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>

4 files changed, 72 insertions, 0 deletions

diff --git a/include/linux/evm.h b/include/linux/evm.h
index 33a92471e463..7c10761916a2 100644
--- a/include/linux/evm.h
+++ b/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 */
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index 375dc3e6015c..a45d0d630a30 100644
--- a/security/integrity/evm/evm.h
+++ b/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);
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index c631b99bda95..c9902bddcb9a 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/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
  */
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 1746c3669c6f..23486355f443 100644
--- a/security/integrity/evm/evm_main.c
+++ b/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)
 {