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Re: md5sum proposal



On Mon, May 24, 1999 at 08:47:00AM -0700, Christoph Lameter wrote:
> The md5sums of individual files are not only helpful for security but
> for the verification of the integrity of installed files in general. RPM
> includes perms etc in their database as well as noted by others before and
> I wish we would do that as well.

As has been pointed out time and time again, md5sums of individual files
are NOT helpful for security in any significant sense.

It is as easy to change the contents of something like a debian/md5sums
file within a package (or after it has been unpacked onto the system) as it
is to change the md5sum of the .deb itself.  We do not have a strong way of
preventing tampering with the md5sums when the .deb is constructed, and
likewise anyone who has sufficient privileges to replace root-owned binary
files (in privileged directories) on the system has sufficient privileges
to modify md5sum checksum files that refer to the replaced files.

Do you assert that an md5sums is a security bonus because an intruder with
root privileges may not be aware of the file's existence, and thus fail to
remove evidence of his attack?  Security only against the ignorant or
careless is hardly security at all.  Security against intruders who know
more about your system than you do is worth something; but this proposal
does not provide that.

The problem of package authentication has come up time and time again, and
adding a debian/md5sums file to a .deb does absolutely nothing to address
it.

I do not think security is a sound basis for the proposal because the
justification lacks merit.

I will formally oppose any proposal to require md5sums files within Debian
packages unless it makes absolutely clear that they are not a defense
against intrusion, but only against "mindless" data corruption like a
failing hard disk.

-- 
G. Branden Robinson              |
Debian GNU/Linux                 |      Music is the brandy of the damned.
branden@ecn.purdue.edu           |      -- George Bernard Shaw
cartoon.ecn.purdue.edu/~branden/ |

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