ext4 crypto: separate kernel and userspace structure for the key

Use struct ext4_encryption_key only for the master key passed via the
kernel keyring.

For internal kernel space users, we now use struct ext4_crypt_info.
This will allow us to put information from the policy structure so we
can cache it and avoid needing to constantly looking up the extended
attribute.  We will do this in a spearate patch.  This patch is mostly
mechnical to make it easier for patch review.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/crypto.c

@@ -118,7 +118,7 @@ struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
 	struct ext4_crypto_ctx *ctx = NULL;
 	int res = 0;
 	unsigned long flags;
-	struct ext4_encryption_key *key = &EXT4_I(inode)->i_encryption_key;
+	struct ext4_crypt_info *ci = &EXT4_I(inode)->i_crypt_info;
 
 	if (!ext4_read_workqueue)
 		ext4_init_crypto();
@@ -152,14 +152,14 @@ struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
 
 	/* Allocate a new Crypto API context if we don't already have
 	 * one or if it isn't the right mode. */
-	BUG_ON(key->mode == EXT4_ENCRYPTION_MODE_INVALID);
-	if (ctx->tfm && (ctx->mode != key->mode)) {
+	BUG_ON(ci->ci_mode == EXT4_ENCRYPTION_MODE_INVALID);
+	if (ctx->tfm && (ctx->mode != ci->ci_mode)) {
 		crypto_free_tfm(ctx->tfm);
 		ctx->tfm = NULL;
 		ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
 	}
 	if (!ctx->tfm) {
-		switch (key->mode) {
+		switch (ci->ci_mode) {
 		case EXT4_ENCRYPTION_MODE_AES_256_XTS:
 			ctx->tfm = crypto_ablkcipher_tfm(
 				crypto_alloc_ablkcipher("xts(aes)", 0, 0));
@@ -177,9 +177,9 @@ struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
 			ctx->tfm = NULL;
 			goto out;
 		}
-		ctx->mode = key->mode;
+		ctx->mode = ci->ci_mode;
 	}
-	BUG_ON(key->size != ext4_encryption_key_size(key->mode));
+	BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_mode));
 
 	/* There shouldn't be a bounce page attached to the crypto
 	 * context at this point. */
@@ -322,7 +322,7 @@ static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
 	int res = 0;
 
 	BUG_ON(!ctx->tfm);
-	BUG_ON(ctx->mode != ei->i_encryption_key.mode);
+	BUG_ON(ctx->mode != ei->i_crypt_info.ci_mode);
 
 	if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) {
 		printk_ratelimited(KERN_ERR
@@ -334,8 +334,8 @@ static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
 	crypto_ablkcipher_clear_flags(atfm, ~0);
 	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 
-	res = crypto_ablkcipher_setkey(atfm, ei->i_encryption_key.raw,
-				       ei->i_encryption_key.size);
+	res = crypto_ablkcipher_setkey(atfm, ei->i_crypt_info.ci_raw,
+				       ei->i_crypt_info.ci_size);
 	if (res) {
 		printk_ratelimited(KERN_ERR
 				   "%s: crypto_ablkcipher_setkey() failed\n",

fs/ext4/crypto_fname.c

@@ -277,34 +277,25 @@ void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
 	*ctx = NULL;
 }
 
-/**
- * ext4_search_fname_crypto_ctx() -
- */
-static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
-		const struct ext4_encryption_key *key)
-{
-	return NULL;
-}
-
 /**
  * ext4_alloc_fname_crypto_ctx() -
  */
 struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
-	const struct ext4_encryption_key *key)
+	const struct ext4_crypt_info *ci)
 {
 	struct ext4_fname_crypto_ctx *ctx;
 
 	ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
 	if (ctx == NULL)
 		return ERR_PTR(-ENOMEM);
-	if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
+	if (ci->ci_mode == EXT4_ENCRYPTION_MODE_INVALID) {
 		/* This will automatically set key mode to invalid
 		 * As enum for ENCRYPTION_MODE_INVALID is zero */
-		memset(&ctx->key, 0, sizeof(ctx->key));
+		memset(&ctx->ci, 0, sizeof(ctx->ci));
 	} else {
-		memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
+		memcpy(&ctx->ci, ci, sizeof(struct ext4_crypt_info));
 	}
-	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
+	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == ci->ci_mode)
 		? 0 : 1;
 	ctx->ctfm_key_is_ready = 0;
 	ctx->ctfm = NULL;
@@ -335,21 +326,17 @@ struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
 	if (!ext4_has_encryption_key(inode))
 		ext4_generate_encryption_key(inode);
 
-	/* Get a crypto context based on the key.
-	 * A new context is allocated if no context matches the requested key.
-	 */
-	ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
-	if (ctx == NULL)
-		ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
+	/* Get a crypto context based on the key. */
+	ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_crypt_info));
 	if (IS_ERR(ctx))
 		return ctx;
 
 	ctx->flags = ei->i_crypt_policy_flags;
 	if (ctx->has_valid_key) {
-		if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
+		if (ctx->ci.ci_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
 			printk_once(KERN_WARNING
 				    "ext4: unsupported key mode %d\n",
-				    ctx->key.mode);
+				    ctx->ci.ci_mode);
 			return ERR_PTR(-ENOKEY);
 		}
 
@@ -389,7 +376,7 @@ struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
 			 * are pretty weak,
 			 * we directly use the inode master key */
 			res = crypto_ablkcipher_setkey(ctx->ctfm,
-					ctx->key.raw, ctx->key.size);
+					ctx->ci.ci_raw, ctx->ci.ci_size);
 			if (res) {
 				ext4_put_fname_crypto_ctx(&ctx);
 				return ERR_PTR(-EIO);

fs/ext4/crypto_key.c

@@ -91,7 +91,7 @@ static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
 int ext4_generate_encryption_key(struct inode *inode)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
+	struct ext4_crypt_info *crypt_info = &ei->i_crypt_info;
 	char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
 				 (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
 	struct key *keyring_key = NULL;
@@ -112,17 +112,17 @@ int ext4_generate_encryption_key(struct inode *inode)
 
 	ei->i_crypt_policy_flags = ctx.flags;
 	if (S_ISREG(inode->i_mode))
-		crypt_key->mode = ctx.contents_encryption_mode;
+		crypt_info->ci_mode = ctx.contents_encryption_mode;
 	else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
-		crypt_key->mode = ctx.filenames_encryption_mode;
+		crypt_info->ci_mode = ctx.filenames_encryption_mode;
 	else {
 		printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n");
 		BUG();
 	}
-	crypt_key->size = ext4_encryption_key_size(crypt_key->mode);
-	BUG_ON(!crypt_key->size);
+	crypt_info->ci_size = ext4_encryption_key_size(crypt_info->ci_mode);
+	BUG_ON(!crypt_info->ci_size);
 	if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
-		memset(crypt_key->raw, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
+		memset(crypt_info->ci_raw, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
 		goto out;
 	}
 	memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
@@ -148,19 +148,20 @@ int ext4_generate_encryption_key(struct inode *inode)
 	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
 		     EXT4_KEY_DERIVATION_NONCE_SIZE);
 	BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
-	res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw);
+	res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
+				  crypt_info->ci_raw);
 out:
 	if (keyring_key)
 		key_put(keyring_key);
 	if (res < 0)
-		crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID;
+		crypt_info->ci_mode = EXT4_ENCRYPTION_MODE_INVALID;
 	return res;
 }
 
 int ext4_has_encryption_key(struct inode *inode)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
+	struct ext4_crypt_info *crypt_info = &ei->i_crypt_info;
 
-	return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID);
+	return (crypt_info->ci_mode != EXT4_ENCRYPTION_MODE_INVALID);
 }

fs/ext4/ext4.h

@@ -955,7 +955,7 @@ struct ext4_inode_info {
 
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 	/* Encryption params */
-	struct ext4_encryption_key i_encryption_key;
+	struct ext4_crypt_info i_crypt_info;
 #endif
 };
 

fs/ext4/ext4_crypto.h

@@ -66,10 +66,17 @@ struct ext4_encryption_context {
 #define EXT4_KEY_DESC_PREFIX "ext4:"
 #define EXT4_KEY_DESC_PREFIX_SIZE 5
 
+/* This is passed in from userspace into the kernel keyring */
 struct ext4_encryption_key {
-	uint32_t mode;
+        __u32 mode;
         char raw[EXT4_MAX_KEY_SIZE];
-	uint32_t size;
+        __u32 size;
+} __attribute__((__packed__));
+
+struct ext4_crypt_info {
+	unsigned char	ci_mode;
+	unsigned char	ci_size;
+	char		ci_raw[EXT4_MAX_KEY_SIZE];
 };
 
 #define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
@@ -125,7 +132,7 @@ struct ext4_fname_crypto_ctx {
 	u32 lim;
 	struct crypto_ablkcipher *ctfm;
 	struct crypto_hash *htfm;
-	struct ext4_encryption_key key;
+	struct ext4_crypt_info ci;
 	unsigned flags : 8;
 	unsigned has_valid_key : 1;
 	unsigned ctfm_key_is_ready : 1;

fs/ext4/super.c

@@ -879,7 +879,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	atomic_set(&ei->i_unwritten, 0);
 	INIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
-	ei->i_encryption_key.mode = EXT4_ENCRYPTION_MODE_INVALID;
+	ei->i_crypt_info.ci_mode = EXT4_ENCRYPTION_MODE_INVALID;
 #endif
 
 	return &ei->vfs_inode;