AMajor/SoftEtherVPN
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Fixed the vulnerability that a malformed packet will cause the buffer overflow at the receive path. This vulnerability may occur abnormal process exit with the buffer security check mechanism built-in with SoftEther VPN binary. Although this buffer overflow can theoretically bypass the security check in theory, in the actual binary it is detected by the buffer security check inserted by the C compiler and the process is forcibly terminated. Therefore, as a result, it can be abused by a DoS attacker. Acknowledgments: The last problems is discovered and reported by Fabrizio Steiner.

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This commit is contained in:
Daiyuu Nobori 2019-02-28 20:40:23 +09:00
parent beef8d6892
commit 98443715d9
1 changed files with 18 additions and 2 deletions
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20
src/Mayaqua/Encrypt.c
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@ -2197,7 +2197,9 @@ bool RsaVerify(void *data, UINT data_size, void *sign, K *k)
bool RsaVerifyEx(void *data, UINT data_size, void *sign, K *k, UINT bits)
{
UCHAR hash_data[SIGN_HASH_SIZE];
UCHAR decrypt_data[SIGN_HASH_SIZE];
UCHAR *decrypt_data;
RSA *rsa;
UINT rsa_size;
// Validate arguments
if (data == NULL || sign == NULL || k == NULL || k->private_key != false)
{
@ -2208,24 +2210,38 @@ bool RsaVerifyEx(void *data, UINT data_size, void *sign, K *k, UINT bits)
bits = RSA_KEY_SIZE;
}
rsa = EVP_PKEY_get0_RSA(k->pkey);
if (rsa == NULL)
{
return false;
}
// Hash the data
if (HashForSign(hash_data, sizeof(hash_data), data, data_size) == false)
{
return false;
}
rsa_size = RSA_size(rsa);
rsa_size = MAX(rsa_size, 1024); // For just in case
decrypt_data = ZeroMalloc(rsa_size);
// Decode the signature
if (RSA_public_decrypt(bits / 8, sign, decrypt_data, EVP_PKEY_get0_RSA(k->pkey), RSA_PKCS1_PADDING) <= 0)
if (RSA_public_decrypt(bits / 8, sign, decrypt_data, rsa, RSA_PKCS1_PADDING) <= 0)
{
Free(decrypt_data);
return false;
}
// Comparison
if (Cmp(decrypt_data, hash_data, SIGN_HASH_SIZE) != 0)
{
Free(decrypt_data);
return false;
}
Free(decrypt_data);
return true;
}