Nginx “邪恶” rewrite

概述

本文主要针对nginx rewrite指令困惑的地方进行讲解，中间会涉及部分原理部分，我尽量用通俗易懂的语言来形容

功能讲解

大致流程

The ngx_http_rewrite_module module directives are processed in the following order:

the directives of this module specified on the server level are executed sequentially;

repeatedly:

a location is searched based on a request URI;
the directives of this module specified inside the found location are executed sequentially;
the loop is repeated if a request URI was rewritten, but not more than 10 times.

涉及phase

NGX_HTTP_SERVER_REWRITE_PHASE,
NGX_HTTP_FIND_CONFIG_PHASE,
NGX_HTTP_REWRITE_PHASE,
NGX_HTTP_POST_REWRITE_PHASE,

环境：

/aaa内容aaa
/bbb内容bbb

Example 1:

server {

listen 80;

location /aaa {

if ($http_user_agent ~ Mozilla) {

rewrite /aaa /bbb;

}

return 403;

}

location /bbb {

return 402；

}

在上述nginx.conf情况下，使用firefox浏览器访问nginx，if匹配成功，执行rewrite重写r->uri（/aaa转换为/bbb），

然后继续执行rewrite模块其他指令，执行到return 403后，该request在nginx中的处理完毕，返回403；

因此浏览器收到应答码为403

Example 2:

server {

listen 80;

location /aaa {

if ($http_user_agent ~ Mozilla) {

rewrite /aaa /bbb;

}

# return 403;

}

location /bbb {

return 402；

}

在上述nginx.conf情况下，使用firefox浏览器访问nginx，if匹配成功，执行rewrite重写r->uri（/aaa转换为/bbb）

rewrite模块执行完毕。因为所有rewrite模块的指令都执行完毕，进入POST_REWRITE_PHASE所在的checker函数ngx_http_core_post_rewrite_phase

中，由于执行了rewrite指令，在函数ngx_http_script_regex_start_code中

if (code->uri) {

r->internal = 1;

r->valid_unparsed_uri = 0;

if (code->break_cycle) {//rewrite ....break 指令分支

r->valid_location = 0;

r->uri_changed = 0;

} else {

r->uri_changed = 1;

}

可以得知r->uri_changed=1，于是在函数ngx_http_core_post_rewrite_phase中执行如下流程

r->uri_changes--;

if (r->uri_changes == 0) {

ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,

"rewrite or internal redirection cycle "

"while processing \"%V\"", &r->uri);

ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);

return NGX_OK;

}

r->phase_handler = ph->next;//ph->next为find_config_index，在ngx_http_init_phase_handlers中可见

cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);

r->loc_conf = cscf->ctx->loc_conf;

由于重新进行server和location匹配，因此在上述例子中，浏览器收到的应答状态吗为402

Example 3:

server {

listen 80;

location /aaa {

if ($http_user_agent ~ Mozilla) {

rewrite /aaa /bbb break;

}

return 403;

}

location /bbb {

return 402；

}

在上述nginx.conf情况下，使用firefox浏览器访问nginx，if匹配成功，执行rewrite重写r->uri（/aaa转换为/bbb），

由于rewrite break标记符存在，从rewrite指令的配置解析函数ngx_http_rewrite和rewrite模块的handler函数ngx_http_rewrite_handler中

如下部分可以得知，将停止执行rewrite模块的其他一切指令；

ngx_http_rewrite {

....

if (cf->args->nelts == 4) {

if (ngx_strcmp(value[3].data, "last") == 0) {

last = 1;

} else if (ngx_strcmp(value[3].data, "break") == 0) {

regex->break_cycle = 1;

last = 1;

} else if (ngx_strcmp(value[3].data, "redirect") == 0) {

regex->status = NGX_HTTP_MOVED_TEMPORARILY;

regex->redirect = 1;

last = 1;

} else if (ngx_strcmp(value[3].data, "permanent") == 0) {

regex->status = NGX_HTTP_MOVED_PERMANENTLY;

regex->redirect = 1;

last = 1;

} else {

ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,

"invalid parameter \"%V\"", &value[3]);

return NGX_CONF_ERROR;

}

.....

if (last) {

code = ngx_http_script_add_code(lcf->codes, sizeof(uintptr_t), &regex);

if (code == NULL) {

return NGX_CONF_ERROR;

}

*code = NULL;

}

ngx_http_rewrite_handler

{

.....

while (*(uintptr_t *) e->ip) {

code = *(ngx_http_script_code_pt *) e->ip;

code(e);

}

if (e->status < NGX_HTTP_BAD_REQUEST) {

//如果rewrite指令后不是break和last标记，而是其他两个重定向标记，则从此处直接结束该request处理流程

return e->status;

}

if (r->err_status == 0) {

return e->status;

}

return r->err_status;

.....

}

进入到POST_REWRITE_PHASE所在的checker函数ngx_http_core_post_rewrite_phase中，由example 2 可知r->uri_changed = 0;

在ngx_http_core_post_rewrite_phase中会执行如下流程，因此会继续执行当前server 和 location 上下文中后续的handler，因此浏览器收到内容为bbb

if (!r->uri_changed) {

r->phase_handler++;

return NGX_AGAIN;

}

Example 4:

server {

listen 80;

location /aaa {

if ($http_user_agent ~ Mozilla) {

rewrite /aaa /bbb last;

}

return 403;

}

location /bbb {

return 402；

}

在上述nginx.conf情况下，使用firefox浏览器访问nginx，if匹配成功，执行rewrite重写r->uri（/aaa转换为/bbb），

由于rewrite last标记符存在，停止执行rewrite模块的其他一切指令，参考example 3。

进入到rewrite模块所在的checker函数ngx_http_core_post_rewrite_phase中，由example 2可知r->uri_changed = 1;

于是重新进行server和location匹配，因此在上述例子中，浏览器收到的内容的状态码为402

转载于:https://www.cnblogs.com/scottieyuyang/p/5722604.html