openGauss数据库源码解析系列文章——安全管理源码解析（二）

SaltedPassword := Hi(password, salt, iteration_count) /*其中，Hi()本质上是PBKDF2*/
ClientKey := HMAC(SaltedPassword, "Client Key")
StoredKey := sha256(ClientKey)
ServerKey := HMAC(SaltedPassword, "Sever Key")
ClientSignature:=HMAC(StoredKey, token)
ServerSignature:= HMAC(ServerKey, token)
ClientProof:= ClientSignature XOR ClientKey

ServerSignature := HMAC(ServerKey, token)

ClientSignature := HMAC(StoredKey,token)

ClientProof := ClientKey XOR ClientSignature

ClientSignature := HMAC(StoredKey, token)
HMAC(ClientProof XOR ClientSignature ) = StoredKey

void ClientAuthentication(Port* port)
{
    int status = STATUS_ERROR;
    char details[PGAUDIT_MAXLENGTH] = {0};
    char token[TOKEN_LENGTH + 1] = {0};
    errno_t rc = EOK;
    GS_UINT32 retval = 0;
hba_getauthmethod(port);
……
    switch (port->hba->auth_method) {
        case uaReject:
……
case uaImplicitReject:
        ……
/*  使用MD5口令认证  */
case uaMD5:
            sendAuthRequest(port, AUTH_REQ_MD5);
            status = recv_and_check_password_packet(port);
            break;
/*  使用sha256认证方法  */
case uaSHA256:
            /*  禁止使用初始用户进行远程连接  */
            if (isRemoteInitialUser(port)) {
                ereport(FATAL,
                  (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION), errmsg("Forbid remote connection with initial user.")));
    }
    rc = memset_s(port->token, TOKEN_LENGTH * 2 + 1, 0, TOKEN_LENGTH * 2 + 1);
    securec_check(rc, "\0", "\0");
    HOLD_INTERRUPTS();
    /*  生成随机数token  */
    retval = RAND_priv_bytes ((GS_UCHAR*)token, (GS_UINT32)TOKEN_LENGTH);
    RESUME_INTERRUPTS();
    CHECK_FOR_INTERRUPTS();
    if (retval != 1) {
        ereport(ERROR, (errmsg("Failed to Generate the random number,errcode:%u", retval)));
    }
    sha_bytes_to_hex8((uint8*)token, port->token);
    port->token[TOKEN_LENGTH * 2] = '\0';
    /*  发送认证请求到前端，认证码为AUTH_REQ_SHA256  */
    sendAuthRequest(port, AUTH_REQ_SHA256);
    /*  接收并校验客户端的信息  */
    status = recv_and_check_password_packet(port);
    break;
……
}
……
if (status == STATUS_OK)
    sendAuthRequest(port, AUTH_REQ_OK);
else {
    auth_failed(port, status);
}
 
/*  完成认证，关闭参数ImmediateInterruptOK  */
t_thrd.int_cxt.ImmediateInterruptOK = false;
}

static int pg_password_sendauth(PGconn* conn, const char* password, AuthRequest areq)
{
int ret;
/*  初始化变量  */
……
    char h[HMAC_LENGTH + 1] = {0};
    char h_string[HMAC_LENGTH * 2 + 1] = {0};
    char hmac_result[HMAC_LENGTH + 1] = {0};
    char client_key_bytes[HMAC_LENGTH + 1] = {0};
    switch (areq) {
      case AUTH_REQ_MD5:
/*  pg_md5_encrypt()通过MD5Salt进行MD5加密  */
……
case AUTH_REQ_MD5_SHA256:
……
      case AUTH_REQ_SHA256: {
        char* crypt_pwd2 = NULL;
        if (SHA256_PASSWORD == conn->password_stored_method || PLAIN_PASSWORD == conn->password_stored_method) {
            /*  通过SHA256方式加密密码  */
            if (!pg_sha256_encrypt(
                    password, conn->salt, strlen(conn->salt), (char*)buf, client_key_buf, conn->iteration_count))
                return STATUS_ERROR;
 
            rc = strncpy_s(server_key_string,
                sizeof(server_key_string),
                &buf[SHA256_LENGTH + SALT_STRING_LENGTH],
                sizeof(server_key_string) - 1);
            securec_check_c(rc, "\0", "\0");
            rc = strncpy_s(stored_key_string,
                sizeof(stored_key_string),
                &buf[SHA256_LENGTH + SALT_STRING_LENGTH + HMAC_STRING_LENGTH],
                sizeof(stored_key_string) - 1);
            securec_check_c(rc, "\0", "\0");
            server_key_string[sizeof(server_key_string) - 1] = '\0';
            stored_key_string[sizeof(stored_key_string) - 1] = '\0';
 
            sha_hex_to_bytes32(server_key_bytes, server_key_string);
            sha_hex_to_bytes4(token, conn->token);
/*  通过server_key和token调用HMAC算法计算，得到client_server_signature_bytes，通过该变量转为字符串变量，用来验证与服务端传来的server_signature是否相等。*/
            CRYPT_hmac_ret1 = CRYPT_hmac(NID_hmacWithSHA256,
                (GS_UCHAR*)server_key_bytes,
                HMAC_LENGTH,
                (GS_UCHAR*)token,
                TOKEN_LENGTH,
                (GS_UCHAR*)client_server_signature_bytes,
                (GS_UINT32*)&hmac_length);
            if (CRYPT_hmac_ret1) {
                return STATUS_ERROR;
            }
            sha_bytes_to_hex64((uint8*)client_server_signature_bytes, client_server_signature_string);
 
/*  调用函数strncmp判断计算的client_server_signature_string和服务端传来的server_signature值是否相等  */
            if (PG_PROTOCOL_MINOR(conn->pversion) < PG_PROTOCOL_GAUSS_BASE &&
                0 != strncmp(conn->server_signature, client_server_signature_string, HMAC_STRING_LENGTH)) {
                pwd_to_send = fail_info;  /*  不相等则认证失败  */
            } else {
                sha_hex_to_bytes32(stored_key_bytes, stored_key_string);
                /*  通过stored_key和token计算得到hmac_result  */
                CRYPT_hmac_ret2 = CRYPT_hmac(NID_hmacWithSHA256,
                    (GS_UCHAR*)stored_key_bytes,
                    STORED_KEY_LENGTH,
                    (GS_UCHAR*)token,
                    TOKEN_LENGTH,
                    (GS_UCHAR*)hmac_result,
                    (GS_UINT32*)&hmac_length);
 
                if (CRYPT_hmac_ret2) {
                    return STATUS_ERROR;
                }
 
                sha_hex_to_bytes32(client_key_bytes, client_key_buf);
/*  hmac_result和client_key_bytes异或得到h，然后将其发送给服务端，用于验证客户端  */
                if (XOR_between_password(hmac_result, client_key_bytes, h, HMAC_LENGTH)) {
                    return STATUS_ERROR;
                }
 
                sha_bytes_to_hex64((uint8*)h, h_string);
                pwd_to_send = h_string; /* 设置要发送给服务端的值  */
            }
        }
……
        break;
/*  清空变量  */
……
    return ret;
}

typedef struct GssConn {
    int sock;
    gss_ctx_id_t gctx;        /*  GSS 上下文  */
    gss_name_t gtarg_nam;   /*  GSS 名称  */
    gss_buffer_desc ginbuf;   /*  GSS 输入token  */
    gss_buffer_desc goutbuf;  /*  GSS 输出token  */
} GssConn; 
/*  客户端、服务端接口,用于封装标准kerberos协议调用,其中客户端接口用于向服务端  */
/*  发起访问，同时响应服务端接口GssServerAuth发起的票据请求  */
int GssClientAuth(int socket, char* server_host);
int GssServerAuth(int socket, const char* krb_keyfile);