cifs: Use data structures to compute NTLMv2 response offsets

A bit of cleanup plus some gratuitous variable renaming. I think using
structures instead of numeric offsets makes this code much more
understandable.

Also added a comment about current time range expected by
the server.

Acked-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Steve French <smfrench@gmail.com>

2 files changed, 31 insertions, 17 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index fc6f4f3a1a9d..4934347321d3 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -548,7 +548,13 @@ static int
 CalcNTLMv2_response(const struct cifs_ses *ses, char *ntlmv2_hash)
 {
         int rc;
-        unsigned int offset = CIFS_SESS_KEY_SIZE + 8;
+        struct ntlmv2_resp *ntlmv2 = (struct ntlmv2_resp *)
+            (ses->auth_key.response + CIFS_SESS_KEY_SIZE);
+        unsigned int hash_len;
+
+        /* The MD5 hash starts at challenge_key.key */
+        hash_len = ses->auth_key.len - (CIFS_SESS_KEY_SIZE +
+                offsetof(struct ntlmv2_resp, challenge.key[0]));
 
         if (!ses->server->secmech.sdeschmacmd5) {
                 cifs_dbg(VFS, "%s: can't generate ntlmv2 hash\n", __func__);
@@ -556,7 +562,7 @@ CalcNTLMv2_response(const struct cifs_ses *ses, char *ntlmv2_hash)
         }
 
         rc = crypto_shash_setkey(ses->server->secmech.hmacmd5,
-                                ntlmv2_hash, CIFS_HMAC_MD5_HASH_SIZE);
+                                 ntlmv2_hash, CIFS_HMAC_MD5_HASH_SIZE);
         if (rc) {
                 cifs_dbg(VFS, "%s: Could not set NTLMV2 Hash as a key\n",
                          __func__);
@@ -570,20 +576,21 @@ CalcNTLMv2_response(const struct cifs_ses *ses, char *ntlmv2_hash)
         }
 
         if (ses->server->negflavor == CIFS_NEGFLAVOR_EXTENDED)
-                memcpy(ses->auth_key.response + offset,
-                        ses->ntlmssp->cryptkey, CIFS_SERVER_CHALLENGE_SIZE);
+                memcpy(ntlmv2->challenge.key,
+                       ses->ntlmssp->cryptkey, CIFS_SERVER_CHALLENGE_SIZE);
         else
-                memcpy(ses->auth_key.response + offset,
-                        ses->server->cryptkey, CIFS_SERVER_CHALLENGE_SIZE);
+                memcpy(ntlmv2->challenge.key,
+                       ses->server->cryptkey, CIFS_SERVER_CHALLENGE_SIZE);
         rc = crypto_shash_update(&ses->server->secmech.sdeschmacmd5->shash,
-                ses->auth_key.response + offset, ses->auth_key.len - offset);
+                                 ntlmv2->challenge.key, hash_len);
         if (rc) {
                 cifs_dbg(VFS, "%s: Could not update with response\n", __func__);
                 return rc;
         }
 
+        /* Note that the MD5 digest over writes anon.challenge_key.key */
         rc = crypto_shash_final(&ses->server->secmech.sdeschmacmd5->shash,
-                ses->auth_key.response + CIFS_SESS_KEY_SIZE);
+                                ntlmv2->ntlmv2_hash);
         if (rc)
                 cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);
 
@@ -627,7 +634,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
         int rc;
         int baselen;
         unsigned int tilen;
-        struct ntlmv2_resp *buf;
+        struct ntlmv2_resp *ntlmv2;
         char ntlmv2_hash[16];
         unsigned char *tiblob = NULL; /* target info blob */
 
@@ -660,13 +667,14 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
         }
         ses->auth_key.len += baselen;
 
-        buf = (struct ntlmv2_resp *)
+        ntlmv2 = (struct ntlmv2_resp *)
                         (ses->auth_key.response + CIFS_SESS_KEY_SIZE);
-        buf->blob_signature = cpu_to_le32(0x00000101);
-        buf->reserved = 0;
-        buf->time = cpu_to_le64(cifs_UnixTimeToNT(CURRENT_TIME));
-        get_random_bytes(&buf->client_chal, sizeof(buf->client_chal));
-        buf->reserved2 = 0;
+        ntlmv2->blob_signature = cpu_to_le32(0x00000101);
+        ntlmv2->reserved = 0;
+        /* Must be within 5 minutes of the server */
+        ntlmv2->time = cpu_to_le64(cifs_UnixTimeToNT(CURRENT_TIME));
+        get_random_bytes(&ntlmv2->client_chal, sizeof(ntlmv2->client_chal));
+        ntlmv2->reserved2 = 0;
 
         memcpy(ses->auth_key.response + baselen, tiblob, tilen);
 
@@ -706,7 +714,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
         }
 
         rc = crypto_shash_update(&ses->server->secmech.sdeschmacmd5->shash,
-                ses->auth_key.response + CIFS_SESS_KEY_SIZE,
+                ntlmv2->ntlmv2_hash,
                 CIFS_HMAC_MD5_HASH_SIZE);
         if (rc) {
                 cifs_dbg(VFS, "%s: Could not update with response\n", __func__);
diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index 9e5ee34de986..33df36ef9d52 100644
--- a/fs/cifs/cifspdu.h
+++ b/fs/cifs/cifspdu.h
@@ -697,7 +697,13 @@ struct ntlmssp2_name {
 } __attribute__((packed));
 
 struct ntlmv2_resp {
-        char ntlmv2_hash[CIFS_ENCPWD_SIZE];
+        union {
+            char ntlmv2_hash[CIFS_ENCPWD_SIZE];
+            struct {
+                __u8 reserved[8];
+                __u8 key[CIFS_SERVER_CHALLENGE_SIZE];
+            } __attribute__((packed)) challenge;
+        } __attribute__((packed));
         __le32 blob_signature;
         __u32  reserved;
         __le64  time;