[PATCH net v3 3/3] esp, ah: modernize the crypto algorithm selections

[Eric Biggers <ebiggers@kernel.org>]

From: Eric Biggers <ebiggers@google.com>

The crypto algorithms selected by the ESP and AH kconfig options are
out-of-date with the guidance of RFC 8221, which lists the legacy
algorithms MD5 and DES as "MUST NOT" be implemented, and some more
modern algorithms like AES-GCM and HMAC-SHA256 as "MUST" be implemented.
But the options select the legacy algorithms, not the modern ones.

Therefore, modify these options to select the MUST algorithms --
and *only* the MUST algorithms.

Also improve the help text.

Suggested-by: Herbert Xu <herbert@gondor.apana.org.au>
Suggested-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 net/ipv4/Kconfig | 21 +++++++++++++++++++--
 net/ipv6/Kconfig | 21 +++++++++++++++++++--
 net/xfrm/Kconfig | 15 +++++++++------
 3 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 39a7a21744dc03..14fc8d6582499b 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -342,7 +342,17 @@ config INET_AH
 	tristate "IP: AH transformation"
 	select XFRM_AH
 	---help---
-	  Support for IPsec AH.
+	  Support for IPsec AH (Authentication Header).
+
+	  AH can be used with various authentication algorithms.  Besides
+	  enabling AH support itself, this option enables the generic
+	  implementations of the algorithms that RFC 8221 lists as MUST be
+	  implemented.  If you need any other algorithms, you'll need to enable
+	  them in the crypto API.  You should also enable accelerated
+	  implementations of any needed algorithms when available.
+
+	  Note that RFC 8221 considers AH itself to be "NOT RECOMMENDED".  It is
+	  better to use ESP only, using an AEAD cipher such as AES-GCM.
 
 	  If unsure, say Y.
 
@@ -350,7 +360,14 @@ config INET_ESP
 	tristate "IP: ESP transformation"
 	select XFRM_ESP
 	---help---
-	  Support for IPsec ESP.
+	  Support for IPsec ESP (Encapsulating Security Payload).
+
+	  ESP can be used with various encryption and authentication algorithms.
+	  Besides enabling ESP support itself, this option enables the generic
+	  implementations of the algorithms that RFC 8221 lists as MUST be
+	  implemented.  If you need any other algorithms, you'll need to enable
+	  them in the crypto API.  You should also enable accelerated
+	  implementations of any needed algorithms when available.
 
 	  If unsure, say Y.
 
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index 70313f16319dd2..7398085ab10d58 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -51,7 +51,17 @@ config INET6_AH
 	tristate "IPv6: AH transformation"
 	select XFRM_AH
 	---help---
-	  Support for IPsec AH.
+	  Support for IPsec AH (Authentication Header).
+
+	  AH can be used with various authentication algorithms.  Besides
+	  enabling AH support itself, this option enables the generic
+	  implementations of the algorithms that RFC 8221 lists as MUST be
+	  implemented.  If you need any other algorithms, you'll need to enable
+	  them in the crypto API.  You should also enable accelerated
+	  implementations of any needed algorithms when available.
+
+	  Note that RFC 8221 considers AH itself to be "NOT RECOMMENDED".  It is
+	  better to use ESP only, using an AEAD cipher such as AES-GCM.
 
 	  If unsure, say Y.
 
@@ -59,7 +69,14 @@ config INET6_ESP
 	tristate "IPv6: ESP transformation"
 	select XFRM_ESP
 	---help---
-	  Support for IPsec ESP.
+	  Support for IPsec ESP (Encapsulating Security Payload).
+
+	  ESP can be used with various encryption and authentication algorithms.
+	  Besides enabling ESP support itself, this option enables the generic
+	  implementations of the algorithms that RFC 8221 lists as MUST be
+	  implemented.  If you need any other algorithms, you'll need to enable
+	  them in the crypto API.  You should also enable accelerated
+	  implementations of any needed algorithms when available.
 
 	  If unsure, say Y.
 
diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
index b2ff8df2c836ef..e77ba529229cf5 100644
--- a/net/xfrm/Kconfig
+++ b/net/xfrm/Kconfig
@@ -67,26 +67,29 @@ config XFRM_STATISTICS
 
 	  If unsure, say N.
 
+# This option selects XFRM_ALGO along with the AH authentication algorithms that
+# RFC 8221 lists as MUST be implemented.
 config XFRM_AH
 	tristate
 	select XFRM_ALGO
 	select CRYPTO
 	select CRYPTO_HMAC
-	select CRYPTO_MD5
-	select CRYPTO_SHA1
+	select CRYPTO_SHA256
 
+# This option selects XFRM_ALGO along with the ESP encryption and authentication
+# algorithms that RFC 8221 lists as MUST be implemented.
 config XFRM_ESP
 	tristate
 	select XFRM_ALGO
 	select CRYPTO
+	select CRYPTO_AES
 	select CRYPTO_AUTHENC
-	select CRYPTO_HMAC
-	select CRYPTO_MD5
 	select CRYPTO_CBC
-	select CRYPTO_SHA1
-	select CRYPTO_DES
 	select CRYPTO_ECHAINIV
+	select CRYPTO_GCM
+	select CRYPTO_HMAC
 	select CRYPTO_SEQIV
+	select CRYPTO_SHA256
 
 config XFRM_IPCOMP
 	tristate
-- 
2.26.2