linux-kernel - Re: [PATCH 2/6] integrity: IMA as an integrity service provider

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1233668170.4263.24.camel@localhost.localdomain>
Date:	Tue, 03 Feb 2009 08:36:10 -0500
From:	david safford <safford@...son.ibm.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Morris <jmorris@...ei.org>,
	Christoph Hellwig <hch@...radead.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Serge Hallyn <serue@...ibm.com>, Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 2/6] integrity: IMA as an integrity service provider

On Mon, 2009-02-02 at 17:02 -0600, Serge E. Hallyn wrote:
> Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> > +
> > +/* Add template entry to the measurement list and hash table,
> > + * and extend the pcr.
> > + */
> > +int ima_add_template_entry(struct ima_template_entry *entry, int violation,
> > +			   const char *op, struct inode *inode)
> > +{
> > +	u8 digest[IMA_DIGEST_SIZE];
> > +	const char *audit_cause = "hash_added";
> > +	int audit_info = 1;
> > +	int result = 0;
> > +
> > +	mutex_lock(&ima_extend_list_mutex);
> > +	if (!violation) {
> > +		memcpy(digest, entry->digest, sizeof digest);
> > +		if (ima_lookup_digest_entry(digest)) {
> > +			audit_cause = "hash_exists";
> > +			goto out;
> 
> Ok so not that I'm saying this would be easy, but an attacker
> compromising say ftpd doesn't need to come up with a compromised
> ftpd where sha1sum(evilftpd)==sha1sum(origftpd) - he just needs to
> come up with one wher sha1sum(evilftpd)==sha1sum(X) where X is
> any pristine program already loaded.  Right?
> 
> Is checking that strcmp(entry->file_name, newfilename)==0 warranted
> here, or am I being silly?

The birthday paradox, which is essential for any practical attack,
requires that the attacker can freely choose both x and y in 
his search for collisions sha1sum(x) == sha1sum(y). Here, the
attacker cannot freely choose x, but can only choose x from a list
of existing files. Even if there are a million valid files, that only
reduces the attack complexity by 2^20, which is still infeasible.

dave

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/