2022-12-20 06:02:44

by Ashwin Kamat

Subject: [PATCH] sctp: Make sha1 as default algorithm if fips is enabled

MD5 is not FIPS compliant. But still md5 was used as the default algorithm
for sctp if fips was enabled.
Due to this, listen() system call in ltp tests was failing for sctp
in fips environment, with below error message.

[ 6397.892677] sctp: failed to load transform for md5: -2

Fix is to not assign md5 as default algorithm for sctp
if fips_enabled is true. Instead make sha1 as default algorithm.

Signed-off-by: Ashwin Dayanand Kamat <[email protected]>
---
net/sctp/protocol.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 909a89a..b6e9810 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -34,6 +34,7 @@
#include <linux/memblock.h>
#include <linux/highmem.h>
#include <linux/slab.h>
+#include <linux/fips.h>
#include <net/net_namespace.h>
#include <net/protocol.h>
#include <net/ip.h>
@@ -1321,14 +1322,13 @@ static int __net_init sctp_defaults_init(struct net *net)
/* Whether Cookie Preservative is enabled(1) or not(0) */
net->sctp.cookie_preserve_enable = 1;

- /* Default sctp sockets to use md5 as their hmac alg */
-#if defined (CONFIG_SCTP_DEFAULT_COOKIE_HMAC_MD5)
- net->sctp.sctp_hmac_alg = "md5";
-#elif defined (CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1)
- net->sctp.sctp_hmac_alg = "sha1";
-#else
- net->sctp.sctp_hmac_alg = NULL;
-#endif
+ /* Default sctp sockets to use md5 as default only if fips is not enabled */
+ if (!fips_enabled && IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_MD5))
+ net->sctp.sctp_hmac_alg = "md5";
+ else if (IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1))
+ net->sctp.sctp_hmac_alg = "sha1";
+ else
+ net->sctp.sctp_hmac_alg = NULL;

/* Max.Burst - 4 */
net->sctp.max_burst = SCTP_DEFAULT_MAX_BURST;
--
2.7.4

2022-12-22 09:38:04

by Paolo Abeni

Subject: Re: [PATCH] sctp: Make sha1 as default algorithm if fips is enabled

On Tue, 2022-12-20 at 10:40 +0530, Ashwin Dayanand Kamat wrote:
> MD5 is not FIPS compliant. But still md5 was used as the default algorithm
> for sctp if fips was enabled.
> Due to this, listen() system call in ltp tests was failing for sctp
> in fips environment, with below error message.
>
> [ 6397.892677] sctp: failed to load transform for md5: -2
>
> Fix is to not assign md5 as default algorithm for sctp
> if fips_enabled is true. Instead make sha1 as default algorithm.
>
> Signed-off-by: Ashwin Dayanand Kamat <[email protected]>

I don't know the fips standard in details, but it feel strange that you
get fips compliance _disabling_ the encryption. Can you please point
which part of the standard states it?

Since this is fix, you should also provide a suitable fixes tag. When
you will repost additionally include the target tree name (net) into
the subject, thanks!

> ---
> net/sctp/protocol.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 909a89a..b6e9810 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -34,6 +34,7 @@
> #include <linux/memblock.h>
> #include <linux/highmem.h>
> #include <linux/slab.h>
> +#include <linux/fips.h>
> #include <net/net_namespace.h>
> #include <net/protocol.h>
> #include <net/ip.h>
> @@ -1321,14 +1322,13 @@ static int __net_init sctp_defaults_init(struct net *net)
> /* Whether Cookie Preservative is enabled(1) or not(0) */
> net->sctp.cookie_preserve_enable = 1;
>
> - /* Default sctp sockets to use md5 as their hmac alg */
> -#if defined (CONFIG_SCTP_DEFAULT_COOKIE_HMAC_MD5)
> - net->sctp.sctp_hmac_alg = "md5";
> -#elif defined (CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1)
> - net->sctp.sctp_hmac_alg = "sha1";
> -#else
> - net->sctp.sctp_hmac_alg = NULL;
> -#endif
> + /* Default sctp sockets to use md5 as default only if fips is not enabled */
> + if (!fips_enabled && IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_MD5))
> + net->sctp.sctp_hmac_alg = "md5";
> + else if (IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1))
> + net->sctp.sctp_hmac_alg = "sha1";
> + else
> + net->sctp.sctp_hmac_alg = NULL;

It looks like the listener can still fail if fips mode is enabled after
that the netns is initialized. I think it would be better to take
action in sctp_listen_start() and buming a ratelimited notice the
selected hmac is changed due to fips.

Thanks,

Paolo

>
> /* Max.Burst - 4 */
> net->sctp.max_burst = SCTP_DEFAULT_MAX_BURST;