)
+{
+        if (server->secmech.md5)
+                crypto_free_shash(server->secmech.md5);
+
+        if (server->secmech.hmacmd5)
+                crypto_free_shash(server->secmech.hmacmd5);
+
+        kfree(server->secmech.sdeschmacmd5);
+
+        kfree(server->secmech.sdescmd5);
+}
+
+int
+cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
+{
+        int rc;
+        unsigned int size;
+
+        server->secmech.hmacmd5 = crypto_alloc_shash("hmac(md5)", 0, 0);
+        if (!server->secmech.hmacmd5 ||
+                        IS_ERR(server->secmech.hmacmd5)) {
+                cERROR(1, "could not allocate crypto hmacmd5\n");
+                return PTR_ERR(server->secmech.hmacmd5);
+        }
+
+        server->secmech.md5 = crypto_alloc_shash("md5", 0, 0);
+        if (!server->secmech.md5 || IS_ERR(server->secmech.md5)) {
+                cERROR(1, "could not allocate crypto md5\n");
+                rc = PTR_ERR(server->secmech.md5);
+                goto crypto_allocate_md5_fail;
+        }
+
+        size = sizeof(struct shash_desc) +
+                        crypto_shash_descsize(server->secmech.hmacmd5);
+        server->secmech.sdeschmacmd5 = kmalloc(size, GFP_KERNEL);
+        if (!server->secmech.sdeschmacmd5) {
+                cERROR(1, "cifs_crypto_shash_allocate: can't alloc hmacmd5\n");
+                rc = -ENOMEM;
+                goto crypto_allocate_hmacmd5_sdesc_fail;
+        }
+        server->secmech.sdeschmacmd5->shash.tfm = server->secmech.hmacmd5;
+        server->secmech.sdeschmacmd5->shash.flags = 0x0;
+
+
+        size = sizeof(struct shash_desc) +
+                        crypto_shash_descsize(server->secmech.md5);
+        server->secmech.sdescmd5 = kmalloc(size, GFP_KERNEL);
+        if (!server->secmech.sdescmd5) {
+                cERROR(1, "cifs_crypto_shash_allocate: can't alloc md5\n");
+                rc = -ENOMEM;
+                goto crypto_allocate_md5_sdesc_fail;
+        }
+        server->secmech.sdescmd5->shash.tfm = server->secmech.md5;
+        server->secmech.sdescmd5->shash.flags = 0x0;
+
+        return 0;
+
+crypto_allocate_md5_sdesc_fail:
+        kfree(server->secmech.sdeschmacmd5);
+
+crypto_allocate_hmacmd5_sdesc_fail:
+        crypto_free_shash(server->secmech.md5);
+
+crypto_allocate_md5_fail:
+        crypto_free_shash(server->secmech.hmacmd5);
+
+        return rc;
+}
+
 void CalcNTLMv2_response(const struct cifsSesInfo *ses)
 {
         unsigned int offset = CIFS_SESS_KEY_SIZE + 8;