where-are-my-friends/src/rcon.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <errno.h>

#include "rcon.h"

int rcon_connect(const char* address, int port) {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    struct timeval tv;
    tv.tv_sec = 2;
    tv.tv_usec = 0;
    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);

    if (inet_pton(AF_INET, address, &server_addr.sin_addr) <= 0) {
        perror("invalid address");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("connection failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    printf("connected to rcon server\n");
    return sockfd;
}

void send_packet(int sockfd, int32_t id, int32_t type, const char *body) {
    size_t body_len = strlen(body);

    size_t packet_size = sizeof(int32_t) * 3 + body_len + 2;
    unsigned char *packet = malloc(packet_size);
    if (!packet) {
        perror("malloc failed");
        return;
    }

    int32_t size = htole32(packet_size - sizeof(int32_t));
    memcpy(packet, &size, sizeof(int32_t));

    int32_t id_ = htole32(id);
    memcpy(packet + 4, &id_, sizeof(int32_t));

    int32_t type_ = htole32(type);
    memcpy(packet + 8, &type_, sizeof(int32_t));

    memcpy(packet + 12, body, body_len);
    packet[3 * sizeof(int32_t) + body_len] = 0;
    packet[3 * sizeof(int32_t) + body_len + 1] = 0;

    ssize_t sent = send(sockfd, packet, packet_size, 0);
    if (sent < 0) {
        perror("send failed");
    }

    free(packet);
}

int recv_packet(int sockfd, rcon_packet_t *packet) {
    ssize_t bytes;

    bytes = recv(sockfd, &packet->size, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        if (bytes == 0) {
            fprintf(stderr, "connection closed by server\n");
        } else if (errno == EAGAIN || errno == EWOULDBLOCK) {
            return -2; // Timeout
        } else {
            perror("recv size failed");
        }
        return -1;
    }
    packet->size = le32toh(packet->size);

    if (packet->size < (int32_t)RCON_PACKET_MIN_SIZE || packet->size > (int32_t)RCON_PACKET_MAX_SIZE) {
        fprintf(stderr, "invalid packet size: %d\n", packet->size);
        return -1;
    }

    bytes = recv(sockfd, &packet->id, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        perror("recv id failed");
        return -1;
    }
    packet->id = le32toh(packet->id);

    bytes = recv(sockfd, &packet->type, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        perror("recv type failed");
        return -1;
    }
    packet->type = le32toh(packet->type);

    int body_size = packet->size - sizeof(int32_t) * 2 - 2;
    if (body_size > 0 && body_size < (int)sizeof(packet->body)) {
        bytes = recv(sockfd, packet->body, body_size, MSG_WAITALL);
        if (bytes <= 0) {
            perror("recv body failed");
            return -1;
        }
        packet->body[body_size] = '\0';

        bytes = recv(sockfd, &packet->_padding, 1, MSG_WAITALL);
        if (bytes <= 0) {
            perror("recv padding failed");
            return -1;
        }
    } else {
        packet->size = sizeof(int32_t) * 2 + 2;
        packet->body[0] = '\0';
    }

    return 0;
}

int rcon_authenticate(int sockfd, const char *password) {
    printf("authenticating with password: '%s'\n", password);

    send_packet(sockfd, 1, RCON_SERVERDATA_AUTH, password);

    printf("waiting for auth response...\n");

    rcon_packet_t response;
    if (recv_packet(sockfd, &response) < 0) {
        fprintf(stderr, "failed to receive auth response\n");
        return -1;
    }

    printf("received auth packet: id=%d, type=%d\n", response.id, response.type);

    // Check if authentication failed (id == -1)
    if (response.id == -1) {
        fprintf(stderr, "authentication failed - invalid password\n");
        return -1;
    }

    // Try to read second packet (may timeout, which is OK)
    rcon_packet_t response2;
    int result = recv_packet(sockfd, &response2);
    if (result == 0) {
        printf("received second auth packet: id=%d, type=%d\n", response2.id, response2.type);
    } else if (result == -2) {
        printf("no second packet (timeout - this is normal)\n");
    }

    printf("authenticated successfully\n");
    return 0;
}

char* rcon_command_multipacket(int sockfd, const char *command) {
    static char result[65536];
    result[0] = '\0';

    int cmd_id = 100;
    int dummy_id = 101;

    send_packet(sockfd, cmd_id, RCON_SERVERDATA_EXECCOMMAND, command);
    send_packet(sockfd, dummy_id, RCON_SERVERDATA_EXECCOMMAND, "");

    while (1) {
        rcon_packet_t response;
        if (recv_packet(sockfd, &response) < 0) {
            fprintf(stderr, "failed to receive command response\n");
            return NULL;
        }
        if (response.id == dummy_id) {
            break;
        }
        if (response.type == RCON_SERVERDATA_RESPONSE_VALUE && response.id == cmd_id) {
            strncat(result, response.body, sizeof(result) - strlen(result) - 1);
        }
    }

    return result;
}