diff options
Diffstat (limited to 'fs/crypto/policy.c')
| -rw-r--r-- | fs/crypto/policy.c | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c new file mode 100644 index 000000000..0f9961eed --- /dev/null +++ b/fs/crypto/policy.c @@ -0,0 +1,229 @@ +/* + * Encryption policy functions for per-file encryption support. + * + * Copyright (C) 2015, Google, Inc. + * Copyright (C) 2015, Motorola Mobility. + * + * Written by Michael Halcrow, 2015. + * Modified by Jaegeuk Kim, 2015. + */ + +#include <linux/random.h> +#include <linux/string.h> +#include <linux/fscrypto.h> + +static int inode_has_encryption_context(struct inode *inode) +{ + if (!inode->i_sb->s_cop->get_context) + return 0; + return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0); +} + +/* + * check whether the policy is consistent with the encryption context + * for the inode + */ +static int is_encryption_context_consistent_with_policy(struct inode *inode, + const struct fscrypt_policy *policy) +{ + struct fscrypt_context ctx; + int res; + + if (!inode->i_sb->s_cop->get_context) + return 0; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res != sizeof(ctx)) + return 0; + + return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor, + FS_KEY_DESCRIPTOR_SIZE) == 0 && + (ctx.flags == policy->flags) && + (ctx.contents_encryption_mode == + policy->contents_encryption_mode) && + (ctx.filenames_encryption_mode == + policy->filenames_encryption_mode)); +} + +static int create_encryption_context_from_policy(struct inode *inode, + const struct fscrypt_policy *policy) +{ + struct fscrypt_context ctx; + int res; + + if (!inode->i_sb->s_cop->set_context) + return -EOPNOTSUPP; + + if (inode->i_sb->s_cop->prepare_context) { + res = inode->i_sb->s_cop->prepare_context(inode); + if (res) + return res; + } + + ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; + memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, + FS_KEY_DESCRIPTOR_SIZE); + + if (!fscrypt_valid_contents_enc_mode( + policy->contents_encryption_mode)) { + printk(KERN_WARNING + "%s: Invalid contents encryption mode %d\n", __func__, + policy->contents_encryption_mode); + return -EINVAL; + } + + if (!fscrypt_valid_filenames_enc_mode( + policy->filenames_encryption_mode)) { + printk(KERN_WARNING + "%s: Invalid filenames encryption mode %d\n", __func__, + policy->filenames_encryption_mode); + return -EINVAL; + } + + if (policy->flags & ~FS_POLICY_FLAGS_VALID) + return -EINVAL; + + ctx.contents_encryption_mode = policy->contents_encryption_mode; + ctx.filenames_encryption_mode = policy->filenames_encryption_mode; + ctx.flags = policy->flags; + BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE); + get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + + return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL); +} + +int fscrypt_process_policy(struct inode *inode, + const struct fscrypt_policy *policy) +{ + if (policy->version != 0) + return -EINVAL; + + if (!inode_has_encryption_context(inode)) { + if (!inode->i_sb->s_cop->empty_dir) + return -EOPNOTSUPP; + if (!inode->i_sb->s_cop->empty_dir(inode)) + return -ENOTEMPTY; + return create_encryption_context_from_policy(inode, policy); + } + + if (is_encryption_context_consistent_with_policy(inode, policy)) + return 0; + + printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n", + __func__); + return -EINVAL; +} +EXPORT_SYMBOL(fscrypt_process_policy); + +int fscrypt_get_policy(struct inode *inode, struct fscrypt_policy *policy) +{ + struct fscrypt_context ctx; + int res; + + if (!inode->i_sb->s_cop->get_context || + !inode->i_sb->s_cop->is_encrypted(inode)) + return -ENODATA; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res != sizeof(ctx)) + return -ENODATA; + if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + return -EINVAL; + + policy->version = 0; + 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, + FS_KEY_DESCRIPTOR_SIZE); + return 0; +} +EXPORT_SYMBOL(fscrypt_get_policy); + +int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) +{ + struct fscrypt_info *parent_ci, *child_ci; + int res; + + if ((parent == NULL) || (child == NULL)) { + printk(KERN_ERR "parent %p child %p\n", parent, child); + BUG_ON(1); + } + + /* no restrictions if the parent directory is not encrypted */ + if (!parent->i_sb->s_cop->is_encrypted(parent)) + return 1; + /* if the child directory is not encrypted, this is always a problem */ + if (!parent->i_sb->s_cop->is_encrypted(child)) + return 0; + res = fscrypt_get_encryption_info(parent); + if (res) + return 0; + res = fscrypt_get_encryption_info(child); + if (res) + return 0; + parent_ci = parent->i_crypt_info; + child_ci = child->i_crypt_info; + if (!parent_ci && !child_ci) + return 1; + if (!parent_ci || !child_ci) + return 0; + + return (memcmp(parent_ci->ci_master_key, + child_ci->ci_master_key, + FS_KEY_DESCRIPTOR_SIZE) == 0 && + (parent_ci->ci_data_mode == child_ci->ci_data_mode) && + (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) && + (parent_ci->ci_flags == child_ci->ci_flags)); +} +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 + * + * Return: Zero on success, non-zero otherwise + */ +int fscrypt_inherit_context(struct inode *parent, struct inode *child, + void *fs_data, bool preload) +{ + struct fscrypt_context ctx; + struct fscrypt_info *ci; + int res; + + if (!parent->i_sb->s_cop->set_context) + return -EOPNOTSUPP; + + res = fscrypt_get_encryption_info(parent); + if (res < 0) + return res; + + ci = parent->i_crypt_info; + if (ci == NULL) + return -ENOKEY; + + ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; + if (fscrypt_dummy_context_enabled(parent)) { + ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS; + ctx.flags = 0; + memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE); + res = 0; + } else { + ctx.contents_encryption_mode = ci->ci_data_mode; + ctx.filenames_encryption_mode = ci->ci_filename_mode; + ctx.flags = ci->ci_flags; + memcpy(ctx.master_key_descriptor, ci->ci_master_key, + FS_KEY_DESCRIPTOR_SIZE); + } + get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + res = parent->i_sb->s_cop->set_context(child, &ctx, + sizeof(ctx), fs_data); + if (res) + return res; + return preload ? fscrypt_get_encryption_info(child): 0; +} +EXPORT_SYMBOL(fscrypt_inherit_context); |