diff options
Diffstat (limited to 'fs/crypto')
| -rw-r--r-- | fs/crypto/crypto.c | 2 | ||||
| -rw-r--r-- | fs/crypto/fname.c | 3 | ||||
| -rw-r--r-- | fs/crypto/fscrypt_private.h | 187 | ||||
| -rw-r--r-- | fs/crypto/keyring.c | 35 | ||||
| -rw-r--r-- | fs/crypto/keysetup.c | 202 | ||||
| -rw-r--r-- | fs/crypto/keysetup_v1.c | 18 | ||||
| -rw-r--r-- | fs/crypto/policy.c | 422 |
7 files changed, 684 insertions, 185 deletions
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 65ca077e8d58..32a7ad0098cc 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -141,7 +141,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, memset(iv, 0, ci->ci_mode->ivsize); iv->lblk_num = cpu_to_le64(lblk_num); - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + if (fscrypt_is_direct_key_policy(&ci->ci_policy)) memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE); if (ci->ci_essiv_tfm != NULL) diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index f4977d44d69b..3da3707c10e3 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -181,7 +181,8 @@ static int base64_decode(const char *src, int len, u8 *dst) bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret) { - int padding = 4 << (inode->i_crypt_info->ci_flags & + const struct fscrypt_info *ci = inode->i_crypt_info; + int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) & FSCRYPT_POLICY_FLAGS_PAD_MASK); u32 encrypted_len; diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 9556e9499dc5..c89e37d38e42 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -20,27 +20,127 @@ #define FSCRYPT_MIN_KEY_SIZE 16 -/** - * Encryption context for inode - * - * Protector format: - * 1 byte: Protector format (1 = this version) - * 1 byte: File contents encryption mode - * 1 byte: File names encryption mode - * 1 byte: Flags - * 8 bytes: Master Key descriptor - * 16 bytes: Encryption Key derivation nonce - */ -struct fscrypt_context { - u8 format; +#define FSCRYPT_CONTEXT_V1 1 +#define FSCRYPT_CONTEXT_V2 2 + +struct fscrypt_context_v1 { + u8 version; /* FSCRYPT_CONTEXT_V1 */ u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; -} __packed; +}; -#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1 +struct fscrypt_context_v2 { + u8 version; /* FSCRYPT_CONTEXT_V2 */ + u8 contents_encryption_mode; + u8 filenames_encryption_mode; + u8 flags; + u8 __reserved[4]; + u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; +}; + +/** + * fscrypt_context - the encryption context of an inode + * + * This is the on-disk equivalent of an fscrypt_policy, stored alongside each + * encrypted file usually in a hidden extended attribute. It contains the + * fields from the fscrypt_policy, in order to identify the encryption algorithm + * and key with which the file is encrypted. It also contains a nonce that was + * randomly generated by fscrypt itself; this is used as KDF input or as a tweak + * to cause different files to be encrypted differently. + */ +union fscrypt_context { + u8 version; + struct fscrypt_context_v1 v1; + struct fscrypt_context_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_context based on its version + * number, or 0 if the context version is unrecognized. + */ +static inline int fscrypt_context_size(const union fscrypt_context *ctx) +{ + switch (ctx->version) { + case FSCRYPT_CONTEXT_V1: + BUILD_BUG_ON(sizeof(ctx->v1) != 28); + return sizeof(ctx->v1); + case FSCRYPT_CONTEXT_V2: + BUILD_BUG_ON(sizeof(ctx->v2) != 40); + return sizeof(ctx->v2); + } + return 0; +} + +#undef fscrypt_policy +union fscrypt_policy { + u8 version; + struct fscrypt_policy_v1 v1; + struct fscrypt_policy_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_policy based on its version + * number, or 0 if the policy version is unrecognized. + */ +static inline int fscrypt_policy_size(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return sizeof(policy->v1); + case FSCRYPT_POLICY_V2: + return sizeof(policy->v2); + } + return 0; +} + +/* Return the contents encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_contents_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.contents_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.contents_encryption_mode; + } + BUG(); +} + +/* Return the filenames encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_fnames_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.filenames_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.filenames_encryption_mode; + } + BUG(); +} + +/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */ +static inline u8 +fscrypt_policy_flags(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.flags; + case FSCRYPT_POLICY_V2: + return policy->v2.flags; + } + BUG(); +} + +static inline bool +fscrypt_is_direct_key_policy(const union fscrypt_policy *policy) +{ + return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY; +} /** * For encrypted symlinks, the ciphertext length is stored at the beginning @@ -70,8 +170,8 @@ struct fscrypt_info { struct crypto_cipher *ci_essiv_tfm; /* - * Encryption mode used for this inode. It corresponds to either - * ci_data_mode or ci_filename_mode, depending on the inode type. + * Encryption mode used for this inode. It corresponds to either the + * contents or filenames encryption mode, depending on the inode type. */ struct fscrypt_mode *ci_mode; @@ -97,11 +197,10 @@ struct fscrypt_info { */ struct fscrypt_direct_key *ci_direct_key; - /* fields from the fscrypt_context */ - u8 ci_data_mode; - u8 ci_filename_mode; - u8 ci_flags; - u8 ci_master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + /* The encryption policy used by this inode */ + union fscrypt_policy ci_policy; + + /* This inode's nonce, copied from the fscrypt_context */ u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; @@ -181,6 +280,17 @@ struct fscrypt_hkdf { extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, unsigned int master_key_size); +/* + * The list of contexts in which fscrypt uses HKDF. These values are used as + * the first byte of the HKDF application-specific info string to guarantee that + * info strings are never repeated between contexts. This ensures that all HKDF + * outputs are unique and cryptographically isolated, i.e. knowledge of one + * output doesn't reveal another. + */ +#define HKDF_CONTEXT_KEY_IDENTIFIER 1 +#define HKDF_CONTEXT_PER_FILE_KEY 2 +#define HKDF_CONTEXT_PER_MODE_KEY 3 + extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, const u8 *info, unsigned int infolen, u8 *okm, unsigned int okmlen); @@ -194,10 +304,16 @@ extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf); */ struct fscrypt_master_key_secret { - /* Size of the raw key in bytes */ + /* + * For v2 policy keys: HKDF context keyed by this master key. + * For v1 policy keys: not set (hkdf.hmac_tfm == NULL). + */ + struct fscrypt_hkdf hkdf; + + /* Size of the raw key in bytes. Set even if ->raw isn't set. */ u32 size; - /* The raw key */ + /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */ u8 raw[FSCRYPT_MAX_KEY_SIZE]; } __randomize_layout; @@ -223,7 +339,12 @@ struct fscrypt_master_key { */ struct fscrypt_master_key_secret mk_secret; - /* Arbitrary key descriptor which was assigned by userspace */ + /* + * For v1 policy keys: an arbitrary key descriptor which was assigned by + * userspace (->descriptor). + * + * For v2 policy keys: a cryptographic hash of this key (->identifier). + */ struct fscrypt_key_specifier mk_spec; /* @@ -242,6 +363,9 @@ struct fscrypt_master_key { struct list_head mk_decrypted_inodes; spinlock_t mk_decrypted_inodes_lock; + /* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */ + struct crypto_skcipher *mk_mode_keys[__FSCRYPT_MODE_MAX + 1]; + } __randomize_layout; static inline bool @@ -263,6 +387,8 @@ static inline const char *master_key_spec_type( switch (spec->type) { case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: return "descriptor"; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + return "identifier"; } return "[unknown]"; } @@ -272,6 +398,8 @@ static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec) switch (spec->type) { case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: return FSCRYPT_KEY_DESCRIPTOR_SIZE; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + return FSCRYPT_KEY_IDENTIFIER_SIZE; } return 0; } @@ -315,5 +443,14 @@ extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings( struct fscrypt_info *ci); +/* policy.c */ + +extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2); +extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u, + const struct inode *inode); +extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u, + const union fscrypt_context *ctx_u, + int ctx_size); #endif /* _FSCRYPT_PRIVATE_H */ diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 8c94c2fa0c13..fca3bdf01e7c 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -17,6 +17,7 @@ * information about these ioctls. */ +#include <crypto/skcipher.h> #include <linux/key-type.h> #include <linux/seq_file.h> @@ -24,6 +25,7 @@ static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret) { + fscrypt_destroy_hkdf(&secret->hkdf); memzero_explicit(secret, sizeof(*secret)); } @@ -36,7 +38,13 @@ static void move_master_key_secret(struct fscrypt_master_key_secret *dst, static void free_master_key(struct fscrypt_master_key *mk) { + size_t i; + wipe_master_key_secret(&mk->mk_secret); + + for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++) + crypto_free_skcipher(mk->mk_mode_keys[i]); + kzfree(mk); } @@ -109,7 +117,7 @@ static struct key *search_fscrypt_keyring(struct key *keyring, #define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id)) -#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1) +#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1) static void format_fs_keyring_description( char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], @@ -314,6 +322,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) if (!capable(CAP_SYS_ADMIN)) goto out_wipe_secret; + if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { + err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size); + if (err) + goto out_wipe_secret; + + /* + * Now that the HKDF context is initialized, the raw key is no + * longer needed. + */ + memzero_explicit(secret.raw, secret.size); + + /* Calculate the key identifier and return it to userspace. */ + err = fscrypt_hkdf_expand(&secret.hkdf, + HKDF_CONTEXT_KEY_IDENTIFIER, + NULL, 0, arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + if (err) + goto out_wipe_secret; + err = -EFAULT; + if (copy_to_user(uarg->key_spec.u.identifier, + arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE)) + goto out_wipe_secret; + } + err = add_master_key(sb, &secret, &arg.key_spec); out_wipe_secret: wipe_master_key_secret(&secret); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index 7b60a47fc73c..f423d48264db 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -52,20 +52,14 @@ static struct fscrypt_mode available_modes[] = { }; static struct fscrypt_mode * -select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) +select_encryption_mode(const union fscrypt_policy *policy, + const struct inode *inode) { - if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { - fscrypt_warn(inode, - "Unsupported encryption modes (contents mode %d, filenames mode %d)", - ci->ci_data_mode, ci->ci_filename_mode); - return ERR_PTR(-EINVAL); - } - if (S_ISREG(inode->i_mode)) - return &available_modes[ci->ci_data_mode]; + return &available_modes[fscrypt_policy_contents_mode(policy)]; if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) - return &available_modes[ci->ci_filename_mode]; + return &available_modes[fscrypt_policy_fnames_mode(policy)]; WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", inode->i_ino, (inode->i_mode & S_IFMT)); @@ -211,6 +205,82 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) return 0; } +static int setup_per_mode_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + struct fscrypt_mode *mode = ci->ci_mode; + u8 mode_num = mode - available_modes; + struct crypto_skcipher *tfm, *prev_tfm; + u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys))) + return -EINVAL; + + /* pairs with cmpxchg() below */ + tfm = READ_ONCE(mk->mk_mode_keys[mode_num]); + if (likely(tfm != NULL)) + goto done; + + BUILD_BUG_ON(sizeof(mode_num) != 1); + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_MODE_KEY, + &mode_num, sizeof(mode_num), + mode_key, mode->keysize); + if (err) + return err; + tfm = fscrypt_allocate_skcipher(mode, mode_key, ci->ci_inode); + memzero_explicit(mode_key, mode->keysize); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + + /* pairs with READ_ONCE() above */ + prev_tfm = cmpxchg(&mk->mk_mode_keys[mode_num], NULL, tfm); + if (prev_tfm != NULL) { + crypto_free_skcipher(tfm); + tfm = prev_tfm; + } +done: + ci->ci_ctfm = tfm; + return 0; +} + +static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + /* + * DIRECT_KEY: instead of deriving per-file keys, the per-file + * nonce will be included in all the IVs. But unlike v1 + * policies, for v2 policies in this case we don't encrypt with + * the master key directly but rather derive a per-mode key. + * This ensures that the master key is consistently used only + * for HKDF, avoiding key reuse issues. + */ + if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) { + fscrypt_warn(ci->ci_inode, + "Direct key flag not allowed with %s", + ci->ci_mode->friendly_name); + return -EINVAL; + } + return setup_per_mode_key(ci, mk); + } + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_FILE_KEY, + ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE, + derived_key, ci->ci_mode->keysize); + if (err) + return err; + + err = fscrypt_set_derived_key(ci, derived_key); + memzero_explicit(derived_key, ci->ci_mode->keysize); + return err; +} + /* * Find the master key, then set up the inode's actual encryption key. * @@ -229,15 +299,36 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, struct fscrypt_key_specifier mk_spec; int err; - mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; - memcpy(mk_spec.u.descriptor, ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); + switch (ci->ci_policy.version) { + case FSCRYPT_POLICY_V1: + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; + memcpy(mk_spec.u.descriptor, + ci->ci_policy.v1.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + break; + case FSCRYPT_POLICY_V2: + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; + memcpy(mk_spec.u.identifier, + ci->ci_policy.v2.master_key_identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + break; + default: + WARN_ON(1); + return -EINVAL; + } key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec); if (IS_ERR(key)) { - if (key != ERR_PTR(-ENOKEY)) + if (key != ERR_PTR(-ENOKEY) || + ci->ci_policy.version != FSCRYPT_POLICY_V1) return PTR_ERR(key); + /* + * As a legacy fallback for v1 policies, search for the key in + * the current task's subscribed keyrings too. Don't move this + * to before the search of ->s_master_keys, since users + * shouldn't be able to override filesystem-level keys. + */ return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); } @@ -250,6 +341,12 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, goto out_release_key; } + /* + * Require that the master key be at least as long as the derived key. + * Otherwise, the derived key cannot possibly contain as much entropy as + * that required by the encryption mode it will be used for. For v1 + * policies it's also required for the KDF to work at all. + */ if (mk->mk_secret.size < ci->ci_mode->keysize) { fscrypt_warn(NULL, "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", @@ -260,7 +357,18 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, goto out_release_key; } - err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + switch (ci->ci_policy.version) { + case FSCRYPT_POLICY_V1: + err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + break; + case FSCRYPT_POLICY_V2: + err = fscrypt_setup_v2_file_key(ci, mk); + break; + default: + WARN_ON(1); + err = -EINVAL; + break; + } if (err) goto out_release_key; @@ -282,7 +390,8 @@ static void put_crypt_info(struct fscrypt_info *ci) if (ci->ci_direct_key) { fscrypt_put_direct_key(ci->ci_direct_key); - } else { + } else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) && + !fscrypt_is_direct_key_policy(&ci->ci_policy)) { crypto_free_skcipher(ci->ci_ctfm); crypto_free_cipher(ci->ci_essiv_tfm); } @@ -312,7 +421,7 @@ static void put_crypt_info(struct fscrypt_info *ci) int fscrypt_get_encryption_info(struct inode *inode) { struct fscrypt_info *crypt_info; - struct fscrypt_context ctx; + union fscrypt_context ctx; struct fscrypt_mode *mode; struct key *master_key = NULL; int res; @@ -335,27 +444,12 @@ int fscrypt_get_encryption_info(struct inode *inode) } /* Fake up a context for an unencrypted directory */ memset(&ctx, 0, sizeof(ctx)); - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, + ctx.version = FSCRYPT_CONTEXT_V1; + ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.v1.master_key_descriptor, 0x42, FSCRYPT_KEY_DESCRIPTOR_SIZE); - } else if (res != sizeof(ctx)) { - fscrypt_warn(inode, - "Unknown encryption context size (%d bytes)", res); - return -EINVAL; - } - - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) { - fscrypt_warn(inode, "Unknown encryption context version (%d)", - ctx.format); - return -EINVAL; - } - - if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) { - fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)", - ctx.flags); - return -EINVAL; + res = sizeof(ctx.v1); } crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); @@ -364,14 +458,34 @@ int fscrypt_get_encryption_info(struct inode *inode) crypt_info->ci_inode = inode; - crypt_info->ci_flags = ctx.flags; - crypt_info->ci_data_mode = ctx.contents_encryption_mode; - crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; - memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res); + if (res) { + fscrypt_warn(inode, + "Unrecognized or corrupt encryption context"); + goto out; + } + + switch (ctx.version) { + case FSCRYPT_CONTEXT_V1: + memcpy(crypt_info->ci_nonce, ctx.v1.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + break; + case FSCRYPT_CONTEXT_V2: + memcpy(crypt_info->ci_nonce, ctx.v2.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + break; + default: + WARN_ON(1); + res = -EINVAL; + goto out; + } + + if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) { + res = -EINVAL; + goto out; + } - mode = select_encryption_mode(crypt_info, inode); + mode = select_encryption_mode(&crypt_info->ci_policy, inode); if (IS_ERR(mode)) { res = PTR_ERR(mode); goto out; diff --git a/fs/crypto/keysetup_v1.c b/fs/crypto/keysetup_v1.c index 631690bb6ed5..ad1a36c370c3 100644 --- a/fs/crypto/keysetup_v1.c +++ b/fs/crypto/keysetup_v1.c @@ -189,12 +189,13 @@ find_or_insert_direct_key(struct fscrypt_direct_key *to_insert, */ BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); + memcpy(&hash_key, ci->ci_policy.v1.master_key_descriptor, + sizeof(hash_key)); spin_lock(&fscrypt_direct_keys_lock); hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) { - if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) + if (memcmp(ci->ci_policy.v1.master_key_descriptor, + dk->dk_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) continue; if (ci->ci_mode != dk->dk_mode) continue; @@ -237,7 +238,7 @@ fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key) dk->dk_ctfm = NULL; goto err_free_dk; } - memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor, + memcpy(dk->dk_descriptor, ci->ci_policy.v1.master_key_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE); memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize); @@ -262,7 +263,8 @@ static int setup_v1_file_key_direct(struct fscrypt_info *ci, return -EINVAL; } - if (ci->ci_data_mode != ci->ci_filename_mode) { + if (ci->ci_policy.v1.contents_encryption_mode != + ci->ci_policy.v1.filenames_encryption_mode) { fscrypt_warn(ci->ci_inode, "Direct key mode not allowed with different contents and filenames modes"); return -EINVAL; @@ -308,7 +310,7 @@ out: int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key) { - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + if (ci->ci_policy.v1.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) return setup_v1_file_key_direct(ci, raw_master_key); else return setup_v1_file_key_derived(ci, raw_master_key); @@ -321,11 +323,11 @@ int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci) int err; key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, - ci->ci_master_key_descriptor, + ci->ci_policy.v1.master_key_descriptor, ci->ci_mode->keysize, &payload); if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) { key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix, - ci->ci_master_key_descriptor, + ci->ci_policy.v1.master_key_descriptor, ci->ci_mode->keysize, &payload); } if (IS_ERR(key)) diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index da7ae9c8b4ad..0141d338c1fd 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -5,8 +5,9 @@ * Copyright (C) 2015, Google, Inc. * Copyright (C) 2015, Motorola Mobility. * - * Written by Michael Halcrow, 2015. + * Originally written by Michael Halcrow, 2015. * Modified by Jaegeuk Kim, 2015. + * Modified by Eric Biggers, 2019 for v2 policy support. */ #include <linux/random.h> @@ -14,70 +15,291 @@ #include <linux/mount.h> #include "fscrypt_private.h" -/* - * check whether an encryption policy is consistent with an encryption context +/** + * fscrypt_policies_equal - check whether two encryption policies are the same + * + * Return: %true if equal, else %false */ -static bool is_encryption_context_consistent_with_policy( - const struct fscrypt_context *ctx, - const struct fscrypt_policy *policy) +bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2) { - return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && - (ctx->flags == policy->flags) && - (ctx->contents_encryption_mode == - policy->contents_encryption_mode) && - (ctx->filenames_encryption_mode == - policy->filenames_encryption_mode); + if (policy1->version != policy2->version) + return false; + + return !memcmp(policy1, policy2, fscrypt_policy_size(policy1)); } -static int create_encryption_context_from_policy(struct inode *inode, - const struct fscrypt_policy *policy) +/** + * 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. (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) { - struct fscrypt_context ctx; + switch (policy_u->version) { + case FSCRYPT_POLICY_V1: { + const struct fscrypt_policy_v1 *policy = &policy_u->v1; + + 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; + } + + return true; + } + case FSCRYPT_POLICY_V2: { + const struct fscrypt_policy_v2 *policy = &policy_u->v2; + + 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 (memchr_inv(policy->__reserved, 0, + sizeof(policy->__reserved))) { + fscrypt_warn(inode, + "Reserved bits set in encryption policy"); + return false; + } + + return true; + } + } + 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(); +} - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); +/** + * 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_valid_enc_modes(policy->contents_encryption_mode, - policy->filenames_encryption_mode)) + if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u)) return -EINVAL; - if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) + 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; + + if (!fscrypt_supported_policy(policy, inode)) 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); + if (policy->version == 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); + } - return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL); + 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) { - struct fscrypt_policy policy; + union fscrypt_policy policy; + union fscrypt_policy existing_policy; struct inode *inode = file_inode(filp); + u8 version; + int size; int ret; - struct fscrypt_context ctx; - if (copy_from_user(&policy, arg, sizeof(policy))) + 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; - if (policy.version != 0) - return -EINVAL; - ret = mnt_want_write_file(filp); if (ret) return ret; inode_lock(inode); - ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + ret = fscrypt_get_policy(inode, &existing_policy); if (ret == -ENODATA) { if (!S_ISDIR(inode->i_mode)) ret = -ENOTDIR; @@ -86,14 +308,10 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) else if (!inode->i_sb->s_cop->empty_dir(inode)) ret = -ENOTEMPTY; else - ret = create_encryption_context_from_policy(inode, - &policy); - } else if (ret == sizeof(ctx) && - is_encryption_context_consistent_with_policy(&ctx, - &policy)) { - /* The file already uses the same encryption policy. */ - ret = 0; - } else if (ret >= 0 || ret == -ERANGE) { + 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; } @@ -105,37 +323,57 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) } 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) { - struct inode *inode = file_inode(filp); - struct fscrypt_context ctx; - struct fscrypt_policy policy; - int res; + union fscrypt_policy policy; + int err; - if (!IS_ENCRYPTED(inode)) - return -ENODATA; + err = fscrypt_get_policy(file_inode(filp), &policy); + if (err) + return err; - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0 && res != -ERANGE) - return res; - if (res != sizeof(ctx)) - return -EINVAL; - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + if (policy.version != FSCRYPT_POLICY_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, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - - if (copy_to_user(arg, &policy, sizeof(policy))) + 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); + /** * fscrypt_has_permitted_context() - is a file's encryption policy permitted * within its directory? @@ -157,10 +395,8 @@ EXPORT_SYMBOL(fscrypt_ioctl_get_policy); */ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { - const struct fscrypt_operations *cops = parent->i_sb->s_cop; - const struct fscrypt_info *parent_ci, *child_ci; - struct fscrypt_context parent_ctx, child_ctx; - int res; + 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) && @@ -190,41 +426,22 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) * In any case, if an unexpected error occurs, fall back to "forbidden". */ - res = fscrypt_get_encryption_info(parent); - if (res) + err = fscrypt_get_encryption_info(parent); + if (err) return 0; - res = fscrypt_get_encryption_info(child); - if (res) + err = fscrypt_get_encryption_info(child); + if (err) return 0; - parent_ci = READ_ONCE(parent->i_crypt_info); - child_ci = READ_ONCE(child->i_crypt_info); - - if (parent_ci && child_ci) { - return memcmp(parent_ci->ci_master_key_descriptor, - child_ci->ci_master_key_descriptor, - FSCRYPT_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); - } - res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx)); - if (res != sizeof(parent_ctx)) + err = fscrypt_get_policy(parent, &parent_policy); + if (err) return 0; - res = cops->get_context(child, &child_ctx, sizeof(child_ctx)); - if (res != sizeof(child_ctx)) + err = fscrypt_get_policy(child, &child_policy); + if (err) return 0; - return memcmp(parent_ctx.master_key_descriptor, - child_ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && - (parent_ctx.contents_encryption_mode == - child_ctx.contents_encryption_mode) && - (parent_ctx.filenames_encryption_mode == - child_ctx.filenames_encryption_mode) && - (parent_ctx.flags == child_ctx.flags); + return fscrypt_policies_equal(&parent_policy, &child_policy); } EXPORT_SYMBOL(fscrypt_has_permitted_context); @@ -240,7 +457,8 @@ EXPORT_SYMBOL(fscrypt_has_permitted_context); int fscrypt_inherit_context(struct inode *parent, struct inode *child, void *fs_data, bool preload) { - struct fscrypt_context ctx; + union fscrypt_context ctx; + int ctxsize; struct fscrypt_info *ci; int res; @@ -252,16 +470,10 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, if (ci == NULL) return -ENOKEY; - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - 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_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + 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, - sizeof(ctx), fs_data); + 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; |