Nginx下编写c模块来阻止HTTP代理服务器的访问

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Nginx下编写c模块来阻止HTTP代理服务器的访问

在这篇使用Apache来阻止http代理服务器的访问文章里，我们使用了Apache的mod_rewrite来判断访客的http head头，如果看到了有代理的迹象，就阻止它，能否进一步提高效率呢？于是想到了用nginx来提高效率，为了最快，编写了C模块，这样效率会达至最高。

下面简单介绍一下nginx模块的编写：
nginx模块分两种，handle和filter。handle是得到输入后，直接控制输出最终结果；而filter是得到输入后，进行变换，传递给下一个filter依次处理，两种模块稍有区别。

我们这里是对Header头进行处理，如果不是代理就放行，如果是代理就阻止，所以应该是用filter。

这篇教程很不错http://www.evanmiller.org/nginx-modules-guide.html，建议大家参看。

关键是要先吃透nginx的数据类型，多使用自带的函数，发现LXR真是一个不错的源代码浏览工具撒：

关键函数部分：

遍历整个Header:
        part = &r->headers_in.headers.part;
        header = part->elts;

        for (i = 0; /* void */ ; i++) {

            if (i >= part->nelts) {
                if (part->next == NULL) {
                    break;
                }

                part = part->next;
                header = part->elts;
                i = 0;
            }
        }
比较Header头：
if (ngx_strncasecmp(header[i].key.data, (u_char *) "via", 3) == 0
||ngx_strncasecmp(header[i].key.data, (u_char *) "forwarded", 7) == 0
||ngx_strncasecmp(header[i].key.data, (u_char *) "useragent_via", 13) == 0
||ngx_strncasecmp(header[i].key.data, (u_char *) "useragent-via", 13) == 0
......
||ngx_strncasecmp(header[i].key.data, (u_char *) "mt_proxy_id", 11) == 0
||ngx_strncasecmp(header[i].key.data, (u_char *)"mt-proxy-id",11)== 0)

涉及的nginx相关数据结构：
ngx_str_t
ngx_table_elt_t
ngx_list_part_t
ngx_http_request_t

源代码下载：ngx_http_proxyblock_module.c.txt

/*
 * Copyright (C) ZhangRanrui , zhangranrui@gmail.com 
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


static ngx_int_t ngx_http_proxyblock_init(ngx_conf_t *cf);

static ngx_http_module_t  ngx_http_proxyblock_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_proxyblock_init,     /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    NULL,                                  /* create location configuration */
    NULL                                   /* merge location configuration */
};

ngx_module_t  ngx_http_proxyblock_module = {
    NGX_MODULE_V1,
    &ngx_http_proxyblock_module_ctx, /* module context */
    NULL,   /* module directives */
    NGX_HTTP_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};

static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;

static ngx_int_t
ngx_http_proxyblock(ngx_http_request_t *r)
{
    ngx_int_t     rc;
    char remote_ip[16] = {0};

    if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) {
        return NGX_HTTP_NOT_ALLOWED;
    }

    rc = ngx_http_discard_request_body(r);

    if (rc != NGX_OK) {
        return rc;
    }

    ngx_list_part_t             *part;
    ngx_table_elt_t             *header;
    ngx_uint_t                   i, hash;

        part = &r->headers_in.headers.part;
        header = part->elts;

        for (i = 0; /* void */ ; i++) {

            if (i >= part->nelts) {
                if (part->next == NULL) {
                    break;
                }

                part = part->next;
                header = part->elts;
                i = 0;
            }

            if (ngx_strncasecmp(header[i].key.data, (u_char *) "via", 3) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "forwarded", 7) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "useragent_via", 13) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "useragent-via", 13) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "x_forwarded_for", 15) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "x-forwarded-for", 15) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "xproxy_connection", 17) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "xproxy-connection", 17) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "proxy_connection", 16) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "proxy-connection", 16) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "http_pc_remote_addr", 19) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "http_pc_remote_addr", 19) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "mt_proxy_id", 11) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "mt-proxy-id", 11) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "http_client_ip", 14) == 0
                || ngx_strncasecmp(header[i].key.data, (u_char *) "http-client-ip", 14) == 0 )
            {
                snprintf(remote_ip, r->connection->addr_text.len, "%s", r->connection->addr_text.data);
                fprintf(stderr, "ip %s was blocked by header (%s:%s)\n", remote_ip, header[i].key.data, header[i].value.data);
                goto found;
            }
        }

    return ngx_http_next_header_filter(r);
found:
    return NGX_HTTP_INTERNAL_SERVER_ERROR;
}

static ngx_int_t
ngx_http_proxyblock_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_proxyblock;

    return NGX_OK;
}

编译过程：

Nginx下编写c模块来阻止HTTP代理服务器的访问

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原文地址：http://my.oschina.net/mickelfeng/blog/516000