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path: root/security/integrity/evm/evm_main.c
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Diffstat (limited to 'security/integrity/evm/evm_main.c')
-rw-r--r--security/integrity/evm/evm_main.c67
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);
generated by cgit (git 2.34.1) at 2024-05-28 09:00:09 +0000