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openssl: Implement HMAC-based IKEv2 PRFs via OpenSSL's HKDF implementation

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This commit is contained in:
Tobias Brunner 2022-03-14 18:17:11 +01:00
parent 0339ce34f6
commit e0fc786ecd
2 changed files with 47 additions and 9 deletions
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55
src/libstrongswan/plugins/openssl/openssl_kdf.c
View File

@ -42,6 +42,11 @@ struct private_kdf_t {
*/
kdf_t public;
/**
* KDF type.
*/
key_derivation_function_t type;
/**
* Hasher to use for underlying PRF.
*/
@ -63,26 +68,51 @@ struct private_kdf_t {
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 EVP_MD_size(this->hasher);
}
/**
* Set the parameters as a appropriate for the given KDF type.
*/
static bool set_params(private_kdf_t *this, EVP_PKEY_CTX *ctx)
{
if (this->type == KDF_PRF)
{
return EVP_PKEY_CTX_hkdf_mode(ctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY) > 0 &&
EVP_PKEY_CTX_set1_hkdf_key(ctx, this->key.ptr, this->key.len) > 0 &&
EVP_PKEY_CTX_set1_hkdf_salt(ctx, this->salt.ptr, this->salt.len) > 0;
}
/* for HKDF-Expand() we map the salt to the "info" field */
return EVP_PKEY_CTX_hkdf_mode(ctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY) > 0 &&
EVP_PKEY_CTX_set1_hkdf_key(ctx, this->key.ptr, this->key.len) > 0 &&
EVP_PKEY_CTX_add1_hkdf_info(ctx, this->salt.ptr, this->salt.len) > 0;
}
METHOD(kdf_t, get_bytes, bool,
private_kdf_t *this, size_t out_len, uint8_t *buffer)
{
EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
EVP_PKEY_CTX *ctx;
if (this->type == KDF_PRF && out_len != get_length(this))
{
return FALSE;
}
ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
if (!ctx ||
EVP_PKEY_derive_init(ctx) <= 0 ||
EVP_PKEY_CTX_set_hkdf_md(ctx, this->hasher) <= 0 ||
EVP_PKEY_CTX_hkdf_mode(ctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY) <= 0 ||
EVP_PKEY_CTX_set1_hkdf_key(ctx, this->key.ptr, this->key.len) <= 0 ||
EVP_PKEY_CTX_add1_hkdf_info(ctx, this->salt.ptr, this->salt.len) <= 0 ||
!set_params(this, ctx) ||
EVP_PKEY_derive(ctx, buffer, &out_len) <= 0)
{
EVP_PKEY_CTX_free(ctx);
@ -95,6 +125,11 @@ 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))
@ -141,9 +176,9 @@ kdf_t *openssl_kdf_create(key_derivation_function_t algo, va_list args)
{
private_kdf_t *this;
pseudo_random_function_t prf_alg;
char *name, buf[8];
char *name, buf[EVP_MAX_MD_SIZE];
if (algo != KDF_PRF_PLUS)
if (algo != KDF_PRF && algo != KDF_PRF_PLUS)
{
return NULL;
}
@ -165,13 +200,15 @@ kdf_t *openssl_kdf_create(key_derivation_function_t algo, va_list args)
.set_param = _set_param,
.destroy = _destroy,
},
.type = algo,
.hasher = EVP_get_digestbyname(name),
/* use a lengthy key to test the implementation below to make sure the
* algorithms are usable, see openssl_hmac.c for details */
.key = chunk_clone(chunk_from_str("00000000000000000000000000000000")),
);
if (!this->hasher || !get_bytes(this, sizeof(buf), buf))
if (!this->hasher ||
!get_bytes(this, algo == KDF_PRF ? get_length(this) : sizeof(buf), buf))
{
destroy(this);
return NULL;

1
src/libstrongswan/plugins/openssl/openssl_plugin.c
View File

@ -658,6 +658,7 @@ METHOD(plugin_t, get_features, int,
#if OPENSSL_VERSION_NUMBER >= 0x10101000L
/* HKDF is available since 1.1.0, expand-only mode only since 1.1.1 */
PLUGIN_REGISTER(KDF, openssl_kdf_create),
PLUGIN_PROVIDE(KDF, KDF_PRF),
PLUGIN_PROVIDE(KDF, KDF_PRF_PLUS),
#endif
#endif /* OPENSSL_NO_HMAC */