https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=27376c60a9b870e7ba456551165897a7408b5886
commit 27376c60a9b870e7ba456551165897a7408b5886 Author: Johannes Schindelin <[email protected]> AuthorDate: Tue Mar 28 10:17:14 2023 +0200 Commit: Corinna Vinschen <[email protected]> CommitDate: Tue Mar 28 12:18:14 2023 +0200 Allow deriving the current user's home directory via the HOME variable 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 <[email protected]> Diff: --- winsup/cygwin/local_includes/cygheap.h | 3 +- winsup/cygwin/uinfo.cc | 51 ++++++++++++++++++++++++++++++++++ winsup/doc/ntsec.xml | 22 +++++++++++++++ 3 files changed, 75 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/local_includes/cygheap.h b/winsup/cygwin/local_includes/cygheap.h index d885ca123085..b6acdf7f18b7 100644 --- a/winsup/cygwin/local_includes/cygheap.h +++ b/winsup/cygwin/local_includes/cygheap.h @@ -358,7 +358,8 @@ 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 30df6db6d8a3..baa670478dfe 100644 --- a/winsup/cygwin/uinfo.cc +++ b/winsup/cygwin/uinfo.cc @@ -733,6 +733,8 @@ 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"); @@ -921,6 +923,42 @@ fetch_from_path (cyg_ldap *pldap, PUSER_INFO_3 ui, cygpsid &sid, PCWSTR str, return ret; } +static char * +fetch_home_env (void) +{ + /* If `HOME` is set, prefer it */ + const char *home = getenv ("HOME"); + if (home) + return strdup (home); + + /* If `HOME` is unset, fall back to `HOMEDRIVE``HOMEPATH` + (without a directory separator, as `HOMEPATH` starts with one). */ + const char *home_drive = getenv ("HOMEDRIVE"); + if (home_drive) + { + const char *home_path = getenv ("HOMEPATH"); + if (home_path) + { + tmp_pathbuf tp; + char *p = tp.c_get (), *q; + + // concatenate HOMEDRIVE and HOMEPATH + q = stpncpy (p, home_drive, NT_MAX_PATH); + strlcpy (q, home_path, NT_MAX_PATH - (q - p)); + return (char *) cygwin_create_path (CCP_WIN_A_TO_POSIX, p); + } + } + + /* If neither `HOME` nor `HOMEDRIVE``HOMEPATH` are set, fall back + to `USERPROFILE`; In corporate setups, this might point to a + disconnected network share, hence this is the last fall back. */ + home = getenv ("USERPROFILE"); + if (home) + 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) @@ -980,6 +1018,10 @@ 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; @@ -1012,6 +1054,10 @@ 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; @@ -1031,6 +1077,7 @@ 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)) @@ -1095,6 +1142,7 @@ 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) @@ -1176,6 +1224,8 @@ 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) @@ -1202,6 +1252,7 @@ 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 c6871ecf051e..1678ff65753b 100644 --- a/winsup/doc/ntsec.xml +++ b/winsup/doc/ntsec.xml @@ -1203,6 +1203,17 @@ 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> @@ -1335,6 +1346,17 @@ 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
