[linux-block.git] / fs / crypto / policy.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Encryption policy functions for per-file encryption support.
 *
 * Copyright (C) 2015, Google, Inc.
 * Copyright (C) 2015, Motorola Mobility.
 *
 * Originally written by Michael Halcrow, 2015.
 * Modified by Jaegeuk Kim, 2015.
 * Modified by Eric Biggers, 2019 for v2 policy support.
 */

#include <linux/random.h>
#include <linux/string.h>
#include <linux/mount.h>
#include "fscrypt_private.h"

/**
 * fscrypt_policies_equal - check whether two encryption policies are the same
 *
 * Return: %true if equal, else %false
 */
bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
			    const union fscrypt_policy *policy2)
{
	if (policy1->version != policy2->version)
		return false;

	return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
}

static bool fscrypt_valid_enc_modes(u32 contents_mode, u32 filenames_mode)
{
	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
	    filenames_mode == FSCRYPT_MODE_AES_256_CTS)
		return true;

	if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
	    filenames_mode == FSCRYPT_MODE_AES_128_CTS)
		return true;

	if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
	    filenames_mode == FSCRYPT_MODE_ADIANTUM)
		return true;

	return false;
}

static bool supported_direct_key_modes(const struct inode *inode,
				       u32 contents_mode, u32 filenames_mode)
{
	const struct fscrypt_mode *mode;

	if (contents_mode != filenames_mode) {
		fscrypt_warn(inode,
			     "Direct key flag not allowed with different contents and filenames modes");
		return false;
	}
	mode = &fscrypt_modes[contents_mode];

	if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
		fscrypt_warn(inode, "Direct key flag not allowed with %s",
			     mode->friendly_name);
		return false;
	}
	return true;
}

static bool supported_iv_ino_lblk_64_policy(
					const struct fscrypt_policy_v2 *policy,
					const struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	int ino_bits = 64, lblk_bits = 64;

	if (policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
		fscrypt_warn(inode,
			     "The DIRECT_KEY and IV_INO_LBLK_64 flags are mutually exclusive");
		return false;
	}
	/*
	 * It's unsafe to include inode numbers in the IVs if the filesystem can
	 * potentially renumber inodes, e.g. via filesystem shrinking.
	 */
	if (!sb->s_cop->has_stable_inodes ||
	    !sb->s_cop->has_stable_inodes(sb)) {
		fscrypt_warn(inode,
			     "Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't have stable inode numbers",
			     sb->s_id);
		return false;
	}
	if (sb->s_cop->get_ino_and_lblk_bits)
		sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
	if (ino_bits > 32 || lblk_bits > 32) {
		fscrypt_warn(inode,
			     "Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't use 32-bit inode and block numbers",
			     sb->s_id);
		return false;
	}
	return true;
}

static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
					const struct inode *inode)
{
	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
				     policy->filenames_encryption_mode)) {
		fscrypt_warn(inode,
			     "Unsupported encryption modes (contents %d, filenames %d)",
			     policy->contents_encryption_mode,
			     policy->filenames_encryption_mode);
		return false;
	}

	if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
			      FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
		fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
			     policy->flags);
		return false;
	}

	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
	    !supported_direct_key_modes(inode, policy->contents_encryption_mode,
					policy->filenames_encryption_mode))
		return false;

	if (IS_CASEFOLDED(inode)) {
		/* With v1, there's no way to derive dirhash keys. */
		fscrypt_warn(inode,
			     "v1 policies can't be used on casefolded directories");
		return false;
	}

	return true;
}

static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy,
					const struct inode *inode)
{
	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
				     policy->filenames_encryption_mode)) {
		fscrypt_warn(inode,
			     "Unsupported encryption modes (contents %d, filenames %d)",
			     policy->contents_encryption_mode,
			     policy->filenames_encryption_mode);
		return false;
	}

	if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
		fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
			     policy->flags);
		return false;
	}

	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
	    !supported_direct_key_modes(inode, policy->contents_encryption_mode,
					policy->filenames_encryption_mode))
		return false;

	if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) &&
	    !supported_iv_ino_lblk_64_policy(policy, inode))
		return false;

	if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {
		fscrypt_warn(inode, "Reserved bits set in encryption policy");
		return false;
	}

	return true;
}

/**
 * fscrypt_supported_policy - check whether an encryption policy is supported
 *
 * Given an encryption policy, check whether all its encryption modes and other
 * settings are supported by this kernel on the given inode.  (But we don't
 * currently don't check for crypto API support here, so attempting to use an
 * algorithm not configured into the crypto API will still fail later.)
 *
 * Return: %true if supported, else %false
 */
bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
			      const struct inode *inode)
{
	switch (policy_u->version) {
	case FSCRYPT_POLICY_V1:
		return fscrypt_supported_v1_policy(&policy_u->v1, inode);
	case FSCRYPT_POLICY_V2:
		return fscrypt_supported_v2_policy(&policy_u->v2, inode);
	}
	return false;
}

/**
 * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy
 *
 * Create an fscrypt_context for an inode that is being assigned the given
 * encryption policy.  A new nonce is randomly generated.
 *
 * Return: the size of the new context in bytes.
 */
static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
					   const union fscrypt_policy *policy_u)
{
	memset(ctx_u, 0, sizeof(*ctx_u));

	switch (policy_u->version) {
	case FSCRYPT_POLICY_V1: {
		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
		struct fscrypt_context_v1 *ctx = &ctx_u->v1;

		ctx->version = FSCRYPT_CONTEXT_V1;
		ctx->contents_encryption_mode =
			policy->contents_encryption_mode;
		ctx->filenames_encryption_mode =
			policy->filenames_encryption_mode;
		ctx->flags = policy->flags;
		memcpy(ctx->master_key_descriptor,
		       policy->master_key_descriptor,
		       sizeof(ctx->master_key_descriptor));
		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
		return sizeof(*ctx);
	}
	case FSCRYPT_POLICY_V2: {
		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
		struct fscrypt_context_v2 *ctx = &ctx_u->v2;

		ctx->version = FSCRYPT_CONTEXT_V2;
		ctx->contents_encryption_mode =
			policy->contents_encryption_mode;
		ctx->filenames_encryption_mode =
			policy->filenames_encryption_mode;
		ctx->flags = policy->flags;
		memcpy(ctx->master_key_identifier,
		       policy->master_key_identifier,
		       sizeof(ctx->master_key_identifier));
		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
		return sizeof(*ctx);
	}
	}
	BUG();
}

/**
 * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy
 *
 * Given an fscrypt_context, build the corresponding fscrypt_policy.
 *
 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
 * version number or size.
 *
 * This does *not* validate the settings within the policy itself, e.g. the
 * modes, flags, and reserved bits.  Use fscrypt_supported_policy() for that.
 */
int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
				const union fscrypt_context *ctx_u,
				int ctx_size)
{
	memset(policy_u, 0, sizeof(*policy_u));

	if (!fscrypt_context_is_valid(ctx_u, ctx_size))
		return -EINVAL;

	switch (ctx_u->version) {
	case FSCRYPT_CONTEXT_V1: {
		const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
		struct fscrypt_policy_v1 *policy = &policy_u->v1;

		policy->version = FSCRYPT_POLICY_V1;
		policy->contents_encryption_mode =
			ctx->contents_encryption_mode;
		policy->filenames_encryption_mode =
			ctx->filenames_encryption_mode;
		policy->flags = ctx->flags;
		memcpy(policy->master_key_descriptor,
		       ctx->master_key_descriptor,
		       sizeof(policy->master_key_descriptor));
		return 0;
	}
	case FSCRYPT_CONTEXT_V2: {
		const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
		struct fscrypt_policy_v2 *policy = &policy_u->v2;

		policy->version = FSCRYPT_POLICY_V2;
		policy->contents_encryption_mode =
			ctx->contents_encryption_mode;
		policy->filenames_encryption_mode =
			ctx->filenames_encryption_mode;
		policy->flags = ctx->flags;
		memcpy(policy->__reserved, ctx->__reserved,
		       sizeof(policy->__reserved));
		memcpy(policy->master_key_identifier,
		       ctx->master_key_identifier,
		       sizeof(policy->master_key_identifier));
		return 0;
	}
	}
	/* unreachable */
	return -EINVAL;
}

/* Retrieve an inode's encryption policy */
static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
{
	const struct fscrypt_info *ci;
	union fscrypt_context ctx;
	int ret;

	ci = READ_ONCE(inode->i_crypt_info);
	if (ci) {
		/* key available, use the cached policy */
		*policy = ci->ci_policy;
		return 0;
	}

	if (!IS_ENCRYPTED(inode))
		return -ENODATA;

	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	if (ret < 0)
		return (ret == -ERANGE) ? -EINVAL : ret;

	return fscrypt_policy_from_context(policy, &ctx, ret);
}

static int set_encryption_policy(struct inode *inode,
				 const union fscrypt_policy *policy)
{
	union fscrypt_context ctx;
	int ctxsize;
	int err;

	if (!fscrypt_supported_policy(policy, inode))
		return -EINVAL;

	switch (policy->version) {
	case FSCRYPT_POLICY_V1:
		/*
		 * The original encryption policy version provided no way of
		 * verifying that the correct master key was supplied, which was
		 * insecure in scenarios where multiple users have access to the
		 * same encrypted files (even just read-only access).  The new
		 * encryption policy version fixes this and also implies use of
		 * an improved key derivation function and allows non-root users
		 * to securely remove keys.  So as long as compatibility with
		 * old kernels isn't required, it is recommended to use the new
		 * policy version for all new encrypted directories.
		 */
		pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
			     current->comm, current->pid);
		break;
	case FSCRYPT_POLICY_V2:
		err = fscrypt_verify_key_added(inode->i_sb,
					       policy->v2.master_key_identifier);
		if (err)
			return err;
		break;
	default:
		WARN_ON(1);
		return -EINVAL;
	}

	ctxsize = fscrypt_new_context_from_policy(&ctx, policy);

	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
}

int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
{
	union fscrypt_policy policy;
	union fscrypt_policy existing_policy;
	struct inode *inode = file_inode(filp);
	u8 version;
	int size;
	int ret;

	if (get_user(policy.version, (const u8 __user *)arg))
		return -EFAULT;

	size = fscrypt_policy_size(&policy);
	if (size <= 0)
		return -EINVAL;

	/*
	 * We should just copy the remaining 'size - 1' bytes here, but a
	 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
	 * think that size can be 0 here (despite the check above!) *and* that
	 * it's a compile-time constant.  Thus it would think copy_from_user()
	 * is passed compile-time constant ULONG_MAX, causing the compile-time
	 * buffer overflow check to fail, breaking the build. This only occurred
	 * when building an i386 kernel with -Os and branch profiling enabled.
	 *
	 * Work around it by just copying the first byte again...
	 */
	version = policy.version;
	if (copy_from_user(&policy, arg, size))
		return -EFAULT;
	policy.version = version;

	if (!inode_owner_or_capable(inode))
		return -EACCES;

	ret = mnt_want_write_file(filp);
	if (ret)
		return ret;

	inode_lock(inode);

	ret = fscrypt_get_policy(inode, &existing_policy);
	if (ret == -ENODATA) {
		if (!S_ISDIR(inode->i_mode))
			ret = -ENOTDIR;
		else if (IS_DEADDIR(inode))
			ret = -ENOENT;
		else if (!inode->i_sb->s_cop->empty_dir(inode))
			ret = -ENOTEMPTY;
		else
			ret = set_encryption_policy(inode, &policy);
	} else if (ret == -EINVAL ||
		   (ret == 0 && !fscrypt_policies_equal(&policy,
							&existing_policy))) {
		/* The file already uses a different encryption policy. */
		ret = -EEXIST;
	}

	inode_unlock(inode);

	mnt_drop_write_file(filp);
	return ret;
}
EXPORT_SYMBOL(fscrypt_ioctl_set_policy);

/* Original ioctl version; can only get the original policy version */
int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
{
	union fscrypt_policy policy;
	int err;

	err = fscrypt_get_policy(file_inode(filp), &policy);
	if (err)
		return err;

	if (policy.version != FSCRYPT_POLICY_V1)
		return -EINVAL;

	if (copy_to_user(arg, &policy, sizeof(policy.v1)))
		return -EFAULT;
	return 0;
}
EXPORT_SYMBOL(fscrypt_ioctl_get_policy);

/* Extended ioctl version; can get policies of any version */
int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
{
	struct fscrypt_get_policy_ex_arg arg;
	union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
	size_t policy_size;
	int err;

	/* arg is policy_size, then policy */
	BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
	BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
		     offsetof(typeof(arg), policy));
	BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));

	err = fscrypt_get_policy(file_inode(filp), policy);
	if (err)
		return err;
	policy_size = fscrypt_policy_size(policy);

	if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
		return -EFAULT;

	if (policy_size > arg.policy_size)
		return -EOVERFLOW;
	arg.policy_size = policy_size;

	if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
		return -EFAULT;
	return 0;
}
EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);

/* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
{
	struct inode *inode = file_inode(filp);
	union fscrypt_context ctx;
	int ret;

	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	if (ret < 0)
		return ret;
	if (!fscrypt_context_is_valid(&ctx, ret))
		return -EINVAL;
	if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
			 FS_KEY_DERIVATION_NONCE_SIZE))
		return -EFAULT;
	return 0;
}
EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);

/**
 * fscrypt_has_permitted_context() - is a file's encryption policy permitted
 *				     within its directory?
 *
 * @parent: inode for parent directory
 * @child: inode for file being looked up, opened, or linked into @parent
 *
 * Filesystems must call this before permitting access to an inode in a
 * situation where the parent directory is encrypted (either before allowing
 * ->lookup() to succeed, or for a regular file before allowing it to be opened)
 * and before any operation that involves linking an inode into an encrypted
 * directory, including link, rename, and cross rename.  It enforces the
 * constraint that within a given encrypted directory tree, all files use the
 * same encryption policy.  The pre-access check is needed to detect potentially
 * malicious offline violations of this constraint, while the link and rename
 * checks are needed to prevent online violations of this constraint.
 *
 * Return: 1 if permitted, 0 if forbidden.
 */
int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
{
	union fscrypt_policy parent_policy, child_policy;
	int err;

	/* No restrictions on file types which are never encrypted */
	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
	    !S_ISLNK(child->i_mode))
		return 1;

	/* No restrictions if the parent directory is unencrypted */
	if (!IS_ENCRYPTED(parent))
		return 1;

	/* Encrypted directories must not contain unencrypted files */
	if (!IS_ENCRYPTED(child))
		return 0;

	/*
	 * Both parent and child are encrypted, so verify they use the same
	 * encryption policy.  Compare the fscrypt_info structs if the keys are
	 * available, otherwise retrieve and compare the fscrypt_contexts.
	 *
	 * Note that the fscrypt_context retrieval will be required frequently
	 * when accessing an encrypted directory tree without the key.
	 * Performance-wise this is not a big deal because we already don't
	 * really optimize for file access without the key (to the extent that
	 * such access is even possible), given that any attempted access
	 * already causes a fscrypt_context retrieval and keyring search.
	 *
	 * In any case, if an unexpected error occurs, fall back to "forbidden".
	 */

	err = fscrypt_get_encryption_info(parent);
	if (err)
		return 0;
	err = fscrypt_get_encryption_info(child);
	if (err)
		return 0;

	err = fscrypt_get_policy(parent, &parent_policy);
	if (err)
		return 0;

	err = fscrypt_get_policy(child, &child_policy);
	if (err)
		return 0;

	return fscrypt_policies_equal(&parent_policy, &child_policy);
}
EXPORT_SYMBOL(fscrypt_has_permitted_context);

/**
 * fscrypt_inherit_context() - Sets a child context from its parent
 * @parent: Parent inode from which the context is inherited.
 * @child:  Child inode that inherits the context from @parent.
 * @fs_data:  private data given by FS.
 * @preload:  preload child i_crypt_info if true
 *
 * Return: 0 on success, -errno on failure
 */
int fscrypt_inherit_context(struct inode *parent, struct inode *child,
						void *fs_data, bool preload)
{
	union fscrypt_context ctx;
	int ctxsize;
	struct fscrypt_info *ci;
	int res;

	res = fscrypt_get_encryption_info(parent);
	if (res < 0)
		return res;

	ci = READ_ONCE(parent->i_crypt_info);
	if (ci == NULL)
		return -ENOKEY;

	ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);

	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
	res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
	if (res)
		return res;
	return preload ? fscrypt_get_encryption_info(child): 0;
}
EXPORT_SYMBOL(fscrypt_inherit_context);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
0b81d077 JK	2	/*
	3	* Encryption policy functions for per-file encryption support.
	4	*
	5	* Copyright (C) 2015, Google, Inc.
	6	* Copyright (C) 2015, Motorola Mobility.
	7	*
5dae460c	8	* Originally written by Michael Halcrow, 2015.
0b81d077	9	* Modified by Jaegeuk Kim, 2015.
5dae460c	10	* Modified by Eric Biggers, 2019 for v2 policy support.
0b81d077 JK	11	*/
	12
	13	#include <linux/random.h>
	14	#include <linux/string.h>
ba63f23d	15	#include <linux/mount.h>
cc4e0df0	16	#include "fscrypt_private.h"
0b81d077	17
5dae460c EB	18	/**
	19	* fscrypt_policies_equal - check whether two encryption policies are the same
	20	*
	21	* Return: %true if equal, else %false
0b81d077	22	*/
5dae460c EB	23	bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
5dae460c EB	24	const union fscrypt_policy *policy2)
0b81d077	25	{
5dae460c EB	26	if (policy1->version != policy2->version)
	27	return false;
	28
	29	return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
0b81d077 JK	30	}
0b81d077 JK	31
ef5b18b0 EB	32	static bool fscrypt_valid_enc_modes(u32 contents_mode, u32 filenames_mode)
	33	{
	34	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
	35	filenames_mode == FSCRYPT_MODE_AES_256_CTS)
	36	return true;
	37
	38	if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
	39	filenames_mode == FSCRYPT_MODE_AES_128_CTS)
	40	return true;
	41
	42	if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
	43	filenames_mode == FSCRYPT_MODE_ADIANTUM)
	44	return true;
	45
	46	return false;
	47	}
	48
85af90e5 EB	49	static bool supported_direct_key_modes(const struct inode *inode,
	50	u32 contents_mode, u32 filenames_mode)
	51	{
	52	const struct fscrypt_mode *mode;
	53
	54	if (contents_mode != filenames_mode) {
	55	fscrypt_warn(inode,
	56	"Direct key flag not allowed with different contents and filenames modes");
	57	return false;
	58	}
	59	mode = &fscrypt_modes[contents_mode];
	60
	61	if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
	62	fscrypt_warn(inode, "Direct key flag not allowed with %s",
	63	mode->friendly_name);
	64	return false;
	65	}
	66	return true;
	67	}
	68
b103fb76 EB	69	static bool supported_iv_ino_lblk_64_policy(
	70	const struct fscrypt_policy_v2 *policy,
	71	const struct inode *inode)
	72	{
	73	struct super_block *sb = inode->i_sb;
	74	int ino_bits = 64, lblk_bits = 64;
	75
	76	if (policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
	77	fscrypt_warn(inode,
	78	"The DIRECT_KEY and IV_INO_LBLK_64 flags are mutually exclusive");
	79	return false;
	80	}
	81	/*
	82	* It's unsafe to include inode numbers in the IVs if the filesystem can
	83	* potentially renumber inodes, e.g. via filesystem shrinking.
	84	*/
	85	if (!sb->s_cop->has_stable_inodes \|\|
	86	!sb->s_cop->has_stable_inodes(sb)) {
	87	fscrypt_warn(inode,
	88	"Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't have stable inode numbers",
	89	sb->s_id);
	90	return false;
	91	}
	92	if (sb->s_cop->get_ino_and_lblk_bits)
	93	sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
	94	if (ino_bits > 32 \|\| lblk_bits > 32) {
	95	fscrypt_warn(inode,
	96	"Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't use 32-bit inode and block numbers",
	97	sb->s_id);
	98	return false;
	99	}
	100	return true;
	101	}
	102
393a24a7 EB	103	static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
	104	const struct inode *inode)
	105	{
	106	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
	107	policy->filenames_encryption_mode)) {
	108	fscrypt_warn(inode,
	109	"Unsupported encryption modes (contents %d, filenames %d)",
	110	policy->contents_encryption_mode,
	111	policy->filenames_encryption_mode);
	112	return false;
	113	}
	114
	115	if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK \|
	116	FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
	117	fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
	118	policy->flags);
	119	return false;
	120	}
	121
85af90e5 EB	122	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
	123	!supported_direct_key_modes(inode, policy->contents_encryption_mode,
	124	policy->filenames_encryption_mode))
	125	return false;
	126
6e1918cf DR	127	if (IS_CASEFOLDED(inode)) {
	128	/* With v1, there's no way to derive dirhash keys. */
	129	fscrypt_warn(inode,
	130	"v1 policies can't be used on casefolded directories");
	131	return false;
	132	}
	133
393a24a7 EB	134	return true;
	135	}
	136
	137	static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy,
	138	const struct inode *inode)
	139	{
	140	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
	141	policy->filenames_encryption_mode)) {
	142	fscrypt_warn(inode,
	143	"Unsupported encryption modes (contents %d, filenames %d)",
	144	policy->contents_encryption_mode,
	145	policy->filenames_encryption_mode);
	146	return false;
	147	}
	148
	149	if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
	150	fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
	151	policy->flags);
	152	return false;
	153	}
	154
85af90e5 EB	155	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
	156	!supported_direct_key_modes(inode, policy->contents_encryption_mode,
	157	policy->filenames_encryption_mode))
	158	return false;
	159
393a24a7 EB	160	if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) &&
	161	!supported_iv_ino_lblk_64_policy(policy, inode))
	162	return false;
	163
	164	if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {
	165	fscrypt_warn(inode, "Reserved bits set in encryption policy");
	166	return false;
	167	}
	168
	169	return true;
	170	}
	171
5dae460c EB	172	/**
	173	* fscrypt_supported_policy - check whether an encryption policy is supported
	174	*
	175	* Given an encryption policy, check whether all its encryption modes and other
393a24a7 EB	176	* settings are supported by this kernel on the given inode. (But we don't
	177	* currently don't check for crypto API support here, so attempting to use an
	178	* algorithm not configured into the crypto API will still fail later.)
5dae460c EB	179	*
	180	* Return: %true if supported, else %false
	181	*/
	182	bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
	183	const struct inode *inode)
0b81d077	184	{
5dae460c	185	switch (policy_u->version) {
393a24a7 EB	186	case FSCRYPT_POLICY_V1:
	187	return fscrypt_supported_v1_policy(&policy_u->v1, inode);
	188	case FSCRYPT_POLICY_V2:
	189	return fscrypt_supported_v2_policy(&policy_u->v2, inode);
5dae460c EB	190	}
	191	return false;
	192	}
	193
	194	/**
	195	* fscrypt_new_context_from_policy - create a new fscrypt_context from a policy
	196	*
	197	* Create an fscrypt_context for an inode that is being assigned the given
	198	* encryption policy. A new nonce is randomly generated.
	199	*
	200	* Return: the size of the new context in bytes.
	201	*/
	202	static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
	203	const union fscrypt_policy *policy_u)
	204	{
	205	memset(ctx_u, 0, sizeof(*ctx_u));
	206
	207	switch (policy_u->version) {
	208	case FSCRYPT_POLICY_V1: {
	209	const struct fscrypt_policy_v1 *policy = &policy_u->v1;
	210	struct fscrypt_context_v1 *ctx = &ctx_u->v1;
	211
	212	ctx->version = FSCRYPT_CONTEXT_V1;
	213	ctx->contents_encryption_mode =
	214	policy->contents_encryption_mode;
	215	ctx->filenames_encryption_mode =
	216	policy->filenames_encryption_mode;
	217	ctx->flags = policy->flags;
	218	memcpy(ctx->master_key_descriptor,
	219	policy->master_key_descriptor,
	220	sizeof(ctx->master_key_descriptor));
	221	get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
	222	return sizeof(*ctx);
	223	}
	224	case FSCRYPT_POLICY_V2: {
	225	const struct fscrypt_policy_v2 *policy = &policy_u->v2;
	226	struct fscrypt_context_v2 *ctx = &ctx_u->v2;
	227
	228	ctx->version = FSCRYPT_CONTEXT_V2;
	229	ctx->contents_encryption_mode =
	230	policy->contents_encryption_mode;
	231	ctx->filenames_encryption_mode =
	232	policy->filenames_encryption_mode;
	233	ctx->flags = policy->flags;
	234	memcpy(ctx->master_key_identifier,
	235	policy->master_key_identifier,
	236	sizeof(ctx->master_key_identifier));
	237	get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
	238	return sizeof(*ctx);
	239	}
	240	}
	241	BUG();
	242	}
0b81d077	243
5dae460c EB	244	/**
	245	* fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy
	246	*
	247	* Given an fscrypt_context, build the corresponding fscrypt_policy.
	248	*
	249	* Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
	250	* version number or size.
	251	*
	252	* This does not validate the settings within the policy itself, e.g. the
	253	* modes, flags, and reserved bits. Use fscrypt_supported_policy() for that.
	254	*/
	255	int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
	256	const union fscrypt_context *ctx_u,
	257	int ctx_size)
	258	{
	259	memset(policy_u, 0, sizeof(*policy_u));
0b81d077	260
e98ad464	261	if (!fscrypt_context_is_valid(ctx_u, ctx_size))
0b81d077	262	return -EINVAL;
0b81d077	263
5dae460c EB	264	switch (ctx_u->version) {
	265	case FSCRYPT_CONTEXT_V1: {
	266	const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
	267	struct fscrypt_policy_v1 *policy = &policy_u->v1;
	268
	269	policy->version = FSCRYPT_POLICY_V1;
	270	policy->contents_encryption_mode =
	271	ctx->contents_encryption_mode;
	272	policy->filenames_encryption_mode =
	273	ctx->filenames_encryption_mode;
	274	policy->flags = ctx->flags;
	275	memcpy(policy->master_key_descriptor,
	276	ctx->master_key_descriptor,
	277	sizeof(policy->master_key_descriptor));
	278	return 0;
	279	}
	280	case FSCRYPT_CONTEXT_V2: {
	281	const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
	282	struct fscrypt_policy_v2 *policy = &policy_u->v2;
	283
	284	policy->version = FSCRYPT_POLICY_V2;
	285	policy->contents_encryption_mode =
	286	ctx->contents_encryption_mode;
	287	policy->filenames_encryption_mode =
	288	ctx->filenames_encryption_mode;
	289	policy->flags = ctx->flags;
	290	memcpy(policy->__reserved, ctx->__reserved,
	291	sizeof(policy->__reserved));
	292	memcpy(policy->master_key_identifier,
	293	ctx->master_key_identifier,
	294	sizeof(policy->master_key_identifier));
	295	return 0;
	296	}
	297	}
	298	/* unreachable */
	299	return -EINVAL;
	300	}
	301
	302	/* Retrieve an inode's encryption policy */
	303	static int fscrypt_get_policy(struct inode inode, union fscrypt_policy policy)
	304	{
	305	const struct fscrypt_info *ci;
	306	union fscrypt_context ctx;
	307	int ret;
	308
	309	ci = READ_ONCE(inode->i_crypt_info);
	310	if (ci) {
	311	/* key available, use the cached policy */
	312	*policy = ci->ci_policy;
	313	return 0;
	314	}
	315
	316	if (!IS_ENCRYPTED(inode))
	317	return -ENODATA;
	318
	319	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	320	if (ret < 0)
	321	return (ret == -ERANGE) ? -EINVAL : ret;
	322
	323	return fscrypt_policy_from_context(policy, &ctx, ret);
	324	}
	325
	326	static int set_encryption_policy(struct inode *inode,
	327	const union fscrypt_policy *policy)
328	{
329	union fscrypt_context ctx;
330	int ctxsize;
5ab7189a	331	int err;
5dae460c EB	332
5dae460c EB	333	if (!fscrypt_supported_policy(policy, inode))
0b81d077 JK	334	return -EINVAL;
0b81d077 JK	335
5ab7189a EB	336	switch (policy->version) {
5ab7189a EB	337	case FSCRYPT_POLICY_V1:
5dae460c EB	338	/*
	339	* The original encryption policy version provided no way of
	340	* verifying that the correct master key was supplied, which was
	341	* insecure in scenarios where multiple users have access to the
	342	* same encrypted files (even just read-only access). The new
	343	* encryption policy version fixes this and also implies use of
	344	* an improved key derivation function and allows non-root users
	345	* to securely remove keys. So as long as compatibility with
	346	* old kernels isn't required, it is recommended to use the new
	347	* policy version for all new encrypted directories.
	348	*/
	349	pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
	350	current->comm, current->pid);
5ab7189a EB	351	break;
	352	case FSCRYPT_POLICY_V2:
	353	err = fscrypt_verify_key_added(inode->i_sb,
	354	policy->v2.master_key_identifier);
	355	if (err)
	356	return err;
	357	break;
	358	default:
	359	WARN_ON(1);
	360	return -EINVAL;
5dae460c	361	}
0b81d077	362
5dae460c EB	363	ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
	364
	365	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
0b81d077 JK	366	}
0b81d077 JK	367
db717d8e	368	int fscrypt_ioctl_set_policy(struct file filp, const void __user arg)
0b81d077	369	{
5dae460c EB	370	union fscrypt_policy policy;
5dae460c EB	371	union fscrypt_policy existing_policy;
ba63f23d	372	struct inode *inode = file_inode(filp);
5dae460c EB	373	u8 version;
5dae460c EB	374	int size;
ba63f23d EB	375	int ret;
ba63f23d EB	376
5dae460c	377	if (get_user(policy.version, (const u8 __user *)arg))
db717d8e EB	378	return -EFAULT;
db717d8e EB	379
5dae460c EB	380	size = fscrypt_policy_size(&policy);
	381	if (size <= 0)
	382	return -EINVAL;
	383
	384	/*
	385	* We should just copy the remaining 'size - 1' bytes here, but a
	386	* bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
	387	* think that size can be 0 here (despite the check above!) and that
	388	* it's a compile-time constant. Thus it would think copy_from_user()
	389	* is passed compile-time constant ULONG_MAX, causing the compile-time
	390	* buffer overflow check to fail, breaking the build. This only occurred
	391	* when building an i386 kernel with -Os and branch profiling enabled.
	392	*
	393	* Work around it by just copying the first byte again...
	394	*/
	395	version = policy.version;
	396	if (copy_from_user(&policy, arg, size))
	397	return -EFAULT;
	398	policy.version = version;
	399
163ae1c6 EB	400	if (!inode_owner_or_capable(inode))
	401	return -EACCES;
	402
ba63f23d EB	403	ret = mnt_want_write_file(filp);
	404	if (ret)
	405	return ret;
	406
8906a822 EB	407	inode_lock(inode);
8906a822 EB	408
5dae460c	409	ret = fscrypt_get_policy(inode, &existing_policy);
efee590e	410	if (ret == -ENODATA) {
002ced4b	411	if (!S_ISDIR(inode->i_mode))
dffd0cfa	412	ret = -ENOTDIR;
5858bdad HF	413	else if (IS_DEADDIR(inode))
5858bdad HF	414	ret = -ENOENT;
ba63f23d EB	415	else if (!inode->i_sb->s_cop->empty_dir(inode))
	416	ret = -ENOTEMPTY;
	417	else
5dae460c EB	418	ret = set_encryption_policy(inode, &policy);
	419	} else if (ret == -EINVAL \|\|
	420	(ret == 0 && !fscrypt_policies_equal(&policy,
	421	&existing_policy))) {
efee590e	422	/* The file already uses a different encryption policy. */
8488cd96	423	ret = -EEXIST;
0b81d077 JK	424	}
0b81d077 JK	425
8906a822 EB	426	inode_unlock(inode);
8906a822 EB	427
ba63f23d EB	428	mnt_drop_write_file(filp);
ba63f23d EB	429	return ret;
0b81d077	430	}
db717d8e	431	EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
0b81d077	432
5dae460c	433	/* Original ioctl version; can only get the original policy version */
db717d8e	434	int fscrypt_ioctl_get_policy(struct file filp, void __user arg)
0b81d077	435	{
5dae460c EB	436	union fscrypt_policy policy;
5dae460c EB	437	int err;
0b81d077	438
5dae460c EB	439	err = fscrypt_get_policy(file_inode(filp), &policy);
	440	if (err)
	441	return err;
0b81d077	442
5dae460c	443	if (policy.version != FSCRYPT_POLICY_V1)
0b81d077 JK	444	return -EINVAL;
0b81d077 JK	445
5dae460c	446	if (copy_to_user(arg, &policy, sizeof(policy.v1)))
db717d8e	447	return -EFAULT;
0b81d077 JK	448	return 0;
0b81d077 JK	449	}
db717d8e	450	EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
0b81d077	451
5dae460c EB	452	/* Extended ioctl version; can get policies of any version */
	453	int fscrypt_ioctl_get_policy_ex(struct file filp, void __user uarg)
	454	{
	455	struct fscrypt_get_policy_ex_arg arg;
	456	union fscrypt_policy policy = (union fscrypt_policy )&arg.policy;
	457	size_t policy_size;
	458	int err;
	459
	460	/* arg is policy_size, then policy */
	461	BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
	462	BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
	463	offsetof(typeof(arg), policy));
	464	BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
	465
	466	err = fscrypt_get_policy(file_inode(filp), policy);
	467	if (err)
	468	return err;
	469	policy_size = fscrypt_policy_size(policy);
	470
	471	if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
	472	return -EFAULT;
	473
	474	if (policy_size > arg.policy_size)
	475	return -EOVERFLOW;
	476	arg.policy_size = policy_size;
	477
	478	if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
	479	return -EFAULT;
	480	return 0;
	481	}
	482	EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
	483
e98ad464 EB	484	/* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
	485	int fscrypt_ioctl_get_nonce(struct file filp, void __user arg)
	486	{
	487	struct inode *inode = file_inode(filp);
	488	union fscrypt_context ctx;
	489	int ret;
	490
	491	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	492	if (ret < 0)
	493	return ret;
	494	if (!fscrypt_context_is_valid(&ctx, ret))
	495	return -EINVAL;
	496	if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
	497	FS_KEY_DERIVATION_NONCE_SIZE))
	498	return -EFAULT;
	499	return 0;
	500	}
	501	EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);
	502
272f98f6 EB	503	/**
	504	* fscrypt_has_permitted_context() - is a file's encryption policy permitted
	505	* within its directory?
	506	*
	507	* @parent: inode for parent directory
	508	* @child: inode for file being looked up, opened, or linked into @parent
	509	*
	510	* Filesystems must call this before permitting access to an inode in a
	511	* situation where the parent directory is encrypted (either before allowing
	512	* ->lookup() to succeed, or for a regular file before allowing it to be opened)
	513	* and before any operation that involves linking an inode into an encrypted
	514	* directory, including link, rename, and cross rename. It enforces the
	515	* constraint that within a given encrypted directory tree, all files use the
	516	* same encryption policy. The pre-access check is needed to detect potentially
	517	* malicious offline violations of this constraint, while the link and rename
	518	* checks are needed to prevent online violations of this constraint.
	519	*
f5e55e77	520	* Return: 1 if permitted, 0 if forbidden.
272f98f6	521	*/
0b81d077 JK	522	int fscrypt_has_permitted_context(struct inode parent, struct inode child)
0b81d077 JK	523	{
5dae460c EB	524	union fscrypt_policy parent_policy, child_policy;
5dae460c EB	525	int err;
0b81d077	526
42d97eb0 EB	527	/* No restrictions on file types which are never encrypted */
	528	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
	529	!S_ISLNK(child->i_mode))
	530	return 1;
	531
272f98f6	532	/* No restrictions if the parent directory is unencrypted */
e0428a26	533	if (!IS_ENCRYPTED(parent))
0b81d077	534	return 1;
272f98f6 EB	535
272f98f6 EB	536	/* Encrypted directories must not contain unencrypted files */
e0428a26	537	if (!IS_ENCRYPTED(child))
0b81d077	538	return 0;
272f98f6 EB	539
	540	/*
	541	* Both parent and child are encrypted, so verify they use the same
	542	* encryption policy. Compare the fscrypt_info structs if the keys are
	543	* available, otherwise retrieve and compare the fscrypt_contexts.
	544	*
	545	* Note that the fscrypt_context retrieval will be required frequently
	546	* when accessing an encrypted directory tree without the key.
	547	* Performance-wise this is not a big deal because we already don't
	548	* really optimize for file access without the key (to the extent that
	549	* such access is even possible), given that any attempted access
	550	* already causes a fscrypt_context retrieval and keyring search.
	551	*
	552	* In any case, if an unexpected error occurs, fall back to "forbidden".
	553	*/
	554
5dae460c EB	555	err = fscrypt_get_encryption_info(parent);
5dae460c EB	556	if (err)
0b81d077	557	return 0;
5dae460c EB	558	err = fscrypt_get_encryption_info(child);
5dae460c EB	559	if (err)
0b81d077	560	return 0;
272f98f6	561
5dae460c EB	562	err = fscrypt_get_policy(parent, &parent_policy);
5dae460c EB	563	if (err)
272f98f6 EB	564	return 0;
272f98f6 EB	565
5dae460c EB	566	err = fscrypt_get_policy(child, &child_policy);
5dae460c EB	567	if (err)
0b81d077 JK	568	return 0;
0b81d077 JK	569
5dae460c	570	return fscrypt_policies_equal(&parent_policy, &child_policy);
0b81d077 JK	571	}
	572	EXPORT_SYMBOL(fscrypt_has_permitted_context);
	573
	574	/**
	575	* fscrypt_inherit_context() - Sets a child context from its parent
	576	* @parent: Parent inode from which the context is inherited.
	577	* @child: Child inode that inherits the context from @parent.
	578	* @fs_data: private data given by FS.
5bbdcbbb	579	* @preload: preload child i_crypt_info if true
0b81d077	580	*
5bbdcbbb	581	* Return: 0 on success, -errno on failure
0b81d077 JK	582	*/
	583	int fscrypt_inherit_context(struct inode parent, struct inode child,
	584	void *fs_data, bool preload)
	585	{
5dae460c EB	586	union fscrypt_context ctx;
5dae460c EB	587	int ctxsize;
0b81d077 JK	588	struct fscrypt_info *ci;
	589	int res;
	590
0b81d077 JK	591	res = fscrypt_get_encryption_info(parent);
	592	if (res < 0)
	593	return res;
	594
e37a784d	595	ci = READ_ONCE(parent->i_crypt_info);
0b81d077 JK	596	if (ci == NULL)
	597	return -ENOKEY;
	598
5dae460c EB	599	ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);
5dae460c EB	600
af65207c	601	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
5dae460c	602	res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
0b81d077 JK	603	if (res)
	604	return res;
	605	return preload ? fscrypt_get_encryption_info(child): 0;
	606	}
	607	EXPORT_SYMBOL(fscrypt_inherit_context);