diff options
| -rw-r--r-- | fs/crypto/hooks.c | 71 | ||||
| -rw-r--r-- | include/linux/fscrypt_notsupp.h | 7 | ||||
| -rw-r--r-- | include/linux/fscrypt_supp.h | 2 |
3 files changed, 80 insertions, 0 deletions
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 4b83e4af2e41..534cfb212cdb 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -200,3 +200,74 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, return 0; } EXPORT_SYMBOL_GPL(__fscrypt_encrypt_symlink); + +/** + * fscrypt_get_symlink - get the target of an encrypted symlink + * @inode: the symlink inode + * @caddr: the on-disk contents of the symlink + * @max_size: size of @caddr buffer + * @done: if successful, will be set up to free the returned target + * + * If the symlink's encryption key is available, we decrypt its target. + * Otherwise, we encode its target for presentation. + * + * This may sleep, so the filesystem must have dropped out of RCU mode already. + * + * Return: the presentable symlink target or an ERR_PTR() + */ +void *fscrypt_get_symlink(struct inode *inode, const void *caddr, + unsigned int max_size) +{ + const struct fscrypt_symlink_data *sd; + struct fscrypt_str cstr, pstr; + int err; + + /* This is for encrypted symlinks only */ + if (WARN_ON(!IS_ENCRYPTED(inode))) + return ERR_PTR(-EINVAL); + + /* + * Try to set up the symlink's encryption key, but we can continue + * regardless of whether the key is available or not. + */ + err = fscrypt_get_encryption_info(inode); + if (err) + return ERR_PTR(err); + + /* + * For historical reasons, encrypted symlink targets are prefixed with + * the ciphertext length, even though this is redundant with i_size. + */ + + if (max_size < sizeof(*sd)) + return ERR_PTR(-EUCLEAN); + sd = caddr; + cstr.name = (unsigned char *)sd->encrypted_path; + cstr.len = le16_to_cpu(sd->len); + + if (cstr.len == 0) + return ERR_PTR(-EUCLEAN); + + if (cstr.len + sizeof(*sd) - 1 > max_size) + return ERR_PTR(-EUCLEAN); + + err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr); + if (err) + return ERR_PTR(err); + + err = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr); + if (err) + goto err_kfree; + + err = -EUCLEAN; + if (pstr.name[0] == '\0') + goto err_kfree; + + pstr.name[pstr.len] = '\0'; + return pstr.name; + +err_kfree: + kfree(pstr.name); + return ERR_PTR(err); +} +EXPORT_SYMBOL_GPL(fscrypt_get_symlink); diff --git a/include/linux/fscrypt_notsupp.h b/include/linux/fscrypt_notsupp.h index 875c83672318..1886b255adcb 100644 --- a/include/linux/fscrypt_notsupp.h +++ b/include/linux/fscrypt_notsupp.h @@ -238,4 +238,11 @@ static inline int __fscrypt_encrypt_symlink(struct inode *inode, return -EOPNOTSUPP; } +static inline void *fscrypt_get_symlink(struct inode *inode, + const void *caddr, + unsigned int max_size) +{ + return ERR_PTR(-EOPNOTSUPP); +} + #endif /* _LINUX_FSCRYPT_NOTSUPP_H */ diff --git a/include/linux/fscrypt_supp.h b/include/linux/fscrypt_supp.h index 6ccaad58d2be..92e50820fd4f 100644 --- a/include/linux/fscrypt_supp.h +++ b/include/linux/fscrypt_supp.h @@ -210,5 +210,7 @@ extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, unsigned int len, struct fscrypt_str *disk_link); +extern void *fscrypt_get_symlink(struct inode *inode, const void *caddr, + unsigned int max_size); #endif /* _LINUX_FSCRYPT_SUPP_H */ |