diff options
Diffstat (limited to 'src/noscrypt.c')
| -rw-r--r-- | src/noscrypt.c | 342 |
1 files changed, 227 insertions, 115 deletions
diff --git a/src/noscrypt.c b/src/noscrypt.c index fb6dd4f..a24c804 100644 --- a/src/noscrypt.c +++ b/src/noscrypt.c @@ -27,8 +27,10 @@ #include <mbedtls/platform_util.h> #include <mbedtls/md.h> #include <mbedtls/hkdf.h> +#include <mbedtls/hmac_drbg.h> #include <mbedtls/chacha20.h> #include <mbedtls/sha256.h> +#include <mbedtls/constant_time.h> /* Non win platforms may need an inline override */ #if !defined(_NC_IS_WINDOWS) && !defined(inline) @@ -41,8 +43,7 @@ #endif // !NULL #define CHACHA_NONCE_SIZE 12 //Size of 12 is set by the cipher spec -#define CHACHA_KEY_SIZE 32 -#define HMAC_KEY_SIZE 32 +#define CHACHA_KEY_SIZE 32 //Size of 32 is set by the cipher spec /* * Local macro for secure zero buffer fill @@ -73,19 +74,31 @@ /* Must include assert.h for assertions */ #include <assert.h> #define DEBUG_ASSERT(x) assert(x); - #define DEBUG_ASSERT2(x, message) assert(x && message); + #define DEBUG_ASSERT2(x, message) assert(x && message); + + /* + * Compiler enabled static assertion keywords are + * only available in C11 and later. Later versions + * have macros built-in from assert.h so we can use + * the static_assert macro directly. + * + * Static assertions are only used for testing such as + * sanity checks and this library targets the c89 standard + * so static_assret very likely will not be available. + */ + #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L + #define STATIC_ASSERT(x, m) static_assert(x, m) + #else + #define STATIC_ASSERT(x, m) + #pragma message("Static assertions are not supported by this language version") + #endif + #else #define DEBUG_ASSERT(x) #define DEBUG_ASSERT2(x, message) + #define STATIC_ASSERT(x, m) #endif - -struct nc_expand_keys { - uint8_t chacha_key[CHACHA_KEY_SIZE]; - uint8_t chacha_nonce[CHACHA_NONCE_SIZE]; - uint8_t hamc_key[HMAC_KEY_SIZE]; -}; - struct shared_secret { uint8_t value[NC_SHARED_SEC_SIZE]; }; @@ -99,6 +112,22 @@ struct message_key { }; /* +* The following struct layout is exactly the same as +* the message key, they may be typecasted to each other. +* as long as the size is the same. +*/ +struct nc_expand_keys { + uint8_t chacha_key[CHACHA_KEY_SIZE]; + uint8_t chacha_nonce[CHACHA_NONCE_SIZE]; + uint8_t hmac_key[NC_HMAC_KEY_SIZE]; +}; + +/* Pointer typecast must work between expanded keys +* and message key, size must be identical to work +*/ +STATIC_ASSERT(sizeof(struct nc_expand_keys) == sizeof(struct message_key), "Expected struct nc_expand_keys to be the same size as struct message_key"); + +/* * Internal helper functions to do common structure conversions */ @@ -115,7 +144,7 @@ static inline int _convertToXonly(const NCContext* ctx, const NCPublicKey* compr static int _convertToPubKey(const NCContext* ctx, const NCPublicKey* compressedPubKey, secp256k1_pubkey* pubKey) { int result; - uint8_t compressed[NC_PUBKEY_SIZE + 1]; + uint8_t compressed[sizeof(NCPublicKey) + 1]; DEBUG_ASSERT2(ctx != NULL, "Expected valid context") DEBUG_ASSERT2(compressedPubKey != NULL, "Expected a valid public 32byte key structure") @@ -125,7 +154,7 @@ static int _convertToPubKey(const NCContext* ctx, const NCPublicKey* compressedP compressed[0] = BIP340_PUBKEY_HEADER_BYTE; //Copy the compressed public key data into a new buffer (offset by 1 to store the header byte) - MEMMOV((compressed + 1), compressedPubKey->key, NC_PUBKEY_SIZE); + MEMMOV((compressed + 1), compressedPubKey, sizeof(NCPublicKey)); result = secp256k1_ec_pubkey_parse(ctx->secpCtx, pubKey, compressed, sizeof(compressed)); @@ -212,7 +241,7 @@ static NCResult _computeSharedSecret( ); //Clean up sensitive data - ZERO_FILL(&pubKey, sizeof(secp256k1_pubkey)); + ZERO_FILL(&pubKey, sizeof(pubKey)); //Result should be 1 on success return result > 0 ? NC_SUCCESS : E_OPERATION_FAILED; @@ -260,65 +289,24 @@ static inline NCResult _computeConversationKey( /* * Explode the hkdf into the chacha key, chacha nonce, and hmac key. */ -static inline void _expandKeysFromHkdf(const struct message_key* hkdf, struct nc_expand_keys* keys) +static inline const struct nc_expand_keys* _expandKeysFromHkdf(const struct message_key* hkdf) { - uint8_t* hkdfBytes; - - DEBUG_ASSERT2(hkdf != NULL, "Expected valid hkdf") - DEBUG_ASSERT2(keys != NULL, "Expected valid key expand structure") - - hkdfBytes = (uint8_t*)hkdf; - - //Copy segments of the hkdf into the keys struct - MEMMOV( - keys->chacha_key, - hkdfBytes, - CHACHA_KEY_SIZE - ); - - hkdfBytes += CHACHA_KEY_SIZE; //Offset by key size - - MEMMOV( - keys->chacha_nonce, - hkdfBytes, - CHACHA_NONCE_SIZE - ); - - hkdfBytes += CHACHA_NONCE_SIZE; //Offset by nonce size - - MEMMOV( - keys->hamc_key, - hkdfBytes, - HMAC_KEY_SIZE - ); + return (const struct nc_expand_keys*)hkdf; } static int _chachaEncipher(const struct nc_expand_keys* keys, NCCryptoData* args) { - int result; - mbedtls_chacha20_context chachaCtx; - DEBUG_ASSERT2(keys != NULL, "Expected valid keys") DEBUG_ASSERT2(args != NULL, "Expected valid encryption args") - //Init the chacha context - mbedtls_chacha20_init(&chachaCtx); - - //Set the key and nonce - result = mbedtls_chacha20_setkey(&chachaCtx, keys->chacha_key); - DEBUG_ASSERT2(result == 0, "Expected chacha setkey to return 0") - - result = mbedtls_chacha20_starts(&chachaCtx, keys->chacha_nonce, 0); - DEBUG_ASSERT2(result == 0, "Expected chacha starts to return 0") - - //Encrypt the plaintext - result = mbedtls_chacha20_update(&chachaCtx, args->dataSize, args->inputData, args->outputData); - DEBUG_ASSERT2(result == 0, "Expected chacha update to return 0") - - //Clean up the chacha context - mbedtls_chacha20_free(&chachaCtx); - - return result; + return mbedtls_chacha20_crypt( + keys->chacha_key, + keys->chacha_nonce, + 0, //Counter (always starts at 0) + args->dataSize, //Data size (input and output are assumed to be the same size) + args->inputData, //Input data + args->outputData //Output data + ); } static inline NCResult _getMessageKey( @@ -353,16 +341,19 @@ static inline NCResult _encryptEx( const NCContext* ctx, const mbedtls_md_info_t* mdINfo, const struct conversation_key* ck, + uint8_t hmacKey[NC_HMAC_KEY_SIZE], NCCryptoData* args ) { NCResult result; struct message_key messageKey; - struct nc_expand_keys cipherKeys; + const struct nc_expand_keys* expandedKeys; DEBUG_ASSERT2(ctx != NULL, "Expected valid context") DEBUG_ASSERT2(ck != NULL, "Expected valid conversation key") DEBUG_ASSERT2(args != NULL, "Expected valid encryption args") + DEBUG_ASSERT2(mdINfo != NULL, "Expected valid md info struct") + DEBUG_ASSERT2(hmacKey != NULL, "Expected valid hmac key buffer") //Failure, bail out if ((result = _getMessageKey(mdINfo, ck, args->nonce, NC_ENCRYPTION_NONCE_SIZE, &messageKey)) != NC_SUCCESS) @@ -371,10 +362,13 @@ static inline NCResult _encryptEx( } //Expand the keys from the hkdf so we can use them in the cipher - _expandKeysFromHkdf(&messageKey, &cipherKeys); + expandedKeys = _expandKeysFromHkdf(&messageKey); - //CHACHA20 - result = _chachaEncipher(&cipherKeys, args); + //Copy the hmac key into the args + MEMMOV(hmacKey, expandedKeys->hmac_key, NC_HMAC_KEY_SIZE); + + //CHACHA20 (the result will be 0 on success) + result = (NCResult)_chachaEncipher(expandedKeys, args); Cleanup: //Clean up sensitive data @@ -392,10 +386,7 @@ static inline NCResult _decryptEx( { NCResult result; struct message_key messageKey; - struct nc_expand_keys cipherKeys; - - //Assume message key buffer is the same size as the expanded key struct - DEBUG_ASSERT2(sizeof(messageKey) == sizeof(cipherKeys), "Message key size and expanded key sizes do not match") + const struct nc_expand_keys* cipherKeys; DEBUG_ASSERT2(ctx != NULL, "Expected valid context") DEBUG_ASSERT2(ck != NULL, "Expected valid conversation key") @@ -409,10 +400,10 @@ static inline NCResult _decryptEx( } //Expand the keys from the hkdf so we can use them in the cipher - _expandKeysFromHkdf(&messageKey, &cipherKeys); + cipherKeys = _expandKeysFromHkdf(&messageKey); - //CHACHA20 - result = _chachaEncipher(&cipherKeys, args); + //CHACHA20 (the result will be 0 on success) + result = (NCResult) _chachaEncipher(cipherKeys, args); Cleanup: //Clean up sensitive data @@ -421,41 +412,65 @@ Cleanup: return result; } -/* -* Compute the sha256 digest of the data. This function should always return 0 -* on success. -*/ -static inline int _computeSha256Digest(const uint8_t* data, size_t length, uint8_t digest[32]) +static NCResult _verifyMacEx( + const NCContext* ctx, + const uint8_t conversationKey[NC_CONV_KEY_SIZE], + NCMacVerifyArgs* args +) { - int result; - mbedtls_sha256_context sha256; + NCResult result; + const mbedtls_md_info_t* sha256Info; + const struct nc_expand_keys* keys; + struct message_key messageKey; + uint8_t hmacOut[NC_ENCRYPTION_MAC_SIZE]; + + DEBUG_ASSERT2(ctx != NULL, "Expected valid context") + DEBUG_ASSERT2(conversationKey != NULL, "Expected valid conversation key") + DEBUG_ASSERT2(args != NULL, "Expected valid mac verification args") - DEBUG_ASSERT2(data != NULL, "Expected valid data buffer") - DEBUG_ASSERT2(digest != NULL, "Expected valid digest buffer") + sha256Info = _getSha256MdInfo(); - //Init the sha256 context - mbedtls_sha256_init(&sha256); + /* + * We need to get the message key in order to + * get the required hmac key + */ + result = _getMessageKey( + sha256Info, + (struct conversation_key*)conversationKey, + args->nonce, + NC_ENCRYPTION_NONCE_SIZE, + &messageKey + ); + + if (result != NC_SUCCESS) + { + goto Cleanup; + } - //starting context should never fail - result = mbedtls_sha256_starts(&sha256, 0); - DEBUG_ASSERT2(result == 0, "Expected sha256 starts to return 0") + /* Expand keys to get the hmac-key */ + keys = _expandKeysFromHkdf(&messageKey); - //may fail if the data is invalid - if ((result = mbedtls_sha256_update(&sha256, data, length)) != 0) + /* + * Compute the hmac of the data using the computed hmac key + */ + if (mbedtls_md_hmac(sha256Info, keys->hmac_key, NC_HMAC_KEY_SIZE, args->payload, args->payloadSize, hmacOut) != 0) { + result = E_OPERATION_FAILED; goto Cleanup; } - //Finishing context should never fail - result = mbedtls_sha256_finish(&sha256, digest); + /* constant time compare the macs */ + result = mbedtls_ct_memcmp(hmacOut, args->mac, NC_ENCRYPTION_MAC_SIZE) == 0 ? NC_SUCCESS : E_OPERATION_FAILED; Cleanup: - //Always free the context - mbedtls_sha256_free(&sha256); + /* Clean up sensitive data */ + ZERO_FILL(&messageKey, sizeof(messageKey)); + ZERO_FILL(hmacOut, sizeof(hmacOut)); return result; } + /* * EXTERNAL API FUNCTIONS */ @@ -535,8 +550,8 @@ NC_EXPORT NCResult NC_CC NCGetPublicKey( DEBUG_ASSERT2(result == 1, "Expected x-only pubkey serialize to return 1") //Clean out keypair - ZERO_FILL(&keyPair, sizeof(secp256k1_keypair)); - ZERO_FILL(&xonly, sizeof(secp256k1_xonly_pubkey)); + ZERO_FILL(&keyPair, sizeof(keyPair)); + ZERO_FILL(&xonly, sizeof(xonly)); return NC_SUCCESS; } @@ -594,8 +609,8 @@ NC_EXPORT NCResult NC_CC NCSignDigest( result = secp256k1_schnorrsig_verify(ctx->secpCtx, sig64, digest32, 32, &xonly); //cleanup any sensitive data - ZERO_FILL(&keyPair, sizeof(secp256k1_keypair)); - ZERO_FILL(&xonly, sizeof(secp256k1_xonly_pubkey)); + ZERO_FILL(&keyPair, sizeof(keyPair)); + ZERO_FILL(&xonly, sizeof(xonly)); return result == 1 ? NC_SUCCESS : E_INVALID_ARG; } @@ -620,7 +635,7 @@ NC_EXPORT NCResult NC_CC NCSignData( CHECK_NULL_ARG(sig64, 5) //Compute sha256 of the data before signing - if(_computeSha256Digest(data, dataSize, digest) != 0) + if(mbedtls_sha256(data, dataSize, digest, 0) != 0) { return E_INVALID_ARG; } @@ -655,7 +670,7 @@ NC_EXPORT NCResult NC_CC NCVerifyDigest( result = secp256k1_schnorrsig_verify(ctx->secpCtx, sig64, digest32, 32, &xonly); //cleanup any sensitive data - ZERO_FILL(&xonly, sizeof(secp256k1_xonly_pubkey)); + ZERO_FILL(&xonly, sizeof(xonly)); return result == 1 ? NC_SUCCESS : E_INVALID_ARG; } @@ -677,7 +692,7 @@ NC_EXPORT NCResult NC_CC NCVerifyData( CHECK_NULL_ARG(sig64, 4) //Compute sha256 of the data before verifying - if (_computeSha256Digest(data, dataSize, digest) != 0) + if (mbedtls_sha256(data, dataSize, digest, 0) != 0) { return E_INVALID_ARG; } @@ -770,23 +785,27 @@ Cleanup: NC_EXPORT NCResult NC_CC NCEncryptEx( const NCContext* ctx, const uint8_t conversationKey[NC_CONV_KEY_SIZE], + uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE], NCCryptoData* args ) { CHECK_NULL_ARG(ctx, 0) CHECK_INVALID_ARG(ctx->secpCtx, 0) CHECK_NULL_ARG(conversationKey, 1) - CHECK_NULL_ARG(args, 2) + CHECK_NULL_ARG(hmacKeyOut, 2) + CHECK_NULL_ARG(args, 3) //Validte ciphertext/plaintext - CHECK_INVALID_ARG(args->inputData, 2) - CHECK_INVALID_ARG(args->outputData, 2) - CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 2) + CHECK_INVALID_ARG(args->inputData, 3) + CHECK_INVALID_ARG(args->outputData, 3) + CHECK_INVALID_ARG(args->nonce, 3) + CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 3) return _encryptEx( ctx, _getSha256MdInfo(), (struct conversation_key*)conversationKey, + hmacKeyOut, args ); } @@ -795,6 +814,7 @@ NC_EXPORT NCResult NC_CC NCEncrypt( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, + uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE], NCCryptoData* args ) { @@ -807,12 +827,14 @@ NC_EXPORT NCResult NC_CC NCEncrypt( CHECK_INVALID_ARG(ctx->secpCtx, 0) CHECK_NULL_ARG(sk, 1) CHECK_NULL_ARG(pk, 2) - CHECK_NULL_ARG(args, 3) + CHECK_NULL_ARG(hmacKeyOut, 3) + CHECK_NULL_ARG(args, 4) //Validate input/output data - CHECK_INVALID_ARG(args->inputData, 3) - CHECK_INVALID_ARG(args->outputData, 3) - CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 3) + CHECK_INVALID_ARG(args->inputData, 4) + CHECK_INVALID_ARG(args->outputData, 4) + CHECK_INVALID_ARG(args->nonce, 4) + CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 4) mdInfo = _getSha256MdInfo(); @@ -828,7 +850,7 @@ NC_EXPORT NCResult NC_CC NCEncrypt( goto Cleanup; } - result = _encryptEx(ctx, mdInfo, &conversationKey, args); + result = _encryptEx(ctx, mdInfo, &conversationKey, hmacKeyOut, args); Cleanup: //Clean up sensitive data @@ -838,7 +860,6 @@ Cleanup: return result; } - NC_EXPORT NCResult NC_CC NCDecryptEx( const NCContext* ctx, const uint8_t conversationKey[NC_CONV_KEY_SIZE], @@ -853,7 +874,8 @@ NC_EXPORT NCResult NC_CC NCDecryptEx( //Validte ciphertext/plaintext CHECK_INVALID_ARG(args->inputData, 2) CHECK_INVALID_ARG(args->outputData, 2) - CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_DEC_MESSAGE_SIZE, NIP44_MAX_DEC_MESSAGE_SIZE, 3) + CHECK_INVALID_ARG(args->nonce, 2) + CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 2) return _decryptEx( ctx, @@ -863,7 +885,6 @@ NC_EXPORT NCResult NC_CC NCDecryptEx( ); } - NC_EXPORT NCResult NC_CC NCDecrypt( const NCContext* ctx, const NCSecretKey* sk, @@ -885,7 +906,8 @@ NC_EXPORT NCResult NC_CC NCDecrypt( //Validte ciphertext/plaintext CHECK_INVALID_ARG(args->inputData, 3) CHECK_INVALID_ARG(args->outputData, 3) - CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_DEC_MESSAGE_SIZE, NIP44_MAX_DEC_MESSAGE_SIZE, 3) + CHECK_INVALID_ARG(args->nonce, 3) + CHECK_ARG_RANGE(args->dataSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 3) mdInfo = _getSha256MdInfo(); @@ -909,3 +931,93 @@ Cleanup: return result; } +NC_EXPORT NCResult NCComputeMac( + const NCContext* ctx, + const uint8_t hmacKey[NC_HMAC_KEY_SIZE], + const uint8_t* payload, + size_t payloadSize, + uint8_t hmacOut[NC_ENCRYPTION_MAC_SIZE] +) +{ + CHECK_NULL_ARG(ctx, 0) + CHECK_INVALID_ARG(ctx->secpCtx, 0) + CHECK_NULL_ARG(hmacKey, 1) + CHECK_NULL_ARG(payload, 2) + CHECK_ARG_RANGE(payloadSize, 1, UINT32_MAX, 3) + CHECK_NULL_ARG(hmacOut, 4) + + /* + * Compute the hmac of the data using the supplied hmac key + */ + return mbedtls_md_hmac( + _getSha256MdInfo(), + hmacKey, + NC_HMAC_KEY_SIZE, + payload, + payloadSize, + hmacOut + ) == 0 ? NC_SUCCESS : E_OPERATION_FAILED; +} + + +NC_EXPORT NCResult NC_CC NCVerifyMacEx( + const NCContext* ctx, + const uint8_t conversationKey[NC_CONV_KEY_SIZE], + NCMacVerifyArgs* args +) +{ + CHECK_NULL_ARG(ctx, 0) + CHECK_INVALID_ARG(ctx->secpCtx, 0) + CHECK_NULL_ARG(conversationKey, 1) + CHECK_NULL_ARG(args, 2) + + CHECK_INVALID_ARG(args->mac, 2) + CHECK_INVALID_ARG(args->payload, 2) + CHECK_INVALID_ARG(args->nonce, 2) + CHECK_ARG_RANGE(args->payloadSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 2) + + return _verifyMacEx(ctx, conversationKey, args); +} + +NC_EXPORT NCResult NC_CC NCVerifyMac( + const NCContext* ctx, + const NCSecretKey* sk, + const NCPublicKey* pk, + NCMacVerifyArgs* args +) +{ + CHECK_NULL_ARG(ctx, 0) + CHECK_INVALID_ARG(ctx->secpCtx, 0) + CHECK_NULL_ARG(sk, 1) + CHECK_NULL_ARG(pk, 2) + CHECK_NULL_ARG(args, 3) + + CHECK_INVALID_ARG(args->mac, 3) + CHECK_INVALID_ARG(args->payload, 3) + CHECK_INVALID_ARG(args->nonce, 3) + CHECK_ARG_RANGE(args->payloadSize, NIP44_MIN_ENC_MESSAGE_SIZE, NIP44_MAX_ENC_MESSAGE_SIZE, 3) + + NCResult result; + struct shared_secret sharedSecret; + struct conversation_key conversationKey; + + /* Computed the shared point so we can get the converstation key */ + if ((result = _computeSharedSecret(ctx, sk, pk, &sharedSecret)) != NC_SUCCESS) + { + goto Cleanup; + } + + if ((result = _computeConversationKey(ctx, _getSha256MdInfo(), &sharedSecret, &conversationKey)) != NC_SUCCESS) + { + goto Cleanup; + } + + result = _verifyMacEx(ctx, (uint8_t*)&conversationKey, args); + +Cleanup: + /* Clean up sensitive data */ + ZERO_FILL(&sharedSecret, sizeof(sharedSecret)); + ZERO_FILL(&conversationKey, sizeof(conversationKey)); + + return result; +}
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