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From: Johannes Schindelin <johannes.schindelin@gmx.de>
To: cygwin-patches@cygwin.com
Subject: [PATCH v3 1/3] Allow deriving the current user's home directory via the HOME variable
Date: Wed, 21 Sep 2022 13:51:54 +0200 (CEST)	[thread overview]
Message-ID: <6f8fe89d9d747a752107fc180f31a6709e0de4f2.1663761086.git.johannes.schindelin@gmx.de> (raw)
In-Reply-To: <cover.1663761086.git.johannes.schindelin@gmx.de>

This patch hails from Git for Windows (where the Cygwin runtime is used
in the form of a slightly modified MSYS2 runtime), where it is a
well-established technique to let the `$HOME` variable define where the
current user's home directory is, falling back to `$HOMEDRIVE$HOMEPATH`
and `$USERPROFILE`.

The idea is that we want to share user-specific settings between
programs, whether they be Cygwin, MSYS2 or not.  Unfortunately, we
cannot blindly activate the "db_home: windows" setting because in some
setups, the user's home directory is set to a hidden directory via an
UNC path (\\share\some\hidden\folder$) -- something many programs
cannot handle correctly, e.g. `cmd.exe` and other native Windows
applications that users want to employ as Git helpers.

The established technique is to allow setting the user's home directory
via the environment variables mentioned above: `$HOMEDRIVE$HOMEPATH` or
`$USERPROFILE`.  This has the additional advantage that it is much
faster than querying the Windows user database.

Of course this scheme needs to be opt-in.  For that reason, it needs
to be activated explicitly via `db_home: env` in `/etc/nsswitch.conf`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 winsup/cygwin/local_includes/cygheap.h |  3 ++-
 winsup/cygwin/uinfo.cc                 | 35 ++++++++++++++++++++++++++
 winsup/doc/ntsec.xml                   | 22 ++++++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/local_includes/cygheap.h b/winsup/cygwin/local_includes/cygheap.h
index 6a844babdb..444ca8b55c 100644
--- a/winsup/cygwin/local_includes/cygheap.h
+++ b/winsup/cygwin/local_includes/cygheap.h
@@ -408,7 +408,8 @@ public:
     NSS_SCHEME_UNIX,
     NSS_SCHEME_DESC,
     NSS_SCHEME_PATH,
-    NSS_SCHEME_FREEATTR
+    NSS_SCHEME_FREEATTR,
+    NSS_SCHEME_ENV
   };
   struct nss_scheme_t {
     nss_scheme_method	method;
diff --git a/winsup/cygwin/uinfo.cc b/winsup/cygwin/uinfo.cc
index ce997c0f82..6e673ee39e 100644
--- a/winsup/cygwin/uinfo.cc
+++ b/winsup/cygwin/uinfo.cc
@@ -754,6 +754,8 @@ cygheap_pwdgrp::nss_init_line (const char *line)
 		    scheme[idx].method = NSS_SCHEME_UNIX;
 		  else if (NSS_CMP ("desc"))
 		    scheme[idx].method = NSS_SCHEME_DESC;
+		  else if (NSS_CMP ("env"))
+		    scheme[idx].method = NSS_SCHEME_ENV;
 		  else if (NSS_NCMP ("/"))
 		    {
 		      const char *e = c + strcspn (c, " \t");
@@ -942,6 +944,26 @@ fetch_from_path (cyg_ldap *pldap, PUSER_INFO_3 ui, cygpsid &sid, PCWSTR str,
   return ret;
 }

+static char *
+fetch_home_env (void)
+{
+  tmp_pathbuf tp;
+  char *p, *q;
+  const char *home, *home_drive, *home_path;
+
+  if ((home = getenv ("HOME"))
+      || ((home_drive = getenv ("HOMEDRIVE"))
+	  && (home_path = getenv ("HOMEPATH"))
+	  // concatenate HOMEDRIVE and HOMEPATH
+          && (home = p = tp.c_get ())
+	  && (q = stpncpy (p, home_drive, NT_MAX_PATH))
+          && strlcpy (q, home_path, NT_MAX_PATH - (q - p)))
+      || (home = getenv ("USERPROFILE")))
+    return (char *) cygwin_create_path (CCP_WIN_A_TO_POSIX, home);
+
+  return NULL;
+}
+
 char *
 cygheap_pwdgrp::get_home (cyg_ldap *pldap, cygpsid &sid, PCWSTR dom,
 			  PCWSTR dnsdomain, PCWSTR name, bool full_qualified)
@@ -1001,6 +1023,10 @@ cygheap_pwdgrp::get_home (cyg_ldap *pldap, cygpsid &sid, PCWSTR dom,
 		}
 	    }
 	  break;
+	case NSS_SCHEME_ENV:
+	  if (RtlEqualSid (sid, cygheap->user.sid ()))
+	    home = fetch_home_env ();
+	  break;
 	}
     }
   return home;
@@ -1033,6 +1059,10 @@ cygheap_pwdgrp::get_home (PUSER_INFO_3 ui, cygpsid &sid, PCWSTR dom,
 	  home = fetch_from_path (NULL, ui, sid, home_scheme[idx].attrib,
 				  dom, NULL, name, full_qualified);
 	  break;
+	case NSS_SCHEME_ENV:
+	  if (RtlEqualSid (sid, cygheap->user.sid ()))
+	    home = fetch_home_env ();
+	  break;
 	}
     }
   return home;
@@ -1052,6 +1082,7 @@ cygheap_pwdgrp::get_shell (cyg_ldap *pldap, cygpsid &sid, PCWSTR dom,
 	case NSS_SCHEME_FALLBACK:
 	  return NULL;
 	case NSS_SCHEME_WINDOWS:
+	case NSS_SCHEME_ENV:
 	  break;
 	case NSS_SCHEME_CYGWIN:
 	  if (pldap->fetch_ad_account (sid, false, dnsdomain))
@@ -1116,6 +1147,7 @@ cygheap_pwdgrp::get_shell (PUSER_INFO_3 ui, cygpsid &sid, PCWSTR dom,
 	case NSS_SCHEME_CYGWIN:
 	case NSS_SCHEME_UNIX:
 	case NSS_SCHEME_FREEATTR:
+	case NSS_SCHEME_ENV:
 	  break;
 	case NSS_SCHEME_DESC:
 	  if (ui)
@@ -1197,6 +1229,8 @@ cygheap_pwdgrp::get_gecos (cyg_ldap *pldap, cygpsid &sid, PCWSTR dom,
 		sys_wcstombs_alloc (&gecos, HEAP_NOTHEAP, val);
 	    }
 	  break;
+	case NSS_SCHEME_ENV:
+	  break;
 	}
     }
   if (gecos)
@@ -1223,6 +1257,7 @@ cygheap_pwdgrp::get_gecos (PUSER_INFO_3 ui, cygpsid &sid, PCWSTR dom,
 	case NSS_SCHEME_CYGWIN:
 	case NSS_SCHEME_UNIX:
 	case NSS_SCHEME_FREEATTR:
+	case NSS_SCHEME_ENV:
 	  break;
 	case NSS_SCHEME_DESC:
 	  if (ui)
diff --git a/winsup/doc/ntsec.xml b/winsup/doc/ntsec.xml
index d089964660..c02b1f72e1 100644
--- a/winsup/doc/ntsec.xml
+++ b/winsup/doc/ntsec.xml
@@ -1359,6 +1359,17 @@ schemata are the following:
 	      See <xref linkend="ntsec-mapping-nsswitch-desc"></xref>
 	      for a more detailed description.</listitem>
   </varlistentry>
+  <varlistentry>
+    <term><literal>env</literal></term>
+    <listitem>Derives the home directory of the current user from the
+	      environment variable <literal>HOME</literal> (falling back to
+	      <literal>HOMEDRIVE\HOMEPATH</literal> and
+	      <literal>USERPROFILE</literal>, in that order).  This is faster
+	      than the <term><literal>windows</literal></term> schema at the
+	      expense of determining only the current user's home directory
+	      correctly.  This schema is skipped for any other account.
+	      </listitem>
+  </varlistentry>
 </variablelist>

 <para>
@@ -1491,6 +1502,17 @@ of each schema when used with <literal>db_home:</literal>
 	      See <xref linkend="ntsec-mapping-nsswitch-desc"></xref>
 	      for a detailed description.</listitem>
   </varlistentry>
+  <varlistentry>
+    <term><literal>env</literal></term>
+    <listitem>Derives the home directory of the current user from the
+	      environment variable <literal>HOME</literal> (falling back to
+	      <literal>HOMEDRIVE\HOMEPATH</literal> and
+	      <literal>USERPROFILE</literal>, in that order).  This is faster
+	      than the <term><literal>windows</literal></term> schema at the
+	      expense of determining only the current user's home directory
+	      correctly.  This schema is skipped for any other account.
+	      </listitem>
+  </varlistentry>
   <varlistentry>
     <term><literal>@ad_attribute</literal></term>
     <listitem>AD only: The user's home directory is set to the path given
--
2.38.0.rc0.windows.1



  reply	other threads:[~2022-09-21 11:51 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-16 13:06 [PATCH] Allow overriding the " Johannes Schindelin
2015-10-21 18:32 ` Corinna Vinschen
2015-10-22 15:38   ` Johannes Schindelin
2015-10-23  9:10     ` Corinna Vinschen
2015-10-23  9:41       ` Corinna Vinschen
2015-10-23 12:00         ` Johannes Schindelin
2015-12-17 18:05 ` [PATCH v2 0/2] Support deriving the current user's home directory via HOME Johannes Schindelin
2015-12-17 18:05   ` [PATCH v2 1/2] Allow deriving the current user's home directory via the HOME variable Johannes Schindelin
2015-12-17 20:20     ` Corinna Vinschen
2022-09-21 11:58       ` Johannes Schindelin
2022-10-18 17:02         ` Corinna Vinschen
2022-10-23 21:04           ` Johannes Schindelin
2022-10-24 11:37             ` Corinna Vinschen
2022-11-10 15:16               ` Johannes Schindelin
2022-11-10 15:22                 ` Corinna Vinschen
2022-11-18  8:18                   ` Johannes Schindelin
2022-11-21 11:41                     ` Corinna Vinschen
2023-03-28  8:21                       ` Johannes Schindelin
2015-12-17 18:05   ` [PATCH v2 2/2] Respect `db_home` setting even for the SYSTEM account Johannes Schindelin
2015-12-17 20:49     ` Corinna Vinschen
2015-12-17 21:02       ` Corinna Vinschen
2022-09-21 12:00       ` Johannes Schindelin
2022-09-21 11:51   ` [PATCH v3 0/3] Support deriving the current user's home directory via HOME Johannes Schindelin
2022-09-21 11:51     ` Johannes Schindelin [this message]
2022-09-21 11:52     ` [PATCH v3 2/3] Respect `db_home` setting even for SYSTEM/Microsoft accounts Johannes Schindelin
2022-09-21 11:52     ` [PATCH v3 3/3] Respect `db_home: env` even when no uid can be determined Johannes Schindelin
2023-03-28  8:17     ` [PATCH v4 0/3] Support deriving the current user's home directory via HOME Johannes Schindelin
2023-03-28  8:17       ` [PATCH v4 1/3] Allow deriving the current user's home directory via the HOME variable Johannes Schindelin
2023-03-28 10:35         ` Corinna Vinschen
2023-03-28 12:34           ` Jon Turney
2023-03-28 13:31             ` Corinna Vinschen
2023-03-29  8:36               ` Corinna Vinschen
2023-04-03  6:39                 ` Johannes Schindelin
2023-03-28  8:17       ` [PATCH v4 2/3] Respect `db_home` setting even for SYSTEM/Microsoft accounts Johannes Schindelin
2023-03-28 10:16         ` Corinna Vinschen
2023-04-03  6:36           ` Johannes Schindelin
2023-04-03 10:59             ` Corinna Vinschen
2023-04-03 13:32               ` Johannes Schindelin
2023-03-28  8:17       ` [PATCH v4 3/3] Respect `db_home: env` even when no uid can be determined Johannes Schindelin
2023-03-28 10:17         ` Corinna Vinschen
2023-04-03  6:45           ` Johannes Schindelin
2023-04-03 13:12             ` Johannes Schindelin
2023-04-03 13:29               ` Corinna Vinschen
2023-04-03 13:57                 ` Johannes Schindelin
2023-04-03 19:23                   ` Corinna Vinschen
2023-04-04 15:11                     ` Johannes Schindelin
2023-04-03 13:19             ` Johannes Schindelin
2023-04-03 14:44       ` [PATCH v5 0/3] Support deriving the current user's home directory via HOME Johannes Schindelin
2023-04-03 14:44         ` [PATCH v5 1/3] Allow deriving the current user's home directory via the HOME variable Johannes Schindelin
2023-04-03 18:36           ` Corinna Vinschen
2023-04-04 15:12             ` Johannes Schindelin
2023-04-03 14:45         ` [PATCH v5 2/3] Respect `db_home` setting even for SYSTEM/Microsoft accounts Johannes Schindelin
2023-04-03 18:37           ` Corinna Vinschen
2023-04-04 15:12             ` Johannes Schindelin
2023-04-03 14:45         ` [PATCH v5 3/3] Respect `db_home: env` even when no uid can be determined Johannes Schindelin
2023-04-04 15:07         ` [PATCH v6 0/4] Support deriving the current user's home directory via HOME Johannes Schindelin
2023-04-04 15:07           ` [PATCH v6 1/4] Allow deriving the current user's home directory via the HOME variable Johannes Schindelin
2023-04-04 15:07           ` [PATCH v6 2/4] Respect `db_home` setting even for SYSTEM/Microsoft accounts Johannes Schindelin
2023-04-04 15:07           ` [PATCH v6 3/4] uinfo: special-case IIS APPPOOL accounts Johannes Schindelin
2023-04-04 15:07           ` [PATCH v6 4/4] Do not rely on `getenv ("HOME")`'s path conversion Johannes Schindelin
2023-04-06  8:37             ` Corinna Vinschen
2023-04-06  9:54               ` Johannes Schindelin
2023-04-06 10:28                 ` Corinna Vinschen
2023-05-22 11:12           ` [PATCH v7 0/4] Support deriving the current user's home directory via HOME Johannes Schindelin
2023-05-22 11:12             ` [PATCH v7 1/4] Allow deriving the current user's home directory via the HOME variable Johannes Schindelin
2023-05-22 11:12             ` [PATCH v7 2/4] Respect `db_home` setting even for SYSTEM/Microsoft accounts Johannes Schindelin
2023-05-22 11:12             ` [PATCH v7 3/4] uinfo: special-case IIS APPPOOL accounts Johannes Schindelin
2023-05-22 11:13             ` [PATCH v7 4/4] Do not rely on `getenv ("HOME")`'s path conversion Johannes Schindelin
2023-06-06 13:33             ` [PATCH v7 0/4] Support deriving the current user's home directory via HOME Corinna Vinschen

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