Bugs found in ehsm

[LeoneChen]

Hello~

Heap OOB

enclave_decrypt defined in EDL set cmk_size as cmk's size, but attacker can feed cmk_size smaller then sizeof(ehsm_keyblob_t), and TBridge only malloc cmk_size for it.

public sgx_status_t enclave_decrypt([in, size=cmk_size] ehsm_keyblob_t* cmk, size_t cmk_size,
                            [in, size=aad_size] ehsm_data_t *aad, size_t aad_size,
                            [in, size=ciphertext_size] ehsm_data_t *ciphertext, size_t ciphertext_size,
                            [in, out, size=plaintext_size] ehsm_data_t *plaintext, size_t plaintext_size);

Then in function enclave_decrypt, cmk->keybloblen will out-of-bound access invalid memory, e.g. cmk->keybloblen is at offset 0x30, but cmk_size is fed with 0x20.

sgx_status_t enclave_decrypt(ehsm_keyblob_t *cmk, size_t cmk_size,
                             ehsm_data_t *aad, size_t aad_size,
                             ehsm_data_t *ciphertext, size_t ciphertext_size,
                             ehsm_data_t *plaintext, size_t plaintext_size)
{
    sgx_status_t ret = SGX_ERROR_UNEXPECTED;

    if (cmk == NULL ||
        cmk_size != APPEND_SIZE_TO_KEYBLOB_T(cmk->keybloblen) ||
        cmk->keybloblen == 0 ||
        cmk->metadata.origin != EH_INTERNAL_KEY)
        return SGX_ERROR_INVALID_PARAMETER;
    ...
}