On Wed, Jan 20, 2021 at 12:12:50PM +0100, Mickaël Salaün wrote: > > On 20/01/2021 04:43, Jarkko Sakkinen wrote: > > On Thu, Jan 14, 2021 at 04:19:01PM +0100, Mickaël Salaün wrote: > >> From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> > >> > >> When looking for a blacklisted hash, bin2hex() is used to transform a > >> binary hash to an ascii (lowercase) hexadecimal string. This string is > >> then search for in the description of the keys from the blacklist > >> keyring. When adding a key to the blacklist keyring, > >> blacklist_vet_description() checks the hash prefix and the hexadecimal > >> string, but not that this string is lowercase. It is then valid to set > >> hashes with uppercase hexadecimal, which will be silently ignored by the > >> kernel. > >> > >> Add an additional check to blacklist_vet_description() to check that > >> hexadecimal strings are in lowercase. > >> > >> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx> > >> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> > >> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > >> Reviewed-by: Ben Boeckel <mathstuf@xxxxxxxxx> > >> --- > >> > >> Changes since v2: > >> * Cherry-pick v1 patch from > >> https://lore.kernel.org/lkml/2659836.1607940186@xxxxxxxxxxxxxxxxxxxxxx/ > >> to rebase on v5.11-rc3. > >> * Rearrange Cc order. > >> --- > >> certs/blacklist.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/certs/blacklist.c b/certs/blacklist.c > >> index 2719fb2fbc1c..a888b934a1cd 100644 > >> --- a/certs/blacklist.c > >> +++ b/certs/blacklist.c > >> @@ -37,7 +37,7 @@ static int blacklist_vet_description(const char *desc) > >> found_colon: > >> desc++; > >> for (; *desc; desc++) { > >> - if (!isxdigit(*desc)) > >> + if (!isxdigit(*desc) || isupper(*desc)) > >> return -EINVAL; > >> n++; > >> } > >> -- > >> 2.30.0 > >> > > > > Shouldn't this rather convert the upper case to lower case? I don't like > > the ABI break that this causes. > > It doesn't break the ABI because keys loaded in the blacklist keyring > can only happen with builtin hashes. Moreover these builtin hashes will > be checked by patch 10/10 at build time. Right the patches are just out of order then. /Jarkko > > This patch is also important to remove a false sense of security and > warns about mis-blacklisted certificates or binaries: > https://lore.kernel.org/lkml/c9664a67-61b7-6b4a-86d7-5aca9ff06fa5@xxxxxxxxxxx/ > > Hot-patching keys doesn't seem a good idea, especially when these keys > are signed. Moreover, it would bring additional complexity and will > require to change the core of the key management. > > > > > /Jarkko > > >
