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From: Jeff Layton <jlayton@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: ceph-devel@vger.kernel.org, lhenriques@suse.de,
	xiubli@redhat.com, linux-fsdevel@vger.kernel.org,
	linux-fscrypt@vger.kernel.org, dhowells@redhat.com
Subject: Re: [RFC PATCH v7 02/24] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode
Date: Mon, 12 Jul 2021 07:55:37 -0400	[thread overview]
Message-ID: <6b701c8dfc9e16964718f2b4c1e52fda954ed26b.camel@kernel.org> (raw)
In-Reply-To: <YOstFfnzitZrAlLZ@quark.localdomain>

On Sun, 2021-07-11 at 12:40 -0500, Eric Biggers wrote:
> Some nits about comments:
> 
> On Fri, Jun 25, 2021 at 09:58:12AM -0400, Jeff Layton wrote:
> > diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> > index 6ca7d16593ff..32b1f50433ba 100644
> > --- a/fs/crypto/fname.c
> > +++ b/fs/crypto/fname.c
> > @@ -178,10 +178,8 @@ static int fname_decrypt(const struct inode *inode,
> >  static const char lookup_table[65] =
> >  	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
> >  
> > -#define BASE64_CHARS(nbytes)	DIV_ROUND_UP((nbytes) * 4, 3)
> > -
> >  /**
> > - * base64_encode() - base64-encode some bytes
> > + * fscrypt_base64_encode() - base64-encode some bytes
> >   * @src: the bytes to encode
> >   * @len: number of bytes to encode
> >   * @dst: (output) the base64-encoded string.  Not NUL-terminated.
> >   *
> >   * Encodes the input string using characters from the set [A-Za-z0-9+,].
> >   * The encoded string is roughly 4/3 times the size of the input string.
> >   *
> >   * Return: length of the encoded string
> >   */
> > -static int base64_encode(const u8 *src, int len, char *dst)
> > +int fscrypt_base64_encode(const u8 *src, int len, char *dst)
> 
> As this function will be used more widely, this comment should be fixed to be
> more precise.  "Roughly 4/3" isn't precise; it's actually exactly
> FSCRYPT_BASE64_CHARS(len), right?  The following would be better:
> 
>  * Encode the input bytes using characters from the set [A-Za-z0-9+,].
>  *
>  * Return: length of the encoded string.  This will be equal to
>  *         FSCRYPT_BASE64_CHARS(len).
> 

I'm not certain, but I thought that FSCRYPT_BASE64_CHARS gave you a
worst-case estimate of the inflation. This returns the actual length of
the resulting encoded string, which may be less than
FSCRYPT_BASE64_CHARS(len).

> > +/**
> > + * fscrypt_base64_decode() - base64-decode some bytes
> > + * @src: the bytes to decode
> > + * @len: number of bytes to decode
> > + * @dst: (output) decoded binary data
> 
> It's a bit confusing to talk about decoding "bytes"; it's really a string.
> How about:
> 
>  * fscrypt_base64_decode() - base64-decode a string
>  * @src: the string to decode
>  * @len: length of the source string, in bytes
>  * @dst: (output) decoded binary data
>  *
>  * Decode a string that was previously encoded using fscrypt_base64_encode().
>  * The string doesn't need to be NUL-terminated.
> 
> > + * Return: length of the decoded binary data
> 
> Also the error return values should be documented, e.g.:
> 
>  * Return: length of the decoded binary data, or a negative number if the source
>  *         string isn't a valid base64-encoded string.
> 

That update looks reasonable.

Thanks,
-- 
Jeff Layton <jlayton@kernel.org>


  reply	other threads:[~2021-07-12 11:55 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-25 13:58 [RFC PATCH v7 00/24] ceph+fscrypt: context, filename and symlink support Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 01/24] vfs: export new_inode_pseudo Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 02/24] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode Jeff Layton
2021-07-11 17:40   ` Eric Biggers
2021-07-12 11:55     ` Jeff Layton [this message]
2021-07-12 14:22       ` Eric Biggers
2021-07-12 14:32         ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 03/24] fscrypt: export fscrypt_fname_encrypt and fscrypt_fname_encrypted_size Jeff Layton
2021-07-11 17:43   ` Eric Biggers
2021-06-25 13:58 ` [RFC PATCH v7 04/24] fscrypt: add fscrypt_context_for_new_inode Jeff Layton
2021-07-11 17:44   ` Eric Biggers
2021-06-25 13:58 ` [RFC PATCH v7 05/24] ceph: preallocate inode for ops that may create one Jeff Layton
2021-07-07  3:37   ` Xiubo Li
2021-07-07 12:05     ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 06/24] ceph: parse new fscrypt_auth and fscrypt_file fields in inode traces Jeff Layton
2021-07-07  3:53   ` Xiubo Li
2021-07-07 12:09     ` Jeff Layton
2021-07-07 12:46       ` Xiubo Li
2021-07-07 10:47   ` Luis Henriques
2021-07-07 11:19     ` Xiubo Li
2021-07-07 12:19       ` Jeff Layton
2021-07-07 14:32         ` Luis Henriques
2021-07-07 14:56           ` Luis Henriques
2021-07-08  2:56             ` Xiubo Li
2021-07-08 11:26             ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 07/24] ceph: add fscrypt_* handling to caps.c Jeff Layton
2021-07-07  7:20   ` Xiubo Li
2021-07-07 12:02     ` Jeff Layton
2021-07-07 12:47       ` Xiubo Li
2021-07-11 23:00   ` Eric Biggers
2021-07-12 13:22     ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 08/24] ceph: add ability to set fscrypt_auth via setattr Jeff Layton
2021-07-07  8:11   ` Xiubo Li
2021-07-07 12:10     ` Jeff Layton
2021-07-07 10:47   ` Luis Henriques
2021-07-07 12:25     ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 09/24] ceph: crypto context handling for ceph Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 10/24] ceph: implement -o test_dummy_encryption mount option Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 11/24] ceph: add routine to create fscrypt context prior to RPC Jeff Layton
2021-07-07 10:48   ` Luis Henriques
2021-07-07 12:29     ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 12/24] ceph: add fscrypt ioctls Jeff Layton
2021-07-08  7:30   ` Xiubo Li
2021-07-08 11:26     ` Jeff Layton
2021-07-08 11:32       ` Xiubo Li
2021-06-25 13:58 ` [RFC PATCH v7 13/24] ceph: decode alternate_name in lease info Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 14/24] ceph: make ceph_msdc_build_path use ref-walk Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 15/24] ceph: add encrypted fname handling to ceph_mdsc_build_path Jeff Layton
2021-07-11 22:53   ` Eric Biggers
2021-07-12 12:36     ` Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 16/24] ceph: send altname in MClientRequest Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 17/24] ceph: properly set DCACHE_NOKEY_NAME flag in lookup Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 18/24] ceph: make d_revalidate call fscrypt revalidator for encrypted dentries Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 19/24] ceph: add helpers for converting names for userland presentation Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 20/24] ceph: add fscrypt support to ceph_fill_trace Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 21/24] ceph: add support to readdir for encrypted filenames Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 22/24] ceph: create symlinks with encrypted and base64-encoded targets Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 23/24] ceph: make ceph_get_name decrypt filenames Jeff Layton
2021-06-25 13:58 ` [RFC PATCH v7 24/24] ceph: add a new ceph.fscrypt.auth vxattr Jeff Layton

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