diff options
Diffstat (limited to 'fs/ext4/crypto_fname.c')
| -rw-r--r-- | fs/ext4/crypto_fname.c | 709 |
1 files changed, 709 insertions, 0 deletions
diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c new file mode 100644 index 000000000000..ca2f5948c1ac --- /dev/null +++ b/fs/ext4/crypto_fname.c @@ -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; +} |