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Allow Dir.home to work for non-login procs when $HOME not set

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Allow the 'Dir.home' method to reliably locate the user's home directory when
all three of the following are true at the same time:

    1. Ruby is running on a Unix-like OS
    2. The $HOME environment variable is not set
    3. The process is not a descendant of login(1) (or a work-alike)

The prior behavior was that the lookup could only work for login-descended
processes.

This is accomplished by looking up the user's record in the password database
by uid (getpwuid_r(3)) as a fallback to the lookup by name (getpwname_r(3))
which is still attempted first (based on the name, if any, returned by
getlogin_r(3)).

If getlogin_r(3), getpwnam_r(3), and/or getpwuid_r(3) is not available at
compile time, will fallback on using their respective non-*_r() variants:
getlogin(3), getpwnam(3), and/or getpwuid(3).

The rationale for attempting to do the lookup by name prior to doing it by uid
is to accommodate the possibility of multiple login names (each with its own
record in the password database, so each with a potentially different home
directory) being mapped to the same uid (as is explicitly allowed for by
POSIX; see getlogin(3posix)).

Preserves the existing behavior for login-descended processes, and adds the
new capability of having Dir.home being able to find the user's home directory
for non-login-descended processes.

Fixes [Bug #16787]

Related discussion:
    https://bugs.ruby-lang.org/issues/16787
    https://github.com/ruby/ruby/pull/3034
This commit is contained in:
Alan D. Salewski 2020-04-15 07:29:16 -04:00 committed by Nobuyoshi Nakada
parent 39cb19303c
commit c15cddd1d5
4 changed files with 311 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
configure.ac
View File

@ -1902,10 +1902,15 @@ AC_CHECK_FUNCS(getgidx)
AC_CHECK_FUNCS(getgrnam)
AC_CHECK_FUNCS(getgrnam_r)
AC_CHECK_FUNCS(getgroups)
AC_CHECK_FUNCS(getlogin)
AC_CHECK_FUNCS(getlogin_r)
AC_CHECK_FUNCS(getpgid)
AC_CHECK_FUNCS(getpgrp)
AC_CHECK_FUNCS(getpriority)
AC_CHECK_FUNCS(getpwnam)
AC_CHECK_FUNCS(getpwnam_r)
AC_CHECK_FUNCS(getpwuid)
AC_CHECK_FUNCS(getpwuid_r)
AC_CHECK_FUNCS(getrandom)
AC_CHECK_FUNCS(getresgid)
AC_CHECK_FUNCS(getresuid)

51
file.c
View File

@ -3603,21 +3603,42 @@ rb_default_home_dir(VALUE result)
#if defined HAVE_PWD_H
if (!dir) {
const char *login = getlogin();
if (login) {
struct passwd *pw = getpwnam(login);
if (pw) {
copy_home_path(result, pw->pw_dir);
endpwent();
return result;
}
endpwent();
rb_raise(rb_eArgError, "couldn't find HOME for login `%s' -- expanding `~'",
login);
}
else {
rb_raise(rb_eArgError, "couldn't find login name -- expanding `~'");
}
/* We'll look up the user's default home dir in the password db by
* login name, if possible, and failing that will fall back to looking
* the information up by uid (as would be needed for processes that
* are not a descendant of login(1) or a work-alike).
*
* While the lookup by uid is more likely to succeed (since we always
* have a uid, but may or may not have a login name), we prefer first
* looking up by name to accommodate the possibility of multiple login
* names (each with its own record in the password database, so each
* with a potentially different home directory) being mapped to the
* same uid (as explicitly allowed for by POSIX; see getlogin(3posix)).
*/
VALUE login_name = rb_getlogin();
# if !defined(HAVE_GETPWUID_R) && !defined(HAVE_GETPWUID)
/* This is a corner case, but for backward compatibility reasons we
* want to emit this error if neither the lookup by login name nor
* lookup by getuid() has a chance of succeeding.
*/
if (NIL_P(login_name)) {
rb_raise(rb_eArgError, "couldn't find login name -- expanding `~'");
}
# endif
VALUE pw_dir = rb_getpwdirnam_for_login(login_name);
if (NIL_P(pw_dir)) {
pw_dir = rb_getpwdiruid();
if (NIL_P(pw_dir)) {
rb_raise(rb_eArgError, "couldn't find home for uid `%ld'", (long)getuid());
}
}
/* found it */
copy_home_path(result, RSTRING_PTR(pw_dir));
rb_str_resize(pw_dir, 0);
return result;
}
#endif
if (!dir) {

6
internal/process.h
View File

@ -79,6 +79,12 @@ void rb_last_status_clear(void);
static inline char **ARGVSTR2ARGV(VALUE argv_str);
static inline size_t ARGVSTR2ARGC(VALUE argv_str);
#ifdef HAVE_PWD_H
VALUE rb_getlogin(void);
VALUE rb_getpwdirnam_for_login(VALUE login); /* read as: "get pwd db home dir by username for login" */
VALUE rb_getpwdiruid(void); /* read as: "get pwd db home dir for getuid()" */
#endif
RUBY_SYMBOL_EXPORT_BEGIN
/* process.c (export) */
int rb_exec_async_signal_safe(const struct rb_execarg *e, char *errmsg, size_t errmsg_buflen);

266
process.c
View File

@ -179,12 +179,40 @@ static int exec_async_signal_safe(const struct rb_execarg *, char *, size_t);
#define p_gid_from_name p_gid_from_name
#endif
#if defined(HAVE_UNISTD_H)
# if defined(HAVE_GETLOGIN_R)
# define USE_GETLOGIN_R 1
# define GETLOGIN_R_SIZE_DEFAULT 0x100
# define GETLOGIN_R_SIZE_LIMIT 0x1000
# if defined(_SC_LOGIN_NAME_MAX)
# define GETLOGIN_R_SIZE_INIT sysconf(_SC_LOGIN_NAME_MAX)
# else
# define GETLOGIN_R_SIZE_INIT GETLOGIN_R_SIZE_DEFAULT
# endif
# elif defined(HAVE_GETLOGIN)
# define USE_GETLOGIN 1
# endif
#endif
#if defined(HAVE_PWD_H)
# if defined(HAVE_GETPWNAM_R) && defined(_SC_GETPW_R_SIZE_MAX)
# if defined(HAVE_GETPWUID_R)
# define USE_GETPWUID_R 1
# elif defined(HAVE_GETPWUID)
# define USE_GETPWUID 1
# endif
# if defined(HAVE_GETPWNAM_R)
# define USE_GETPWNAM_R 1
# define GETPW_R_SIZE_INIT sysconf(_SC_GETPW_R_SIZE_MAX)
# elif defined(HAVE_GETPWNAM)
# define USE_GETPWNAM 1
# endif
# if defined(HAVE_GETPWNAM_R) || defined(HAVE_GETPWUID_R)
# define GETPW_R_SIZE_DEFAULT 0x1000
# define GETPW_R_SIZE_LIMIT 0x10000
# if defined(_SC_GETPW_R_SIZE_MAX)
# define GETPW_R_SIZE_INIT sysconf(_SC_GETPW_R_SIZE_MAX)
# else
# define GETPW_R_SIZE_INIT GETPW_R_SIZE_DEFAULT
# endif
# endif
# ifdef USE_GETPWNAM_R
# define PREPARE_GETPWNAM \
@ -5531,6 +5559,240 @@ check_gid_switch(void)
}
#if defined(HAVE_PWD_H)
/**
* Best-effort attempt to obtain the name of the login user, if any,
* associated with the process. Processes not descended from login(1) (or
* similar) may not have a logged-in user; returns Qnil in that case.
*/
VALUE
rb_getlogin(void)
{
#if ( !defined(USE_GETLOGIN_R) && !defined(USE_GETLOGIN) )
return Qnil;
#else
char MAYBE_UNUSED(*login) = NULL;
# ifdef USE_GETLOGIN_R
long loginsize = GETLOGIN_R_SIZE_INIT; /* maybe -1 */
if (loginsize < 0)
loginsize = GETLOGIN_R_SIZE_DEFAULT;
VALUE maybe_result = rb_str_buf_new(loginsize);
login = RSTRING_PTR(maybe_result);
loginsize = rb_str_capacity(maybe_result);
rb_str_set_len(maybe_result, loginsize);
int gle;
errno = 0;
while ((gle = getlogin_r(login, loginsize)) != 0) {
if (gle == ENOTTY || gle == ENXIO || gle == ENOENT) {
rb_str_resize(maybe_result, 0);
return Qnil;
}
if (gle != ERANGE || loginsize >= GETLOGIN_R_SIZE_LIMIT) {
rb_str_resize(maybe_result, 0);
rb_syserr_fail(gle, "getlogin_r");
}
rb_str_modify_expand(maybe_result, loginsize);
login = RSTRING_PTR(maybe_result);
loginsize = rb_str_capacity(maybe_result);
}
if (login == NULL) {
rb_str_resize(maybe_result, 0);
return Qnil;
}
return maybe_result;
# elif USE_GETLOGIN
errno = 0;
login = getlogin();
if (errno) {
if (errno == ENOTTY || errno == ENXIO || errno == ENOENT) {
return Qnil;
}
rb_syserr_fail(errno, "getlogin");
}
return login ? rb_str_new_cstr(login) : Qnil;
# endif
#endif
}
VALUE
rb_getpwdirnam_for_login(VALUE login_name)
{
#if ( !defined(USE_GETPWNAM_R) && !defined(USE_GETPWNAM) )
return Qnil;
#else
if (NIL_P(login_name)) {
/* nothing to do; no name with which to query the password database */
return Qnil;
}
char *login = RSTRING_PTR(login_name);
struct passwd *pwptr;
# ifdef USE_GETPWNAM_R
struct passwd pwdnm;
char *bufnm;
long bufsizenm = GETPW_R_SIZE_INIT; /* maybe -1 */
if (bufsizenm < 0)
bufsizenm = GETPW_R_SIZE_DEFAULT;
VALUE getpwnm_tmp = rb_str_tmp_new(bufsizenm);
bufnm = RSTRING_PTR(getpwnm_tmp);
bufsizenm = rb_str_capacity(getpwnm_tmp);
rb_str_set_len(getpwnm_tmp, bufsizenm);
int enm;
errno = 0;
while ((enm = getpwnam_r(login, &pwdnm, bufnm, bufsizenm, &pwptr)) != 0) {
if (enm == ENOENT || enm== ESRCH || enm == EBADF || enm == EPERM) {
/* not found; non-errors */
rb_str_resize(getpwnm_tmp, 0);
return Qnil;
}
if (enm != ERANGE || bufsizenm >= GETPW_R_SIZE_LIMIT) {
rb_str_resize(getpwnm_tmp, 0);
rb_syserr_fail(enm, "getpwnam_r");
}
rb_str_modify_expand(getpwnm_tmp, bufsizenm);
bufnm = RSTRING_PTR(getpwnm_tmp);
bufsizenm = rb_str_capacity(getpwnm_tmp);
}
if (pwptr == NULL) {
/* no record in the password database for the login name */
rb_str_resize(getpwnm_tmp, 0);
return Qnil;
}
/* found it */
VALUE result = rb_str_new_cstr(pwptr->pw_dir);
rb_str_resize(getpwnm_tmp, 0);
return result;
# elif USE_GETPWNAM
errno = 0;
pwptr = getpwnam(login);
if (pwptr) {
/* found it */
return rb_str_new_cstr(pwptr->pw_dir);
}
if (errno
/* avoid treating as errors errno values that indicate "not found" */
&& ( errno != ENOENT && errno != ESRCH && errno != EBADF && errno != EPERM)) {
rb_syserr_fail(errno, "getpwnam");
}
return Qnil; /* not found */
# endif
#endif
}
/**
* Look up the user's dflt home dir in the password db, by uid.
*/
VALUE
rb_getpwdiruid(void)
{
# if !defined(USE_GETPWUID_R) && !defined(USE_GETPWUID)
/* Should never happen... </famous-last-words> */
return Qnil;
# else
uid_t ruid = getuid();
struct passwd *pwptr;
# ifdef USE_GETPWUID_R
struct passwd pwdid;
char *bufid;
long bufsizeid = GETPW_R_SIZE_INIT; /* maybe -1 */
if (bufsizeid < 0)
bufsizeid = GETPW_R_SIZE_DEFAULT;
VALUE getpwid_tmp = rb_str_tmp_new(bufsizeid);
bufid = RSTRING_PTR(getpwid_tmp);
bufsizeid = rb_str_capacity(getpwid_tmp);
rb_str_set_len(getpwid_tmp, bufsizeid);
int eid;
errno = 0;
while ((eid = getpwuid_r(ruid, &pwdid, bufid, bufsizeid, &pwptr)) != 0) {
if (eid == ENOENT || eid== ESRCH || eid == EBADF || eid == EPERM) {
/* not found; non-errors */
rb_str_resize(getpwid_tmp, 0);
return Qnil;
}
if (eid != ERANGE || bufsizeid >= GETPW_R_SIZE_LIMIT) {
rb_str_resize(getpwid_tmp, 0);
rb_syserr_fail(eid, "getpwuid_r");
}
rb_str_modify_expand(getpwid_tmp, bufsizeid);
bufid = RSTRING_PTR(getpwid_tmp);
bufsizeid = rb_str_capacity(getpwid_tmp);
}
if (pwptr == NULL) {
/* no record in the password database for the uid */
rb_str_resize(getpwid_tmp, 0);
return Qnil;
}
/* found it */
VALUE result = rb_str_new_cstr(pwptr->pw_dir);
rb_str_resize(getpwid_tmp, 0);
return result;
# elif defined(USE_GETPWUID)
errno = 0;
pwptr = getpwuid(ruid);
if (pwptr) {
/* found it */
return rb_str_new_cstr(pwptr->pw_dir);
}
if (errno
/* avoid treating as errors errno values that indicate "not found" */
&& ( errno == ENOENT || errno == ESRCH || errno == EBADF || errno == EPERM)) {
rb_syserr_fail(errno, "getpwuid");
}
return Qnil; /* not found */
# endif
#endif /* !defined(USE_GETPWUID_R) && !defined(USE_GETPWUID) */
}
#endif /* HAVE_PWD_H */
/*********************************************************************
* Document-class: Process::Sys
*