Magisk/native/src/core/socket.cpp

#include <fcntl.h>
#include <endian.h>

#include <socket.hpp>
#include <base.hpp>

using namespace std;

bool get_client_cred(int fd, sock_cred *cred) {
    socklen_t len = sizeof(ucred);
    if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, cred, &len) != 0)
        return false;
    char buf[4096];
    len = sizeof(buf);
    if (getsockopt(fd, SOL_SOCKET, SO_PEERSEC, buf, &len) != 0)
        len = 0;
    buf[len] = '\0';
    cred->context = buf;
    return true;
}

static int send_fds(int sockfd, void *cmsgbuf, size_t bufsz, const int *fds, int cnt) {
    iovec iov = {
        .iov_base = &cnt,
        .iov_len  = sizeof(cnt),
    };
    msghdr msg = {
        .msg_iov        = &iov,
        .msg_iovlen     = 1,
    };

    if (cnt) {
        msg.msg_control    = cmsgbuf;
        msg.msg_controllen = bufsz;
        cmsghdr *cmsg    = CMSG_FIRSTHDR(&msg);
        cmsg->cmsg_len   = CMSG_LEN(sizeof(int) * cnt);
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type  = SCM_RIGHTS;

        memcpy(CMSG_DATA(cmsg), fds, sizeof(int) * cnt);
    }

    return xsendmsg(sockfd, &msg, 0);
}

int send_fds(int sockfd, const int *fds, int cnt) {
    if (cnt == 0) {
        return send_fds(sockfd, nullptr, 0, nullptr, 0);
    }
    vector<char> cmsgbuf;
    cmsgbuf.resize(CMSG_SPACE(sizeof(int) * cnt));
    return send_fds(sockfd, cmsgbuf.data(), cmsgbuf.size(), fds, cnt);
}

int send_fd(int sockfd, int fd) {
    if (fd < 0) {
        return send_fds(sockfd, nullptr, 0, nullptr, 0);
    }
    char cmsgbuf[CMSG_SPACE(sizeof(int))];
    return send_fds(sockfd, cmsgbuf, sizeof(cmsgbuf), &fd, 1);
}

static void *recv_fds(int sockfd, char *cmsgbuf, size_t bufsz, int cnt) {
    iovec iov = {
        .iov_base = &cnt,
        .iov_len  = sizeof(cnt),
    };
    msghdr msg = {
        .msg_iov        = &iov,
        .msg_iovlen     = 1,
        .msg_control    = cmsgbuf,
        .msg_controllen = bufsz
    };

    xrecvmsg(sockfd, &msg, MSG_WAITALL);
    if (msg.msg_controllen != bufsz) {
        LOGE("recv_fd: msg_flags = %d, msg_controllen(%zu) != %zu\n",
             msg.msg_flags, msg.msg_controllen, bufsz);
        return nullptr;
    }

    cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
    if (cmsg == nullptr) {
        LOGE("recv_fd: cmsg == nullptr\n");
        return nullptr;
    }
    if (cmsg->cmsg_len != CMSG_LEN(sizeof(int) * cnt)) {
        LOGE("recv_fd: cmsg_len(%zu) != %zu\n", cmsg->cmsg_len, CMSG_LEN(sizeof(int) * cnt));
        return nullptr;
    }
    if (cmsg->cmsg_level != SOL_SOCKET) {
        LOGE("recv_fd: cmsg_level != SOL_SOCKET\n");
        return nullptr;
    }
    if (cmsg->cmsg_type != SCM_RIGHTS) {
        LOGE("recv_fd: cmsg_type != SCM_RIGHTS\n");
        return nullptr;
    }

    return CMSG_DATA(cmsg);
}

vector<int> recv_fds(int sockfd) {
    vector<int> results;

    // Peek fd count to allocate proper buffer
    int cnt;
    recv(sockfd, &cnt, sizeof(cnt), MSG_PEEK);
    if (cnt == 0) {
        // Consume data
        recv(sockfd, &cnt, sizeof(cnt), MSG_WAITALL);
        return results;
    }

    vector<char> cmsgbuf;
    cmsgbuf.resize(CMSG_SPACE(sizeof(int) * cnt));

    void *data = recv_fds(sockfd, cmsgbuf.data(), cmsgbuf.size(), cnt);
    if (data == nullptr)
        return results;

    results.resize(cnt);
    memcpy(results.data(), data, sizeof(int) * cnt);

    return results;
}

int recv_fd(int sockfd) {
    // Peek fd count
    int cnt;
    recv(sockfd, &cnt, sizeof(cnt), MSG_PEEK);
    if (cnt == 0) {
        // Consume data
        recv(sockfd, &cnt, sizeof(cnt), MSG_WAITALL);
        return -1;
    }

    char cmsgbuf[CMSG_SPACE(sizeof(int))];

    void *data = recv_fds(sockfd, cmsgbuf, sizeof(cmsgbuf), 1);
    if (data == nullptr)
        return -1;

    int result;
    memcpy(&result, data, sizeof(int));
    return result;
}

int read_int(int fd) {
    int val;
    if (xxread(fd, &val, sizeof(val)) != sizeof(val))
        return -1;
    return val;
}

int read_int_be(int fd) {
    return ntohl(read_int(fd));
}

void write_int(int fd, int val) {
    if (fd < 0) return;
    xwrite(fd, &val, sizeof(val));
}

void write_int_be(int fd, int val) {
    write_int(fd, htonl(val));
}

bool read_string(int fd, std::string &str) {
    int len = read_int(fd);
    str.clear();
    if (len < 0)
        return false;
    str.resize(len);
    return xxread(fd, str.data(), len) == len;
}

string read_string(int fd) {
    string str;
    read_string(fd, str);
    return str;
}

void write_string(int fd, string_view str) {
    if (fd < 0) return;
    write_int(fd, str.size());
    xwrite(fd, str.data(), str.size());
}