From patchwork Tue Oct 10 20:40:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josef Bacik X-Patchwork-Id: 13416102 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 6B60BCD8CBF for ; Tue, 10 Oct 2023 20:41:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343758AbjJJUlV (ORCPT ); Tue, 10 Oct 2023 16:41:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229734AbjJJUlP (ORCPT ); Tue, 10 Oct 2023 16:41:15 -0400 Received: from mail-yw1-x112f.google.com (mail-yw1-x112f.google.com [IPv6:2607:f8b0:4864:20::112f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0FCDDE for ; Tue, 10 Oct 2023 13:41:12 -0700 (PDT) Received: by mail-yw1-x112f.google.com with SMTP id 00721157ae682-5a7be88e9ccso14561787b3.2 for ; Tue, 10 Oct 2023 13:41:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20230601.gappssmtp.com; s=20230601; t=1696970472; x=1697575272; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=3ubwOKPnw/IU4g90S+kgqMqAvosFRnP9dYqQa/ogHNg=; b=IsgsZQ53c2ojlz4XL8cwdY0o08WZpPXIKBe0B1nn+50H16Sh3BBg2Shl/YhN5QltyM YuHIcONRdMn/rQmIJ5MamwgOOhpWK6AEJoTcWHgQJIY0FaBzawfanoWdRZ/oqr8wfQbB PFBFM7UP0JSXdn3rBlT9vjglFIxBIkwCk3tJtyA6xdGiBsNJ3IpLfaLnWxZqAsA6LB9L 4r5HuQlehIjPNg4JfQtnkAfLBDx5oSAoSPJhusCcTXBJSsRk/XyV+NpuH/rVh6OEIdKi 3FTu76qTbwmUB+78UdO2lytbsYBVzccuZObr1k1M/shqeeuOrzhksYIq+5/4ahs93krf PPIg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696970472; x=1697575272; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=3ubwOKPnw/IU4g90S+kgqMqAvosFRnP9dYqQa/ogHNg=; b=eCSQBLRpzTAYf8qcTUkZyf30hKb+LDKpeJ9pHhs9Lneq8a/cK3XDCcSWmtgA7XPhdk S4yYy0S5kgjoLkJuJZLVeT30q7th8gIAD7SxguxuPAbUApIZchKVF6z9VXANjSqCUYu2 OvoVds857QClYGhfU7m0S8WncqtifbQABpoIYQ8zj7LaNXR9OUFct7LO0cV32oVxiriF KLDD1wXewxcWE5gEaUAVFhQfw0Kkcvk3u8xELxuJG6bGuOJblsRDWD3ft+a5jKQYuCHr xKMTK4RohDUhWb/AU2nawFod06dSNnzfFBbIpkodcg5MEyxNjum07DCS+jJZXKiDR7v9 2Xrg== X-Gm-Message-State: AOJu0YxSt+RtAe1UutSlvhiVltE3vBOagM3JNm5Yg6ygzJTxcnHeQLxi LLHsSt6DiNLp8vSzt/29zUW4FQ== X-Google-Smtp-Source: AGHT+IH0MlH/PDspUNysTV3KeSuwCl0LUpu4ueM813c521XL7wiLcvRf96YhXEAhQolyRKkNPb4LdQ== X-Received: by 2002:a81:a156:0:b0:5a7:dbf4:6a1a with SMTP id y83-20020a81a156000000b005a7dbf46a1amr350771ywg.7.1696970471523; Tue, 10 Oct 2023 13:41:11 -0700 (PDT) Received: from localhost (cpe-76-182-20-124.nc.res.rr.com. [76.182.20.124]) by smtp.gmail.com with ESMTPSA id v203-20020a8148d4000000b005a7c00bdc79sm696290ywa.49.2023.10.10.13.41.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Oct 2023 13:41:11 -0700 (PDT) From: Josef Bacik To: linux-fscrypt@vger.kernel.org, ebiggers@kernel.org, linux-btrfs@vger.kernel.org Cc: Omar Sandoval , Sweet Tea Dorminy Subject: [PATCH v2 06/36] fscrypt: expose fscrypt_nokey_name Date: Tue, 10 Oct 2023 16:40:21 -0400 Message-ID: <5f7c3adb304bc3b5263af215f6b476275fdecc47.1696970227.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Omar Sandoval btrfs stores its data structures, including filenames in directories, in its own buffer implementation, struct extent_buffer, composed of several non-contiguous pages. We could copy filenames into a temporary buffer and use fscrypt_match_name() against that buffer, such extensive memcpying would be expensive. Instead, exposing fscrypt_nokey_name as in this change allows btrfs to recapitulate fscrypt_match_name() using methods on struct extent_buffer instead of dealing with a raw byte array. Signed-off-by: Omar Sandoval Signed-off-by: Sweet Tea Dorminy Signed-off-by: Josef Bacik --- fs/crypto/fname.c | 39 +-------------------------------------- include/linux/fscrypt.h | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+), 38 deletions(-) diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 7b3fc189593a..5607ee52703e 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -14,7 +14,6 @@ #include #include #include -#include #include #include "fscrypt_private.h" @@ -26,43 +25,7 @@ #define FSCRYPT_FNAME_MIN_MSG_LEN 16 /* - * struct fscrypt_nokey_name - identifier for directory entry when key is absent - * - * When userspace lists an encrypted directory without access to the key, the - * filesystem must present a unique "no-key name" for each filename that allows - * it to find the directory entry again if requested. Naively, that would just - * mean using the ciphertext filenames. However, since the ciphertext filenames - * can contain illegal characters ('\0' and '/'), they must be encoded in some - * way. We use base64url. But that can cause names to exceed NAME_MAX (255 - * bytes), so we also need to use a strong hash to abbreviate long names. - * - * The filesystem may also need another kind of hash, the "dirhash", to quickly - * find the directory entry. Since filesystems normally compute the dirhash - * over the on-disk filename (i.e. the ciphertext), it's not computable from - * no-key names that abbreviate the ciphertext using the strong hash to fit in - * NAME_MAX. It's also not computable if it's a keyed hash taken over the - * plaintext (but it may still be available in the on-disk directory entry); - * casefolded directories use this type of dirhash. At least in these cases, - * each no-key name must include the name's dirhash too. - * - * To meet all these requirements, we base64url-encode the following - * variable-length structure. It contains the dirhash, or 0's if the filesystem - * didn't provide one; up to 149 bytes of the ciphertext name; and for - * ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes. - * - * This ensures that each no-key name contains everything needed to find the - * directory entry again, contains only legal characters, doesn't exceed - * NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only - * take the performance hit of SHA-256 on very long filenames (which are rare). - */ -struct fscrypt_nokey_name { - u32 dirhash[2]; - u8 bytes[149]; - u8 sha256[SHA256_DIGEST_SIZE]; -}; /* 189 bytes => 252 bytes base64url-encoded, which is <= NAME_MAX (255) */ - -/* - * Decoded size of max-size no-key name, i.e. a name that was abbreviated using + * Decoded size of max-size nokey name, i.e. a name that was abbreviated using * the strong hash and thus includes the 'sha256' field. This isn't simply * sizeof(struct fscrypt_nokey_name), as the padding at the end isn't included. */ diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index a3576da6a9fa..9a7cd1e2146e 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -17,6 +17,7 @@ #include #include #include +#include #include /* @@ -56,6 +57,42 @@ struct fscrypt_name { #define fname_name(p) ((p)->disk_name.name) #define fname_len(p) ((p)->disk_name.len) +/* + * struct fscrypt_nokey_name - identifier for directory entry when key is absent + * + * When userspace lists an encrypted directory without access to the key, the + * filesystem must present a unique "no-key name" for each filename that allows + * it to find the directory entry again if requested. Naively, that would just + * mean using the ciphertext filenames. However, since the ciphertext filenames + * can contain illegal characters ('\0' and '/'), they must be encoded in some + * way. We use base64url. But that can cause names to exceed NAME_MAX (255 + * bytes), so we also need to use a strong hash to abbreviate long names. + * + * The filesystem may also need another kind of hash, the "dirhash", to quickly + * find the directory entry. Since filesystems normally compute the dirhash + * over the on-disk filename (i.e. the ciphertext), it's not computable from + * no-key names that abbreviate the ciphertext using the strong hash to fit in + * NAME_MAX. It's also not computable if it's a keyed hash taken over the + * plaintext (but it may still be available in the on-disk directory entry); + * casefolded directories use this type of dirhash. At least in these cases, + * each no-key name must include the name's dirhash too. + * + * To meet all these requirements, we base64url-encode the following + * variable-length structure. It contains the dirhash, or 0's if the filesystem + * didn't provide one; up to 149 bytes of the ciphertext name; and for + * ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes. + * + * This ensures that each no-key name contains everything needed to find the + * directory entry again, contains only legal characters, doesn't exceed + * NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only + * take the performance hit of SHA-256 on very long filenames (which are rare). + */ +struct fscrypt_nokey_name { + u32 dirhash[2]; + u8 bytes[149]; + u8 sha256[SHA256_DIGEST_SIZE]; +}; /* 189 bytes => 252 bytes base64url-encoded, which is <= NAME_MAX (255) */ + /* Maximum value for the third parameter of fscrypt_operations.set_context(). */ #define FSCRYPT_SET_CONTEXT_MAX_SIZE 40