Re: IMA signature generated by evmctl has unexpected key identifier

[Mimi Zohar <zohar@linux.ibm.com>]

On Tue, 2019-05-14 at 10:18 -0700, Lakshmi wrote:
> On 5/12/19 5:37 PM, nramas@linux.microsoft.com wrote:
> > Hello,
> > 
> > I am trying to test IMA signature validation using EVMCTL version 1.1
> > Am running kernel version 5.1.0 rc2 on an Ubuntu desktop.
> > 
> > I have followed the steps given in the README below:
> > https://sourceforge.net/p/linux-ima/ima-evm-utils/ci/master/tree/README
> > 
> > I have created private\public key pair and the DER encoded certificate 
> > for the private key. Imported the signed DER encoded cert to IMA keyring.
> > 
> > keyctl show %keyring:.ima
> > Keyring
> > 1054868458 ---lswrv      0     0  keyring: .ima
> >   740136756 --als--v      0     0   \_ asymmetric: hostname: whoami signing
> > key: 85512d09fc12c7f38b9679352651dcb365903336
> > 
> > cat /proc/keys | grep -i signing
> > 2c1d9734 I--Q---     1 perm 39010000     0     0 asymmetri hostname:
> > whoami signing key: 85512d09fc12c7f38b9679352651dcb365903336: X509.rsa
> > 65903336 []
> > 
> > evmctl ima_sign -a sha256 --key /etc/keys/privkey_evm.pem 
> > /boot/vmlinuz-5.1.0-rc2+
> > 
> > In the key identifier set in security.ima attribute the key identifier 
> > should be 65903336 to match the key in the IMA keyring. But it is b8847de9.
> > 
> > getfattr -d -m ima -e hex /boot/vmlinuz-5.1.0-rc2+
> > getfattr: Removing leading '/' from absolute path names
> > # file: boot/vmlinuz-5.1.0-rc2+
> > security.ima=0x030204b8847de90080b06c8d5517a6afea64805c2871581b256a4efcf7ce4ba079a85545e5e70a2603596366c4e342f11052291e9b558ccb1a1208747f12c45bbe4cee59c727f308a46e951c0df9b1f6b443a8c0a4f5ac881d49e0cce9927b64eeab29c5688aba0758e5cfb30c26fd5b131c2206f1b208d48a427c53a77ae5baf98f4994a19f67b163 
> > 
> > 
> > When trying to verify the IMA signature I get the following error
> > 
> > evmctl ima_verify --key /etc/keys/x509_evm.der /boot/vmlinuz-5.1.0-rc2+
> > /boot/vmlinuz-5.1.0-rc2+: RSA_public_decrypt() failed: -1
> > error:0407008A:rsa routines:RSA_padding_check_PKCS1_type_1:invalid padding
> > error:04067072:rsa routines:rsa_ossl_public_decrypt:padding check failed
> > 
> > This looks very similar to the issue discussed here
> > https://sourceforge.net/p/linux-ima/mailman/message/34290588/
> > 
> > But the bug discussed in the above thread looks to be fixed though.
> > 
> > Am I missing something?
> > 
> > Thank you.
> > 
> >   -lakshmi
> > 
> 
> I have tried the above on Linux kernel 4.18.0-17 as well and am seeing 
> the same behavior.
> 
> I am unable to find older versions (prior to Version 1.1) of evmctl to 
> check if the behavior is different.

Missing from this log is the list of keys on the .ima keyring.

Mimi