Question

我写了一个小动态库，插入了对getaddrinfo和connect的调用。我在Firefox和Safari上使用DYLD_INSERT_LIBRARIES插入此库来劫持www.apple.com的请求并将它们发送到www.microsoft.com。该代码适用于Firefox，但是当Safari调用我的插入函数时，它会忽略重定向。

我想知道是否有人深入了解为什么Safari会忽略重定向，以及是否有办法（可能通过addrinfo标志）让Safari像Firefox一样运行。我的代码清单如下。

// -*- mode: c++ -*-

#include <sys/socket.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <dlfcn.h>
#include <dns_sd.h>
#include <cstdio>
#include <cstdlib>
#include <cstdarg>
#include <cstring>
#include <string>

typedef int (*connect_type) (int, struct sockaddr const*, socklen_t);
typedef int (*getaddrinfo_type)(
        const char*, const char*, struct addrinfo const*, addrinfo**);

connect_type     real_connect     = 0;
getaddrinfo_type real_getaddrinfo = 0;

int
do_getaddrinfo_impl(const char* nodename, const char* servname,
                    struct addrinfo const* hints, struct addrinfo** ppai) 
{
    int result = real_getaddrinfo (nodename, servname, hints, ppai);
    if(result != 0) {
        fprintf(stderr, "! real_getaddrinfo error on %s: %s\n", nodename, gai_strerror(result));
    }

    return result;
}

int
do_getaddrinfo(const char* nodename, const char* servname,
               struct addrinfo const* hints, struct addrinfo** ppai) 
{
    if (0 == nodename) {
        return do_getaddrinfo_impl(nodename, servname, hints, ppai);
    }

    if (hints->ai_family == AF_INET6) {
        printf ("# do_getaddrinfo : IPv6 resolution\n");
        return do_getaddrinfo_impl(nodename, servname, hints, ppai);
    }

    if (   hints->ai_flags & AI_PASSIVE 
        || hints->ai_flags & AI_CANONNAME 
        || hints->ai_flags & AI_NUMERICHOST 
        || hints->ai_flags & AI_NUMERICSERV) {
        printf ("# do_getaddrinfo : unsupported resolution flags\n");
        return do_getaddrinfo_impl (nodename, servname, hints, ppai);
    }

    if ((hints->ai_flags & AI_V4MAPPED) && !(hints->ai_flags & AI_ALL)) {
        printf ("# do_getaddrinfo : unsupported IPv6-mapping\n");
        return do_getaddrinfo_impl (nodename, servname, hints, ppai);
    }

    // redirect requests for www.apple.com to microsoft at 65.55.57.80 (0x41373950)
    if(0 == strcmp(nodename, "www.apple.com")) {
        addrinfo* pai = (addrinfo*)calloc (1, sizeof (addrinfo));

        pai->ai_flags    = hints->ai_flags;
        pai->ai_family   = AF_INET;
        pai->ai_socktype = hints->ai_socktype;
        pai->ai_protocol = IPPROTO_TCP;
        pai->ai_addrlen  = sizeof (sockaddr_in);

        sockaddr* psa = reinterpret_cast< sockaddr* > (
            calloc (1, sizeof (sockaddr)));

        sockaddr_in& sain = reinterpret_cast< sockaddr_in& > (*psa);

#if !defined (POS_NO_SIN_LEN)
        sain.sin_len = sizeof *psa;
#endif // POS_NO_SIN_LEN

        sain.sin_family = AF_INET;
        sain.sin_addr.s_addr = htonl(0x41373950);

        pai->ai_addr = psa;
        pai->ai_canonname = 0;
        pai->ai_next = 0;

        *ppai = pai;

        return 0;
    }
    else {
        return do_getaddrinfo_impl(nodename, servname, hints, ppai);
    }
}

////////////////////////////////////////////////////////////////////////
extern "C" {

int
fake_getaddrinfo(const char* nodename, const char* servname,
                 struct addrinfo const* hints, struct addrinfo** ppai)
{
    if (real_getaddrinfo == 0)
        real_getaddrinfo = &getaddrinfo;

    return do_getaddrinfo (nodename, servname, hints, ppai);
}

int
fake_connect (int s, sockaddr const* ptr, socklen_t len)
{
    if (real_connect == 0)
        real_connect = &connect;

    return do_connect (s, ptr, len);
}

__attribute__((used)) static struct {
    void const *a, *b; 
} arr [] __attribute__ ((section ("__DATA, __interpose"))) = {
    { (void*)fake_connect, (void*)connect },
    { (void*)fake_getaddrinfo, (void*)getaddrinfo }
};

} // extern "C"

Answer 1

通过跟进，我发现Safari在hints参数中设置了AI_NUMERICHOST标志，因此对该标志的测试作为不支持的解析标志导致我的重定向代码永远不会被调用。我删除了AI_NUMERICHOST的测试并添加了以下位来解决问题。

 if (hints->ai_flags & AI_NUMERICHOST) {

    //
    // Safari makes name resolution requests using AI_NUMERICHOST
    //

    in_addr_t addr = inet_addr (nodename);
    if (addr != INADDR_NONE)
        return do_getaddrinfo_impl (nodename, servname, hints, ppai);
}

希望能帮助别人。

Safari和getaddrinfo介入

1 个答案: