On Fri, 2019-06-07 at 17:14 +0200, Roberto Sassu wrote: > On 6/7/2019 5:08 PM, Mimi Zohar wrote: > > On Fri, 2019-06-07 at 16:40 +0200, Roberto Sassu wrote: > >>> On Thu, 2019-06-06 at 13:26 +0200, Roberto Sassu wrote: > > > >>>> Although this choice appears legitimate, it might not be suitable for > >>>> hardened systems, where the administrator expects that access is denied if > >>>> there is any error. An attacker could intentionally delete the EVM keys > >>>> from the system and set the file digest in security.ima to the actual file > >>>> digest so that the final appraisal status is INTEGRITY_PASS. > >>> > >>> Assuming that the EVM HMAC key is stored in the initramfs, not on some > >>> other file system, and the initramfs is signed, INTEGRITY_UNKNOWN > >>> would be limited to the rootfs filesystem. > >> > >> There is another issue. The HMAC key, like the public keys, should be > >> loaded when appraisal is disabled. This means that we have to create a > >> trusted key at early boot and defer the unsealing. > > > > There is no need for IMA to appraise the public key file signature, > > since the certificate is signed by a key on the builtin/secondary > > trusted keyring. With CONFIG_IMA_LOAD_X509 enabled, the public key > > can be loaded onto the IMA keyring with IMA-appraisal enabled, but > > without verifying the file signature. > > Yes, but access to the files containing the master key and the EVM key > is denied if appraisal is enabled. This is a key loading ordering issue. Assuming you load the IMA key first, you should be able to verify the master and EVM keys. Mimi
