Function decrypt_string_gcm

libcppcryptfs/crypt/crypt.cpp:376–410

}

bool decrypt_string_gcm(const string& base64_in, const BYTE *key, wstring& str)
{
	bool rval = true;

	auto context = get_crypt_context(BLOCK_IV_LEN, AES_MODE_GCM);

	if (!context)
		return false;

	try {
		vector<BYTE> v;

		BYTE adata[8];
		memset(adata, 0, sizeof(adata));

		if (!base64_decode(&base64_in[0], v, false, true))
			throw(-1);

		vector<char> plaintext(v.size() - BLOCK_IV_LEN - BLOCK_TAG_LEN + 1);
		int ptlen = decrypt((const BYTE*)(&v[0] + BLOCK_IV_LEN), (int)v.size() - BLOCK_IV_LEN - BLOCK_TAG_LEN, adata, sizeof(adata), &v[0] + v.size() - BLOCK_TAG_LEN, key, &v[0], (BYTE*)&plaintext[0], context.get());

		if (ptlen != v.size() - BLOCK_IV_LEN - BLOCK_TAG_LEN)
			throw(-1);

		plaintext[ptlen] = '\0';

		if (!utf8_to_unicode(&plaintext[0], str))
			throw(-1);

	} catch (...) {
			rval = false;
	}	

	return rval;
}

const char *hkdfInfoEMENames = "EME filename encryption";
const char *hkdfInfoGCMContent = "AES-GCM file content encryption";