1 files changed, 384 insertions, 0 deletions

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
new file mode 100644
index 000000000000..92d3d99a9f7b
--- /dev/null
+++ b/security/integrity/evm/evm_main.c
@@ -0,0 +1,384 @@
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm_main.c
+ *      implements evm_inode_setxattr, evm_inode_post_setxattr,
+ *      evm_inode_removexattr, and evm_verifyxattr
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <linux/integrity.h>
+#include <linux/evm.h>
+#include <crypto/hash.h>
+#include "evm.h"
+
+int evm_initialized;
+
+char *evm_hmac = "hmac(sha1)";
+
+char *evm_config_xattrnames[] = {
+#ifdef CONFIG_SECURITY_SELINUX
+        XATTR_NAME_SELINUX,
+#endif
+#ifdef CONFIG_SECURITY_SMACK
+        XATTR_NAME_SMACK,
+#endif
+        XATTR_NAME_CAPS,
+        NULL
+};
+
+static int evm_fixmode;
+static int __init evm_set_fixmode(char *str)
+{
+        if (strncmp(str, "fix", 3) == 0)
+                evm_fixmode = 1;
+        return 0;
+}
+__setup("evm=", evm_set_fixmode);
+
+/*
+ * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
+ *
+ * Compute the HMAC on the dentry's protected set of extended attributes
+ * and compare it against the stored security.evm xattr.
+ *
+ * For performance:
+ * - use the previoulsy retrieved xattr value and length to calculate the
+ *   HMAC.)
+ * - cache the verification result in the iint, when available.
+ *
+ * Returns integrity status
+ */
+static enum integrity_status evm_verify_hmac(struct dentry *dentry,
+                                             const char *xattr_name,
+                                             char *xattr_value,
+                                             size_t xattr_value_len,
+                                             struct integrity_iint_cache *iint)
+{
+        struct evm_ima_xattr_data xattr_data;
+        enum integrity_status evm_status = INTEGRITY_PASS;
+        int rc;
+
+        if (iint && iint->evm_status == INTEGRITY_PASS)
+                return iint->evm_status;
+
+        /* if status is not PASS, try to check again - against -ENOMEM */
+
+        rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+                           xattr_value_len, xattr_data.digest);
+        if (rc < 0) {
+                evm_status = (rc == -ENODATA)
+                    ? INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
+                goto out;
+        }
+
+        xattr_data.type = EVM_XATTR_HMAC;
+        rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
+                           sizeof xattr_data, GFP_NOFS);
+        if (rc < 0)
+                evm_status = (rc == -ENODATA)
+                    ? INTEGRITY_NOLABEL : INTEGRITY_FAIL;
+out:
+        if (iint)
+                iint->evm_status = evm_status;
+        return evm_status;
+}
+
+static int evm_protected_xattr(const char *req_xattr_name)
+{
+        char **xattrname;
+        int namelen;
+        int found = 0;
+
+        namelen = strlen(req_xattr_name);
+        for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+                if ((strlen(*xattrname) == namelen)
+                    && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
+                        found = 1;
+                        break;
+                }
+                if (strncmp(req_xattr_name,
+                            *xattrname + XATTR_SECURITY_PREFIX_LEN,
+                            strlen(req_xattr_name)) == 0) {
+                        found = 1;
+                        break;
+                }
+        }
+        return found;
+}
+
+/**
+ * evm_verifyxattr - verify the integrity of the requested xattr
+ * @dentry: object of the verify xattr
+ * @xattr_name: requested xattr
+ * @xattr_value: requested xattr value
+ * @xattr_value_len: requested xattr value length
+ *
+ * Calculate the HMAC for the given dentry and verify it against the stored
+ * security.evm xattr. For performance, use the xattr value and length
+ * previously retrieved to calculate the HMAC.
+ *
+ * Returns the xattr integrity status.
+ *
+ * This function requires the caller to lock the inode's i_mutex before it
+ * is executed.
+ */
+enum integrity_status evm_verifyxattr(struct dentry *dentry,
+                                      const char *xattr_name,
+                                      void *xattr_value, size_t xattr_value_len,
+                                      struct integrity_iint_cache *iint)
+{
+        if (!evm_initialized || !evm_protected_xattr(xattr_name))
+                return INTEGRITY_UNKNOWN;
+
+        if (!iint) {
+                iint = integrity_iint_find(dentry->d_inode);
+                if (!iint)
+                        return INTEGRITY_UNKNOWN;
+        }
+        return evm_verify_hmac(dentry, xattr_name, xattr_value,
+                                 xattr_value_len, iint);
+}
+EXPORT_SYMBOL_GPL(evm_verifyxattr);
+
+/*
+ * evm_verify_current_integrity - verify the dentry's metadata integrity
+ * @dentry: pointer to the affected dentry
+ *
+ * Verify and return the dentry's metadata integrity. The exceptions are
+ * before EVM is initialized or in 'fix' mode.
+ */
+static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
+{
+        struct inode *inode = dentry->d_inode;
+
+        if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
+                return 0;
+        return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
+}
+
+/*
+ * evm_protect_xattr - protect the EVM extended attribute
+ *
+ * Prevent security.evm from being modified or removed without the
+ * necessary permissions or when the existing value is invalid.
+ *
+ * The posix xattr acls are 'system' prefixed, which normally would not
+ * 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.
+ */
+static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
+                             const void *xattr_value, size_t xattr_value_len)
+{
+        enum integrity_status evm_status;
+
+        if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+        } else if (!evm_protected_xattr(xattr_name)) {
+                if (!posix_xattr_acl(xattr_name))
+                        return 0;
+                evm_status = evm_verify_current_integrity(dentry);
+                if ((evm_status == INTEGRITY_PASS) ||
+                    (evm_status == INTEGRITY_NOXATTRS))
+                        return 0;
+                return -EPERM;
+        }
+        evm_status = evm_verify_current_integrity(dentry);
+        return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
+}
+
+/**
+ * evm_inode_setxattr - protect the EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ * @xattr_value: pointer to the new extended attribute value
+ * @xattr_value_len: pointer to the new extended attribute value length
+ *
+ * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
+ * the current value is valid.
+ */
+int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
+                       const void *xattr_value, size_t xattr_value_len)
+{
+        return evm_protect_xattr(dentry, xattr_name, xattr_value,
+                                 xattr_value_len);
+}
+
+/**
+ * evm_inode_removexattr - protect the EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ *
+ * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
+ * the current value is valid.
+ */
+int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+        return evm_protect_xattr(dentry, xattr_name, NULL, 0);
+}
+
+/**
+ * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ * @xattr_value: pointer to the new extended attribute value
+ * @xattr_value_len: pointer to the new extended attribute value length
+ *
+ * Update the HMAC stored in 'security.evm' to reflect the change.
+ *
+ * No need to take the i_mutex lock here, as this function is called from
+ * __vfs_setxattr_noperm().  The caller of which has taken the inode's
+ * i_mutex lock.
+ */
+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)))
+                return;
+
+        evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
+        return;
+}
+
+/**
+ * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ *
+ * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
+ */
+void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+        struct inode *inode = dentry->d_inode;
+
+        if (!evm_initialized || !evm_protected_xattr(xattr_name))
+                return;
+
+        mutex_lock(&inode->i_mutex);
+        evm_update_evmxattr(dentry, xattr_name, NULL, 0);
+        mutex_unlock(&inode->i_mutex);
+        return;
+}
+
+/**
+ * evm_inode_setattr - prevent updating an invalid EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ */
+int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
+{
+        unsigned int ia_valid = attr->ia_valid;
+        enum integrity_status evm_status;
+
+        if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
+                return 0;
+        evm_status = evm_verify_current_integrity(dentry);
+        if ((evm_status == INTEGRITY_PASS) ||
+            (evm_status == INTEGRITY_NOXATTRS))
+                return 0;
+        return -EPERM;
+}
+
+/**
+ * evm_inode_post_setattr - update 'security.evm' after modifying metadata
+ * @dentry: pointer to the affected dentry
+ * @ia_valid: for the UID and GID status
+ *
+ * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
+ * changes.
+ *
+ * This function is called from notify_change(), which expects the caller
+ * to lock the inode's i_mutex.
+ */
+void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
+{
+        if (!evm_initialized)
+                return;
+
+        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
+                evm_update_evmxattr(dentry, NULL, NULL, 0);
+        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 0;
+
+        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 int __init init_evm(void)
+{
+        int error;
+
+        error = evm_init_secfs();
+        if (error < 0) {
+                printk(KERN_INFO "EVM: Error registering secfs\n");
+                goto err;
+        }
+err:
+        return error;
+}
+
+static void __exit cleanup_evm(void)
+{
+        evm_cleanup_secfs();
+        if (hmac_tfm)
+                crypto_free_shash(hmac_tfm);
+}
+
+/*
+ * evm_display_config - list the EVM protected security extended attributes
+ */
+static int __init evm_display_config(void)
+{
+        char **xattrname;
+
+        for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
+                printk(KERN_INFO "EVM: %s\n", *xattrname);
+        return 0;
+}
+
+pure_initcall(evm_display_config);
+late_initcall(init_evm);
+
+MODULE_DESCRIPTION("Extended Verification Module");
+MODULE_LICENSE("GPL");