uhttpd作为一个简单的web服务器，其代码量并不多，而且组织结构比较清楚。和其它网络服务器差不多，其main函数进行一些初始化（首先parse config-file，然后parse argv），然后进入一个循环，不断地监听，每当有一个客户请求到达时，则对它进行处理。

1、uhttpd uci配置参数说明

/etc/init.d/uhttpd脚本会使用procd的方式启动uhttpd进程，该工具后面可以带很多参数，如下：

root@zihome:~# uhttpd -h
uhttpd: option requires an argument -- h
Usage: uhttpd -p [addr:]port -h docroot
        -f              Do not fork to background
        -c file         Configuration file, default is '/etc/httpd.conf'
        -p [addr:]port  Bind to specified address and port, multiple allowed
        -s [addr:]port  Like -p but provide HTTPS on this port
        -C file         ASN.1 server certificate file
        -K file         ASN.1 server private key file
        -h directory    Specify the document root, default is '.'
        -E string       Use given virtual URL as 404 error handler
        -I string       Use given filename as index for directories, multiple allowed
        -S              Do not follow symbolic links outside of the docroot
        -D              Do not allow directory listings, send 403 instead
        -R              Enable RFC1918 filter
        -n count        Maximum allowed number of concurrent script requests
        -N count        Maximum allowed number of concurrent connections
        -l string       URL prefix for Lua handler, default is '/lua'
        -L file         Lua handler script, omit to disable Lua
        -u string       URL prefix for UBUS via JSON-RPC handler
        -U file         Override ubus socket path
        -a              Do not authenticate JSON-RPC requests against UBUS session api
        -X              Enable CORS HTTP headers on JSON-RPC api
        -x string       URL prefix for CGI handler, default is '/cgi-bin'
        -i .ext=path    Use interpreter at path for files with the given extension
        -t seconds      CGI, Lua and UBUS script timeout in seconds, default is 60
        -T seconds      Network timeout in seconds, default is 30
        -k seconds      HTTP keepalive timeout
        -d string       URL decode given string
        -r string       Specify basic auth realm
        -m string       MD5 crypt given string

openwrt上面还是通过uci来配置uhttpd，配置文件如下：

config uhttpd 'main'
        list listen_http '0.0.0.0:80'
        list listen_http '[::]:80'
        list listen_https '0.0.0.0:443'
        list listen_https '[::]:443'
        option home '/www'
        option rfc1918_filter '1'
        option max_requests '3'
        option max_connections '10'
        option cert '/etc/uhttpd.crt'
        option key '/etc/uhttpd.key'
        option cgi_prefix '/cgi-bin'
        option script_timeout '120'
        option network_timeout '60'
        option http_keepalive '60'
        option tcp_keepalive '5'
        option no_ubusauth '0'
        option ubus_prefix '/ubus'

uHTTPd 配置项含义:

/etc/init.d/uhttpd脚本在启动的时候会去获取/etc/config/uhttpd配置里面的信息然后进行启动，我们现在用到的参数如下：

root@zihome:/# ps | grep uhttp
 1395 root      1556 S    /usr/sbin/uhttpd -f -h /www -r openwrt -x /cgi-bin -t 120 -T 60 -k 60 -A 5 -n 3 -N 10 -R -p 0.0.0.0:80 -p [::]:80
31572 root      1520 S    grep uhttp

https://openwrt.org/docs/guide-user/services/webserver/uhttpd

2、uhttpd的登录认证超时机制

登录做为web登录最基础的功能，其背后是由rpcd提供的session模式实现的。

session模式实现了创建、更新、退出、添加acl权限等功能。

具体使用可以查看rpcd的介绍：

'session' @3602a25d
        "create":{"timeout":"Integer"}
        "list":{"ubus_rpc_session":"String"}
        "grant":{"ubus_rpc_session":"String","scope":"String","objects":"Array"}
        "revoke":{"ubus_rpc_session":"String","scope":"String","objects":"Array"}
        "access":{"ubus_rpc_session":"String","scope":"String","object":"String","function":"String"}
        "set":{"ubus_rpc_session":"String","values":"Table"}
        "get":{"ubus_rpc_session":"String","keys":"Array"}
        "unset":{"ubus_rpc_session":"String","keys":"Array"}
        "destroy":{"ubus_rpc_session":"String"}
        "login":{"username":"String","password":"String","timeout":"Integer"

3、ubus over http功能

在openwrt默认的web应用中，很主要的一共功能点，就是展示和设置信息。因为ubus -v list里面覆盖了大部分我们需要的信息，所以如果可以通过一种简单的rpc方案，通过http直接访问ubus的内容那就方便了。

这就是ubus over http功能，web发送一个http请求，这个请求的结构根据ubus命令封装之后，直接从ubus接口里面获取内容返回给web页面。

因为ubus接口里面包含了太多的信息，我们不想把所有信息都暴露给web，所以有了rpcd里面的acls权限管理。权限管理里面说明了只能执行那些命令。

使用该功能需要在uci里面把配置打开

option ubus_prefix  /ubus

之后可以用postman发送post请求

登录：

{
    "jsonrpc":"2.0",
    "id":1,
    "method":"call",
    "params":[
        "00000000000000000000000000000000",
        "session",
        "login",
        {
            "username":"root",
            "password":"admin"
        }
    ]
}

此时会返回该账号的session，还有权限之类的

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": [
        0,
        {
            "ubus_rpc_session": "e5333f3fe2ed4601be3b0a8da0a6998e",
            "timeout": 300,
            "expires": 300,
            "acls": {
                "access-group": {
                    "luci-access": [
                        "read",
                        "write"
                    ],
                    "luci-app-firewall": [
                        "read",
                        "write"
                    ],
                    ...
                    "uci-access": [
                        "read",
                        "write"
                    ],
                    "unauthenticated": [
                        "read"
                    ]
                },
                "cgi-io": {
                    "backup": [
                        "read"
                    ],
                    "download": [
                        "read"
                    ],
                    "exec": [
                        "read"
                    ],
                    "upload": [
                        "write"
                    ]
                },
                "file": {
                    "/": [
                        "list"
                    ],
                    "/*": [
                        "list"
                    ],
                    "/bin/dmesg -r": [
                        "exec"
                    ],
                   ...
                    "/usr/sbin/logread -e ^": [
                        "exec"
                    ]
                },
                "ubus": {
                    "file": [
                        "list",
                        "read",
                        "stat",
                        "write",
                        "remove",
                        "exec"
                    ],
                    "hostapd.*": [
                        "del_client"
                    ],
                    "iwinfo": [
                        "assoclist",
                        "freqlist",
                        "txpowerlist",
                        "countrylist",
                        "scan"
                    ],
                    "luci": [
                        "getFeatures",
                        "getConntrackList",
                        "getInitList",
                        "getLocaltime",
                        "getProcessList",
                        "getRealtimeStats",
                        "getTimezones",
                        "getLEDs",
                        "getUSBDevices",
                        "getSwconfigFeatures",
                        "getSwconfigPortState",
                        "getBlockDevices",
                        "getMountPoints",
                        "setInitAction",
                        "setLocaltime",
                        "setPassword",
                        "setBlockDetect",
                        "getConntrackHelpers"
                    ],
                    "luci-rpc": [
                        "getBoardJSON",
                        "getDHCPLeases",
                        "getDSLStatus",
                        "getDUIDHints",
                        "getHostHints",
                        "getNetworkDevices",
                        "getWirelessDevices"
                    ],
                    "network": [
                        "get_proto_handlers"
                    ],
                    "network.interface": [
                        "dump"
                    ],
                    "network.rrdns": [
                        "lookup"
                    ],
                    "session": [
                        "access",
                        "login"
                    ],
                    "system": [
                        "board",
                        "info",
                        "validate_firmware_image"
                    ],
                    "uci": [
                        "changes",
                        "get",
                        "add",
                        "apply",
                        "confirm",
                        "delete",
                        "order",
                        "set",
                        "rename"
                    ]
                },
                "uci": {
                    "*": [
                        "read",
                        "write"
                    ],
                    ...
                    "uhttpd": [
                        "read",
                        "write"
                    ]
                }
            },
            "data": {
                "username": "root"
            }
        }
    ]
}

之后我们就可以使用这个session进行发送ubus请求，比如系统信息

{
    "jsonrpc":"2.0",
    "id":1,
    "method":"call",
    "params":[
        "2cd182b0120310db8869b43d4340a307",
        "system",
        "board",
        {
           
        }
    ]
}

返回内容：

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": [
        0,
        {
            "kernel": "4.14.275",
            "hostname": "OpenWrt",
            "system": "Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz",
            "model": "VMware, Inc. VMware Virtual Platform",
            "board_name": "vmware-inc-vmware-virtual-platform",
            "release": {
                "distribution": "OpenWrt",
                "version": "19.07-SNAPSHOT",
                "revision": "r11430-ecbbb37",
                "target": "x86/64",
                "description": "OpenWrt 19.07-SNAPSHOT r11430-ecbbb37"
            }
        }
    ]
}

可以看到返回的内容跟直接输入ubus call一致

root@OpenWrt:~# ubus call system board
{
    "kernel": "4.14.275",
    "hostname": "OpenWrt",
    "system": "Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz",
    "model": "VMware, Inc. VMware Virtual Platform",
    "board_name": "vmware-inc-vmware-virtual-platform",
    "release": {
        "distribution": "OpenWrt",
        "version": "19.07-SNAPSHOT",
        "revision": "r11430-ecbbb37",
        "target": "x86/64",
        "description": "OpenWrt 19.07-SNAPSHOT r11430-ecbbb37"
    }
}

当然如果不属于上面权限的ubus消息是无法发送的，比如

{
    "jsonrpc":"2.0",
    "id":1,
    "method":"call",
    "params":[
        "2cd182b0120310db8869b43d4340a307",
        "network.interface.lan",
        "status",
        {
           
        }
    ]
}

返回没有权限

{
    "jsonrpc": "2.0",
    "id": 1,
    "error": {
        "code": -32002,
        "message": "Access denied"
    }
}

这些权限的配置都位于/usr/share/rpcd/acl.d/目录下面配置，我们可以自己按照规则增删。

上面json请求的结构体描述如下：

{ "jsonrpc": "2.0",
  "id": <unique-id-to-identify-request>, 
  "method": "call",
  "params": [
             <ubus_rpc_session>, <ubus_object>, <ubus_method>, 
             { <ubus_arguments> }
            ]
}

{ "jsonrpc": "2.0", "id": 1, "method": "call", "params": [ "c1ed6c7b025d0caca723a816fa61b668", "file", "read", { "path": "/etc/board.json" } ] }

how to use ubus over http in openwrt 12.09
：https://www.cnblogs.com/nicephil/p/6768381.html#e4bdbfe794a8e696b9e6b395_2

openwrt-rpcd服务ACL配置错误风险分析：https://www.cnblogs.com/hac425/p/9416854.html

https://openwrt.org/docs/techref/ubus#access_to_ubus_over_http

4、cgi框架

要运行cgi程序，首先意味着需fork出一个子进程，并通过execl函数替换进程空间为cgi程序；其次，数据传递，子进程替换了进程空间后，怎么获得原信息，有怎么把回馈数据传输给父进程（即uhttpd），父进程又怎么接收这些数据。

https://www.cnblogs.com/zmkeil/archive/2013/05/14/3078766.html