diff options
| -rw-r--r-- | Documentation/keys-ecryptfs.txt | 68 | ||||
| -rw-r--r-- | Documentation/security/keys-trusted-encrypted.txt | 6 | ||||
| -rw-r--r-- | security/keys/Makefile | 2 | ||||
| -rw-r--r-- | security/keys/ecryptfs_format.c | 81 | ||||
| -rw-r--r-- | security/keys/ecryptfs_format.h | 30 | ||||
| -rw-r--r-- | security/keys/encrypted.c | 75 |
6 files changed, 252 insertions, 10 deletions
diff --git a/Documentation/keys-ecryptfs.txt b/Documentation/keys-ecryptfs.txt new file mode 100644 index 0000000..c3bbeba --- /dev/null +++ b/Documentation/keys-ecryptfs.txt @@ -0,0 +1,68 @@ + Encrypted keys for the eCryptfs filesystem + +ECryptfs is a stacked filesystem which transparently encrypts and decrypts each +file using a randomly generated File Encryption Key (FEK). + +Each FEK is in turn encrypted with a File Encryption Key Encryption Key (FEFEK) +either in kernel space or in user space with a daemon called 'ecryptfsd'. In +the former case the operation is performed directly by the kernel CryptoAPI +using a key, the FEFEK, derived from a user prompted passphrase; in the latter +the FEK is encrypted by 'ecryptfsd' with the help of external libraries in order +to support other mechanisms like public key cryptography, PKCS#11 and TPM based +operations. + +The data structure defined by eCryptfs to contain information required for the +FEK decryption is called authentication token and, currently, can be stored in a +kernel key of the 'user' type, inserted in the user's session specific keyring +by the userspace utility 'mount.ecryptfs' shipped with the package +'ecryptfs-utils'. + +The 'encrypted' key type has been extended with the introduction of the new +format 'ecryptfs' in order to be used in conjunction with the eCryptfs +filesystem. Encrypted keys of the newly introduced format store an +authentication token in its payload with a FEFEK randomly generated by the +kernel and protected by the parent master key. + +In order to avoid known-plaintext attacks, the datablob obtained through +commands 'keyctl print' or 'keyctl pipe' does not contain the overall +authentication token, which content is well known, but only the FEFEK in +encrypted form. + +The eCryptfs filesystem may really benefit from using encrypted keys in that the +required key can be securely generated by an Administrator and provided at boot +time after the unsealing of a 'trusted' key in order to perform the mount in a +controlled environment. Another advantage is that the key is not exposed to +threats of malicious software, because it is available in clear form only at +kernel level. + +Usage: + keyctl add encrypted name "new ecryptfs key-type:master-key-name keylen" ring + keyctl add encrypted name "load hex_blob" ring + keyctl update keyid "update key-type:master-key-name" + +name:= '<16 hexadecimal characters>' +key-type:= 'trusted' | 'user' +keylen:= 64 + + +Example of encrypted key usage with the eCryptfs filesystem: + +Create an encrypted key "1000100010001000" of length 64 bytes with format +'ecryptfs' and save it using a previously loaded user key "test": + + $ keyctl add encrypted 1000100010001000 "new ecryptfs user:test 64" @u + 19184530 + + $ keyctl print 19184530 + ecryptfs user:test 64 490045d4bfe48c99f0d465fbbbb79e7500da954178e2de0697 + dd85091f5450a0511219e9f7cd70dcd498038181466f78ac8d4c19504fcc72402bfc41c2 + f253a41b7507ccaa4b2b03fff19a69d1cc0b16e71746473f023a95488b6edfd86f7fdd40 + 9d292e4bacded1258880122dd553a661 + + $ keyctl pipe 19184530 > ecryptfs.blob + +Mount an eCryptfs filesystem using the created encrypted key "1000100010001000" +into the '/secret' directory: + + $ mount -i -t ecryptfs -oecryptfs_sig=1000100010001000,\ + ecryptfs_cipher=aes,ecryptfs_key_bytes=32 /secret /secret diff --git a/Documentation/security/keys-trusted-encrypted.txt b/Documentation/security/keys-trusted-encrypted.txt index 0afcb50..5f50cca 100644 --- a/Documentation/security/keys-trusted-encrypted.txt +++ b/Documentation/security/keys-trusted-encrypted.txt @@ -63,7 +63,7 @@ Usage: keyctl add encrypted name "load hex_blob" ring keyctl update keyid "update key-type:master-key-name" -format:= 'default' +format:= 'default | ecryptfs' key-type:= 'trusted' | 'user' @@ -154,4 +154,6 @@ Load an encrypted key "evm" from saved blob: 24717c64 5972dcb82ab2dde83376d82b2e3c09ffc Other uses for trusted and encrypted keys, such as for disk and file encryption -are anticipated. +are anticipated. In particular the new format 'ecryptfs' has been defined in +in order to use encrypted keys to mount an eCryptfs filesystem. More details +about the usage can be found in the file 'Documentation/keys-ecryptfs.txt'. diff --git a/security/keys/Makefile b/security/keys/Makefile index 1bf090a..b34cc6e 100644 --- a/security/keys/Makefile +++ b/security/keys/Makefile @@ -14,7 +14,7 @@ obj-y := \ user_defined.o obj-$(CONFIG_TRUSTED_KEYS) += trusted.o -obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted.o +obj-$(CONFIG_ENCRYPTED_KEYS) += ecryptfs_format.o encrypted.o obj-$(CONFIG_KEYS_COMPAT) += compat.o obj-$(CONFIG_PROC_FS) += proc.o obj-$(CONFIG_SYSCTL) += sysctl.o diff --git a/security/keys/ecryptfs_format.c b/security/keys/ecryptfs_format.c new file mode 100644 index 0000000..6daa3b6 --- /dev/null +++ b/security/keys/ecryptfs_format.c @@ -0,0 +1,81 @@ +/* + * ecryptfs_format.c: helper functions for the encrypted key type + * + * Copyright (C) 2006 International Business Machines Corp. + * Copyright (C) 2010 Politecnico di Torino, Italy + * TORSEC group -- http://security.polito.it + * + * Authors: + * Michael A. Halcrow <mahalcro@us.ibm.com> + * Tyler Hicks <tyhicks@ou.edu> + * Roberto Sassu <roberto.sassu@polito.it> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, version 2 of the License. + */ + +#include <linux/module.h> +#include "ecryptfs_format.h" + +u8 *ecryptfs_get_auth_tok_key(struct ecryptfs_auth_tok *auth_tok) +{ + return auth_tok->token.password.session_key_encryption_key; +} +EXPORT_SYMBOL(ecryptfs_get_auth_tok_key); + +/* + * ecryptfs_get_versions() + * + * Source code taken from the software 'ecryptfs-utils' version 83. + * + */ +void ecryptfs_get_versions(int *major, int *minor, int *file_version) +{ + *major = ECRYPTFS_VERSION_MAJOR; + *minor = ECRYPTFS_VERSION_MINOR; + if (file_version) + *file_version = ECRYPTFS_SUPPORTED_FILE_VERSION; +} +EXPORT_SYMBOL(ecryptfs_get_versions); + +/* + * ecryptfs_fill_auth_tok - fill the ecryptfs_auth_tok structure + * + * Fill the ecryptfs_auth_tok structure with required ecryptfs data. + * The source code is inspired to the original function generate_payload() + * shipped with the software 'ecryptfs-utils' version 83. + * + */ +int ecryptfs_fill_auth_tok(struct ecryptfs_auth_tok *auth_tok, + const char *key_desc) +{ + int major, minor; + + ecryptfs_get_versions(&major, &minor, NULL); + auth_tok->version = (((uint16_t)(major << 8) & 0xFF00) + | ((uint16_t)minor & 0x00FF)); + auth_tok->token_type = ECRYPTFS_PASSWORD; + strncpy((char *)auth_tok->token.password.signature, key_desc, + ECRYPTFS_PASSWORD_SIG_SIZE); + auth_tok->token.password.session_key_encryption_key_bytes = + ECRYPTFS_MAX_KEY_BYTES; + /* + * Removed auth_tok->token.password.salt and + * auth_tok->token.password.session_key_encryption_key + * initialization from the original code + */ + /* TODO: Make the hash parameterizable via policy */ + auth_tok->token.password.flags |= + ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET; + /* The kernel code will encrypt the session key. */ + auth_tok->session_key.encrypted_key[0] = 0; + auth_tok->session_key.encrypted_key_size = 0; + /* Default; subject to change by kernel eCryptfs */ + auth_tok->token.password.hash_algo = PGP_DIGEST_ALGO_SHA512; + auth_tok->token.password.flags &= ~(ECRYPTFS_PERSISTENT_PASSWORD); + return 0; +} +EXPORT_SYMBOL(ecryptfs_fill_auth_tok); + +MODULE_LICENSE("GPL"); diff --git a/security/keys/ecryptfs_format.h b/security/keys/ecryptfs_format.h new file mode 100644 index 0000000..40294de --- /dev/null +++ b/security/keys/ecryptfs_format.h @@ -0,0 +1,30 @@ +/* + * ecryptfs_format.h: helper functions for the encrypted key type + * + * Copyright (C) 2006 International Business Machines Corp. + * Copyright (C) 2010 Politecnico di Torino, Italy + * TORSEC group -- http://security.polito.it + * + * Authors: + * Michael A. Halcrow <mahalcro@us.ibm.com> + * Tyler Hicks <tyhicks@ou.edu> + * Roberto Sassu <roberto.sassu@polito.it> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, version 2 of the License. + */ + +#ifndef __KEYS_ECRYPTFS_H +#define __KEYS_ECRYPTFS_H + +#include <linux/ecryptfs.h> + +#define PGP_DIGEST_ALGO_SHA512 10 + +u8 *ecryptfs_get_auth_tok_key(struct ecryptfs_auth_tok *auth_tok); +void ecryptfs_get_versions(int *major, int *minor, int *file_version); +int ecryptfs_fill_auth_tok(struct ecryptfs_auth_tok *auth_tok, + const char *key_desc); + +#endif /* __KEYS_ECRYPTFS_H */ diff --git a/security/keys/encrypted.c b/security/keys/encrypted.c index 89981c9..e7eca9e 100644 --- a/security/keys/encrypted.c +++ b/security/keys/encrypted.c @@ -29,11 +29,13 @@ #include <linux/rcupdate.h> #include <linux/scatterlist.h> #include <linux/crypto.h> +#include <linux/ctype.h> #include <crypto/hash.h> #include <crypto/sha.h> #include <crypto/aes.h> #include "encrypted.h" +#include "ecryptfs_format.h" static const char KEY_TRUSTED_PREFIX[] = "trusted:"; static const char KEY_USER_PREFIX[] = "user:"; @@ -41,11 +43,13 @@ static const char hash_alg[] = "sha256"; static const char hmac_alg[] = "hmac(sha256)"; static const char blkcipher_alg[] = "cbc(aes)"; static const char key_format_default[] = "default"; +static const char key_format_ecryptfs[] = "ecryptfs"; static unsigned int ivsize; static int blksize; #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1) #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1) +#define KEY_ECRYPTFS_DESC_LEN 16 #define HASH_SIZE SHA256_DIGEST_SIZE #define MAX_DATA_SIZE 4096 #define MIN_DATA_SIZE 20 @@ -63,11 +67,12 @@ enum { }; enum { - Opt_error = -1, Opt_default + Opt_error = -1, Opt_default, Opt_ecryptfs }; static const match_table_t key_format_tokens = { {Opt_default, "default"}, + {Opt_ecryptfs, "ecryptfs"}, {Opt_error, NULL} }; @@ -95,6 +100,34 @@ static int aes_get_sizes(void) } /* + * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key + * + * The description of a encrypted key with format 'ecryptfs' must contain + * exactly 16 hexadecimal characters. + * + */ +static int valid_ecryptfs_desc(const char *ecryptfs_desc) +{ + int i; + + if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) { + pr_err("encrypted_key: key description must be %d hexadecimal " + "characters long\n", KEY_ECRYPTFS_DESC_LEN); + return -EINVAL; + } + + for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) { + if (!isxdigit(ecryptfs_desc[i])) { + pr_err("encrypted_key: key description must contain " + "only hexadecimal characters\n"); + return -EINVAL; + } + } + + return 0; +} + +/* * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key * * key-type:= "trusted:" | "user:" @@ -158,7 +191,7 @@ static int datablob_parse(char *datablob, const char **format, } key_cmd = match_token(keyword, key_tokens, args); - /* Get optional format: default */ + /* Get optional format: default | ecryptfs */ p = strsep(&datablob, " \t"); if (!p) { pr_err("encrypted_key: insufficient parameters specified\n"); @@ -167,6 +200,7 @@ static int datablob_parse(char *datablob, const char **format, key_format = match_token(p, key_format_tokens, args); switch (key_format) { + case Opt_ecryptfs: case Opt_default: *format = p; *master_desc = strsep(&datablob, " \t"); @@ -601,6 +635,17 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, format_len = (!format) ? strlen(key_format_default) : strlen(format); decrypted_datalen = dlen; payload_datalen = decrypted_datalen; + if (format && !strcmp(format, key_format_ecryptfs)) { + if (dlen != ECRYPTFS_MAX_KEY_BYTES) { + pr_err("encrypted_key: keylen for the ecryptfs format " + "must be equal to %d bytes\n", + ECRYPTFS_MAX_KEY_BYTES); + return ERR_PTR(-EINVAL); + } + decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES; + payload_datalen = sizeof(struct ecryptfs_auth_tok); + } + encrypted_datalen = roundup(decrypted_datalen, blksize); datablob_len = format_len + 1 + strlen(master_desc) + 1 @@ -686,8 +731,14 @@ static void __ekey_init(struct encrypted_key_payload *epayload, if (!format) memcpy(epayload->format, key_format_default, format_len); - else + else { + if (!strcmp(format, key_format_ecryptfs)) + epayload->decrypted_data = + ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data); + memcpy(epayload->format, format, format_len); + } + memcpy(epayload->master_desc, master_desc, strlen(master_desc)); memcpy(epayload->datalen, datalen, strlen(datalen)); } @@ -699,11 +750,21 @@ static void __ekey_init(struct encrypted_key_payload *epayload, * itself. For an old key, decrypt the hex encoded data. */ static int encrypted_init(struct encrypted_key_payload *epayload, - const char *format, const char *master_desc, - const char *datalen, const char *hex_encoded_iv) + const char *key_desc, const char *format, + const char *master_desc, const char *datalen, + const char *hex_encoded_iv) { int ret = 0; + if (format && !strcmp(format, key_format_ecryptfs)) { + ret = valid_ecryptfs_desc(key_desc); + if (ret < 0) + return ret; + + ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data, + key_desc); + } + __ekey_init(epayload, format, master_desc, datalen); if (!hex_encoded_iv) { get_random_bytes(epayload->iv, ivsize); @@ -753,8 +814,8 @@ static int encrypted_instantiate(struct key *key, const void *data, ret = PTR_ERR(epayload); goto out; } - ret = encrypted_init(epayload, format, master_desc, decrypted_datalen, - hex_encoded_iv); + ret = encrypted_init(epayload, key->description, format, master_desc, + decrypted_datalen, hex_encoded_iv); if (ret < 0) { kfree(epayload); goto out; |
