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>

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index fc6f4f3..4934347 100644 (file)
--- 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 9e5ee34..33df36e 100644 (file)
--- 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;