接口定位

抓包+输入翻译关键词

全局搜索关键词,定位到接口https://fanyi.baidu.com/v2transapi

全局搜索sign

多次尝试定位变化参数sign

断点调试b函数

估值整个function，并测试函数运行结果

缺少r参数，可以通过多次输入调试，定位r参数的变化。

经过多次的测试，获取到r参数为字符串"320305.131321201"

再次运行加密函数b，发现n函数没有定义。通过调试，定位到n函数的位置，n函数如下：

function n(t, e) {
            for (var n = 0; n < e.length - 2; n += 3) {
                var r = e.charAt(n + 2);
                r = "a" <= r ? r.charCodeAt(0) - 87 : Number(r),
                r = "+" === e.charAt(n + 1) ? t >>> r : t << r,
                t = "+" === e.charAt(n) ? t + r & 4294967295 : t ^ r
            }
            return t
        };

添加n函数之后，b函数正确运行。对比浏览器生成的sign与函数生成的sign，发现整个sign的加密函数生成结果与浏览器生成结果一致。以下为加密函数的源码：

function b(t) {
            var r = "320305.131321201";
            var o, i = t.match(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g);
            if (null === i) {
                var a = t.length;
                a > 30 && (t = "".concat(t.substr(0, 10)).concat(t.substr(Math.floor(a / 2) - 5, 10)).concat(t.substr(-10, 10)))
            } else {
                for (var s = t.split(/[\uD800-\uDBFF][\uDC00-\uDFFF]/), c = 0, u = s.length, l = []; c < u; c++)
                    "" !== s[c] && l.push.apply(l, function(t) {
                        if (Array.isArray(t))
                            return e(t)
                    }(o = s[c].split("")) || function(t) {
                        if ("undefined" != typeof Symbol && null != t[Symbol.iterator] || null != t["@@iterator"])
                            return Array.from(t)
                    }(o) || function(t, n) {
                        if (t) {
                            if ("string" == typeof t)
                                return e(t, n);
                            var r = Object.prototype.toString.call(t).slice(8, -1);
                            return "Object" === r && t.constructor && (r = t.constructor.name),
                            "Map" === r || "Set" === r ? Array.from(t) : "Arguments" === r || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(r) ? e(t, n) : void 0
                        }
                    }(o) || function() {
                        throw new TypeError("Invalid attempt to spread non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method.")
                    }()),
                    c !== u - 1 && l.push(i[c]);
                var p = l.length;
                p > 30 && (t = l.slice(0, 10).join("") + l.slice(Math.floor(p / 2) - 5, Math.floor(p / 2) + 5).join("") + l.slice(-10).join(""))
            }
            for (var d = "".concat(String.fromCharCode(103)).concat(String.fromCharCode(116)).concat(String.fromCharCode(107)), h = (null !== r ? r : ("") || "").split("."), f = Number(h[0]) || 0, m = Number(h[1]) || 0, g = [], y = 0, v = 0; v < t.length; v++) {
                var _ = t.charCodeAt(v);
                _ < 128 ? g[y++] = _ : (_ < 2048 ? g[y++] = _ >> 6 | 192 : (55296 == (64512 & _) && v + 1 < t.length && 56320 == (64512 & t.charCodeAt(v + 1)) ? (_ = 65536 + ((1023 & _) << 10) + (1023 & t.charCodeAt(++v)),
                g[y++] = _ >> 18 | 240,
                g[y++] = _ >> 12 & 63 | 128) : g[y++] = _ >> 12 | 224,
                g[y++] = _ >> 6 & 63 | 128),
                g[y++] = 63 & _ | 128)
            }
            for (var b = f, w = "".concat(String.fromCharCode(43)).concat(String.fromCharCode(45)).concat(String.fromCharCode(97)) + "".concat(String.fromCharCode(94)).concat(String.fromCharCode(43)).concat(String.fromCharCode(54)), k = "".concat(String.fromCharCode(43)).concat(String.fromCharCode(45)).concat(String.fromCharCode(51)) + "".concat(String.fromCharCode(94)).concat(String.fromCharCode(43)).concat(String.fromCharCode(98)) + "".concat(String.fromCharCode(43)).concat(String.fromCharCode(45)).concat(String.fromCharCode(102)), x = 0; x < g.length; x++)
                b = n(b += g[x], w);
            return b = n(b, k),
            (b ^= m) < 0 && (b = 2147483648 + (2147483647 & b)),
            "".concat((b %= 1e6).toString(), ".").concat(b ^ f)
        };

function n(t, e) {
            for (var n = 0; n < e.length - 2; n += 3) {
                var r = e.charAt(n + 2);
                r = "a" <= r ? r.charCodeAt(0) - 87 : Number(r),
                r = "+" === e.charAt(n + 1) ? t >>> r : t << r,
                t = "+" === e.charAt(n) ? t + r & 4294967295 : t ^ r
            }
            return t
        };

var e = "水";
console.log(b(e));