evm: add evm_inode_init_security to initialize new files

Initialize 'security.evm' for new files.

Changelog v7:
- renamed evm_inode_post_init_security to evm_inode_init_security
- moved struct xattr definition to earlier patch
- allocate xattr name
Changelog v6:
- Use 'struct evm_ima_xattr_data'
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>

include/linux/evm.h

@@ -9,6 +9,7 @@
 #define _LINUX_EVM_H
 
 #include <linux/integrity.h>
+#include <linux/xattr.h>
 
 #ifdef CONFIG_EVM
 extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
@@ -25,6 +26,9 @@ extern void evm_inode_post_setxattr(struct dentry *dentry,
 extern int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name);
 extern void evm_inode_post_removexattr(struct dentry *dentry,
 				       const char *xattr_name);
+extern int evm_inode_init_security(struct inode *inode,
+				   const struct xattr *xattr_array,
+				   struct xattr *evm);
 #else
 #ifdef CONFIG_INTEGRITY
 static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
@@ -67,5 +71,12 @@ static inline void evm_inode_post_removexattr(struct dentry *dentry,
 	return;
 }
 
+static inline int evm_inode_init_security(struct inode *inode,
+					  const struct xattr *xattr_array,
+					  struct xattr *evm)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif /* CONFIG_EVM_H */
 #endif /* LINUX_EVM_H */

security/integrity/evm/evm.h

@@ -12,6 +12,7 @@
  * File: evm.h
  *
  */
+#include <linux/xattr.h>
 #include <linux/security.h>
 #include "../integrity.h"
 
@@ -29,5 +30,7 @@ extern int evm_update_evmxattr(struct dentry *dentry,
 extern int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
 			 const char *req_xattr_value,
 			 size_t req_xattr_value_len, char *digest);
+extern int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
+			 char *hmac_val);
 extern int evm_init_secfs(void);
 extern void evm_cleanup_secfs(void);

security/integrity/evm/evm_crypto.c

@@ -157,6 +157,26 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
 	return rc;
 }
 
+int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
+		  char *hmac_val)
+{
+	struct hash_desc desc;
+	struct scatterlist sg[1];
+	int error;
+
+	error = init_desc(&desc);
+	if (error != 0) {
+		printk(KERN_INFO "init_desc failed\n");
+		return error;
+	}
+
+	sg_init_one(sg, lsm_xattr->value, lsm_xattr->value_len);
+	crypto_hash_update(&desc, sg, lsm_xattr->value_len);
+	hmac_add_misc(&desc, inode, hmac_val);
+	crypto_free_hash(desc.tfm);
+	return 0;
+}
+
 /*
  * Get the key from the TPM for the SHA1-HMAC
  */

security/integrity/evm/evm_main.c

@@ -98,6 +98,12 @@ static int evm_protected_xattr(const char *req_xattr_name)
 			found = 1;
 			break;
 		}
+		if (strncmp(req_xattr_name,
+			    *xattrname + XATTR_SECURITY_PREFIX_LEN,
+			    strlen(req_xattr_name)) == 0) {
+			found = 1;
+			break;
+		}
 	}
 	return found;
 }
@@ -245,6 +251,38 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 	return;
 }
 
+/*
+ * evm_inode_init_security - initializes security.evm
+ */
+int evm_inode_init_security(struct inode *inode,
+				 const struct xattr *lsm_xattr,
+				 struct xattr *evm_xattr)
+{
+	struct evm_ima_xattr_data *xattr_data;
+	int rc;
+
+	if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
+		return -EOPNOTSUPP;
+
+	xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
+	if (!xattr_data)
+		return -ENOMEM;
+
+	xattr_data->type = EVM_XATTR_HMAC;
+	rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
+	if (rc < 0)
+		goto out;
+
+	evm_xattr->value = xattr_data;
+	evm_xattr->value_len = sizeof(*xattr_data);
+	evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
+	return 0;
+out:
+	kfree(xattr_data);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(evm_inode_init_security);
+
 static struct crypto_hash *tfm_hmac;	/* preload crypto alg */
 static int __init init_evm(void)
 {