From patchwork Wed Dec 29 21:53:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yael Tzur X-Patchwork-Id: 12701125 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 22BCBC433F5 for ; Wed, 29 Dec 2021 21:54:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232680AbhL2VyG (ORCPT ); Wed, 29 Dec 2021 16:54:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231234AbhL2VyF (ORCPT ); Wed, 29 Dec 2021 16:54:05 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F31EC06173F for ; Wed, 29 Dec 2021 13:54:05 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id b10-20020a251b0a000000b0060a7fbb7a64so29720355ybb.23 for ; Wed, 29 Dec 2021 13:54:05 -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=sWjORqABOdOtCeJq4LhyQJ9mB4LVqlD/Y4aoFLyP20c=; b=E4G4E/ZYBEC7Hau2pCewdeMnYUhT4PDZoqdLtC7UA+3Yv7qVvoHHNszhGpdOVRz75I fdC/vCXCTJyBQcYKn6lgpVeEhx2/HGMwKof1r/iycf+pVrBXpRPSvFJ4Fa+lnBw4ZfLN A4NY5g3HoRmF8jWpuaR0QVcwdeF1mF8VCjQqgqDZe+PZH8NC7Tb5ZPEdzEJSAv6U9t0m Tw5JWtda0Hjv2od0KZQ9LUPGmhQQfxo7na78ELvLRXdu29/eSzysM0cDKWbbMtTGzNJK 0985xsWwG5NZvNHXNg9hM67GI6ZfgmhULcT4JuQhucEVRL6tMEivruZXGegf9rqxAEfv 5Rvw== 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=sWjORqABOdOtCeJq4LhyQJ9mB4LVqlD/Y4aoFLyP20c=; b=fG3NIUmGYTCNvc4oAHyf8caHHshfMLBJ98Q/aFEQ+asyRLf1vpVoI2ao1BYUV+sCEp gHv+mYJvj9Nj+Ywsr6rRhsKG1qMkm73Aq08ZdVt+3ATQm+bVzI2wAjARZDjQcNtyFNMV a3pG8U3RkmHAKqBZGzT0tE3mlwYrk9KkIifqNWV5RDzqaxcOtFJoi8CFyl24UiE2yCHf O2m5zuwNO6GWdRDjoO0dr5KaqWomQ5R02SBN1h/Y6ikWfQ8dNP3EG8AT2YcNnmwEpFA3 VzBdynugk915MQAfJRDr8hf1Pq7N7Ylfjw8Te5OYUoQn9WSIxYfkbiZYuZA0/ZH+rDhD 9qmA== X-Gm-Message-State: AOAM533q2biBAVbt7vqnzkdPc9e0j+ihpfItIjMIUvYdXYyWhpVb0/tB w9HW+yA1ytBmyKdCRNOcWFL6l+TD1A== X-Google-Smtp-Source: ABdhPJzcw0GCm56DEx+tsE86Jr7lIzH9bwMfnb7zB8Pv11yK1M4TASLlfJ5NiuG1ubcTR0BwNFtltNuZMQ== X-Received: from yaelt.nyc.corp.google.com ([2620:0:1003:415:20d1:e249:eb05:ae62]) (user=yaelt job=sendgmr) by 2002:a25:aa8e:: with SMTP id t14mr21363549ybi.363.1640814844152; Wed, 29 Dec 2021 13:54:04 -0800 (PST) Date: Wed, 29 Dec 2021 16:53:30 -0500 Message-Id: <20211229215330.4134835-1-yaelt@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.1.448.ga2b2bfdf31-goog Subject: [PATCH v4] KEYS: encrypted: Instantiate key with user-provided decrypted data From: Yael Tiomkin 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 Tiomkin Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org 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 instantiate encrypted keys using user-provided decrypted data, and therefore allows to perform key encryption from userspace. The decrypted key material will be inaccessible from userspace. Reviewed-by: Mimi Zohar Signed-off-by: Yael Tiomkin --- Notes: v -> v2: fixed compilation error. v2 -> v3: modified documentation. v3 -> v4: modified commit message. .../security/keys/trusted-encrypted.rst | 25 ++++++-- security/keys/encrypted-keys/encrypted.c | 62 +++++++++++++------ 2 files changed, 63 insertions(+), 24 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/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 87432b35d771..baf6fba5e05e 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -159,6 +159,7 @@ static int valid_master_desc(const char *new_desc, const char *orig_desc) * * datablob format: * new [] + * new [] * load [] * * update @@ -170,7 +171,7 @@ 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 +232,8 @@ 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 +598,8 @@ 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 +608,7 @@ 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 +618,20 @@ 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 (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 (!isalnum(decrypted_data[i])) { + pr_err("encrypted key: decrypted data provided must be alphanumeric\n"); + return ERR_PTR(-EINVAL); + } + } + } + if (format) { if (!strcmp(format, key_format_ecryptfs)) { if (dlen != ECRYPTFS_MAX_KEY_BYTES) { @@ -740,13 +759,14 @@ 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 +780,26 @@ 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 +812,7 @@ 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 +825,18 @@ 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 +886,7 @@ 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 +895,7 @@ 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;