ntlm: fix negotiated flags usage

According to Microsoft document MS-NLMP, current flags usage is not
accurate: flag NTLMFLAG_NEGOTIATE_NTLM2_KEY controls the use of
extended security in an NTLM authentication message and NTLM version 2
cannot be negotiated within the protocol.

The solution implemented here is: if the extended security flag is set,
prefer using NTLM version 2 (as a server featuring extended security
should also support version 2). If version 2 has been disabled at
compile time, use extended security.

Tests involving NTLM are adjusted to this new behavior.

Fixes #6813
Closes #6849

1 files changed, 19 insertions, 13 deletions

diff --git a/lib/vauth/ntlm.c b/lib/vauth/ntlm.c
index 5831c5662..4adf49704 100644
--- a/lib/vauth/ntlm.c
+++ b/lib/vauth/ntlm.c
@@ -403,7 +403,8 @@ CURLcode Curl_auth_create_ntlm_type1_message(struct Curl_easy *data,
   /* Clean up any former leftovers and initialise to defaults */
   Curl_auth_cleanup_ntlm(ntlm);
 
-#if defined(USE_NTRESPONSES) && defined(USE_NTLM2SESSION)
+#if defined(USE_NTRESPONSES) && \
+    (defined(USE_NTLM2SESSION) || defined(USE_NTLM_V2))
 #define NTLM2FLAG NTLMFLAG_NEGOTIATE_NTLM2_KEY
 #else
 #define NTLM2FLAG 0
@@ -559,12 +560,20 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
     hostlen = strlen(host);
   }
 
-#if defined(USE_NTRESPONSES) && defined(USE_NTLM_V2)
+#if defined(USE_NTRESPONSES) && \
+    (defined(USE_NTLM2SESSION) || defined(USE_NTLM_V2))
+  /* We don't support NTLM2 or extended security if we don't have
+     USE_NTRESPONSES */
   if(ntlm->flags & NTLMFLAG_NEGOTIATE_NTLM2_KEY) {
+# if defined(USE_NTLM_V2)
     unsigned char ntbuffer[0x18];
     unsigned char entropy[8];
     unsigned char ntlmv2hash[0x18];
 
+    /* Full NTLM version 2
+       Although this cannot be negotiated, it is used here if available, as
+       servers featuring extended security are likely supporting also
+       NTLMv2. */
     result = Curl_rand(data, entropy, 8);
     if(result)
       return result;
@@ -591,21 +600,14 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
       return result;
 
     ptr_ntresp = ntlmv2resp;
-  }
-  else
-#endif
-
-#if defined(USE_NTRESPONSES) && defined(USE_NTLM2SESSION)
-
-#define CURL_MD5_DIGEST_LENGTH 16 /* fixed size */
-
-  /* We don't support NTLM2 if we don't have USE_NTRESPONSES */
-  if(ntlm->flags & NTLMFLAG_NEGOTIATE_NTLM_KEY) {
+# else /* defined(USE_NTLM_V2) */
     unsigned char ntbuffer[0x18];
     unsigned char tmp[0x18];
-    unsigned char md5sum[CURL_MD5_DIGEST_LENGTH];
+    unsigned char md5sum[MD5_DIGEST_LEN];
     unsigned char entropy[8];
 
+    /* NTLM version 1 with extended security. */
+
     /* Need to create 8 bytes random data */
     result = Curl_rand(data, entropy, 8);
     if(result)
@@ -635,6 +637,7 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
     /* NTLM v2 session security is a misnomer because it is not NTLM v2.
        It is NTLM v1 using the extended session security that is also
        in NTLM v2 */
+# endif /* defined(USE_NTLM_V2) */
   }
   else
 #endif
@@ -645,6 +648,8 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
 #endif
     unsigned char lmbuffer[0x18];
 
+    /* NTLM version 1 */
+
 #ifdef USE_NTRESPONSES
     result = Curl_ntlm_core_mk_nt_hash(data, passwdp, ntbuffer);
     if(result)
@@ -658,6 +663,7 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
       return result;
 
     Curl_ntlm_core_lm_resp(lmbuffer, &ntlm->nonce[0], lmresp);
+    ntlm->flags &= ~NTLMFLAG_NEGOTIATE_NTLM2_KEY;
 
     /* A safer but less compatible alternative is:
      *   Curl_ntlm_core_lm_resp(ntbuffer, &ntlm->nonce[0], lmresp);