CIFS: Enable signing in SMB2

Use hmac-sha256 and rather than hmac-md5 that is used for CIFS/SMB.

Signature field in SMB2 header is 16 bytes instead of 8 bytes.

Automatically enable signing by client when requested by the server
when signing ability is available to the client.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

9 files changed, 253 insertions, 28 deletions

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index a08306a8bec9..802930179c2b 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -9,6 +9,7 @@ config CIFS
         select CRYPTO_ARC4
         select CRYPTO_ECB
         select CRYPTO_DES
+        select CRYPTO_SHA256
         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 6a0d741159f0..724738c1a560 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -686,12 +686,17 @@ calc_seckey(struct cifs_ses *ses)
 void
 cifs_crypto_shash_release(struct TCP_Server_Info *server)
 {
+        if (server->secmech.hmacsha256)
+                crypto_free_shash(server->secmech.hmacsha256);
+
         if (server->secmech.md5)
                 crypto_free_shash(server->secmech.md5);
 
         if (server->secmech.hmacmd5)
                 crypto_free_shash(server->secmech.hmacmd5);
 
+        kfree(server->secmech.sdeschmacsha256);
+
         kfree(server->secmech.sdeschmacmd5);
 
         kfree(server->secmech.sdescmd5);
@@ -716,6 +721,13 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
                 goto crypto_allocate_md5_fail;
         }
 
+        server->secmech.hmacsha256 = crypto_alloc_shash("hmac(sha256)", 0, 0);
+        if (IS_ERR(server->secmech.hmacsha256)) {
+                cERROR(1, "could not allocate crypto hmacsha256\n");
+                rc = PTR_ERR(server->secmech.hmacsha256);
+                goto crypto_allocate_hmacsha256_fail;
+        }
+
         size = sizeof(struct shash_desc) +
                         crypto_shash_descsize(server->secmech.hmacmd5);
         server->secmech.sdeschmacmd5 = kmalloc(size, GFP_KERNEL);
@@ -727,7 +739,6 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
         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);
@@ -739,12 +750,29 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
         server->secmech.sdescmd5->shash.tfm = server->secmech.md5;
         server->secmech.sdescmd5->shash.flags = 0x0;
 
+        size = sizeof(struct shash_desc) +
+                        crypto_shash_descsize(server->secmech.hmacsha256);
+        server->secmech.sdeschmacsha256 = kmalloc(size, GFP_KERNEL);
+        if (!server->secmech.sdeschmacsha256) {
+                cERROR(1, "%s: Can't alloc hmacsha256\n", __func__);
+                rc = -ENOMEM;
+                goto crypto_allocate_hmacsha256_sdesc_fail;
+        }
+        server->secmech.sdeschmacsha256->shash.tfm = server->secmech.hmacsha256;
+        server->secmech.sdeschmacsha256->shash.flags = 0x0;
+
         return 0;
 
+crypto_allocate_hmacsha256_sdesc_fail:
+        kfree(server->secmech.sdescmd5);
+
 crypto_allocate_md5_sdesc_fail:
         kfree(server->secmech.sdeschmacmd5);
 
 crypto_allocate_hmacmd5_sdesc_fail:
+        crypto_free_shash(server->secmech.hmacsha256);
+
+crypto_allocate_hmacsha256_fail:
         crypto_free_shash(server->secmech.md5);
 
 crypto_allocate_md5_fail:
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 48c7c83a7a99..6217df707909 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -128,8 +128,10 @@ struct sdesc {
 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 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 */
 };
 
 /* per smb session structure/fields */
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index f20d0c8ee7ce..541738fcaebc 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -65,6 +65,7 @@ extern char *cifs_compose_mount_options(const char *sb_mountdata,
 extern struct mid_q_entry *AllocMidQEntry(const struct smb_hdr *smb_buffer,
                                         struct TCP_Server_Info *server);
 extern void DeleteMidQEntry(struct mid_q_entry *midEntry);
+extern void cifs_delete_mid(struct mid_q_entry *mid);
 extern void cifs_wake_up_task(struct mid_q_entry *mid);
 extern int cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
                            unsigned int nvec, mid_receive_t *receive,
diff --git a/fs/cifs/smb2glob.h b/fs/cifs/smb2glob.h
index 11505d73ff32..8635574ea8b6 100644
--- a/fs/cifs/smb2glob.h
+++ b/fs/cifs/smb2glob.h
@@ -47,4 +47,8 @@
 #define END_OF_CHAIN 4
 #define RELATED_REQUEST 8
 
+#define SMB2_SIGNATURE_SIZE (16)
+#define SMB2_NTLMV2_SESSKEY_SIZE (16)
+#define SMB2_HMACSHA256_SIZE (32)
+
 #endif  /* _SMB2_GLOB_H */
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 00dc45a7881c..30c92c847fe8 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -118,9 +118,9 @@ smb2_hdr_assemble(struct smb2_hdr *hdr, __le16 smb2_cmd /* command */ ,
         /* BB how does SMB2 do case sensitive? */
         /* if (tcon->nocase)
                 hdr->Flags |= SMBFLG_CASELESS; */
-        /* if (tcon->ses && tcon->ses->server &&
+        if (tcon->ses && tcon->ses->server &&
             (tcon->ses->server->sec_mode & SECMODE_SIGN_REQUIRED))
-                hdr->Flags |= SMB2_FLAGS_SIGNED; */
+                hdr->Flags |= SMB2_FLAGS_SIGNED;
 out:
         pdu->StructureSize2 = cpu_to_le16(parmsize);
         return;
@@ -441,6 +441,38 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
                 rc = -EIO;
                 goto neg_exit;
         }
+
+        cFYI(1, "sec_flags 0x%x", sec_flags);
+        if (sec_flags & CIFSSEC_MUST_SIGN) {
+                cFYI(1, "Signing required");
+                if (!(server->sec_mode & (SMB2_NEGOTIATE_SIGNING_REQUIRED |
+                      SMB2_NEGOTIATE_SIGNING_ENABLED))) {
+                        cERROR(1, "signing required but server lacks support");
+                        rc = -EOPNOTSUPP;
+                        goto neg_exit;
+                }
+                server->sec_mode |= SECMODE_SIGN_REQUIRED;
+        } else if (sec_flags & CIFSSEC_MAY_SIGN) {
+                cFYI(1, "Signing optional");
+                if (server->sec_mode & SMB2_NEGOTIATE_SIGNING_REQUIRED) {
+                        cFYI(1, "Server requires signing");
+                        server->sec_mode |= SECMODE_SIGN_REQUIRED;
+                } else {
+                        server->sec_mode &=
+                                ~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
+                }
+        } else {
+                cFYI(1, "Signing disabled");
+                if (server->sec_mode & SMB2_NEGOTIATE_SIGNING_REQUIRED) {
+                        cERROR(1, "Server requires packet signing to be enabled"
+                                  " in /proc/fs/cifs/SecurityFlags.");
+                        rc = -EOPNOTSUPP;
+                        goto neg_exit;
+                }
+                server->sec_mode &=
+                        ~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
+        }
+
 #ifdef CONFIG_SMB2_ASN1  /* BB REMOVEME when updated asn1.c ready */
         rc = decode_neg_token_init(security_blob, blob_length,
                                    &server->sec_type);
@@ -669,6 +701,8 @@ SMB2_logoff(const unsigned int xid, struct cifs_ses *ses)
 
          /* since no tcon, smb2_init can not do this, so do here */
         req->hdr.SessionId = ses->Suid;
+        if (server->sec_mode & SECMODE_SIGN_REQUIRED)
+                req->hdr.Flags |= SMB2_FLAGS_SIGNED;
 
         rc = SendReceiveNoRsp(xid, ses, (char *) &req->hdr, 0);
         /*
@@ -1268,10 +1302,16 @@ smb2_readv_callback(struct mid_q_entry *mid)
         case MID_RESPONSE_RECEIVED:
                 credits_received = le16_to_cpu(buf->CreditRequest);
                 /* result already set, check signature */
-                /* if (server->sec_mode &
-                    (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED))
-                        if (smb2_verify_signature(mid->resp_buf, server))
-                                cERROR(1, "Unexpected SMB signature"); */
+                if (server->sec_mode &
+                    (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED)) {
+                        int rc;
+
+                        rc = smb2_verify_signature2(rdata->iov, rdata->nr_iov,
+                                                    server);
+                        if (rc)
+                                cERROR(1, "SMB signature verification returned "
+                                       "error = %d", rc);
+                }
                 /* FIXME: should this be counted toward the initiating task? */
                 task_io_account_read(rdata->bytes);
                 cifs_stats_bytes_read(tcon, rdata->bytes);
diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
index 192d0c7d91eb..dbbdc39fa209 100644
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -39,6 +39,8 @@ extern char *smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *hdr);
 extern __le16 *cifs_convert_path_to_utf16(const char *from,
                                           struct cifs_sb_info *cifs_sb);
 
+extern int smb2_verify_signature2(struct kvec *, unsigned int,
+                                  struct TCP_Server_Info *);
 extern int smb2_check_receive(struct mid_q_entry *mid,
                               struct TCP_Server_Info *server, bool log_error);
 extern int smb2_setup_request(struct cifs_ses *ses, struct kvec *iov,
diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index 31f5d420b3ea..66479f252ae5 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -36,6 +36,149 @@
 #include "smb2proto.h"
 #include "cifs_debug.h"
 #include "smb2status.h"
+#include "smb2glob.h"
+
+static int
+smb2_calc_signature2(const struct kvec *iov, int n_vec,
+                     struct TCP_Server_Info *server)
+{
+        int i, rc;
+        unsigned char smb2_signature[SMB2_HMACSHA256_SIZE];
+        unsigned char *sigptr = smb2_signature;
+        struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)iov[0].iov_base;
+
+        memset(smb2_signature, 0x0, SMB2_HMACSHA256_SIZE);
+        memset(smb2_pdu->Signature, 0x0, SMB2_SIGNATURE_SIZE);
+
+        rc = crypto_shash_setkey(server->secmech.hmacsha256,
+                server->session_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
+        if (rc) {
+                cERROR(1, "%s: Could not update with response\n", __func__);
+                return rc;
+        }
+
+        rc = crypto_shash_init(&server->secmech.sdeschmacsha256->shash);
+        if (rc) {
+                cERROR(1, "%s: Could not init md5\n", __func__);
+                return rc;
+        }
+
+        for (i = 0; i < n_vec; i++) {
+                if (iov[i].iov_len == 0)
+                        continue;
+                if (iov[i].iov_base == NULL) {
+                        cERROR(1, "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.sdeschmacsha256->shash,
+                                iov[i].iov_base + 4, iov[i].iov_len - 4);
+                } else {
+                        rc =
+                        crypto_shash_update(
+                                &server->secmech.sdeschmacsha256->shash,
+                                iov[i].iov_base, iov[i].iov_len);
+                }
+                if (rc) {
+                        cERROR(1, "%s: Could not update with payload\n",
+                                                        __func__);
+                        return rc;
+                }
+        }
+
+        rc = crypto_shash_final(&server->secmech.sdeschmacsha256->shash,
+                                sigptr);
+        if (rc)
+                cERROR(1, "%s: Could not generate sha256 hash\n", __func__);
+
+        memcpy(smb2_pdu->Signature, sigptr, SMB2_SIGNATURE_SIZE);
+
+        return rc;
+}
+
+/* must be called with server->srv_mutex held */
+static int
+smb2_sign_smb2(struct kvec *iov, int n_vec, struct TCP_Server_Info *server)
+{
+        int rc = 0;
+        struct smb2_hdr *smb2_pdu = iov[0].iov_base;
+
+        if (!(smb2_pdu->Flags & SMB2_FLAGS_SIGNED) ||
+            server->tcpStatus == CifsNeedNegotiate)
+                return rc;
+
+        if (!server->session_estab) {
+                strncpy(smb2_pdu->Signature, "BSRSPYL", 8);
+                return rc;
+        }
+
+        rc = smb2_calc_signature2(iov, n_vec, server);
+
+        return rc;
+}
+
+int
+smb2_verify_signature2(struct kvec *iov, unsigned int n_vec,
+                       struct TCP_Server_Info *server)
+{
+        unsigned int rc;
+        char server_response_sig[16];
+        struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)iov[0].iov_base;
+
+        if ((smb2_pdu->Command == SMB2_NEGOTIATE) ||
+            (smb2_pdu->Command == SMB2_OPLOCK_BREAK) ||
+            (!server->session_estab))
+                return 0;
+
+        /*
+         * BB what if signatures are supposed to be on for session but
+         * server does not send one? BB
+         */
+
+        /* Do not need to verify session setups with signature "BSRSPYL " */
+        if (memcmp(smb2_pdu->Signature, "BSRSPYL ", 8) == 0)
+                cFYI(1, "dummy signature received for smb command 0x%x",
+                        smb2_pdu->Command);
+
+        /*
+         * Save off the origiginal signature so we can modify the smb and check
+         * our calculated signature against what the server sent.
+         */
+        memcpy(server_response_sig, smb2_pdu->Signature, SMB2_SIGNATURE_SIZE);
+
+        memset(smb2_pdu->Signature, 0, SMB2_SIGNATURE_SIZE);
+
+        mutex_lock(&server->srv_mutex);
+        rc = smb2_calc_signature2(iov, n_vec, server);
+        mutex_unlock(&server->srv_mutex);
+
+        if (rc)
+                return rc;
+
+        if (memcmp(server_response_sig, smb2_pdu->Signature,
+                   SMB2_SIGNATURE_SIZE))
+                return -EACCES;
+        else
+                return 0;
+}
+
+static int
+smb2_verify_signature(struct smb2_hdr *smb2_pdu, struct TCP_Server_Info *server)
+{
+        struct kvec iov;
+
+        iov.iov_base = (char *)smb2_pdu;
+        iov.iov_len = get_rfc1002_length(smb2_pdu) + 4;
+        return smb2_verify_signature2(&iov, 1, server);
+}
 
 /*
  * Set message id for the request. Should be called after wait_for_free_request
@@ -118,12 +261,15 @@ smb2_check_receive(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 
         dump_smb(mid->resp_buf, min_t(u32, 80, len));
         /* convert the length into a more usable form */
-        /* BB - uncomment with SMB2 signing implementation */
-        /* if ((len > 24) &&
+        if ((len > 24) &&
             (server->sec_mode & (SECMODE_SIGN_REQUIRED|SECMODE_SIGN_ENABLED))) {
-                if (smb2_verify_signature(mid->resp_buf, server))
-                        cERROR(1, "Unexpected SMB signature");
-        } */
+                int rc;
+
+                rc = smb2_verify_signature(mid->resp_buf, server);
+                if (rc)
+                        cERROR(1, "SMB signature verification returned error = "
+                               "%d", rc);
+        }
 
         return map_smb2_to_linux_error(mid->resp_buf, log_error);
 }
@@ -141,9 +287,9 @@ smb2_setup_request(struct cifs_ses *ses, struct kvec *iov,
         rc = smb2_get_mid_entry(ses, hdr, &mid);
         if (rc)
                 return rc;
-        /* rc = smb2_sign_smb2(iov, nvec, ses->server);
+        rc = smb2_sign_smb2(iov, nvec, ses->server);
         if (rc)
-                delete_mid(mid); */
+                cifs_delete_mid(mid);
         *ret_mid = mid;
         return rc;
 }
@@ -162,11 +308,12 @@ smb2_setup_async_request(struct TCP_Server_Info *server, struct kvec *iov,
         if (mid == NULL)
                 return -ENOMEM;
 
-        /* rc = smb2_sign_smb2(iov, nvec, server);
+        rc = smb2_sign_smb2(iov, nvec, server);
         if (rc) {
                 DeleteMidQEntry(mid);
                 return rc;
-        }*/
+        }
+
         *ret_mid = mid;
         return rc;
 }
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index d9b639b95fa8..c4d7825dfc0a 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -109,8 +109,8 @@ DeleteMidQEntry(struct mid_q_entry *midEntry)
         mempool_free(midEntry, cifs_mid_poolp);
 }
 
-static void
-delete_mid(struct mid_q_entry *mid)
+void
+cifs_delete_mid(struct mid_q_entry *mid)
 {
         spin_lock(&GlobalMid_Lock);
         list_del(&mid->qhead);
@@ -419,7 +419,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
         if (rc == 0)
                 return 0;
 
-        delete_mid(mid);
+        cifs_delete_mid(mid);
         add_credits(server, 1, optype);
         wake_up(&server->request_q);
         return rc;
@@ -532,7 +532,7 @@ cifs_setup_request(struct cifs_ses *ses, struct kvec *iov,
                 return rc;
         rc = cifs_sign_smbv(iov, nvec, ses->server, &mid->sequence_number);
         if (rc)
-                delete_mid(mid);
+                cifs_delete_mid(mid);
         *ret_mid = mid;
         return rc;
 }
@@ -652,11 +652,11 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
         rc = ses->server->ops->check_receive(midQ, ses->server,
                                              flags & CIFS_LOG_ERROR);
 
-        /* mark it so buf will not be freed by delete_mid */
+        /* mark it so buf will not be freed by cifs_delete_mid */
         if ((flags & CIFS_NO_RESP) == 0)
                 midQ->resp_buf = NULL;
 out:
-        delete_mid(midQ);
+        cifs_delete_mid(midQ);
         add_credits(ses->server, credits, optype);
 
         return rc;
@@ -762,7 +762,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
         memcpy(out_buf, midQ->resp_buf, *pbytes_returned + 4);
         rc = cifs_check_receive(midQ, ses->server, 0);
 out:
-        delete_mid(midQ);
+        cifs_delete_mid(midQ);
         add_credits(ses->server, 1, 0);
 
         return rc;
@@ -846,7 +846,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
 
         rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
         if (rc) {
-                delete_mid(midQ);
+                cifs_delete_mid(midQ);
                 mutex_unlock(&ses->server->srv_mutex);
                 return rc;
         }
@@ -859,7 +859,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
         mutex_unlock(&ses->server->srv_mutex);
 
         if (rc < 0) {
-                delete_mid(midQ);
+                cifs_delete_mid(midQ);
                 return rc;
         }
 
@@ -880,7 +880,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
                            blocking lock to return. */
                         rc = send_cancel(ses->server, in_buf, midQ);
                         if (rc) {
-                                delete_mid(midQ);
+                                cifs_delete_mid(midQ);
                                 return rc;
                         }
                 } else {
@@ -892,7 +892,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
                         /* If we get -ENOLCK back the lock may have
                            already been removed. Don't exit in this case. */
                         if (rc && rc != -ENOLCK) {
-                                delete_mid(midQ);
+                                cifs_delete_mid(midQ);
                                 return rc;
                         }
                 }
@@ -929,7 +929,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
         memcpy(out_buf, midQ->resp_buf, *pbytes_returned + 4);
         rc = cifs_check_receive(midQ, ses->server, 0);
 out:
-        delete_mid(midQ);
+        cifs_delete_mid(midQ);
         if (rstart && rc == -EACCES)
                 return -ERESTARTSYS;
         return rc;