[Python-Dev] Remove tempfile.mktemp()

[eryk sun]

On 3/23/19, Cameron Simpson <cs at cskk.id.au> wrote:
>
> Also, the common examples are attackers who are not the user making the
> tempfile, in which case the _default_ mktemp is sort of secure with the
> above because it gets made in /tmp which on a modern POSIX system
> prevents _other_ uses from removing/renaming a file. (And Eryk I think
> described the Windows situation which is similarly protected).

Using NamedTemporaryFile(delete=False) or mkstemp() ensures that the
file is created and opened securely. in contrast, the filename from
mktemp() might be used naively in POSIX, such as open(path, "w"). This
file might grant read access to everyone depending on the file-mode
creation mask (umask). Also, since it neglects to use exclusive mode
("x"), it might open an existing file that grants read-write
permission to the world, or maybe it's a symlink.

By default, even naive use of the mktemp() name in Windows remains
secure, since every user has a separate temp directory that's only
accessible by privileged users such as SYSTEM, Administrators, and
Backup Operators (with SeBackupPrivilege and SeRestorePrivilege
enabled). The primary issue with a short name is an accidental name
collision with another program that's not as careful as Python's
tempfile. Using a longer name decreases the chance of this to
practically nothing.