ensure FileFd doesn't try to open /dev/null as atomic and co

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

diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 1be782bac8c4629dd7fc81e1f276189db107d701..368380af7817837f5c37a3ee8afa1c56be94e2ff 100644 (file)
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -158,24 +158,18 @@ bool CopyFile(FileFd &From,FileFd &To)
    if (From.IsOpen() == false || To.IsOpen() == false ||
         From.Failed() == true || To.Failed() == true)
       return false;
-   
+
    // Buffered copy between fds
    std::unique_ptr<unsigned char[]> Buf(new unsigned char[64000]);
-   unsigned long long Size = From.Size();
-   while (Size != 0)
-   {
-      unsigned long long ToRead = Size;
-      if (Size > 64000)
-        ToRead = 64000;
-      
-      if (From.Read(Buf.get(),ToRead) == false ||
+   constexpr unsigned long long BufSize = sizeof(Buf.get())/sizeof(Buf.get()[0]);
+   unsigned long long ToRead = 0;
+   do {
+      if (From.Read(Buf.get(),BufSize, &ToRead) == false ||
          To.Write(Buf.get(),ToRead) == false)
         return false;
-      
-      Size -= ToRead;
-   }
+   } while (ToRead != 0);
 
-   return true;   
+   return true;
 }
                                                                        /*}}}*/
 // GetLock - Gets a lock file                                          /*{{{*/
@@ -671,7 +665,7 @@ string flAbsPath(string File)
    char *p = realpath(File.c_str(), NULL);
    if (p == NULL)
    {
-      _error->Errno("realpath", "flAbsPath failed");
+      _error->Errno("realpath", "flAbsPath on %s failed", File.c_str());
       return "";
    }
    std::string AbsPath(p);
@@ -1130,16 +1124,20 @@ bool FileFd::Open(string FileName,unsigned int const Mode,APT::Configuration::Co
    if ((Mode & ReadWrite) == 0)
       return FileFdError("No openmode provided in FileFd::Open for %s", FileName.c_str());
 
-   if ((Mode & Atomic) == Atomic)
+   unsigned int OpenMode = Mode;
+   if (FileName == "/dev/null")
+      OpenMode = OpenMode & ~(Atomic | Exclusive | Create | Empty);
+
+   if ((OpenMode & Atomic) == Atomic)
    {
       Flags |= Replace;
    }
-   else if ((Mode & (Exclusive | Create)) == (Exclusive | Create))
+   else if ((OpenMode & (Exclusive | Create)) == (Exclusive | Create))
    {
       // for atomic, this will be done by rename in Close()
       unlink(FileName.c_str());
    }
-   if ((Mode & Empty) == Empty)
+   if ((OpenMode & Empty) == Empty)
    {
       struct stat Buf;
       if (lstat(FileName.c_str(),&Buf) == 0 && S_ISLNK(Buf.st_mode))
@@ -1147,7 +1145,7 @@ bool FileFd::Open(string FileName,unsigned int const Mode,APT::Configuration::Co
    }
 
    int fileflags = 0;
-   #define if_FLAGGED_SET(FLAG, MODE) if ((Mode & FLAG) == FLAG) fileflags |= MODE
+   #define if_FLAGGED_SET(FLAG, MODE) if ((OpenMode & FLAG) == FLAG) fileflags |= MODE
    if_FLAGGED_SET(ReadWrite, O_RDWR);
    else if_FLAGGED_SET(ReadOnly, O_RDONLY);
    else if_FLAGGED_SET(WriteOnly, O_WRONLY);
@@ -1157,7 +1155,7 @@ bool FileFd::Open(string FileName,unsigned int const Mode,APT::Configuration::Co
    if_FLAGGED_SET(Exclusive, O_EXCL);
    #undef if_FLAGGED_SET
 
-   if ((Mode & Atomic) == Atomic)
+   if ((OpenMode & Atomic) == Atomic)
    {
       char *name = strdup((FileName + ".XXXXXX").c_str());
 
@@ -1184,7 +1182,7 @@ bool FileFd::Open(string FileName,unsigned int const Mode,APT::Configuration::Co
       iFd = open(FileName.c_str(), fileflags, AccessMode);
 
    this->FileName = FileName;
-   if (iFd == -1 || OpenInternDescriptor(Mode, compressor) == false)
+   if (iFd == -1 || OpenInternDescriptor(OpenMode, compressor) == false)
    {
       if (iFd != -1)
       {
@@ -2006,12 +2004,13 @@ bool FileFd::Close()
    {
       if ((Flags & Compressed) != Compressed && iFd > 0 && close(iFd) != 0)
         Res &= _error->Errno("close",_("Problem closing the file %s"), FileName.c_str());
-      if (d != NULL)
-      {
-        Res &= d->CloseDown(FileName);
-        delete d;
-        d = NULL;
-      }
+   }
+
+   if (d != NULL)
+   {
+      Res &= d->CloseDown(FileName);
+      delete d;
+      d = NULL;
    }
 
    if ((Flags & Replace) == Replace) {
@@ -2122,12 +2121,39 @@ std::string GetTempDir()                                                /*{{{*/
 
    struct stat st;
    if (!tmpdir || strlen(tmpdir) == 0 || // tmpdir is set
-        stat(tmpdir, &st) != 0 || (st.st_mode & S_IFDIR) == 0 || // exists and is directory
-        access(tmpdir, R_OK | W_OK | X_OK) != 0 // current user has rwx access to directory
-      )
+        stat(tmpdir, &st) != 0 || (st.st_mode & S_IFDIR) == 0) // exists and is directory
+      tmpdir = "/tmp";
+   else if (geteuid() != 0 && // root can do everything anyway
+        faccessat(-1, tmpdir, R_OK | W_OK | X_OK, AT_EACCESS | AT_SYMLINK_NOFOLLOW) != 0) // current user has rwx access to directory
       tmpdir = "/tmp";
 
    return string(tmpdir);
+}
+std::string GetTempDir(std::string const &User)
+{
+   // no need/possibility to drop privs
+   if(getuid() != 0 || User.empty() || User == "root")
+      return GetTempDir();
+
+   struct passwd const * const pw = getpwnam(User.c_str());
+   if (pw == NULL)
+      return GetTempDir();
+
+   gid_t const old_euid = geteuid();
+   gid_t const old_egid = getegid();
+   if (setegid(pw->pw_gid) != 0)
+      _error->Errno("setegid", "setegid %u failed", pw->pw_gid);
+   if (seteuid(pw->pw_uid) != 0)
+      _error->Errno("seteuid", "seteuid %u failed", pw->pw_uid);
+
+   std::string const tmp = GetTempDir();
+
+   if (seteuid(old_euid) != 0)
+      _error->Errno("seteuid", "seteuid %u failed", old_euid);
+   if (setegid(old_egid) != 0)
+      _error->Errno("setegid", "setegid %u failed", old_egid);
+
+   return tmp;
 }
                                                                        /*}}}*/
 FileFd* GetTempFile(std::string const &Prefix, bool ImmediateUnlink, FileFd * const TmpFd)     /*{{{*/
@@ -2208,11 +2234,14 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode)/
    {
       close(Pipe[1]);
       fd = Pipe[0];
-   } else if(Mode == FileFd::WriteOnly)
+   }
+   else if(Mode == FileFd::WriteOnly)
    {
       close(Pipe[0]);
       fd = Pipe[1];
    }
+   else
+      return _error->Error("Popen supports ReadOnly (x)or WriteOnly mode only");
    Fd.OpenDescriptor(fd, Mode, FileFd::None, true);
 
    return true;