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* [newlib-cygwin/main] Do not rely on `getenv ("HOME")`'s path conversion
@ 2023-06-06 13:32 Corinna Vinschen
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From: Corinna Vinschen @ 2023-06-06 13:32 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=80ff7bc26ca97a7e2194554c21fe25cbdf227813
commit 80ff7bc26ca97a7e2194554c21fe25cbdf227813
Author: Johannes Schindelin <johannes.schindelin@gmx.de>
AuthorDate: Mon May 22 13:13:02 2023 +0200
Commit: Corinna Vinschen <corinna@vinschen.de>
CommitDate: Tue Jun 6 15:18:53 2023 +0200
Do not rely on `getenv ("HOME")`'s path conversion
In the very early code path where `dll_crt0_1 ()` calls
`user_shared->initialize ()`, the Cygwin runtime calls `internal_pwsid ()`
to initialize the user name in preparation for reading the `fstab` file.
In case `db_home: env` is defined in `/etc/nsswitch.conf`, we need to
look at the environment variable `HOME` and use it, if set.
When all of this happens, though, the `pinfo_init ()` function has had no
chance to run yet (and therefore, `environ_init ()`). At this stage,
therefore, `getenv ()`'s `findenv_func ()` call still finds `getearly ()`
and we get the _verbatim_ value of `HOME`. That is, the Windows form.
But we need the "POSIX" form.
To add insult to injury, later calls to `getpwuid (getuid ())` will
receive a cached version of the home directory via
`cygheap->pg.pwd_cache.win.find_user ()` thanks to the first
`internal_pwsid ()` call caching the result via
`add_user_from_cygserver ()`, read: we will never receive the converted
`HOME` but always the Windows variant.
So, contrary to the assumptions made in 27376c60a9 (Allow deriving the
current user's home directory via the HOME variable, 2023-03-28), we
cannot assume that `getenv ("HOME")` returned a "POSIX" path.
This is a real problem. Even setting aside that common callers of
`getpwuid ()` (such as OpenSSH) are unable to handle Windows paths in the
`pw_dir` attribute, the Windows path never makes it back to the caller
unscathed. The value returned from `fetch_home_env ()` is not actually
used as-is. Instead, the `fetch_account_from_windows ()` method uses it
to write a pseudo `/etc/passwd`-formatted line that is _then_ parsed via
the `pwdgrp::parse_passwd ()` method which sees no problem with
misinterpreting the colon after the drive letter as a field separator of
that `/etc/passwd`-formatted line, and instead of a Windows path, we now
have a mere drive letter.
Let's detect when the `HOME` value is still in Windows format in
`fetch_home_env ()`, and convert it in that case.
For good measure, interpret this "Windows format" not only to include
absolute paths with drive prefixes, but also UNC paths.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Diff:
---
winsup/cygwin/uinfo.cc | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/winsup/cygwin/uinfo.cc b/winsup/cygwin/uinfo.cc
index 5e2d88bcd7ab..21d729d5dcbc 100644
--- a/winsup/cygwin/uinfo.cc
+++ b/winsup/cygwin/uinfo.cc
@@ -929,7 +929,13 @@ fetch_home_env (void)
/* If `HOME` is set, prefer it */
const char *home = getenv ("HOME");
if (home)
- return strdup (home);
+ {
+ /* In the very early code path of `user_info::initialize ()`, the value
+ of the environment variable `HOME` is still in its Windows form. */
+ if (isdrive (home) || home[0] == '\\')
+ return (char *) cygwin_create_path (CCP_WIN_A_TO_POSIX, home);
+ return strdup (home);
+ }
/* If `HOME` is unset, fall back to `HOMEDRIVE``HOMEPATH`
(without a directory separator, as `HOMEPATH` starts with one). */
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