[CIFS] SMB3 Signing enablement

SMB3 uses a much faster method of signing (which is also better in other ways),
AES-CMAC.  With the kernel now supporting AES-CMAC since last release, we
are overdue to allow SMB3 signing (today only CIFS and SMB2 and SMB2.1,
but not SMB3 and SMB3.1 can sign) - and we need this also for checking
secure negotation and also per-share encryption (two other new SMB3 features
which we need to implement).

This patch needs some work in a few areas - for example we need to
move signing for SMB2/SMB3 from per-socket to per-user (we may be able to
use the "nosharesock" mount option in the interim for the multiuser case),
and Shirish found a bug in the earlier authentication overhaul
(setting signing flags properly) - but those can be done in followon
patches.

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

8 files changed, 188 insertions, 2 deletions

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 2906ee276408..603f18a65c12 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -10,6 +10,7 @@ config CIFS
         select CRYPTO_ECB
         select CRYPTO_DES
         select CRYPTO_SHA256
+        select CRYPTO_CMAC
         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 330875948f18..3d8bf941d126 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -705,6 +705,9 @@ calc_seckey(struct cifs_ses *ses)
 void
 cifs_crypto_shash_release(struct TCP_Server_Info *server)
 {
+        if (server->secmech.cmacaes)
+                crypto_free_shash(server->secmech.cmacaes);
+
         if (server->secmech.hmacsha256)
                 crypto_free_shash(server->secmech.hmacsha256);
 
@@ -714,6 +717,8 @@ cifs_crypto_shash_release(struct TCP_Server_Info *server)
         if (server->secmech.hmacmd5)
                 crypto_free_shash(server->secmech.hmacmd5);
 
+        kfree(server->secmech.sdesccmacaes);
+
         kfree(server->secmech.sdeschmacsha256);
 
         kfree(server->secmech.sdeschmacmd5);
@@ -747,6 +752,13 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
                 goto crypto_allocate_hmacsha256_fail;
         }
 
+        server->secmech.cmacaes = crypto_alloc_shash("cmac(aes)", 0, 0);
+        if (IS_ERR(server->secmech.cmacaes)) {
+                cifs_dbg(VFS, "could not allocate crypto cmac-aes");
+                rc = PTR_ERR(server->secmech.cmacaes);
+                goto crypto_allocate_cmacaes_fail;
+        }
+
         size = sizeof(struct shash_desc) +
                         crypto_shash_descsize(server->secmech.hmacmd5);
         server->secmech.sdeschmacmd5 = kmalloc(size, GFP_KERNEL);
@@ -777,8 +789,22 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
         server->secmech.sdeschmacsha256->shash.tfm = server->secmech.hmacsha256;
         server->secmech.sdeschmacsha256->shash.flags = 0x0;
 
+        size = sizeof(struct shash_desc) +
+                        crypto_shash_descsize(server->secmech.cmacaes);
+        server->secmech.sdesccmacaes = kmalloc(size, GFP_KERNEL);
+        if (!server->secmech.sdesccmacaes) {
+                cifs_dbg(VFS, "%s: Can't alloc cmacaes\n", __func__);
+                rc = -ENOMEM;
+                goto crypto_allocate_cmacaes_sdesc_fail;
+        }
+        server->secmech.sdesccmacaes->shash.tfm = server->secmech.cmacaes;
+        server->secmech.sdesccmacaes->shash.flags = 0x0;
+
         return 0;
 
+crypto_allocate_cmacaes_sdesc_fail:
+        kfree(server->secmech.sdeschmacsha256);
+
 crypto_allocate_hmacsha256_sdesc_fail:
         kfree(server->secmech.sdescmd5);
 
@@ -786,6 +812,9 @@ crypto_allocate_md5_sdesc_fail:
         kfree(server->secmech.sdeschmacmd5);
 
 crypto_allocate_hmacmd5_sdesc_fail:
+        crypto_free_shash(server->secmech.cmacaes);
+
+crypto_allocate_cmacaes_fail:
         crypto_free_shash(server->secmech.hmacsha256);
 
 crypto_allocate_hmacsha256_fail:
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 9a1e37aad3b8..2d0f524ebeee 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -125,9 +125,11 @@ struct cifs_secmech {
         struct crypto_shash *hmacmd5; /* hmac-md5 hash function */
         struct crypto_shash *md5; /* md5 hash function */
         struct crypto_shash *hmacsha256; /* hmac-sha256 hash function */
+        struct crypto_shash *cmacaes; /* block-cipher based MAC function */
         struct sdesc *sdeschmacmd5;  /* ctxt to generate ntlmv2 hash, CR1 */
         struct sdesc *sdescmd5; /* ctxt to generate cifs/smb signature */
         struct sdesc *sdeschmacsha256;  /* ctxt to generate smb2 signature */
+        struct sdesc *sdesccmacaes;  /* ctxt to generate smb3 signature */
 };
 
 /* per smb session structure/fields */
@@ -538,6 +540,7 @@ struct TCP_Server_Info {
         int timeAdj;  /* Adjust for difference in server time zone in sec */
         __u64 CurrentMid;         /* multiplex id - rotating counter */
         char cryptkey[CIFS_CRYPTO_KEY_SIZE]; /* used by ntlm, ntlmv2 etc */
+        char smb3signingkey[SMB3_SIGN_KEY_SIZE]; /* for signing smb3 packets */
         /* 16th byte of RFC1001 workstation name is always null */
         char workstation_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
         __u32 sequence_number; /* for signing, protected by srv_mutex */
diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index 7e8523c5c18e..11ca24a8e054 100644
--- a/fs/cifs/cifspdu.h
+++ b/fs/cifs/cifspdu.h
@@ -142,6 +142,11 @@
  */
 #define CIFS_SESS_KEY_SIZE (16)
 
+/*
+ * Size of the smb3 signing key
+ */
+#define SMB3_SIGN_KEY_SIZE (16)
+
 #define CIFS_CLIENT_CHALLENGE_SIZE (8)
 #define CIFS_SERVER_CHALLENGE_SIZE (8)
 #define CIFS_HMAC_MD5_HASH_SIZE (16)
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index a82b3c09888b..ff669e7c5857 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -436,6 +436,7 @@ extern int setup_ntlmv2_rsp(struct cifs_ses *, 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 cifs_ses *);
+extern int generate_smb3signingkey(struct TCP_Server_Info *);
 
 #ifdef CONFIG_CIFS_WEAK_PW_HASH
 extern int calc_lanman_hash(const char *password, const char *cryptkey,
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 53a1780cd073..354ea7782dba 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3841,6 +3841,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
                         server->sequence_number = 0x2;
                         server->session_estab = true;
                         ses->auth_key.response = NULL;
+                        generate_smb3signingkey(server);
                 }
                 mutex_unlock(&server->srv_mutex);
 
diff --git a/fs/cifs/smb2glob.h b/fs/cifs/smb2glob.h
index 7c0e2143e775..c38350851b08 100644
--- a/fs/cifs/smb2glob.h
+++ b/fs/cifs/smb2glob.h
@@ -54,5 +54,7 @@
 #define SMB2_SIGNATURE_SIZE (16)
 #define SMB2_NTLMV2_SESSKEY_SIZE (16)
 #define SMB2_HMACSHA256_SIZE (32)
+#define SMB2_CMACAES_SIZE (16)
+#define SMB3_SIGNKEY_SIZE (16)
 
 #endif  /* _SMB2_GLOB_H */
diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index c802ecfa770e..87563ee58d30 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -117,10 +117,154 @@ smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 }
 
 int
+generate_smb3signingkey(struct TCP_Server_Info *server)
+{
+        unsigned char zero = 0x0;
+        __u8 i[4] = {0, 0, 0, 1};
+        __u8 L[4] = {0, 0, 0, 128};
+        int rc = 0;
+        unsigned char prfhash[SMB2_HMACSHA256_SIZE];
+        unsigned char *hashptr = prfhash;
+
+        memset(prfhash, 0x0, SMB2_HMACSHA256_SIZE);
+        memset(server->smb3signingkey, 0x0, SMB3_SIGNKEY_SIZE);
+
+        rc = crypto_shash_setkey(server->secmech.hmacsha256,
+                server->session_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not set with session key\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_init(&server->secmech.sdeschmacsha256->shash);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not init sign hmac\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+                                i, 4);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not update with n\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+                                "SMB2AESCMAC", 12);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not update with label\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+                                &zero, 1);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not update with zero\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+                                "SmbSign", 8);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not update with context\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+                                L, 4);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not update with L\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        rc = crypto_shash_final(&server->secmech.sdeschmacsha256->shash,
+                                hashptr);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not generate sha256 hash\n", __func__);
+                goto smb3signkey_ret;
+        }
+
+        memcpy(server->smb3signingkey, hashptr, SMB3_SIGNKEY_SIZE);
+
+smb3signkey_ret:
+        return rc;
+}
+
+int
 smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
-        cifs_dbg(FYI, "smb3 signatures not supported yet\n");
-        return -EOPNOTSUPP;
+        int i, rc;
+        unsigned char smb3_signature[SMB2_CMACAES_SIZE];
+        unsigned char *sigptr = smb3_signature;
+        struct kvec *iov = rqst->rq_iov;
+        int n_vec = rqst->rq_nvec;
+        struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)iov[0].iov_base;
+
+        memset(smb3_signature, 0x0, SMB2_CMACAES_SIZE);
+        memset(smb2_pdu->Signature, 0x0, SMB2_SIGNATURE_SIZE);
+
+        rc = crypto_shash_setkey(server->secmech.cmacaes,
+                server->smb3signingkey, SMB2_CMACAES_SIZE);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not set key for cmac aes\n", __func__);
+                return rc;
+        }
+
+        rc = crypto_shash_init(&server->secmech.sdesccmacaes->shash);
+        if (rc) {
+                cifs_dbg(VFS, "%s: Could not init cmac aes\n", __func__);
+                return rc;
+        }
+
+        for (i = 0; i < n_vec; i++) {
+                if (iov[i].iov_len == 0)
+                        continue;
+                if (iov[i].iov_base == NULL) {
+                        cifs_dbg(VFS, "null iovec entry");
+                        return -EIO;
+                }
+                /*
+                 * The first entry includes a length field (which does not get
+                 * signed that occupies the first 4 bytes before the header).
+                 */
+                if (i == 0) {
+                        if (iov[0].iov_len <= 8) /* cmd field at offset 9 */
+                                break; /* nothing to sign or corrupt header */
+                        rc =
+                        crypto_shash_update(
+                                &server->secmech.sdesccmacaes->shash,
+                                iov[i].iov_base + 4, iov[i].iov_len - 4);
+                } else {
+                        rc =
+                        crypto_shash_update(
+                                &server->secmech.sdesccmacaes->shash,
+                                iov[i].iov_base, iov[i].iov_len);
+                }
+                if (rc) {
+                        cifs_dbg(VFS, "%s: Couldn't update cmac aes with payload\n",
+                                                        __func__);
+                        return rc;
+                }
+        }
+
+        /* now hash over the rq_pages array */
+        for (i = 0; i < rqst->rq_npages; i++) {
+                struct kvec p_iov;
+
+                cifs_rqst_page_to_kvec(rqst, i, &p_iov);
+                crypto_shash_update(&server->secmech.sdesccmacaes->shash,
+                                        p_iov.iov_base, p_iov.iov_len);
+                kunmap(rqst->rq_pages[i]);
+        }
+
+        rc = crypto_shash_final(&server->secmech.sdesccmacaes->shash,
+                                                sigptr);
+        if (rc)
+                cifs_dbg(VFS, "%s: Could not generate cmac aes\n", __func__);
+
+        memcpy(smb2_pdu->Signature, sigptr, SMB2_SIGNATURE_SIZE);
+
+        return rc;
 }
 
 /* must be called with server->srv_mutex held */