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* On systems that have the setresuid() and setresgid() system calls to

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set the real uid and gid to the effective uid and gid, the Nix
  binaries can be installed as owned by the Nix user and group instead
  of root, so no root involvement of any kind is necessary.

  Linux and FreeBSD have these functions.
This commit is contained in:
Eelco Dolstra 2004-08-20 15:22:33 +00:00
parent 2d35116c13
commit e77fbe0fa2
3 changed files with 32 additions and 8 deletions
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6
configure.ac
View file

@ -151,6 +151,12 @@ if test "$setuid_hack" = "yes"; then
AC_DEFINE(SETUID_HACK, 1, [whether to install Nix setuid])
fi
AC_CHECK_FUNC(setresuid, [HAVE_SETRESUID=1], [HAVE_SETRESUID=])
AM_CONDITIONAL(HAVE_SETRESUID, test "$HAVE_SETRESUID" = "1")
if test "$HAVE_SETRESUID" = "1"; then
AC_DEFINE(HAVE_SETRESUID, 1, [whether we have setresuid()])
fi
AC_ARG_WITH(nix-user, AC_HELP_STRING([--with-nix-user=USER],
[user for Nix setuid binaries]),
NIX_USER=$withval, NIX_USER=nix)

5
src/Makefile.am
View file

@ -4,5 +4,10 @@ SUBDIRS = bin2c boost libutil libstore libmain nix-store nix-hash \
SETUID_PROGS = nix-store nix-instantiate nix-env
install-exec-hook:
if SETUID_HACK
if HAVE_SETRESUID
cd $(DESTDIR)$(bindir) && chown @NIX_USER@ $(SETUID_PROGS) \
&& chgrp @NIX_GROUP@ $(SETUID_PROGS) && chmod ug+s $(SETUID_PROGS)
else
cd $(DESTDIR)$(bindir) && chown root $(SETUID_PROGS) && chmod u+s $(SETUID_PROGS)
endif
endif

29
src/libmain/shared.cc
View file

@ -163,6 +163,16 @@ static void initAndRun(int argc, char * * argv)
}
#if HAVE_SETRESUID
#define _setuid(uid) setresuid(uid, uid, uid)
#define _setgid(gid) setresgid(gid, gid, gid)
#else
/* Only works properly when run by root. */
#define _setuid(uid) setuid(uid)
#define _setgid(gid) setgid(gid)
#endif
void switchToNixUser()
{
#if SETUID_HACK
@ -186,6 +196,13 @@ void switchToNixUser()
exit(1);
}
/* !!! Apparently it is unspecified whether getgroups() includes
the effective gid. In that case the following test is always
true *if* the program is installed setgid (which we do when we
have setresuid()). On Linux this doesn't appear to be the
case, but we should switch to the real gid before doing this
test, and then switch back to the saved gid. */
/* Check that the current user is a member of the Nix group. */
bool found = false;
for (int i = 0; i < nrGids; ++i)
@ -196,15 +213,15 @@ void switchToNixUser()
if (!found) {
/* Not in the Nix group - drop all root/Nix privileges. */
setgid(getgid());
setuid(getuid());
_setgid(getgid());
_setuid(getuid());
return;
}
/* Set the real, effective and saved gids to gr->gr_gid. Also
make very sure that this succeeded. We switch the gid first
because we cannot do it after we have dropped root uid. */
if (setgid(gr->gr_gid) != 0 ||
if (_setgid(gr->gr_gid) != 0 ||
getgid() != gr->gr_gid ||
getegid() != gr->gr_gid)
{
@ -222,7 +239,7 @@ void switchToNixUser()
/* This will drop all root privileges, setting the real, effective
and saved uids to pw->pw_uid. Also make very sure that this
succeeded.*/
if (setuid(pw->pw_uid) != 0 ||
if (_setuid(pw->pw_uid) != 0 ||
getuid() != pw->pw_uid ||
geteuid() != pw->pw_uid)
{
@ -240,11 +257,7 @@ int main(int argc, char * * argv)
{
/* If we are setuid root, we have to get rid of the excess
privileges ASAP. */
printMsg(lvlError, format("%1% %2% %3% %4%\n") % getuid() % geteuid()
% getgid() % getegid());
switchToNixUser();
printMsg(lvlError, format("%1% %2% %3% %4%\n") % getuid() % geteuid()
% getgid() % getegid());
/* ATerm setup. */
ATerm bottomOfStack;