sctp: Make hmac algorithm selection for cookie generation dynamic
Currently sctp allows for the optional use of md5 of sha1 hmac algorithms to
generate cookie values when establishing new connections via two build time
config options. Theres no real reason to make this a static selection. We can
add a sysctl that allows for the dynamic selection of these algorithms at run
time, with the default value determined by the corresponding crypto library
availability.
This comes in handy when, for example running a system in FIPS mode, where use
of md5 is disallowed, but SHA1 is permitted.
Note: This new sysctl has no corresponding socket option to select the cookie
hmac algorithm. I chose not to implement that intentionally, as RFC 6458
contains no option for this value, and I opted not to pollute the socket option
namespace.
Change notes:
v2)
* Updated subject to have the proper sctp prefix as per Dave M.
* Replaced deafult selection options with new options that allow
developers to explicitly select available hmac algs at build time
as per suggestion by Vlad Y.
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev@vger.kernel.org
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 2d51842..456bc3d 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1190,6 +1190,15 @@
/* 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_CRYPTO_MD5)
+ net->sctp.sctp_hmac_alg = "md5";
+#elif defined (CONFIG_CRYPTO_SHA1)
+ net->sctp.sctp_hmac_alg = "sha1";
+#else
+ net->sctp.sctp_hmac_alg = NULL;
+#endif
+
/* Max.Burst - 4 */
net->sctp.max_burst = SCTP_DEFAULT_MAX_BURST;