1 files changed, 297 insertions, 0 deletions
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
new file mode 100644
index 000000000000..995003cb5301
--- /dev/null
+++ b/fs/crypto/keyinfo.c
@@ -0,0 +1,297 @@
+/*
+ * key management facility for FS encryption support.
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This contains encryption key functions.
+ *
+ * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ */
+
+#include <keys/user-type.h>
+#include <linux/scatterlist.h>
+#include "fscrypt_private.h"
+
+static void derive_crypt_complete(struct crypto_async_request *req, int rc)
+{
+	struct fscrypt_completion_result *ecr = req->data;
+
+	if (rc == -EINPROGRESS)
+		return;
+
+	ecr->res = rc;
+	complete(&ecr->completion);
+}
+
+/**
+ * derive_key_aes() - Derive a key using AES-128-ECB
+ * @deriving_key: Encryption key used for derivation.
+ * @source_key:   Source key to which to apply derivation.
+ * @derived_key:  Derived key.
+ *
+ * Return: Zero on success; non-zero otherwise.
+ */
+static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
+				u8 source_key[FS_AES_256_XTS_KEY_SIZE],
+				u8 derived_key[FS_AES_256_XTS_KEY_SIZE])
+{
+	int res = 0;
+	struct ablkcipher_request *req = NULL;
+	DECLARE_FS_COMPLETION_RESULT(ecr);
+	struct scatterlist src_sg, dst_sg;
+	struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0, 0);
+
+	if (IS_ERR(tfm)) {
+		res = PTR_ERR(tfm);
+		tfm = NULL;
+		goto out;
+	}
+	crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
+	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+	if (!req) {
+		res = -ENOMEM;
+		goto out;
+	}
+	ablkcipher_request_set_callback(req,
+			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+			derive_crypt_complete, &ecr);
+	res = crypto_ablkcipher_setkey(tfm, deriving_key,
+					FS_AES_128_ECB_KEY_SIZE);
+	if (res < 0)
+		goto out;
+
+	sg_init_one(&src_sg, source_key, FS_AES_256_XTS_KEY_SIZE);
+	sg_init_one(&dst_sg, derived_key, FS_AES_256_XTS_KEY_SIZE);
+	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
+					FS_AES_256_XTS_KEY_SIZE, NULL);
+	res = crypto_ablkcipher_encrypt(req);
+	if (res == -EINPROGRESS || res == -EBUSY) {
+		wait_for_completion(&ecr.completion);
+		res = ecr.res;
+	}
+out:
+	if (req)
+		ablkcipher_request_free(req);
+	if (tfm)
+		crypto_free_ablkcipher(tfm);
+	return res;
+}
+
+static int validate_user_key(struct fscrypt_info *crypt_info,
+			struct fscrypt_context *ctx, u8 *raw_key,
+			const char *prefix)
+{
+	char *description;
+	struct key *keyring_key;
+	struct fscrypt_key *master_key;
+	const struct user_key_payload *ukp;
+	int prefix_size = strlen(prefix);
+	int full_key_len = prefix_size + (FS_KEY_DESCRIPTOR_SIZE * 2) + 1;
+	int res;
+
+	/* FIXME: 3.18 causes kernel panic.
+	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
+				FS_KEY_DESCRIPTOR_SIZE,
+				ctx->master_key_descriptor);
+	*/
+	description = kmalloc(full_key_len, GFP_NOFS);
+	if (!description)
+		return -ENOMEM;
+
+	memcpy(description, prefix, prefix_size);
+	sprintf(description + prefix_size,
+			"%*phN", FS_KEY_DESCRIPTOR_SIZE,
+			ctx->master_key_descriptor);
+	description[full_key_len - 1] = '\0';
+
+	keyring_key = request_key(&key_type_logon, description, NULL);
+	kfree(description);
+	if (IS_ERR(keyring_key))
+		return PTR_ERR(keyring_key);
+	down_read(&keyring_key->sem);
+
+	if (keyring_key->type != &key_type_logon) {
+		printk_once(KERN_WARNING
+				"%s: key type must be logon\n", __func__);
+		res = -ENOKEY;
+		goto out;
+	}
+	ukp = user_key_payload(keyring_key);
+	if (ukp->datalen != sizeof(struct fscrypt_key)) {
+		res = -EINVAL;
+		goto out;
+	}
+	master_key = (struct fscrypt_key *)ukp->data;
+	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
+
+	if (master_key->size != FS_AES_256_XTS_KEY_SIZE) {
+		printk_once(KERN_WARNING
+				"%s: key size incorrect: %d\n",
+				__func__, master_key->size);
+		res = -ENOKEY;
+		goto out;
+	}
+	res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
+out:
+	up_read(&keyring_key->sem);
+	key_put(keyring_key);
+	return res;
+}
+
+static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
+				 const char **cipher_str_ret, int *keysize_ret)
+{
+	if (S_ISREG(inode->i_mode)) {
+		if (ci->ci_data_mode == FS_ENCRYPTION_MODE_AES_256_XTS) {
+			*cipher_str_ret = "xts(aes)";
+			*keysize_ret = FS_AES_256_XTS_KEY_SIZE;
+			return 0;
+		}
+		pr_warn_once("fscrypto: unsupported contents encryption mode "
+			     "%d for inode %lu\n",
+			     ci->ci_data_mode, inode->i_ino);
+		return -ENOKEY;
+	}
+
+	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
+		if (ci->ci_filename_mode == FS_ENCRYPTION_MODE_AES_256_CTS) {
+			*cipher_str_ret = "cts(cbc(aes))";
+			*keysize_ret = FS_AES_256_CTS_KEY_SIZE;
+			return 0;
+		}
+		pr_warn_once("fscrypto: unsupported filenames encryption mode "
+			     "%d for inode %lu\n",
+			     ci->ci_filename_mode, inode->i_ino);
+		return -ENOKEY;
+	}
+
+	pr_warn_once("fscrypto: unsupported file type %d for inode %lu\n",
+		     (inode->i_mode & S_IFMT), inode->i_ino);
+	return -ENOKEY;
+}
+
+static void put_crypt_info(struct fscrypt_info *ci)
+{
+	if (!ci)
+		return;
+
+	crypto_free_ablkcipher(ci->ci_ctfm);
+	kmem_cache_free(fscrypt_info_cachep, ci);
+}
+
+int fscrypt_get_encryption_info(struct inode *inode)
+{
+	struct fscrypt_info *crypt_info;
+	struct fscrypt_context ctx;
+	struct crypto_ablkcipher *ctfm;
+	const char *cipher_str;
+	int keysize;
+	u8 *raw_key = NULL;
+	int res;
+
+	if (inode->i_crypt_info)
+		return 0;
+
+	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
+	if (res)
+		return res;
+
+	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	if (res < 0) {
+		if (!fscrypt_dummy_context_enabled(inode) ||
+		    inode->i_sb->s_cop->is_encrypted(inode))
+			return res;
+		/* Fake up a context for an unencrypted directory */
+		memset(&ctx, 0, sizeof(ctx));
+		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
+		ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
+		ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
+		memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
+	} else if (res != sizeof(ctx)) {
+		return -EINVAL;
+	}
+
+	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
+		return -EINVAL;
+
+	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
+		return -EINVAL;
+
+	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
+	if (!crypt_info)
+		return -ENOMEM;
+
+	crypt_info->ci_flags = ctx.flags;
+	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
+	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
+	crypt_info->ci_ctfm = NULL;
+	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
+				sizeof(crypt_info->ci_master_key));
+
+	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
+	if (res)
+		goto out;
+
+	/*
+	 * This cannot be a stack buffer because it is passed to the scatterlist
+	 * crypto API as part of key derivation.
+	 */
+	res = -ENOMEM;
+	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
+	if (!raw_key)
+		goto out;
+
+	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX);
+	if (res && inode->i_sb->s_cop->key_prefix) {
+		int res2 = validate_user_key(crypt_info, &ctx, raw_key,
+					     inode->i_sb->s_cop->key_prefix);
+		if (res2) {
+			if (res2 == -ENOKEY)
+				res = -ENOKEY;
+			goto out;
+		}
+	} else if (res) {
+		goto out;
+	}
+	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
+	if (!ctfm || IS_ERR(ctfm)) {
+		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
+		printk(KERN_DEBUG
+		       "%s: error %d (inode %u) allocating crypto tfm\n",
+		       __func__, res, (unsigned) inode->i_ino);
+		goto out;
+	}
+	crypt_info->ci_ctfm = ctfm;
+	crypto_ablkcipher_clear_flags(ctfm, ~0);
+	crypto_ablkcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
+	res = crypto_ablkcipher_setkey(ctfm, raw_key, keysize);
+	if (res)
+		goto out;
+
+	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
+		crypt_info = NULL;
+out:
+	if (res == -ENOKEY)
+		res = 0;
+	put_crypt_info(crypt_info);
+	kzfree(raw_key);
+	return res;
+}
+EXPORT_SYMBOL(fscrypt_get_encryption_info);
+
+void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
+{
+	struct fscrypt_info *prev;
+
+	if (ci == NULL)
+		ci = ACCESS_ONCE(inode->i_crypt_info);
+	if (ci == NULL)
+		return;
+
+	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
+	if (prev != ci)
+		return;
+
+	put_crypt_info(ci);
+}
+EXPORT_SYMBOL(fscrypt_put_encryption_info);