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我编写了一个小型动态库，它插入对 getaddrinfo 和连接的调用。我在 Firefox 和 Safari 上使用 DYLD_INSERT_LIBRARIES 插入这个库，以劫持对 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，它忽略了重定向。

我想知道是否有人了解为什么 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"
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1 回答 1

0

通过跟进，我发现 Safari 在hints 参数中设置了 AI_NUMERICHOST 标志，因此将该标志作为不受支持的分辨率标志的测试导致我的重定向代码从未被调用。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);
}

希望对其他人有所帮助。

于 2012-06-12T14:22:21.290 回答