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Drop Privileges to "Debian-apt" in most acquire methods

Add a new "Debian-apt" user that owns the /var/lib/apt/lists
and /var/cache/apt/archive directories. The methods
http, https, ftp, gpgv, gzip switch to this user when they
start.

Thanks to Julian and "ioerror" and tors "switch_id()" code.
debian/1.8.y
Michael Vogt 8 years ago
parent
commit
3927c6da48
  1. 34
      apt-pkg/contrib/fileutl.cc
  2. 7
      debian/apt.postinst
  3. 2
      methods/copy.cc
  4. 3
      methods/ftp.cc
  5. 3
      methods/gpgv.cc
  6. 2
      methods/gzip.cc
  7. 4
      methods/http_main.cc
  8. 2
      methods/https.cc

34
apt-pkg/contrib/fileutl.cc

@ -48,6 +48,7 @@
#include <errno.h>
#include <glob.h>
#include <pwd.h>
#include <grp.h>
#include <set>
#include <algorithm>
@ -64,6 +65,10 @@
#include <endian.h>
#include <stdint.h>
#if __gnu_linux__
#include <sys/prctl.h>
#endif
#include <apti18n.h>
/*}}}*/
@ -2173,14 +2178,41 @@ bool DropPrivs()
if (getuid() != 0)
return true;
const std::string nobody = _config->Find("APT::User::Nobody", "nobody");
if(_config->FindB("Debug::NoDropPrivs", false) == true)
return true;
const std::string nobody = _config->Find("APT::User::Nobody", "Debian-apt");
struct passwd *pw = getpwnam(nobody.c_str());
if (pw == NULL)
return _error->Warning("No user %s, can not drop rights", nobody.c_str());
#if __gnu_linux__
// see prctl(2), needs linux3.5
int ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0,0, 0);
if(ret < 0)
_error->Warning("PR_SET_NO_NEW_PRIVS failed with %i", ret);
#endif
if (setgroups(1, &pw->pw_gid) != 1)
return _error->Errno("setgroups", "Failed to setgroups");
if (setegid(pw->pw_gid) != 0)
return _error->Errno("setgid", "Failed to setgid");
if (setgid(pw->pw_gid) != 0)
return _error->Errno("setgid", "Failed to setgid");
if (setuid(pw->pw_uid) != 0)
return _error->Errno("setuid", "Failed to setuid");
// the seteuid() is probably uneeded (at least thats what the linux
// man-page says about setuid(2)) but we cargo culted it anyway
if (setuid(pw->pw_uid) != 0)
return _error->Errno("setuid", "Failed to setuid");
// be defensive
if(setgid(0) != -1 || setegid(0) != -1)
return _error->Error("Could restore gid to root, privilege dropping does not work");
if(setuid(0) != -1 || seteuid(0) != -1)
return _error->Error("Could restore uid to root, privilege dropping does not work");
return true;
}

7
debian/apt.postinst

@ -26,6 +26,13 @@ case "$1" in
fi
fi
# add unprivileged user for the apt methods
adduser --force-badname --system --no-create-home \
--quiet Debian-apt || true
chown -R Debian-apt:root \
/var/lib/apt/lists \
/var/cache/apt/archives
# ensure tighter permissons on the logs, see LP: #975199
if dpkg --compare-versions "$2" lt-nl 0.9.7.7; then
# ensure permissions are right

2
methods/copy.cc

@ -118,6 +118,8 @@ int main()
{
setlocale(LC_ALL, "");
DropPrivs();
CopyMethod Mth;
return Mth.Run();
}

3
methods/ftp.cc

@ -1107,6 +1107,9 @@ int main(int, const char *argv[])
{
setlocale(LC_ALL, "");
// no more active ftp, sorry
DropPrivs();
/* See if we should be come the http client - we do this for http
proxy urls */
if (getenv("ftp_proxy") != 0)

3
methods/gpgv.cc

@ -5,6 +5,7 @@
#include <apt-pkg/error.h>
#include <apt-pkg/gpgv.h>
#include <apt-pkg/strutl.h>
#include <apt-pkg/fileutl.h>
#include <ctype.h>
#include <errno.h>
@ -262,6 +263,8 @@ int main()
{
setlocale(LC_ALL, "");
DropPrivs();
GPGVMethod Mth;
return Mth.Run();

2
methods/gzip.cc

@ -135,6 +135,8 @@ int main(int, char *argv[])
{
setlocale(LC_ALL, "");
DropPrivs();
Prog = strrchr(argv[0],'/');
++Prog;

4
methods/http_main.cc

@ -1,5 +1,5 @@
#include <config.h>
#include <apt-pkg/fileutl.h>
#include <signal.h>
#include "http.h"
@ -12,6 +12,8 @@ int main()
// closes the connection (this is dealt with via ServerDie())
signal(SIGPIPE, SIG_IGN);
DropPrivs();
HttpMethod Mth;
return Mth.Loop();
}

2
methods/https.cc

@ -443,6 +443,8 @@ int main()
{
setlocale(LC_ALL, "");
DropPrivs();
HttpsMethod Mth;
curl_global_init(CURL_GLOBAL_SSL) ;

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