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botan: Implement HMAC-based IKEv2 PRFs via Botan's HKDF implementation

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This commit is contained in:
Tobias Brunner 2022-03-15 09:34:10 +01:00
parent e0fc786ecd
commit 7498769aba
2 changed files with 41 additions and 11 deletions
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51
src/libstrongswan/plugins/botan/botan_kdf.c
View File

@ -42,6 +42,11 @@ struct private_kdf_t {
*/
kdf_t public;
/**
* KDF type.
*/
key_derivation_function_t type;
/**
* Name of the KDF algorithm in Botan.
*/
@ -57,29 +62,42 @@ struct private_kdf_t {
*/
chunk_t salt;
#if BOTAN_VERSION_MAJOR == 2
/**
* Used for a manual length check in get_bytes().
* Length of the hash output.
*/
size_t hash_size;
#endif
};
METHOD(kdf_t, get_type, key_derivation_function_t,
private_kdf_t *this)
{
return KDF_PRF_PLUS;
return this->type;
}
METHOD(kdf_t, get_length, size_t,
private_kdf_t *this)
{
return SIZE_MAX;
if (this->type == KDF_PRF_PLUS)
{
return SIZE_MAX;
}
return this->hash_size;
}
METHOD(kdf_t, get_bytes, bool,
private_kdf_t *this, size_t out_len, uint8_t *buffer)
{
if (this->type == KDF_PRF)
{
if (out_len != get_length(this) ||
botan_kdf(this->name, buffer, out_len, this->key.ptr, this->key.len,
this->salt.ptr, this->salt.len, NULL, 0))
{
return FALSE;
}
return TRUE;
}
#if BOTAN_VERSION_MAJOR == 2
/* Botan 2 doesn't check the length, just silently prevents wrapping the
* counter and returns truncated output, so do this manually */
@ -99,6 +117,11 @@ METHOD(kdf_t, get_bytes, bool,
METHOD(kdf_t, allocate_bytes, bool,
private_kdf_t *this, size_t out_len, chunk_t *chunk)
{
if (this->type == KDF_PRF)
{
out_len = out_len ?: get_length(this);
}
*chunk = chunk_alloc(out_len);
if (!get_bytes(this, out_len, chunk->ptr))
@ -147,9 +170,9 @@ kdf_t *botan_kdf_create(key_derivation_function_t algo, va_list args)
private_kdf_t *this;
pseudo_random_function_t prf_alg;
const char *hash_name;
char *name, buf[8];
char *name, buf[HASH_SIZE_SHA512];
if (algo != KDF_PRF_PLUS)
if (algo != KDF_PRF && algo != KDF_PRF_PLUS)
{
return NULL;
}
@ -160,7 +183,14 @@ kdf_t *botan_kdf_create(key_derivation_function_t algo, va_list args)
{
return NULL;
}
if (asprintf(&name, "HKDF-Expand(%s)", hash_name) <= 0)
if (algo == KDF_PRF)
{
if (asprintf(&name, "HKDF-Extract(%s)", hash_name) <= 0)
{
return NULL;
}
}
else if (asprintf(&name, "HKDF-Expand(%s)", hash_name) <= 0)
{
return NULL;
}
@ -174,14 +204,13 @@ kdf_t *botan_kdf_create(key_derivation_function_t algo, va_list args)
.set_param = _set_param,
.destroy = _destroy,
},
.type = algo,
.name = name,
#if BOTAN_VERSION_MAJOR == 2
.hash_size = hasher_hash_size(hasher_algorithm_from_prf(prf_alg)),
#endif
);
/* test if we can actually use the algorithm */
if (!get_bytes(this, sizeof(buf), buf))
if (!get_bytes(this, algo == KDF_PRF ? get_length(this) : sizeof(buf), buf))
{
destroy(this);
return NULL;

1
src/libstrongswan/plugins/botan/botan_plugin.c
View File

@ -213,6 +213,7 @@ METHOD(plugin_t, get_features, int,
/* kdfs */
#ifdef BOTAN_HAS_HKDF
PLUGIN_REGISTER(SIGNER, botan_kdf_create),
PLUGIN_PROVIDE(KDF, KDF_PRF),
PLUGIN_PROVIDE(KDF, KDF_PRF_PLUS),
#endif /* BOTAN_HAS_HKDF */