libipsec: Fix crypter lookup for AES-CTR

Due to the nonce, the ESP key material is four bytes longer than needed for
the actual AES key.  The crypto plugins, however, register their AES-CTR
implementations with the AES key length, so the lookup here failed.

For IKEv2 the key material is allocated after creating a crypter instance
with the negotiated AES key size.  The length of the actual key material is
retrieved via get_key_size(), which adds the four bytes to the AES key length.

Fixes #1124.

diff --git a/src/libipsec/esp_context.c b/src/libipsec/esp_context.c
index b742d15..a9e0e5b 100644 (file)
--- a/src/libipsec/esp_context.c
+++ b/src/libipsec/esp_context.c
@@ -247,7 +247,18 @@ static bool create_traditional(private_esp_context_t *this, int enc_alg,
        signer_t *signer = NULL;
        iv_gen_t *ivg;
 
-       crypter = lib->crypto->create_crypter(lib->crypto, enc_alg, enc_key.len);
+       switch (enc_alg)
+       {
+               case ENCR_AES_CTR:
+                       /* the key includes a 4 byte salt */
+                       crypter = lib->crypto->create_crypter(lib->crypto, enc_alg,
+                                                                                                 enc_key.len - 4);
+                       break;
+               default:
+                       crypter = lib->crypto->create_crypter(lib->crypto, enc_alg,
+                                                                                                 enc_key.len);
+                       break;
+       }
        if (!crypter)
        {
                DBG1(DBG_ESP, "failed to create ESP context: unsupported encryption "