Merge pull request git-for-windows#57 from rglidden/main

msys2-runtime: restore fast path for current user primary group

winsup/cygwin/include/sys/cygwin.h

@@ -219,7 +219,8 @@ enum
 enum
 {
   NSS_SRC_FILES = 1,
-  NSS_SRC_DB = 2
+  NSS_SRC_DB = 2,
+  NSS_SRC_DB_ACCURATE = 4
 };
 
 /* Enumeration source constants for CW_SETENT called from mkpasswd/mkgroup. */

winsup/cygwin/local_includes/cygheap.h

@@ -454,6 +454,7 @@ class cygheap_pwdgrp
   inline int  nss_pwd_src () const { return pwd_src; } /* CW_GETNSS_PWD_SRC */
   inline bool nss_grp_files () const { return !!(grp_src & NSS_SRC_FILES); }
   inline bool nss_grp_db () const { return !!(grp_src & NSS_SRC_DB); }
+  inline bool nss_grp_db_accurate () const { return !!(grp_src & NSS_SRC_DB_ACCURATE); }
   inline int  nss_grp_src () const { return grp_src; } /* CW_GETNSS_GRP_SRC */
   inline bool nss_cygserver_caching () const { return caching; }
   inline void nss_disable_cygserver_caching () { caching = false; }

winsup/cygwin/uinfo.cc

@@ -637,6 +637,11 @@ cygheap_pwdgrp::nss_init_line (const char *line)
 		    *src |= NSS_SRC_DB;
 		    c += 2;
 		  }
+		else if (NSS_CMP ("db-accurate"))
+		  {
+		    *src |= NSS_SRC_DB | NSS_SRC_DB_ACCURATE;
+		    c += 11;
+		  }
 		else
 		  {
 		    c += strcspn (c, " \t");
@@ -1906,6 +1911,7 @@ pwdgrp::fetch_account_from_windows (fetch_user_arg_t &arg, cyg_ldap *pldap)
   gid_t gid = ILLEGAL_GID;
   bool is_domain_account = true;
   PCWSTR domain = NULL;
+  bool get_default_group_from_current_user_token = false;
   char *shell = NULL;
   char *home = NULL;
   char *gecos = NULL;
@@ -2371,9 +2377,19 @@ pwdgrp::fetch_account_from_windows (fetch_user_arg_t &arg, cyg_ldap *pldap)
 	    uid = posix_offset + sid_sub_auth_rid (sid);
 	  if (!is_group () && acc_type == SidTypeUser)
 	    {
-	      /* Default primary group.  Make the educated guess that the user
-		 is in group "Domain Users" or "None". */
-	      gid = posix_offset + DOMAIN_GROUP_RID_USERS;
+	      /* Default primary group.  If the sid is the current user, and
+		 we are not configured for accurate mode, fetch
+		 the default group from the current user token, otherwise make
+		 the educated guess that the user is in group "Domain Users"
+		 or "None". */
+	      if (!cygheap->pg.nss_grp_db_accurate() && sid == cygheap->user.sid ())
+		{
+		  get_default_group_from_current_user_token = true;
+		  gid = posix_offset
+			+ sid_sub_auth_rid (cygheap->user.groups.pgsid);
+		}
+	      else
+		gid = posix_offset + DOMAIN_GROUP_RID_USERS;
 	    }
 
 	  if (is_domain_account)
@@ -2384,9 +2400,11 @@ pwdgrp::fetch_account_from_windows (fetch_user_arg_t &arg, cyg_ldap *pldap)
 	      /* On AD machines, use LDAP to fetch domain account infos. */
 	      if (cygheap->dom.primary_dns_name ())
 		{
-		  /* Fetch primary group from AD and overwrite the one we
-		     just guessed above. */
-		  if (cldap->fetch_ad_account (sid, false, domain))
+		  /* For the current user we got correctly cased username and
+		     the primary group via process token.  For any other user
+		     we fetch it from AD and overwrite it. */
+		  if (!get_default_group_from_current_user_token
+		      && cldap->fetch_ad_account (sid, false, domain))
 		    {
 		      if ((val = cldap->get_account_name ()))
 			wcscpy (name, val);

winsup/doc/ntsec.xml

@@ -930,7 +930,16 @@ The two lines starting with the keywords <literal>passwd:</literal> and
 information from.  <literal>files</literal> means, fetch the information
 from the corresponding file in the /etc directory.  <literal>db</literal>
 means, fetch the information from the Windows account databases, the SAM
-for local accounts, Active Directory for domain account.  Examples:
+for local accounts, Active Directory for domain account.  For the current
+user, the default group is obtained from the current user token to avoid
+additional lookups to the group database. <literal>db-accurate</literal>
+is only valid on <literal>group:</literal> line, and performs the same 
+lookups as the <literal>db</literal> option, but disables using the
+current user token to retrieve the default group as this optimization
+is not accurate in all cases.  For example, if you run a native process
+with the primary group set to the Administrators builtin group, the 
+<literal>db</literal> option will return a non-existent group as primary
+group. Examples:
 </para>
 
 <screen>
@@ -949,6 +958,15 @@ Read passwd entries only from /etc/passwd.
 Read group entries only from SAM/AD.
 </para>
 
+<screen>
+  group: db-accurate
+</screen>
+
+<para>
+Read group entries only from SAM/AD. Force the use of the group database
+for the current user.
+</para>
+
 <screen>
   group: files # db
 </screen>