Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull integrity updates from James Morris:
 "This contains a mixture of bug fixes, code cleanup, and new
  functionality. Of note is the integrity cache locking fix, file change
  detection, and support for a new EVM portable and immutable signature
  type.

  The re-introduction of the integrity cache lock (iint) fixes the
  problem of attempting to take the i_rwsem shared a second time, when
  it was previously taken exclusively. Defining atomic flags resolves
  the original iint/i_rwsem circular locking - accessing the file data
  vs. modifying the file metadata. Although it fixes the O_DIRECT
  problem as well, a subsequent patch is needed to remove the explicit
  O_DIRECT prevention.

  For performance reasons, detecting when a file has changed and needs
  to be re-measured, re-appraised, and/or re-audited, was limited to
  after the last writer has closed, and only if the file data has
  changed. Detecting file change is based on i_version. For filesystems
  that do not support i_version, remote filesystems, or userspace
  filesystems, the file was measured, appraised and/or audited once and
  never re-evaluated. Now local filesystems, which do not support
  i_version or are not mounted with the i_version option, assume the
  file has changed and are required to re-evaluate the file. This change
  does not address detecting file change on remote or userspace
  filesystems.

  Unlike file data signatures, which can be included and distributed in
  software packages (eg. rpm, deb), the existing EVM signature, which
  protects the file metadata, could not be included in software
  packages, as it includes file system specific information (eg. i_ino,
  possibly the UUID). This pull request defines a new EVM portable and
  immutable file metadata signature format, which can be included in
  software packages"

* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  ima/policy: fix parsing of fsuuid
  ima: Use i_version only when filesystem supports it
  integrity: remove unneeded initializations in integrity_iint_cache entries
  ima: log message to module appraisal error
  ima: pass filename to ima_rdwr_violation_check()
  ima: Fix line continuation format
  ima: support new "hash" and "dont_hash" policy actions
  ima: re-introduce own integrity cache lock
  EVM: Add support for portable signature format
  EVM: Allow userland to permit modification of EVM-protected metadata
  ima: relax requiring a file signature for new files with zero length

1 files changed, 50 insertions, 17 deletions

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 9826c02e2db8..a8d502827270 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -31,7 +31,7 @@
 int evm_initialized;
 
 static char *integrity_status_msg[] = {
-	"pass", "fail", "no_label", "no_xattrs", "unknown"
+	"pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
 };
 char *evm_hmac = "hmac(sha1)";
 char *evm_hash = "sha1";
@@ -76,6 +76,11 @@ static void __init evm_init_config(void)
 	pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
 }
 
+static bool evm_key_loaded(void)
+{
+	return (bool)(evm_initialized & EVM_KEY_MASK);
+}
+
 static int evm_find_protected_xattrs(struct dentry *dentry)
 {
 	struct inode *inode = d_backing_inode(dentry);
@@ -123,7 +128,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 	enum integrity_status evm_status = INTEGRITY_PASS;
 	int rc, xattr_len;
 
-	if (iint && iint->evm_status == INTEGRITY_PASS)
+	if (iint && (iint->evm_status == INTEGRITY_PASS ||
+		     iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
 		return iint->evm_status;
 
 	/* if status is not PASS, try to check again - against -ENOMEM */
@@ -164,22 +170,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 			rc = -EINVAL;
 		break;
 	case EVM_IMA_XATTR_DIGSIG:
+	case EVM_XATTR_PORTABLE_DIGSIG:
 		rc = evm_calc_hash(dentry, xattr_name, xattr_value,
-				xattr_value_len, calc.digest);
+				   xattr_value_len, xattr_data->type,
+				   calc.digest);
 		if (rc)
 			break;
 		rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
 					(const char *)xattr_data, xattr_len,
 					calc.digest, sizeof(calc.digest));
 		if (!rc) {
-			/* Replace RSA with HMAC if not mounted readonly and
-			 * not immutable
-			 */
-			if (!IS_RDONLY(d_backing_inode(dentry)) &&
-			    !IS_IMMUTABLE(d_backing_inode(dentry)))
+			if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
+				if (iint)
+					iint->flags |= EVM_IMMUTABLE_DIGSIG;
+				evm_status = INTEGRITY_PASS_IMMUTABLE;
+			} else if (!IS_RDONLY(d_backing_inode(dentry)) &&
+				   !IS_IMMUTABLE(d_backing_inode(dentry))) {
 				evm_update_evmxattr(dentry, xattr_name,
 						    xattr_value,
 						    xattr_value_len);
+			}
 		}
 		break;
 	default:
@@ -241,7 +251,7 @@ enum integrity_status evm_verifyxattr(struct dentry *dentry,
 				      void *xattr_value, size_t xattr_value_len,
 				      struct integrity_iint_cache *iint)
 {
-	if (!evm_initialized || !evm_protected_xattr(xattr_name))
+	if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
 		return INTEGRITY_UNKNOWN;
 
 	if (!iint) {
@@ -265,7 +275,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
 {
 	struct inode *inode = d_backing_inode(dentry);
 
-	if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
+	if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
 		return 0;
 	return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
 }
@@ -280,7 +290,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
  * affect security.evm.  An interesting side affect of writing posix xattr
  * acls is their modifying of the i_mode, which is included in security.evm.
  * For posix xattr acls only, permit security.evm, even if it currently
- * doesn't exist, to be updated.
+ * doesn't exist, to be updated unless the EVM signature is immutable.
  */
 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
 			     const void *xattr_value, size_t xattr_value_len)
@@ -299,6 +309,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
 			return 0;
 		goto out;
 	}
+
 	evm_status = evm_verify_current_integrity(dentry);
 	if (evm_status == INTEGRITY_NOXATTRS) {
 		struct integrity_iint_cache *iint;
@@ -345,10 +356,17 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 {
 	const struct evm_ima_xattr_data *xattr_data = xattr_value;
 
+	/* Policy permits modification of the protected xattrs even though
+	 * there's no HMAC key loaded
+	 */
+	if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+		return 0;
+
 	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
 		if (!xattr_value_len)
 			return -EINVAL;
-		if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
+		if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
+		    xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
 			return -EPERM;
 	}
 	return evm_protect_xattr(dentry, xattr_name, xattr_value,
@@ -365,6 +383,12 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
  */
 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
 {
+	/* Policy permits modification of the protected xattrs even though
+	 * there's no HMAC key loaded
+	 */
+	if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+		return 0;
+
 	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
 }
 
@@ -393,8 +417,8 @@ static void evm_reset_status(struct inode *inode)
 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
 			     const void *xattr_value, size_t xattr_value_len)
 {
-	if (!evm_initialized || (!evm_protected_xattr(xattr_name)
-				 && !posix_xattr_acl(xattr_name)))
+	if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name)
+				  && !posix_xattr_acl(xattr_name)))
 		return;
 
 	evm_reset_status(dentry->d_inode);
@@ -414,7 +438,7 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
  */
 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
 {
-	if (!evm_initialized || !evm_protected_xattr(xattr_name))
+	if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
 		return;
 
 	evm_reset_status(dentry->d_inode);
@@ -425,12 +449,21 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
 /**
  * evm_inode_setattr - prevent updating an invalid EVM extended attribute
  * @dentry: pointer to the affected dentry
+ *
+ * Permit update of file attributes when files have a valid EVM signature,
+ * except in the case of them having an immutable portable signature.
  */
 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
 {
 	unsigned int ia_valid = attr->ia_valid;
 	enum integrity_status evm_status;
 
+	/* Policy permits modification of the protected attrs even though
+	 * there's no HMAC key loaded
+	 */
+	if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+		return 0;
+
 	if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
 		return 0;
 	evm_status = evm_verify_current_integrity(dentry);
@@ -456,7 +489,7 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
  */
 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 {
-	if (!evm_initialized)
+	if (!evm_key_loaded())
 		return;
 
 	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
@@ -473,7 +506,7 @@ int evm_inode_init_security(struct inode *inode,
 	struct evm_ima_xattr_data *xattr_data;
 	int rc;
 
-	if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
+	if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
 		return 0;
 
 	xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);