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Wed, 25 Mar 2026 21:33:51 +0000 (GMT) From: Stefan Berger To: linux-integrity@vger.kernel.org Cc: linux-kernel@vger.kernel.org, ebiggers@kernel.org, zohar@linux.ibm.com, roberto.sassu@huawei.com, Stefan Berger Subject: [PATCH] evm: Enforce signatures version 3 with new EVM policy 'bit 3' Date: Wed, 25 Mar 2026 17:33:49 -0400 Message-ID: <20260325213349.1061363-1-stefanb@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=IqITsb/g c=1 sm=1 tr=0 ts=69c454c3 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=dtBzxhyFjFcZ9BccNZMA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDE1NyBTYWx0ZWRfX+I42OWb+8gWt VE7tjoPJw0x6WI4oX3by7w+se+Im9RKeN2l7PnGiYAL0JFpa2oNqlPu1iRtAv51Q6PN0+8UWMpQ d9ng1h5mHxbKGfHrFvzhPj7K7e0vZ1SZNI6AN4vgnJzp3TbObUvMPB5G2Buk1W1pauRIo4Bp5uv fAmcQsCcAQ0WAIo4OWXXLCLxLDHSyz0BYmJz19n18BXoP9GBOCN4gkpIMRVxkEOVrc+pddYKi38 SgtQw/4EL7waIODj4sR0j9/aeZ9P7/w1dDJ15QfNodrksLUCpb4Rt9Vngqy9b/twXFuKl6j1SNB SYuaXPh4ZxapabWfb3uWJ/kFqVgVJV+YhzaxGRL959TxiZbkUmsJdhxI+1wTLQuVXoXjEnjhk0Z SBXp1X1KO1wSAVUL0zwPkuk0TavFANxnh2Uw+zIAxdx8RdxS0jf+S0yvUgzqbdJgOaxsm+07Xsb zvldeVFk4vWK8mVqcpg== X-Proofpoint-GUID: 33MzyhSLC_fOzn02VHAqT-SJwxA8pA25 X-Proofpoint-ORIG-GUID: 33MzyhSLC_fOzn02VHAqT-SJwxA8pA25 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-25_05,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 clxscore=1015 spamscore=0 impostorscore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250157 Content-Type: text/plain; charset="utf-8" Enable the configuration of EVM so that it requires that asymmetric signatures it accepts are of version 3 (sigv3). To enable this, introduce bit 3 (value 0x0008) that the user may write to EVM's securityfs policy configuration file 'evm' for sigv3 enforcement. Mention bit 3 in the documentation. Signed-off-by: Stefan Berger --- Documentation/ABI/testing/evm | 1 + security/integrity/evm/evm.h | 3 ++- security/integrity/evm/evm_main.c | 14 ++++++++++++++ 3 files changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm index 44750a933db4..db3007babb58 100644 --- a/Documentation/ABI/testing/evm +++ b/Documentation/ABI/testing/evm @@ -26,6 +26,7 @@ Description: 2 Permit modification of EVM-protected metadata at runtime. Not supported if HMAC validation and creation is enabled (deprecated). + 3 Require asymmetric signatures to be version 3 31 Disable further runtime modification of EVM policy =3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D =20 diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index 51aba5a54275..694552aceaf8 100644 --- a/security/integrity/evm/evm.h +++ b/security/integrity/evm/evm.h @@ -20,11 +20,12 @@ #define EVM_INIT_HMAC 0x0001 #define EVM_INIT_X509 0x0002 #define EVM_ALLOW_METADATA_WRITES 0x0004 +#define EVM_SIGV3_REQUIRED 0x0008 #define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */ =20 #define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509) #define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE = | \ - EVM_ALLOW_METADATA_WRITES) + EVM_ALLOW_METADATA_WRITES | EVM_SIGV3_REQUIRED) =20 struct xattr_list { struct list_head list; diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm= _main.c index b15d9d933b84..b59e3f121b8a 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -136,6 +136,14 @@ static bool evm_hmac_disabled(void) return true; } =20 +static bool evm_sigv3_required(void) +{ + if (evm_initialized & EVM_SIGV3_REQUIRED) + return true; + + return false; +} + static int evm_find_protected_xattrs(struct dentry *dentry) { struct inode *inode =3D d_backing_inode(dentry); @@ -258,6 +266,12 @@ static enum integrity_status evm_verify_hmac(struct de= ntry *dentry, } =20 hdr =3D (struct signature_v2_hdr *)xattr_data; + + if (evm_sigv3_required() && hdr->version !=3D 3) { + evm_status =3D INTEGRITY_FAIL; + goto out; + } + digest.hdr.algo =3D hdr->hash_algo; rc =3D evm_calc_hash(dentry, xattr_name, xattr_value, xattr_value_len, xattr_data->type, &digest, base-commit: e5797456e49041238b131c78e90e5d36a7fc0656 --=20 2.53.0