evm: Enforce signatures version 3 with new EVM policy 'bit 3' 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 <stefanb@linux.ibm.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm index 44750a9..db3007b 100644 --- a/Documentation/ABI/testing/evm +++ b/Documentation/ABI/testing/evm
@@ -26,6 +26,7 @@ 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 === ==================================================
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index 51aba5a..694552ace 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 */ #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) struct xattr_list { struct list_head list;
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index b15d9d9..b59e3f1 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; } +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 = d_backing_inode(dentry); @@ -258,6 +266,12 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, } hdr = (struct signature_v2_hdr *)xattr_data; + + if (evm_sigv3_required() && hdr->version != 3) { + evm_status = INTEGRITY_FAIL; + goto out; + } + digest.hdr.algo = hdr->hash_algo; rc = evm_calc_hash(dentry, xattr_name, xattr_value, xattr_value_len, xattr_data->type, &digest,