vauth: Added check for supported SSPI based authentication mechanisms

Completing commit 00417fd66c and 2708d4259b.

lib/vauth/digest_sspi.c

@@ -54,9 +54,14 @@
 */
 bool Curl_auth_is_digest_supported(void)
 {
-  /* TODO: Return true for now which maintains compatability with the existing
-     code */
-  return TRUE;
+  PSecPkgInfo SecurityPackage;
+  SECURITY_STATUS status;
+
+  /* Query the security package for Digest */
+  status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_DIGEST),
+                                              &SecurityPackage);
+
+  return (status == SEC_E_OK ? TRUE : FALSE);
 }
 
 /*

lib/vauth/krb5_sspi.c

@@ -50,9 +50,15 @@
  */
 bool Curl_auth_is_gssapi_supported(void)
 {
-  /* TODO: Return true for now which maintains compatability with the existing
-     code */
-  return TRUE;
+  PSecPkgInfo SecurityPackage;
+  SECURITY_STATUS status;
+
+  /* Query the security package for Kerberos */
+  status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *)
+                                              TEXT(SP_NAME_KERBEROS),
+                                              &SecurityPackage);
+
+  return (status == SEC_E_OK ? TRUE : FALSE);
 }
 
 /*

lib/vauth/ntlm_sspi.c

@@ -48,9 +48,14 @@
  */
 bool Curl_auth_is_ntlm_supported(void)
 {
-  /* TODO: Return true for now which maintains compatability with the existing
-     code */
-  return TRUE;
+  PSecPkgInfo SecurityPackage;
+  SECURITY_STATUS status;
+
+  /* Query the security package for NTLM */
+  status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_NTLM),
+                                              &SecurityPackage);
+
+  return (status == SEC_E_OK ? TRUE : FALSE);
 }
 
 /*

lib/vauth/spnego_sspi.c

@@ -50,9 +50,15 @@
  */
 bool Curl_auth_is_spnego_supported(void)
 {
-  /* TODO: Return true for now which maintains compatability with the existing
-     code */
-  return TRUE;
+  PSecPkgInfo SecurityPackage;
+  SECURITY_STATUS status;
+
+  /* Query the security package for Negotiate */
+  status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *)
+                                              TEXT(SP_NAME_NEGOTIATE),
+                                              &SecurityPackage);
+
+  return (status == SEC_E_OK ? TRUE : FALSE);
 }
 
 /*