From 5d439467b802f5c6393b20d57662500dfb177c8f Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 17 Nov 2021 15:48:06 +0000 Subject: cachefiles: Implement key to filename encoding Implement a function to encode a binary cookie key as something that can be used as a filename. Four options are considered: (1) All printable chars with no '/' characters. Prepend a 'D' to indicate the encoding but otherwise use as-is. (2) Appears to be an array of __be32. Encode as 'S' plus a list of hex-encoded 32-bit ints separated by commas. If a number is 0, it is rendered as "" instead of "0". (3) Appears to be an array of __le32. Encoded as (2) but with a 'T' encoding prefix. (4) Encoded as base64 with an 'E' prefix plus a second char indicating how much padding is involved. A non-standard base64 encoding is used because '/' cannot be used in the encoded form. If (1) is not possible, whichever of (2), (3) or (4) produces the shortest string is selected (hex-encoding a number may be less dense than base64 encoding it). Note that the prefix characters have to be selected from the set [DEIJST@] lest cachefilesd remove the files because it recognise the name. Changes ======= ver #2: - Fix a short allocation that didn't allow for a string terminator[1] Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/bcefb8f2-576a-b3fc-cc29-89808ebfd7c1@linux.alibaba.com/ [1] Link: https://lore.kernel.org/r/163819640393.215744.15212364106412961104.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906940529.143852.17352132319136117053.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967149827.1823006.6088580775428487961.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021549223.640689.14762875188193982341.stgit@warthog.procyon.org.uk/ # v4 --- fs/cachefiles/internal.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'fs/cachefiles/internal.h') diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index 8763ee4a0df2..dbc37f5d4714 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -173,6 +173,11 @@ extern struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object extern void cachefiles_put_object(struct cachefiles_object *object, enum cachefiles_obj_ref_trace why); +/* + * key.c + */ +extern bool cachefiles_cook_key(struct cachefiles_object *object); + /* * main.c */ -- cgit