On Tue, 21 Sep 2010 13:26:08 -0500
Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote:
> On Tue, Sep 21, 2010 at 12:52 PM, Jeff Layton <jlayton@xxxxxxxxx> wrote:
> > On Sat, 18 Sep 2010 22:02:35 -0500
> > shirishpargaonkar@xxxxxxxxx wrote:
> >
> >> From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
> >>
> >>
> >> 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 and filed cphready is defined as per smb connection.
> >>
> >> ntlmssp_auth holds secondary key which is a nonce that gets used as a key
> >> to generate signatures, ciphertext is genereated by rc4/arc4 encryption of
> >> secondary key using ntlmv2 session key and sent in the session key field of
> >> the type 3 message sent by the client during ntlmssp negotiation/exchange
> >> These are per session structures and secondary key and cipher text
> >> get calculated only once per smb connection, during first smb session setup
> >> for that smb connection.
> >>
> >> Field cphready is used to mark such that once secondary keys and ciphertext
> >> are calculated during very first smb session setup for a smb connection
> >> and ciphertext is sent to the server, the same does not happen during
> >> subsequent smb session setups/establishments.
> >>
> >> 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.
> >>
> >> 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. cphready is reset when a reconnect of the smb connection
> >> happens as sessions get set up again.
> >>
> >> Calculation of ciphertext and setting cphready, is done within
> >> mutex lock to prevent race of smb session setups on a new smb connection.
> >>
> >>
> >> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
> >> ---
> >> fs/cifs/Kconfig | 3 +
> >> fs/cifs/cifsencrypt.c | 125 +++++++++++++++++++++++++++++++++++++++++++++++++
> >> fs/cifs/cifsglob.h | 28 +++++++++++
> >> fs/cifs/cifspdu.h | 7 +++
> >> fs/cifs/cifsproto.h | 3 +
> >> fs/cifs/connect.c | 18 ++++++-
> >> fs/cifs/sess.c | 26 +++++++---
> >> 7 files changed, 200 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
> >> index 917b7d4..0ed2139 100644
> >> --- a/fs/cifs/Kconfig
> >> +++ b/fs/cifs/Kconfig
> >> @@ -2,6 +2,9 @@ config CIFS
> >> tristate "CIFS support (advanced network filesystem, SMBFS successor)"
> >> depends on INET
> >> select NLS
> >> + select CRYPTO
> >> + select CRYPTO_MD5
> >> + select CRYPTO_ARC4
> >> help
> >> This is the client VFS module for the Common Internet File System
> >> (CIFS) protocol which is the successor to the Server Message Block
> >> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
> >> index 730038a..48026c6 100644
> >> --- a/fs/cifs/cifsencrypt.c
> >> +++ b/fs/cifs/cifsencrypt.c
> >> @@ -477,3 +477,128 @@ void CalcNTLMv2_response(const struct cifsSesInfo *ses,
> >> hmac_md5_final(v2_session_response, &context);
> >> /* 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 crypto API arc4\n");
> >> + mutex_unlock(&server->srv_mutex);
> >> + return PTR_ERR(tfm_arc4);
> >> + }
> >> +
> >> + 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);
> >> + crypto_free_blkcipher(tfm_arc4);
> >> + 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)
> >> +{
> >> + 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;
> >> +}
> >> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> >> index c68f31c..c7da866 100644
> >> --- a/fs/cifs/cifsglob.h
> >> +++ b/fs/cifs/cifsglob.h
> >> @@ -25,6 +25,9 @@
> >> #include <linux/workqueue.h>
> >> #include "cifs_fs_sb.h"
> >> #include "cifsacl.h"
> >> +#include <crypto/internal/hash.h>
> >> +#include <linux/scatterlist.h>
> >> +
> >> /*
> >> * The sizes of various internal tables and strings
> >> */
> >> @@ -109,6 +112,28 @@ struct session_key {
> >> } data;
> >> };
> >>
> >> +/* crypto security descriptor definition */
> >> +struct sdesc {
> >> + struct shash_desc shash;
> >> + char ctx[];
> >> +};
> >> +
> >> +/* crypto hashing related structure/fields, not speicific to a sec mech */
> >> +struct cifs_secmech {
> >> + struct crypto_shash *hmacmd5; /* hmac-md5 hash function */
> >> + struct crypto_shash *md5; /* md5 hash function */
> >> + struct sdesc *sdeschmacmd5; /* ctxt to generate ntlmv2 hash, CR1 */
> >> + struct sdesc *sdescmd5; /* ctxt to generate cifs/smb signature */
> >> +};
> >> +
> >> +/* per smb connection structure/fields */
> >> +struct ntlmssp_auth {
> >> + __u32 client_flags; /* sent by client in type 1 ntlmsssp exchange */
> >> + __u32 server_flags; /* sent by server in type 2 ntlmssp exchange */
> >> + unsigned char sec_key[CIFS_CPHTXT_SIZE]; /* a nonce client generates */
> >> + unsigned char ciphertext[CIFS_CPHTXT_SIZE]; /* sent to server */
> >> +};
> >> +
> >> struct cifs_cred {
> >> int uid;
> >> int gid;
> >> @@ -187,6 +212,9 @@ struct TCP_Server_Info {
> >> unsigned long lstrp; /* when we got last response from this server */
> >> u16 dialect; /* dialect index that server chose */
> >> /* extended security flavors that server supports */
> >> + struct cifs_secmech secmech; /* crypto sec mech functs, descriptors */
> >> + struct ntlmssp_auth ntlmssp; /* sec key, ciphertext, flags */
> >> + bool cphready; /* ciphertext is calculated */
> >> bool sec_kerberos; /* supports plain Kerberos */
> >> bool sec_mskerberos; /* supports legacy MS Kerberos */
> >> bool sec_kerberosu2u; /* supports U2U Kerberos */
> >> diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
> >> index b0f4b56..dc90a36 100644
> >> --- a/fs/cifs/cifspdu.h
> >> +++ b/fs/cifs/cifspdu.h
> >> @@ -134,6 +134,13 @@
> >> * Size of the session key (crypto key encrypted with the password
> >> */
> >> #define CIFS_SESS_KEY_SIZE (24)
> >> +#define CIFS_CLIENT_CHALLENGE_SIZE (8)
> >> +#define CIFS_SERVER_CHALLENGE_SIZE (8)
> >> +#define CIFS_HMAC_MD5_HASH_SIZE (16)
> >> +#define CIFS_CPHTXT_SIZE (16)
> >> +#define CIFS_NTLMV2_SESSKEY_SIZE (16)
> >> +#define CIFS_NTHASH_SIZE (16)
> >> +
> >>
> >> /*
> >> * Maximum user name length
> >> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> >> index c155479..d89a87a 100644
> >> --- a/fs/cifs/cifsproto.h
> >> +++ b/fs/cifs/cifsproto.h
> >> @@ -369,6 +369,9 @@ extern int cifs_calculate_session_key(struct session_key *key, const char *rn,
> >> extern void CalcNTLMv2_response(const struct cifsSesInfo *, char *);
> >> 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 c99760a..4818089 100644
> >> --- a/fs/cifs/connect.c
> >> +++ b/fs/cifs/connect.c
> >> @@ -199,6 +199,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
> >> if (server->tcpStatus != CifsExiting)
> >> server->tcpStatus = CifsGood;
> >> server->sequence_number = 0;
> >> + server->cphready = false;
> >> spin_unlock(&GlobalMid_Lock);
> >> /* atomic_set(&server->inFlight,0);*/
> >> wake_up(&server->response_q);
> >> @@ -1502,6 +1503,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server)
> >> server->tcpStatus = CifsExiting;
> >> spin_unlock(&GlobalMid_Lock);
> >>
> >> + cifs_crypto_shash_release(server);
> >> cifs_fscache_release_client_cookie(server);
> >>
> >> task = xchg(&server->tsk, NULL);
> >> @@ -1556,12 +1558,19 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
> >> goto out_err;
> >> }
> >>
> >> + rc = cifs_crypto_shash_allocate(tcp_ses);
> >> + if (rc) {
> >> + cERROR(1, "could not setup hash structures rc %d", rc);
> >> + goto out_err;
> >> + }
> >> +
> >> tcp_ses->hostname = extract_hostname(volume_info->UNC);
> >> if (IS_ERR(tcp_ses->hostname)) {
> >> rc = PTR_ERR(tcp_ses->hostname);
> >> - goto out_err;
> >> + goto out_err2;
> >> }
> >>
> >> + tcp_ses->cphready = false;
> >> tcp_ses->noblocksnd = volume_info->noblocksnd;
> >> tcp_ses->noautotune = volume_info->noautotune;
> >> tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
> >> @@ -1600,7 +1609,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
> >> }
> >> if (rc < 0) {
> >> cERROR(1, "Error connecting to socket. Aborting operation");
> >> - goto out_err;
> >> + goto out_err2;
> >> }
> >>
> >> /*
> >> @@ -1614,7 +1623,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
> >> rc = PTR_ERR(tcp_ses->tsk);
> >> cERROR(1, "error %d create cifsd thread", rc);
> >> module_put(THIS_MODULE);
> >> - goto out_err;
> >> + goto out_err2;
> >> }
> >>
> >> /* thread spawned, put it on the list */
> >> @@ -1626,6 +1635,9 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
> >>
> >> return tcp_ses;
> >>
> >> +out_err2:
> >> + cifs_crypto_shash_release(tcp_ses);
> >> +
> >> out_err:
> >> if (tcp_ses) {
> >> if (!IS_ERR(tcp_ses->hostname))
> >> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> >> index af18a50..45555de 100644
> >> --- a/fs/cifs/sess.c
> >> +++ b/fs/cifs/sess.c
> >> @@ -407,7 +407,7 @@ static int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
> >> /* In particular we can examine sign flags */
> >> /* BB spec says that if AvId field of MsvAvTimestamp is populated then
> >> we must set the MIC field of the AUTHENTICATE_MESSAGE */
> >> -
> >> + ses->server->ntlmssp.server_flags = le32_to_cpu(pblob->NegotiateFlags);
> >> tioffset = cpu_to_le16(pblob->TargetInfoArray.BufferOffset);
> >> tilen = cpu_to_le16(pblob->TargetInfoArray.Length);
> >> ses->tilen = tilen;
> >> @@ -443,10 +443,12 @@ 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);
> >>
> >> @@ -553,9 +555,19 @@ 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;
> >
> >
> > Ok, so this patch adds this cphready flag to the server struct and
> > changes the ntlmssp code to use it. What about the other authtypes?
> > NTLMv1 and Kerberos use a local "first_time" flag in CIFS_SessSetup.
> >
> > Why did you choose to add cphready instead of using that? If there is a
> > good reason for it, the other authtypes should be changed to use
> > cphready for consistency.
>
> The use of cphready which is a per smb connection structure is to make
> sure that we calculate secondary session key and ciphertext only once
> per smb connection, by the first session setup over that connection.
> The secondary key which becomes session key is used to calculate signatures.
>
Right. I'm just not sure why we need a separate flag attached to the
server struct for this. Why was the "first_time" mechanism not good
enough here? I see no reason why that wouldn't have worked for NTLMSSP
too.
Note that I'm not attached to that mechanism, but I think it should be
consistent for all sectypes. It makes no sense to use this cphready
flag for NTLMSSP and then a completely different mechanism for other
sectypes. If you want to add this, you should convert the other
sectypes to use your new mechanism.
> We do not have NTLMv1 any more and session key is not used to calculate
> signature for kerberos auth type.
>
Wrong. From the Kerberos section of CIFS_SessSetup:
if (first_time) {
ses->server->session_key.len = msg->sesskey_len;
memcpy(ses->server->session_key.data.krb5,
msg->data, msg->sesskey_len);
}
It's most definitely used for calculating signatures on sockets that
use krb5 auth.
> >
> > Also, not directly related to your changes, but it looks like the
> > "plain" ntlmv2 code sets the session_key without any regard for whether
> > it's the first session on the socket. I think that also ought to be
> > fixed, probably in a separate patch.
>
> The same reason for "plain" ntlmv2, session key is not used to
> calcuate signatures.
>
But it is...the session_key struct holds the pointer to the data that's
used precisely for this.
> SMB connection/setup combo using NTLMSSP security mechanism is stricter
> about authentication response and signature compared to "plain" ntlmv2 or ntlmv1
> or ntlm I think.
>
--
Jeff Layton <jlayton@xxxxxxxxx>
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