Use _apt as our unprivileged user name

[apt.git] / apt-pkg / contrib / fileutl.cc

diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 02b30dc1f17ce3abd401ddb731a91b7a71eadbcd..8e7313e8fcca69d3557d2b1cfc975a976cfc05af 100644 (file)
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -47,6 +47,8 @@
 #include <signal.h>
 #include <errno.h>
 #include <glob.h>
+#include <pwd.h>
+#include <grp.h>
 
 #include <set>
 #include <algorithm>
@@ -63,6 +65,10 @@
 #include <endian.h>
 #include <stdint.h>
 
+#if __gnu_linux__
+#include <sys/prctl.h>
+#endif
+
 #include <apti18n.h>
                                                                        /*}}}*/
 
@@ -1278,7 +1284,8 @@ bool FileFd::OpenInternDescriptor(unsigned int const Mode, APT::Configuration::C
         if (d->lzma == NULL)
            d->lzma = new FileFdPrivate::LZMAFILE;
         d->lzma->file = (FILE*) compress_struct;
-        d->lzma->stream = LZMA_STREAM_INIT;
+         lzma_stream tmp_stream = LZMA_STREAM_INIT;
+        d->lzma->stream = tmp_stream;
 
         if ((Mode & ReadWrite) == ReadWrite)
            return FileFdError("ReadWrite mode is not supported for file %s", FileName.c_str());
@@ -1834,7 +1841,8 @@ static bool StatFileFd(char const * const msg, int const iFd, std::string const
         // higher-level code will generate more meaningful messages,
         // even translated this would be meaningless for users
         return _error->Errno("fstat", "Unable to determine %s for fd %i", msg, iFd);
-      ispipe = S_ISFIFO(Buf.st_mode);
+      if (FileName.empty() == false)
+        ispipe = S_ISFIFO(Buf.st_mode);
    }
 
    // for compressor pipes st_size is undefined and at 'best' zero
@@ -2164,3 +2172,71 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode)
 
    return true;
 }
+
+bool DropPrivs()
+{
+   /* uid will be 0 in the end, but gid might be different anyway */
+   uid_t old_uid = getuid();
+   gid_t old_gid = getgid();
+
+   if (old_uid != 0)
+      return true;
+   if(_config->FindB("Debug::NoDropPrivs", false) == true)
+      return true;
+
+   const std::string nobody = _config->Find("APT::User::Nobody", "_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("setegid", "Failed to setegid");
+
+   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 (seteuid(pw->pw_uid) != 0)
+      return _error->Errno("seteuid", "Failed to seteuid");
+
+   /* Try changing GID/EGID */
+   if (pw->pw_gid != old_gid && (setgid(old_gid) != -1 || setegid(old_gid) != -1))
+      return _error->Error("Could restore a gid to root, privilege dropping did not work");
+
+   if (pw->pw_uid != old_uid && (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
+      return _error->Error("Could restore a uid to root, privilege dropping did not work");
+
+   /* Verify the list of supplementary groups is what we expected */
+   gid_t groups[1];
+   if (getgroups(1, groups) != 1)
+      return _error->Errno("getgroups", "Could not get new groups");
+   if (groups[0] != pw->pw_gid)
+      return _error->Error("Could not switch group");
+   /* Verify gid, egid, uid, and euid */
+   if (getgid() != pw->pw_gid)
+      return _error->Error("Could not switch group");
+   if (getegid() != pw->pw_gid)
+      return _error->Error("Could not switch effective group");
+   if (getuid() != pw->pw_uid)
+      return _error->Error("Could not switch user");
+   if (geteuid() != pw->pw_uid)
+      return _error->Error("Could not switch effective user");
+
+   /* TODO: Check saved uid/saved gid as well */
+   return true;
+}