On Wed, 8 Sep 2010 12:04:38 -0500
[email protected] wrote:
> From: Shirish Pargaonkar <[email protected]>
>
>
> 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. ciphertext is calculated within a mutex lock.
>
> If authentication is successful, the secondary key is the that client
> uses to calculate cifs/smb signature in the messages that client sends
> and to verify the messages sent by server.
> This key stays with the smb connection for its life and is the key used
> to generate (and verify) signatures for all the subsequent smb sessions
> for this smb connection.
>
> So only for the first smb session on any smb connection, type 1 message
> of ntlmssp negotiation selects the flag NTLMSSP_NEGOTIATE_KEY_XCH.
> It is not used for subsequent smb sessions on this smb connection i.e.
> no need to generate secondary key, create ciphertext and send it etc.
>
> After the very first successful smb session, sequence number gets set
> to 0 and variable cphready is used to mark that the key calculations
> are done, this is done within a mutex lock.
>
>
> Signed-off-by: Shirish Pargaonkar <[email protected]>
> ---
> fs/cifs/cifsencrypt.c | 52
> +++++++++++++++++++++++++++++++++++++++++++++++++
> fs/cifs/cifsproto.h | 1 +
> fs/cifs/connect.c | 1 +
> fs/cifs/sess.c | 24 +++++++++++++++++-----
> 4 files changed, 72 insertions(+), 6 deletions(-)
>
> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
> index f9c140a..197fc85 100644
> --- a/fs/cifs/cifsencrypt.c
> +++ b/fs/cifs/cifsencrypt.c
> @@ -470,6 +470,58 @@ void CalcNTLMv2_response(const struct cifsSesInfo *ses,
> /* cifs_dump_mem("v2_sess_rsp: ", v2_session_response, 32); */
> }
>
> +int
> +calc_seckey(struct TCP_Server_Info *server)
> +{
> + int rc;
> + struct crypto_blkcipher *tfm_arc4;
> + struct scatterlist sgin, sgout;
> + struct blkcipher_desc desc;
> +
> + if (!server) {
> + cERROR(1, "%s: Can't determine ciphertext key\n", __func__);
> + return 1;
> + }
> +
> + mutex_lock(&server->srv_mutex);
> + if (server->cphready) {
> + mutex_unlock(&server->srv_mutex);
> + return 0;
> + }
> +
> + get_random_bytes(server->ntlmssp.sec_key, CIFS_NTLMV2_SESSKEY_SIZE);
> +
> + tfm_arc4 = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
> + if (!tfm_arc4 || IS_ERR(tfm_arc4)) {
> + cERROR(1, "could not allocate arc4 crypto function\n");
> + mutex_unlock(&server->srv_mutex);
> + return 1;
> + }
> +
> + desc.tfm = tfm_arc4;
> +
> + crypto_blkcipher_setkey(tfm_arc4, server->session_key.data.ntlmv2.key,
> + CIFS_CPHTXT_SIZE);
> +
> + sg_init_one(&sgin, server->ntlmssp.sec_key, CIFS_CPHTXT_SIZE);
> + sg_init_one(&sgout, server->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);
> + mutex_unlock(&server->srv_mutex);
> + return rc;
> + }
> +
> + crypto_free_blkcipher(tfm_arc4);
> +
> + server->sequence_number = 0;
> + server->cphready = true;
> + mutex_unlock(&server->srv_mutex);
> +
> + return 0;
> +}
> +
> void
> cifs_crypto_shash_release(struct TCP_Server_Info *server)
> {
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index fbfdd8e..b78bb77 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -370,6 +370,7 @@ extern int setup_ntlmv2_rsp(struct cifsSesInfo *, char *,
> const struct nls_table *);
> extern int cifs_crypto_shash_allocate(struct TCP_Server_Info *);
> extern void cifs_crypto_shash_release(struct TCP_Server_Info *);
> +extern int calc_seckey(struct TCP_Server_Info *);
> #ifdef CONFIG_CIFS_WEAK_PW_HASH
> extern void calc_lanman_hash(const char *password, const char *cryptkey,
> bool encrypt, char *lnm_session_key);
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 0621a72..e3883f3 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1587,6 +1587,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
> goto out_err2;
> }
>
> + tcp_ses->cphready = false;
I see that you're setting this when you spawn a new tcp session. What
about reconnects though? Don't you also need to set this to false when
the socket needs to be reconnected?
> tcp_ses->noblocksnd = volume_info->noblocksnd;
> tcp_ses->noautotune = volume_info->noautotune;
> tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> index 68ea153..7c94d7b 100644
> --- a/fs/cifs/sess.c
> +++ b/fs/cifs/sess.c
> @@ -444,10 +444,12 @@ static void build_ntlmssp_negotiate_blob(unsigned char
> *pbuffer,
> NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |
> NTLMSSP_NEGOTIATE_NTLM;
> if (ses->server->secMode &
> - (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED))
> + (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED)) {
> flags |= NTLMSSP_NEGOTIATE_SIGN;
> - if (ses->server->secMode & SECMODE_SIGN_REQUIRED)
> - flags |= NTLMSSP_NEGOTIATE_ALWAYS_SIGN;
> + if (!ses->server->cphready)
> + flags |= NTLMSSP_NEGOTIATE_KEY_XCH |
> + NTLMSSP_NEGOTIATE_EXTENDED_SEC;
> + }
>
> sec_blob->NegotiateFlags |= cpu_to_le32(flags);
>
> @@ -554,9 +556,19 @@ static int build_ntlmssp_auth_blob(unsigned char
> *pbuffer,
> sec_blob->WorkstationName.MaximumLength = 0;
> tmp += 2;
>
> - sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
> - sec_blob->SessionKey.Length = 0;
> - sec_blob->SessionKey.MaximumLength = 0;
> + if ((ses->server->ntlmssp.server_flags & NTLMSSP_NEGOTIATE_KEY_XCH) &&
> + !calc_seckey(ses->server)) {
> + memcpy(tmp, ses->server->ntlmssp.ciphertext, CIFS_CPHTXT_SIZE);
> + sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->SessionKey.Length = cpu_to_le16(CIFS_CPHTXT_SIZE);
> + sec_blob->SessionKey.MaximumLength =
> + cpu_to_le16(CIFS_CPHTXT_SIZE);
> + tmp += CIFS_CPHTXT_SIZE;
> + } else {
> + sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->SessionKey.Length = 0;
> + sec_blob->SessionKey.MaximumLength = 0;
> + }
>
> setup_ntlmv2_ret:
> return tmp - pbuffer;
--
Jeff Layton <[email protected]>
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