From patchwork Tue Feb 15 14:19:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yael Tzur X-Patchwork-Id: 12747145 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F042C433FE for ; Tue, 15 Feb 2022 14:20:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238584AbiBOOUS (ORCPT ); Tue, 15 Feb 2022 09:20:18 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:48728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238578AbiBOOUR (ORCPT ); Tue, 15 Feb 2022 09:20:17 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D3EEC8F81 for ; Tue, 15 Feb 2022 06:20:06 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id b64-20020a256743000000b0061e169a5f19so40532256ybc.11 for ; Tue, 15 Feb 2022 06:20:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=GUpyRZejn9Pwp27JxxD0pUffrRYlyMDKoKZilOQs1zg=; b=ZT3OQfsZ54iVJEPKmgnr6hFCGXDZyAiFXDqjcgogSLta37V38o2S575RNzSUmFaYlQ sBcNLxR0aousgBT7pc3TimkUjD7hG0UxRA+ol/5xFlFPc9A44J2+cwpB5isbrElaADWg ByLLlcew3BUlw28GvalAoynFSY691tLCRPhJS44fdgw/GgNgksCzfvnRLd8hgCBNXyYj QRziQIOlDb0mwfus4ltBYK1+uIRCUMDizFQqNkHeRs4I6MIkMvRGLgfai//StkfUZCGN HrHjzFKmZFXD6mgE909pV+QiuO0WbjAuUvyoYKTF+F7vsye5L4YSOXSbWfYBWSQJcjbm wHrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=GUpyRZejn9Pwp27JxxD0pUffrRYlyMDKoKZilOQs1zg=; b=nb2+uKxsu/f75a5o3/vi1n0n4cdRwhJCj5mssMq6iL8cq+U9oqvoT3pJLlqJw3H5zv h7lA1IVZFQXTmAO7idDtNxDtrNpHJuxuoREVw7ZERcQlGYx1a6ANN8uiDhRztEsNjxZ/ Q1/ZEmKeh6PL1YSLaNFvZn4I9Qn+3yrEGQoBtVv7vCMSlZDW94Z9Jpz8ntulxexv7HI6 1ZCWOOsex13MjvZ6vLWHNgjhzGW953d/cVCmDFe3WwnK8Vl8yvTqffYMEQuZt2+63YKX ycKoptHQkgg+94DLPxkUp+3NrmN6A2c8mYB/CsVeoxSwrNIYWSZ/tUIvLPemc+KlH72Y 6SjQ== X-Gm-Message-State: AOAM531xM9Frt3PcUKC6U8ualwm7jEmyLF6Tvi28xHnmcw+lSej6RXLS uvXLDk/MOzyLAv4V2010pc/TmfnNVA== X-Google-Smtp-Source: ABdhPJzcCCkgAq2s1mmwNW6OZq/24SwP0p0I0cyzx87weaxppuFpiwOk92W7HltKnDkACdBa+pjsXQVyQQ== X-Received: from yaelt.nyc.corp.google.com ([2620:0:1003:415:4733:5913:aeb8:dca6]) (user=yaelt job=sendgmr) by 2002:a81:4417:: with SMTP id r23mr3907750ywa.443.1644934805301; Tue, 15 Feb 2022 06:20:05 -0800 (PST) Date: Tue, 15 Feb 2022 09:19:53 -0500 Message-Id: <20220215141953.1557009-1-yaelt@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.265.g69c8d7142f-goog Subject: [PATCH v5] KEYS: encrypted: Instantiate key with user-provided decrypted data From: Yael Tzur To: linux-integrity@vger.kernel.org Cc: jejb@linux.ibm.com, jarkko@kernel.org, zohar@linux.ibm.com, corbet@lwn.net, dhowells@redhat.com, jmorris@namei.org, serge@hallyn.com, keyrings@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Yael Tzur Precedence: bulk List-ID: For availability and performance reasons master keys often need to be released outside of a Key Management Service (KMS) to clients. It would be beneficial to provide a mechanism where the wrapping/unwrapping of data encryption keys (DEKs) is not dependent on a remote call at runtime yet security is not (or only minimally) compromised. Master keys could be securely stored in the Kernel and be used to wrap/unwrap keys from Userspace. The encrypted.c class supports instantiation of encrypted keys with either an already-encrypted key material, or by generating new key material based on random numbers. This patch defines a new datablob format: [] that allows to inject and encrypt user-provided decrypted data. The decrypted data must be hex-ascii encoded. Reviewed-by: Mimi Zohar Signed-off-by: Yael Tzur Reviewed-by: Sumit Garg Reviewed-by: Jarkko Sakkinen --- Notes: v -> v2: fixed compilation error. v2 -> v3: modified documentation. v3 -> v4: modified commit message. v4 -> v5: added config option to enable feature, and modified input validation. .../security/keys/trusted-encrypted.rst | 25 +++++-- security/keys/Kconfig | 19 +++-- security/keys/encrypted-keys/encrypted.c | 72 ++++++++++++++----- 3 files changed, 87 insertions(+), 29 deletions(-) diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index 80d5a5af62a1..f614dad7de12 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -107,12 +107,13 @@ Encrypted Keys -------------- Encrypted keys do not depend on a trust source, and are faster, as they use AES -for encryption/decryption. New keys are created from kernel-generated random -numbers, and are encrypted/decrypted using a specified ‘master’ key. The -‘master’ key can either be a trusted-key or user-key type. The main disadvantage -of encrypted keys is that if they are not rooted in a trusted key, they are only -as secure as the user key encrypting them. The master user key should therefore -be loaded in as secure a way as possible, preferably early in boot. +for encryption/decryption. New keys are created either from kernel-generated +random numbers or user-provided decrypted data, and are encrypted/decrypted +using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or +user-key type. The main disadvantage of encrypted keys is that if they are not +rooted in a trusted key, they are only as secure as the user key encrypting +them. The master user key should therefore be loaded in as secure a way as +possible, preferably early in boot. Usage @@ -199,6 +200,8 @@ Usage:: keyctl add encrypted name "new [format] key-type:master-key-name keylen" ring + keyctl add encrypted name "new [format] key-type:master-key-name keylen + decrypted-data" ring keyctl add encrypted name "load hex_blob" ring keyctl update keyid "update key-type:master-key-name" @@ -303,6 +306,16 @@ Load an encrypted key "evm" from saved blob:: 82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0 24717c64 5972dcb82ab2dde83376d82b2e3c09ffc +Instantiate an encrypted key "evm" using user-provided decrypted data:: + + $ keyctl add encrypted evm "new default user:kmk 32 `cat evm_decrypted_data.blob`" @u + 794890253 + + $ keyctl print 794890253 + default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d + bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247 + 17c64 5972dcb82ab2dde83376d82b2e3c09ffc + Other uses for trusted and encrypted keys, such as for disk and file encryption are anticipated. In particular the new format 'ecryptfs' has been defined in order to use encrypted keys to mount an eCryptfs filesystem. More details diff --git a/security/keys/Kconfig b/security/keys/Kconfig index 969122c7b92f..0e30b361e1c1 100644 --- a/security/keys/Kconfig +++ b/security/keys/Kconfig @@ -98,10 +98,21 @@ config ENCRYPTED_KEYS select CRYPTO_RNG help This option provides support for create/encrypting/decrypting keys - in the kernel. Encrypted keys are kernel generated random numbers, - which are encrypted/decrypted with a 'master' symmetric key. The - 'master' key can be either a trusted-key or user-key type. - Userspace only ever sees/stores encrypted blobs. + in the kernel. Encrypted keys are instantiated using kernel + generated random numbers or provided decrypted data, and are + encrypted/decrypted with a 'master' symmetric key. The 'master' + key can be either a trusted-key or user-key type. Only encrypted + blobs are ever output to Userspace. + + If you are unsure as to whether this is required, answer N. + +config USER_DECRYPTED_DATA + bool "Allow encrypted keys with user decrypted data" + depends on ENCRYPTED_KEYS + help + This option provides support for instantiating encrypted keys using + user-provided decrypted data. The decrypted data must be hex-ascii + encoded. If you are unsure as to whether this is required, answer N. diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 87432b35d771..ebfb8129fb92 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -78,6 +78,11 @@ static const match_table_t key_tokens = { {Opt_err, NULL} }; +static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA); +module_param(user_decrypted_data, bool, 0); +MODULE_PARM_DESC(user_decrypted_data, + "Allow instantiation of encrypted keys using provided decrypted data"); + static int aes_get_sizes(void) { struct crypto_skcipher *tfm; @@ -158,7 +163,7 @@ static int valid_master_desc(const char *new_desc, const char *orig_desc) * datablob_parse - parse the keyctl data * * datablob format: - * new [] + * new [] [] * load [] * * update @@ -170,7 +175,7 @@ static int valid_master_desc(const char *new_desc, const char *orig_desc) */ static int datablob_parse(char *datablob, const char **format, char **master_desc, char **decrypted_datalen, - char **hex_encoded_iv) + char **hex_encoded_iv, char **decrypted_data) { substring_t args[MAX_OPT_ARGS]; int ret = -EINVAL; @@ -231,6 +236,7 @@ static int datablob_parse(char *datablob, const char **format, "when called from .update method\n", keyword); break; } + *decrypted_data = strsep(&datablob, " \t"); ret = 0; break; case Opt_load: @@ -595,7 +601,8 @@ static int derived_key_decrypt(struct encrypted_key_payload *epayload, static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, const char *format, const char *master_desc, - const char *datalen) + const char *datalen, + const char *decrypted_data) { struct encrypted_key_payload *epayload = NULL; unsigned short datablob_len; @@ -604,6 +611,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, unsigned int encrypted_datalen; unsigned int format_len; long dlen; + int i; int ret; ret = kstrtol(datalen, 10, &dlen); @@ -613,6 +620,24 @@ 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 (decrypted_data) { + if (!user_decrypted_data) { + pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n"); + return ERR_PTR(-EINVAL); + } + if (strlen(decrypted_data) != decrypted_datalen) { + pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n"); + return ERR_PTR(-EINVAL); + } + for (i = 0; i < strlen(decrypted_data); i++) { + if (!isxdigit(decrypted_data[i])) { + pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n"); + return ERR_PTR(-EINVAL); + } + } + } + if (format) { if (!strcmp(format, key_format_ecryptfs)) { if (dlen != ECRYPTFS_MAX_KEY_BYTES) { @@ -740,13 +766,14 @@ static void __ekey_init(struct encrypted_key_payload *epayload, /* * encrypted_init - initialize an encrypted key * - * For a new key, use a random number for both the iv and data - * itself. For an old key, decrypt the hex encoded data. + * For a new key, use either a random number or user-provided decrypted data in + * case it is provided. A random number is used for the iv in both cases. For + * an old key, decrypt the hex encoded data. */ static int encrypted_init(struct encrypted_key_payload *epayload, const char *key_desc, const char *format, const char *master_desc, const char *datalen, - const char *hex_encoded_iv) + const char *hex_encoded_iv, const char *decrypted_data) { int ret = 0; @@ -760,21 +787,26 @@ static int encrypted_init(struct encrypted_key_payload *epayload, } __ekey_init(epayload, format, master_desc, datalen); - if (!hex_encoded_iv) { - get_random_bytes(epayload->iv, ivsize); - - get_random_bytes(epayload->decrypted_data, - epayload->decrypted_datalen); - } else + if (hex_encoded_iv) { ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv); + } else if (decrypted_data) { + get_random_bytes(epayload->iv, ivsize); + memcpy(epayload->decrypted_data, decrypted_data, + epayload->decrypted_datalen); + } else { + get_random_bytes(epayload->iv, ivsize); + get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen); + } return ret; } /* * encrypted_instantiate - instantiate an encrypted key * - * Decrypt an existing encrypted datablob or create a new encrypted key - * based on a kernel random number. + * Instantiates the key: + * - by decrypting an existing encrypted datablob, or + * - by creating a new encrypted key based on a kernel random number, or + * - using provided decrypted data. * * On success, return 0. Otherwise return errno. */ @@ -787,6 +819,7 @@ static int encrypted_instantiate(struct key *key, char *master_desc = NULL; char *decrypted_datalen = NULL; char *hex_encoded_iv = NULL; + char *decrypted_data = NULL; size_t datalen = prep->datalen; int ret; @@ -799,18 +832,18 @@ static int encrypted_instantiate(struct key *key, datablob[datalen] = 0; memcpy(datablob, prep->data, datalen); ret = datablob_parse(datablob, &format, &master_desc, - &decrypted_datalen, &hex_encoded_iv); + &decrypted_datalen, &hex_encoded_iv, &decrypted_data); if (ret < 0) goto out; epayload = encrypted_key_alloc(key, format, master_desc, - decrypted_datalen); + decrypted_datalen, decrypted_data); if (IS_ERR(epayload)) { ret = PTR_ERR(epayload); goto out; } ret = encrypted_init(epayload, key->description, format, master_desc, - decrypted_datalen, hex_encoded_iv); + decrypted_datalen, hex_encoded_iv, decrypted_data); if (ret < 0) { kfree_sensitive(epayload); goto out; @@ -860,7 +893,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) buf[datalen] = 0; memcpy(buf, prep->data, datalen); - ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL); + ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL); if (ret < 0) goto out; @@ -869,7 +902,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) goto out; new_epayload = encrypted_key_alloc(key, epayload->format, - new_master_desc, epayload->datalen); + new_master_desc, epayload->datalen, NULL); if (IS_ERR(new_epayload)) { ret = PTR_ERR(new_epayload); goto out;