Use of a structure aids in the understanding of this
seemingly simple bit of code. The addition of a couple
of comments also helps.
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: Steve French <sfrench@xxxxxxxxx>
Signed-off-by: Tim Gardner <timg@xxxxxxx>
---
I'd just like to be sure that the destructive copy is
really what was intended. I can't tell from reading the MSDN
section 3.3.2 NTLM v2 Authentication. It sort of makes
my head hurt.
rtg
fs/cifs/cifsencrypt.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index fc6f4f3..fecbfd0 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -548,7 +548,9 @@ 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 *resp = (struct ntlmv2_resp *)
+ (ses->auth_key.response + CIFS_SESS_KEY_SIZE);
+ unsigned int hashed_len = ses->auth_key.len - (CIFS_SESS_KEY_SIZE + 8);
if (!ses->server->secmech.sdeschmacmd5) {
cifs_dbg(VFS, "%s: can't generate ntlmv2 hash\n", __func__);
@@ -569,21 +571,30 @@ CalcNTLMv2_response(const struct cifs_ses *ses, char *ntlmv2_hash)
return rc;
}
+ /*
+ * The cryptkey is part of the buffer that feeds the MD5 hash, but
+ * gets over written later by the digest. See crypto_shash_final()
+ * below.
+ */
if (ses->server->negflavor == CIFS_NEGFLAVOR_EXTENDED)
- memcpy(ses->auth_key.response + offset,
+ memcpy(&resp->ntlmv2_hash[CIFS_SERVER_CHALLENGE_SIZE],
ses->ntlmssp->cryptkey, CIFS_SERVER_CHALLENGE_SIZE);
else
- memcpy(ses->auth_key.response + offset,
+ memcpy(&resp->ntlmv2_hash[CIFS_SERVER_CHALLENGE_SIZE],
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);
+ &resp->ntlmv2_hash[8], hashed_len);
if (rc) {
cifs_dbg(VFS, "%s: Could not update with response\n", __func__);
return rc;
}
+ /*
+ * Yes - this is destructive. The 16 byte MD5 digest clobbers the
+ * cryptkey that was just copied into &resp->ntlmv2_hash[8].
+ */
rc = crypto_shash_final(&ses->server->secmech.sdeschmacmd5->shash,
- ses->auth_key.response + CIFS_SESS_KEY_SIZE);
+ resp->ntlmv2_hash);
if (rc)
cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);
--
1.7.9.5
--
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