ext4 crypto: filename encryption facilities
Michael Halcrow [Wed, 15 Apr 2015 00:50:49 +0000 (20:50 -0400)]
Change-Id: I3747c17790c296dbef4ee8d8d4405796ef462aa8
Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Ildar Muslukhov <ildarm@google.com>
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Theodore Ts'o <tytso@google.com>

fs/ext4/Makefile
fs/ext4/crypto_fname.c [new file with mode: 0644]
fs/ext4/crypto_policy.c
fs/ext4/ext4.h
fs/ext4/ext4_crypto.h

index 4e5af21..75285ea 100644 (file)
@@ -12,4 +12,5 @@ ext4-y        := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
 
 ext4-$(CONFIG_EXT4_FS_POSIX_ACL)       += acl.o
 ext4-$(CONFIG_EXT4_FS_SECURITY)                += xattr_security.o
-ext4-$(CONFIG_EXT4_FS_ENCRYPTION)      += crypto_policy.o crypto.o crypto_key.o
+ext4-$(CONFIG_EXT4_FS_ENCRYPTION)      += crypto_policy.o crypto.o \
+               crypto_key.o crypto_fname.o
diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c
new file mode 100644 (file)
index 0000000..5042985
--- /dev/null
@@ -0,0 +1,709 @@
+/*
+ * linux/fs/ext4/crypto_fname.c
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This contains functions for filename crypto management in ext4
+ *
+ * Written by Uday Savagaonkar, 2014.
+ *
+ * This has not yet undergone a rigorous security audit.
+ *
+ */
+
+#include <crypto/hash.h>
+#include <crypto/sha.h>
+#include <keys/encrypted-type.h>
+#include <keys/user-type.h>
+#include <linux/crypto.h>
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include <linux/key.h>
+#include <linux/key.h>
+#include <linux/list.h>
+#include <linux/mempool.h>
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+#include <linux/spinlock_types.h>
+
+#include "ext4.h"
+#include "ext4_crypto.h"
+#include "xattr.h"
+
+/**
+ * ext4_dir_crypt_complete() -
+ */
+static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
+{
+       struct ext4_completion_result *ecr = req->data;
+
+       if (res == -EINPROGRESS)
+               return;
+       ecr->res = res;
+       complete(&ecr->completion);
+}
+
+bool ext4_valid_filenames_enc_mode(uint32_t mode)
+{
+       return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
+}
+
+/**
+ * ext4_fname_encrypt() -
+ *
+ * This function encrypts the input filename, and returns the length of the
+ * ciphertext. Errors are returned as negative numbers.  We trust the caller to
+ * allocate sufficient memory to oname string.
+ */
+static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
+                             const struct qstr *iname,
+                             struct ext4_str *oname)
+{
+       u32 ciphertext_len;
+       struct ablkcipher_request *req = NULL;
+       DECLARE_EXT4_COMPLETION_RESULT(ecr);
+       struct crypto_ablkcipher *tfm = ctx->ctfm;
+       int res = 0;
+       char iv[EXT4_CRYPTO_BLOCK_SIZE];
+       struct scatterlist sg[1];
+       char *workbuf;
+
+       if (iname->len <= 0 || iname->len > ctx->lim)
+               return -EIO;
+
+       ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
+               EXT4_CRYPTO_BLOCK_SIZE : iname->len;
+       ciphertext_len = (ciphertext_len > ctx->lim)
+                       ? ctx->lim : ciphertext_len;
+
+       /* Allocate request */
+       req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+       if (!req) {
+               printk_ratelimited(
+                   KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
+               return -ENOMEM;
+       }
+       ablkcipher_request_set_callback(req,
+               CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+               ext4_dir_crypt_complete, &ecr);
+
+       /* Map the workpage */
+       workbuf = kmap(ctx->workpage);
+
+       /* Copy the input */
+       memcpy(workbuf, iname->name, iname->len);
+       if (iname->len < ciphertext_len)
+               memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
+
+       /* Initialize IV */
+       memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
+
+       /* Create encryption request */
+       sg_init_table(sg, 1);
+       sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
+       ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
+       res = crypto_ablkcipher_encrypt(req);
+       if (res == -EINPROGRESS || res == -EBUSY) {
+               BUG_ON(req->base.data != &ecr);
+               wait_for_completion(&ecr.completion);
+               res = ecr.res;
+       }
+       if (res >= 0) {
+               /* Copy the result to output */
+               memcpy(oname->name, workbuf, ciphertext_len);
+               res = ciphertext_len;
+       }
+       kunmap(ctx->workpage);
+       ablkcipher_request_free(req);
+       if (res < 0) {
+               printk_ratelimited(
+                   KERN_ERR "%s: Error (error code %d)\n", __func__, res);
+       }
+       oname->len = ciphertext_len;
+       return res;
+}
+
+/*
+ * ext4_fname_decrypt()
+ *     This function decrypts the input filename, and returns
+ *     the length of the plaintext.
+ *     Errors are returned as negative numbers.
+ *     We trust the caller to allocate sufficient memory to oname string.
+ */
+static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
+                             const struct ext4_str *iname,
+                             struct ext4_str *oname)
+{
+       struct ext4_str tmp_in[2], tmp_out[1];
+       struct ablkcipher_request *req = NULL;
+       DECLARE_EXT4_COMPLETION_RESULT(ecr);
+       struct scatterlist sg[1];
+       struct crypto_ablkcipher *tfm = ctx->ctfm;
+       int res = 0;
+       char iv[EXT4_CRYPTO_BLOCK_SIZE];
+       char *workbuf;
+
+       if (iname->len <= 0 || iname->len > ctx->lim)
+               return -EIO;
+
+       tmp_in[0].name = iname->name;
+       tmp_in[0].len = iname->len;
+       tmp_out[0].name = oname->name;
+
+       /* Allocate request */
+       req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+       if (!req) {
+               printk_ratelimited(
+                   KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
+               return -ENOMEM;
+       }
+       ablkcipher_request_set_callback(req,
+               CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+               ext4_dir_crypt_complete, &ecr);
+
+       /* Map the workpage */
+       workbuf = kmap(ctx->workpage);
+
+       /* Copy the input */
+       memcpy(workbuf, iname->name, iname->len);
+
+       /* Initialize IV */
+       memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
+
+       /* Create encryption request */
+       sg_init_table(sg, 1);
+       sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
+       ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
+       res = crypto_ablkcipher_decrypt(req);
+       if (res == -EINPROGRESS || res == -EBUSY) {
+               BUG_ON(req->base.data != &ecr);
+               wait_for_completion(&ecr.completion);
+               res = ecr.res;
+       }
+       if (res >= 0) {
+               /* Copy the result to output */
+               memcpy(oname->name, workbuf, iname->len);
+               res = iname->len;
+       }
+       kunmap(ctx->workpage);
+       ablkcipher_request_free(req);
+       if (res < 0) {
+               printk_ratelimited(
+                   KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
+                   __func__, res);
+               return res;
+       }
+
+       oname->len = strnlen(oname->name, iname->len);
+       return oname->len;
+}
+
+/**
+ * ext4_fname_encode_digest() -
+ *
+ * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
+ * The encoded string is roughly 4/3 times the size of the input string.
+ */
+int ext4_fname_encode_digest(char *dst, char *src, u32 len)
+{
+       static const char *lookup_table =
+               "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+";
+       u32 current_chunk, num_chunks, i;
+       char tmp_buf[3];
+       u32 c0, c1, c2, c3;
+
+       current_chunk = 0;
+       num_chunks = len/3;
+       for (i = 0; i < num_chunks; i++) {
+               c0 = src[3*i] & 0x3f;
+               c1 = (((src[3*i]>>6)&0x3) | ((src[3*i+1] & 0xf)<<2)) & 0x3f;
+               c2 = (((src[3*i+1]>>4)&0xf) | ((src[3*i+2] & 0x3)<<4)) & 0x3f;
+               c3 = (src[3*i+2]>>2) & 0x3f;
+               dst[4*i] = lookup_table[c0];
+               dst[4*i+1] = lookup_table[c1];
+               dst[4*i+2] = lookup_table[c2];
+               dst[4*i+3] = lookup_table[c3];
+       }
+       if (i*3 < len) {
+               memset(tmp_buf, 0, 3);
+               memcpy(tmp_buf, &src[3*i], len-3*i);
+               c0 = tmp_buf[0] & 0x3f;
+               c1 = (((tmp_buf[0]>>6)&0x3) | ((tmp_buf[1] & 0xf)<<2)) & 0x3f;
+               c2 = (((tmp_buf[1]>>4)&0xf) | ((tmp_buf[2] & 0x3)<<4)) & 0x3f;
+               c3 = (tmp_buf[2]>>2) & 0x3f;
+               dst[4*i] = lookup_table[c0];
+               dst[4*i+1] = lookup_table[c1];
+               dst[4*i+2] = lookup_table[c2];
+               dst[4*i+3] = lookup_table[c3];
+               i++;
+       }
+       return (i * 4);
+}
+
+/**
+ * ext4_fname_hash() -
+ *
+ * This function computes the hash of the input filename, and sets the output
+ * buffer to the *encoded* digest.  It returns the length of the digest as its
+ * return value.  Errors are returned as negative numbers.  We trust the caller
+ * to allocate sufficient memory to oname string.
+ */
+static int ext4_fname_hash(struct ext4_fname_crypto_ctx *ctx,
+                          const struct ext4_str *iname,
+                          struct ext4_str *oname)
+{
+       struct scatterlist sg;
+       struct hash_desc desc = {
+               .tfm = (struct crypto_hash *)ctx->htfm,
+               .flags = CRYPTO_TFM_REQ_MAY_SLEEP
+       };
+       int res = 0;
+
+       if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
+               res = ext4_fname_encode_digest(oname->name, iname->name,
+                                              iname->len);
+               oname->len = res;
+               return res;
+       }
+
+       sg_init_one(&sg, iname->name, iname->len);
+       res = crypto_hash_init(&desc);
+       if (res) {
+               printk(KERN_ERR
+                      "%s: Error initializing crypto hash; res = [%d]\n",
+                      __func__, res);
+               goto out;
+       }
+       res = crypto_hash_update(&desc, &sg, iname->len);
+       if (res) {
+               printk(KERN_ERR
+                      "%s: Error updating crypto hash; res = [%d]\n",
+                      __func__, res);
+               goto out;
+       }
+       res = crypto_hash_final(&desc,
+               &oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE]);
+       if (res) {
+               printk(KERN_ERR
+                      "%s: Error finalizing crypto hash; res = [%d]\n",
+                      __func__, res);
+               goto out;
+       }
+       /* Encode the digest as a printable string--this will increase the
+        * size of the digest */
+       oname->name[0] = 'I';
+       res = ext4_fname_encode_digest(oname->name+1,
+               &oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE],
+               EXT4_FNAME_CRYPTO_DIGEST_SIZE) + 1;
+       oname->len = res;
+out:
+       return res;
+}
+
+/**
+ * ext4_free_fname_crypto_ctx() -
+ *
+ * Frees up a crypto context.
+ */
+void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
+{
+       if (ctx == NULL || IS_ERR(ctx))
+               return;
+
+       if (ctx->ctfm && !IS_ERR(ctx->ctfm))
+               crypto_free_ablkcipher(ctx->ctfm);
+       if (ctx->htfm && !IS_ERR(ctx->htfm))
+               crypto_free_hash(ctx->htfm);
+       if (ctx->workpage && !IS_ERR(ctx->workpage))
+               __free_page(ctx->workpage);
+       kfree(ctx);
+}
+
+/**
+ * ext4_put_fname_crypto_ctx() -
+ *
+ * Return: The crypto context onto free list. If the free list is above a
+ * threshold, completely frees up the context, and returns the memory.
+ *
+ * TODO: Currently we directly free the crypto context. Eventually we should
+ * add code it to return to free list. Such an approach will increase
+ * efficiency of directory lookup.
+ */
+void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
+{
+       if (*ctx == NULL || IS_ERR(*ctx))
+               return;
+       ext4_free_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)
+{
+       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) {
+               /* This will automatically set key mode to invalid
+                * As enum for ENCRYPTION_MODE_INVALID is zero */
+               memset(&ctx->key, 0, sizeof(ctx->key));
+       } else {
+               memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
+       }
+       ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
+               ? 0 : 1;
+       ctx->ctfm_key_is_ready = 0;
+       ctx->ctfm = NULL;
+       ctx->htfm = NULL;
+       ctx->workpage = NULL;
+       return ctx;
+}
+
+/**
+ * ext4_get_fname_crypto_ctx() -
+ *
+ * Allocates a free crypto context and initializes it to hold
+ * the crypto material for the inode.
+ *
+ * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
+ */
+struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
+       struct inode *inode, u32 max_ciphertext_len)
+{
+       struct ext4_fname_crypto_ctx *ctx;
+       struct ext4_inode_info *ei = EXT4_I(inode);
+       int res;
+
+       /* Check if the crypto policy is set on the inode */
+       res = ext4_encrypted_inode(inode);
+       if (res == 0)
+               return NULL;
+
+       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));
+       if (IS_ERR(ctx))
+               return ctx;
+
+       if (ctx->has_valid_key) {
+               if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
+                       printk_once(KERN_WARNING
+                                   "ext4: unsupported key mode %d\n",
+                                   ctx->key.mode);
+                       return ERR_PTR(-ENOKEY);
+               }
+
+               /* As a first cut, we will allocate new tfm in every call.
+                * later, we will keep the tfm around, in case the key gets
+                * re-used */
+               if (ctx->ctfm == NULL) {
+                       ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
+                                       0, 0);
+               }
+               if (IS_ERR(ctx->ctfm)) {
+                       res = PTR_ERR(ctx->ctfm);
+                       printk(
+                           KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
+                           __func__, res);
+                       ctx->ctfm = NULL;
+                       ext4_put_fname_crypto_ctx(&ctx);
+                       return ERR_PTR(res);
+               }
+               if (ctx->ctfm == NULL) {
+                       printk(
+                           KERN_DEBUG "%s: could not allocate crypto tfm\n",
+                           __func__);
+                       ext4_put_fname_crypto_ctx(&ctx);
+                       return ERR_PTR(-ENOMEM);
+               }
+               if (ctx->workpage == NULL)
+                       ctx->workpage = alloc_page(GFP_NOFS);
+               if (IS_ERR(ctx->workpage)) {
+                       res = PTR_ERR(ctx->workpage);
+                       printk(
+                           KERN_DEBUG "%s: error (%d) allocating work page\n",
+                           __func__, res);
+                       ctx->workpage = NULL;
+                       ext4_put_fname_crypto_ctx(&ctx);
+                       return ERR_PTR(res);
+               }
+               if (ctx->workpage == NULL) {
+                       printk(
+                           KERN_DEBUG "%s: could not allocate work page\n",
+                           __func__);
+                       ext4_put_fname_crypto_ctx(&ctx);
+                       return ERR_PTR(-ENOMEM);
+               }
+               ctx->lim = max_ciphertext_len;
+               crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
+               crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
+                       CRYPTO_TFM_REQ_WEAK_KEY);
+
+               /* If we are lucky, we will get a context that is already
+                * set up with the right key. Else, we will have to
+                * set the key */
+               if (!ctx->ctfm_key_is_ready) {
+                       /* Since our crypto objectives for filename encryption
+                        * are pretty weak,
+                        * we directly use the inode master key */
+                       res = crypto_ablkcipher_setkey(ctx->ctfm,
+                                       ctx->key.raw, ctx->key.size);
+                       if (res) {
+                               ext4_put_fname_crypto_ctx(&ctx);
+                               return ERR_PTR(-EIO);
+                       }
+                       ctx->ctfm_key_is_ready = 1;
+               } else {
+                       /* In the current implementation, key should never be
+                        * marked "ready" for a context that has just been
+                        * allocated. So we should never reach here */
+                        BUG();
+               }
+       }
+       if (ctx->htfm == NULL)
+               ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
+       if (IS_ERR(ctx->htfm)) {
+               res = PTR_ERR(ctx->htfm);
+               printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
+                       __func__, res);
+               ctx->htfm = NULL;
+               ext4_put_fname_crypto_ctx(&ctx);
+               return ERR_PTR(res);
+       }
+       if (ctx->htfm == NULL) {
+               printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
+                               __func__);
+               ext4_put_fname_crypto_ctx(&ctx);
+               return ERR_PTR(-ENOMEM);
+       }
+
+       return ctx;
+}
+
+/**
+ * ext4_fname_crypto_round_up() -
+ *
+ * Return: The next multiple of block size
+ */
+u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
+{
+       return ((size+blksize-1)/blksize)*blksize;
+}
+
+/**
+ * ext4_fname_crypto_namelen_on_disk() -
+ */
+int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
+                                     u32 namelen)
+{
+       u32 ciphertext_len;
+
+       if (ctx == NULL)
+               return -EIO;
+       if (!(ctx->has_valid_key))
+               return -EACCES;
+       ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
+               EXT4_CRYPTO_BLOCK_SIZE : namelen;
+       ciphertext_len = (ciphertext_len > ctx->lim)
+                       ? ctx->lim : ciphertext_len;
+       return (int) ciphertext_len;
+}
+
+/**
+ * ext4_fname_crypto_alloc_obuff() -
+ *
+ * Allocates an output buffer that is sufficient for the crypto operation
+ * specified by the context and the direction.
+ */
+int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
+                                  u32 ilen, struct ext4_str *crypto_str)
+{
+       unsigned int olen;
+
+       if (!ctx)
+               return -EIO;
+       olen = ext4_fname_crypto_round_up(ilen, EXT4_CRYPTO_BLOCK_SIZE);
+       crypto_str->len = olen;
+       if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
+               olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
+       /* Allocated buffer can hold one more character to null-terminate the
+        * string */
+       crypto_str->name = kmalloc(olen+1, GFP_NOFS);
+       if (!(crypto_str->name))
+               return -ENOMEM;
+       return 0;
+}
+
+/**
+ * ext4_fname_crypto_free_buffer() -
+ *
+ * Frees the buffer allocated for crypto operation.
+ */
+void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
+{
+       if (!crypto_str)
+               return;
+       kfree(crypto_str->name);
+       crypto_str->name = NULL;
+}
+
+/**
+ * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
+ */
+int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
+                          const struct ext4_str *iname,
+                          struct ext4_str *oname)
+{
+       if (ctx == NULL)
+               return -EIO;
+       if (iname->len < 3) {
+               /*Check for . and .. */
+               if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
+                       oname->name[0] = '.';
+                       oname->name[iname->len-1] = '.';
+                       oname->len = iname->len;
+                       return oname->len;
+               }
+       }
+       if (ctx->has_valid_key)
+               return ext4_fname_decrypt(ctx, iname, oname);
+       else
+               return ext4_fname_hash(ctx, iname, oname);
+}
+
+int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
+                          const struct ext4_dir_entry_2 * de,
+                          struct ext4_str *oname)
+{
+       struct ext4_str iname = {.name = (unsigned char *) de->name,
+                                .len = de->name_len };
+
+       return _ext4_fname_disk_to_usr(ctx, &iname, oname);
+}
+
+
+/**
+ * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
+ */
+int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
+                          const struct qstr *iname,
+                          struct ext4_str *oname)
+{
+       int res;
+
+       if (ctx == NULL)
+               return -EIO;
+       if (iname->len < 3) {
+               /*Check for . and .. */
+               if (iname->name[0] == '.' &&
+                               iname->name[iname->len-1] == '.') {
+                       oname->name[0] = '.';
+                       oname->name[iname->len-1] = '.';
+                       oname->len = iname->len;
+                       return oname->len;
+               }
+       }
+       if (ctx->has_valid_key) {
+               res = ext4_fname_encrypt(ctx, iname, oname);
+               return res;
+       }
+       /* Without a proper key, a user is not allowed to modify the filenames
+        * in a directory. Consequently, a user space name cannot be mapped to
+        * a disk-space name */
+       return -EACCES;
+}
+
+/*
+ * Calculate the htree hash from a filename from user space
+ */
+int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
+                           const struct qstr *iname,
+                           struct dx_hash_info *hinfo)
+{
+       struct ext4_str tmp, tmp2;
+       int ret = 0;
+
+       if (!ctx || !ctx->has_valid_key ||
+           ((iname->name[0] == '.') &&
+            ((iname->len == 1) ||
+             ((iname->name[1] == '.') && (iname->len == 2))))) {
+               ext4fs_dirhash(iname->name, iname->len, hinfo);
+               return 0;
+       }
+
+       /* First encrypt the plaintext name */
+       ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
+       if (ret < 0)
+               return ret;
+
+       ret = ext4_fname_encrypt(ctx, iname, &tmp);
+       if (ret < 0)
+               goto out;
+
+       tmp2.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
+       tmp2.name = kmalloc(tmp2.len + 1, GFP_KERNEL);
+       if (tmp2.name == NULL) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       ret = ext4_fname_hash(ctx, &tmp, &tmp2);
+       if (ret > 0)
+               ext4fs_dirhash(tmp2.name, tmp2.len, hinfo);
+       ext4_fname_crypto_free_buffer(&tmp2);
+out:
+       ext4_fname_crypto_free_buffer(&tmp);
+       return ret;
+}
+
+/**
+ * ext4_fname_disk_to_htree() - converts a filename from disk space to htree-access string
+ */
+int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,
+                           const struct ext4_dir_entry_2 * de,
+                           struct dx_hash_info *hinfo)
+{
+       struct ext4_str iname = {.name = (unsigned char *) de->name,
+                                .len = de->name_len};
+       struct ext4_str tmp;
+       int ret;
+
+       if (!ctx ||
+           ((iname.name[0] == '.') &&
+            ((iname.len == 1) ||
+             ((iname.name[1] == '.') && (iname.len == 2))))) {
+               ext4fs_dirhash(iname.name, iname.len, hinfo);
+               return 0;
+       }
+
+       tmp.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
+       tmp.name = kmalloc(tmp.len + 1, GFP_KERNEL);
+       if (tmp.name == NULL)
+               return -ENOMEM;
+
+       ret = ext4_fname_hash(ctx, &iname, &tmp);
+       if (ret > 0)
+               ext4fs_dirhash(tmp.name, tmp.len, hinfo);
+       ext4_fname_crypto_free_buffer(&tmp);
+       return ret;
+}
index a4bf762..749ed6e 100644 (file)
@@ -59,6 +59,13 @@ static int ext4_create_encryption_context_from_policy(
                res = -EINVAL;
                goto out;
        }
+       if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
+               printk(KERN_WARNING
+                      "%s: Invalid filenames encryption mode %d\n", __func__,
+                       policy->filenames_encryption_mode);
+               res = -EINVAL;
+               goto out;
+       }
        ctx.contents_encryption_mode = policy->contents_encryption_mode;
        ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
        BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
index 45d7e28..a38d804 100644 (file)
@@ -2070,6 +2070,47 @@ static inline int ext4_sb_has_crypto(struct super_block *sb)
 }
 #endif
 
+/* crypto_fname.c */
+bool ext4_valid_filenames_enc_mode(uint32_t mode);
+u32 ext4_fname_crypto_round_up(u32 size, u32 blksize);
+int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
+                                  u32 ilen, struct ext4_str *crypto_str);
+int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
+                           const struct ext4_str *iname,
+                           struct ext4_str *oname);
+int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
+                          const struct ext4_dir_entry_2 * de,
+                          struct ext4_str *oname);
+int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
+                          const struct qstr *iname,
+                          struct ext4_str *oname);
+int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
+                          const struct qstr *iname,
+                          struct dx_hash_info *hinfo);
+int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,
+                           const struct ext4_dir_entry_2 * de,
+                           struct dx_hash_info *hinfo);
+int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
+                                     u32 namelen);
+
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx);
+struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(struct inode *inode,
+                                                       u32 max_len);
+void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str);
+#else
+static inline
+void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx) { }
+static inline
+struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(struct inode *inode,
+                                                       u32 max_len)
+{
+       return NULL;
+}
+static inline void ext4_fname_crypto_free_buffer(struct ext4_str *p) { }
+#endif
+
+
 /* crypto_key.c */
 int ext4_generate_encryption_key(struct inode *inode);
 
index 6a7c0c0..f7d46e8 100644 (file)
@@ -104,4 +104,24 @@ static inline int ext4_encryption_key_size(int mode)
        return 0;
 }
 
+#define EXT4_FNAME_NUM_SCATTER_ENTRIES 4
+#define EXT4_CRYPTO_BLOCK_SIZE         16
+#define EXT4_FNAME_CRYPTO_DIGEST_SIZE  32
+
+struct ext4_str {
+       unsigned char *name;
+       u32 len;
+};
+
+struct ext4_fname_crypto_ctx {
+       u32 lim;
+       char tmp_buf[EXT4_CRYPTO_BLOCK_SIZE];
+       struct crypto_ablkcipher *ctfm;
+       struct crypto_hash *htfm;
+       struct page *workpage;
+       struct ext4_encryption_key key;
+       unsigned has_valid_key : 1;
+       unsigned ctfm_key_is_ready : 1;
+};
+
 #endif /* _EXT4_CRYPTO_H */