diff options
| -rw-r--r-- | security/integrity/evm/evm_main.c | 113 |
1 files changed, 112 insertions, 1 deletions
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 300df6906e05..0196168aeb7d 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -18,6 +18,7 @@ #include <linux/integrity.h> #include <linux/evm.h> #include <linux/magic.h> +#include <linux/posix_acl_xattr.h> #include <crypto/hash.h> #include <crypto/hash_info.h> @@ -331,6 +332,92 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) } /* + * evm_xattr_acl_change - check if passed ACL changes the inode mode + * @mnt_userns: user namespace of the idmapped mount + * @dentry: pointer to the affected dentry + * @xattr_name: requested xattr + * @xattr_value: requested xattr value + * @xattr_value_len: requested xattr value length + * + * Check if passed ACL changes the inode mode, which is protected by EVM. + * + * Returns 1 if passed ACL causes inode mode change, 0 otherwise. + */ +static int evm_xattr_acl_change(struct user_namespace *mnt_userns, + struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ +#ifdef CONFIG_FS_POSIX_ACL + umode_t mode; + struct posix_acl *acl = NULL, *acl_res; + struct inode *inode = d_backing_inode(dentry); + int rc; + + /* + * user_ns is not relevant here, ACL_USER/ACL_GROUP don't have impact + * on the inode mode (see posix_acl_equiv_mode()). + */ + acl = posix_acl_from_xattr(&init_user_ns, xattr_value, xattr_value_len); + if (IS_ERR_OR_NULL(acl)) + return 1; + + acl_res = acl; + /* + * Passing mnt_userns is necessary to correctly determine the GID in + * an idmapped mount, as the GID is used to clear the setgid bit in + * the inode mode. + */ + rc = posix_acl_update_mode(mnt_userns, inode, &mode, &acl_res); + + posix_acl_release(acl); + + if (rc) + return 1; + + if (inode->i_mode != mode) + return 1; +#endif + return 0; +} + +/* + * evm_xattr_change - check if passed xattr value differs from current value + * @mnt_userns: user namespace of the idmapped mount + * @dentry: pointer to the affected dentry + * @xattr_name: requested xattr + * @xattr_value: requested xattr value + * @xattr_value_len: requested xattr value length + * + * Check if passed xattr value differs from current value. + * + * Returns 1 if passed xattr value differs from current value, 0 otherwise. + */ +static int evm_xattr_change(struct user_namespace *mnt_userns, + struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + char *xattr_data = NULL; + int rc = 0; + + if (posix_xattr_acl(xattr_name)) + return evm_xattr_acl_change(mnt_userns, dentry, xattr_name, + xattr_value, xattr_value_len); + + rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data, + 0, GFP_NOFS); + if (rc < 0) + return 1; + + if (rc == xattr_value_len) + rc = !!memcmp(xattr_value, xattr_data, rc); + else + rc = 1; + + kfree(xattr_data); + return rc; +} + +/* * evm_protect_xattr - protect the EVM extended attribute * * Prevent security.evm from being modified or removed without the @@ -397,7 +484,13 @@ out: if (evm_status == INTEGRITY_FAIL_IMMUTABLE) return 0; - if (evm_status != INTEGRITY_PASS) + if (evm_status == INTEGRITY_PASS_IMMUTABLE && + !evm_xattr_change(mnt_userns, dentry, xattr_name, xattr_value, + xattr_value_len)) + return 0; + + if (evm_status != INTEGRITY_PASS && + evm_status != INTEGRITY_PASS_IMMUTABLE) integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), dentry->d_name.name, "appraise_metadata", integrity_status_msg[evm_status], @@ -553,6 +646,19 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) evm_update_evmxattr(dentry, xattr_name, NULL, 0); } +static int evm_attr_change(struct dentry *dentry, struct iattr *attr) +{ + struct inode *inode = d_backing_inode(dentry); + unsigned int ia_valid = attr->ia_valid; + + if ((!(ia_valid & ATTR_UID) || uid_eq(attr->ia_uid, inode->i_uid)) && + (!(ia_valid & ATTR_GID) || gid_eq(attr->ia_gid, inode->i_gid)) && + (!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode)) + return 0; + + return 1; +} + /** * evm_inode_setattr - prevent updating an invalid EVM extended attribute * @dentry: pointer to the affected dentry @@ -584,6 +690,11 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL || evm_status == INTEGRITY_UNKNOWN))) return 0; + + if (evm_status == INTEGRITY_PASS_IMMUTABLE && + !evm_attr_change(dentry, attr)) + return 0; + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), dentry->d_name.name, "appraise_metadata", integrity_status_msg[evm_status], -EPERM, 0); |