1 files changed, 102 insertions, 0 deletions
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
new file mode 100644
index 000000000..e99c00350
--- /dev/null
+++ b/fs/verity/measure.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ioctl to get a verity file's digest
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include "fsverity_private.h"
+
+#include <linux/uaccess.h>
+
+/**
+ * fsverity_ioctl_measure() - get a verity file's digest
+ * @filp: file to get digest of
+ * @_uarg: user pointer to fsverity_digest
+ *
+ * Retrieve the file digest that the kernel is enforcing for reads from a verity
+ * file.  See the "FS_IOC_MEASURE_VERITY" section of
+ * Documentation/filesystems/fsverity.rst for the documentation.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
+{
+	const struct inode *inode = file_inode(filp);
+	struct fsverity_digest __user *uarg = _uarg;
+	const struct fsverity_info *vi;
+	const struct fsverity_hash_alg *hash_alg;
+	struct fsverity_digest arg;
+
+	vi = fsverity_get_info(inode);
+	if (!vi)
+		return -ENODATA; /* not a verity file */
+	hash_alg = vi->tree_params.hash_alg;
+
+	/*
+	 * The user specifies the digest_size their buffer has space for; we can
+	 * return the digest if it fits in the available space.  We write back
+	 * the actual size, which may be shorter than the user-specified size.
+	 */
+
+	if (get_user(arg.digest_size, &uarg->digest_size))
+		return -EFAULT;
+	if (arg.digest_size < hash_alg->digest_size)
+		return -EOVERFLOW;
+
+	memset(&arg, 0, sizeof(arg));
+	arg.digest_algorithm = hash_alg - fsverity_hash_algs;
+	arg.digest_size = hash_alg->digest_size;
+
+	if (copy_to_user(uarg, &arg, sizeof(arg)))
+		return -EFAULT;
+
+	if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size))
+		return -EFAULT;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
+
+/**
+ * fsverity_get_digest() - get a verity file's digest
+ * @inode: inode to get digest of
+ * @digest: (out) pointer to the digest
+ * @alg: (out) pointer to the hash algorithm enumeration
+ *
+ * Return the file hash algorithm and digest of an fsverity protected file.
+ * Assumption: before calling fsverity_get_digest(), the file must have been
+ * opened.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_get_digest(struct inode *inode,
+			u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
+			enum hash_algo *alg)
+{
+	const struct fsverity_info *vi;
+	const struct fsverity_hash_alg *hash_alg;
+	int i;
+
+	vi = fsverity_get_info(inode);
+	if (!vi)
+		return -ENODATA; /* not a verity file */
+
+	hash_alg = vi->tree_params.hash_alg;
+	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
+
+	/* convert the verity hash algorithm name to a hash_algo_name enum */
+	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
+	if (i < 0)
+		return -EINVAL;
+	*alg = i;
+
+	if (WARN_ON_ONCE(hash_alg->digest_size != hash_digest_size[*alg]))
+		return -EINVAL;
+	memcpy(digest, vi->file_digest, hash_alg->digest_size);
+
+	pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
+		 hash_digest_size[*alg], digest);
+
+	return 0;
+}