Address some issues with PR 492

Adds copyright notices for Juraj Somorovsky and Christian Mainka of Hackmanit
for the changes in 7c7fcecbe6a and 6d327f879c

Add Policy::check_peer_key_acceptable which lets the app set an arbitrary
callback for examining keys - both the end entity signature keys from
certificates and the peer PFS public keys. Default impl checks that the
algorithm size matches the min keylength. This centralizes this logic
and lets the application do interesting things.

Adds a policy for ECDSA group size checks.

Increases default policy minimums to 2048 RSA and 256 ECC.
(Maybe I'm an optimist after all.)

1 files changed, 36 insertions, 1 deletions

diff --git a/src/lib/tls/tls_policy.h b/src/lib/tls/tls_policy.h
index 3a09a1747..76e80ddde 100644
--- a/src/lib/tls/tls_policy.h
+++ b/src/lib/tls/tls_policy.h
@@ -131,18 +131,47 @@ class BOTAN_DLL Policy
 
       /**
       * Return the minimum DH group size we're willing to use
+      * Default is currently 1024 (insecure), should be 2048
       */
       virtual size_t minimum_dh_group_size() const;
       
       /**
+      * For ECDSA authenticated ciphersuites, the smallest key size the
+      * client will accept.
+      * This policy is currently only enforced on the server by the client.
+      */
+      virtual size_t minimum_ecdsa_group_size() const;
+      
+      /**
       * Return the minimum ECDH group size we're willing to use
+      * for key exchange
+      *
+      * Default 256, allowing P-256 and larger
+      * P-256 is the smallest curve we will negotiate
       */
       virtual size_t minimum_ecdh_group_size() const;
       
       /**
-      * Return the minimum RSA bit size we're willing to use
+      * Return the minimum bit size we're willing to accept for RSA
+      * key exchange or server signatures.
+      *
+      * It does not place any requirements on the size of any RSA signature(s)
+      * which were used to check the server certificate. This is only
+      * concerned with the server's public key.
+      *
+      * Default is 2048 which is smallest RSA key size still secure
+      * for medium term security.
       */
       virtual size_t minimum_rsa_bits() const;
+
+      /**
+      * Throw an exception if you don't like the peer's key.
+      * Default impl checks the key size against minimum_rsa_bits, minimum_ecdsa_group_size,
+      * or minimum_ecdh_group_size depending on the key's type.
+      * Override if you'd like to perform some other kind of test on
+      * (or logging of) the peer's keys.
+      */
+      virtual void check_peer_key_acceptable(const Public_Key& public_key) const;
       
       /**
       * If this function returns false, unknown SRP/PSK identifiers
@@ -352,6 +381,12 @@ class BOTAN_DLL Text_Policy : public Policy
       std::string dh_group() const override
          { return get_str("dh_group", Policy::dh_group()); }
 
+      size_t minimum_ecdh_group_size() const override
+         { return get_len("minimum_ecdh_group_size", Policy::minimum_ecdh_group_size()); }
+
+      size_t minimum_ecdsa_group_size() const override
+         { return get_len("minimum_ecdsa_group_size", Policy::minimum_ecdsa_group_size()); }
+
       size_t minimum_dh_group_size() const override
          { return get_len("minimum_dh_group_size", Policy::minimum_dh_group_size()); }