# 小程序分享签名

// RSAwithSHA256
const crypto = require("crypto")

// 仅做演示，敏感信息请勿硬编码
function getCtx() {
    let ctx = {
        local_private_key: "-----BEGIN RSA PRIVATE KEY-----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\nGbQuzzFxz/UKDDKf3/ON41k8UP20Gdvmv/+c6qQjKPayME81elus\n-----END RSA PRIVATE KEY-----",
        local_sn: "97845f6ed842ea860df6fdf65941ff56"
    }
    return ctx
}

function getReq() {
    let req = {
        appid: "wxba6223c06417af7b",
        title: "WXA分享测试",
        path: "/pages/index/share?input=%E6%B5%8B%E8%AF%95",
        thumbDataHash: "12c593c5bd2f0972188eb30e32bee7ad4060be582c2c6826caff89372ca84707"
    }
    return req
}

function getShareParams() {
    let param_list = ["appid", "title", "path", "thumbDataHash"]
    return param_list
}

function getSignature(ctx, req) {
    const { local_private_key } = ctx // 开发者本地信息
    const param_list = getShareParams()
    param_list.sort() // 确保参数列表按字典序排序

    let payload = ""
    for (let i = 0; i < param_list.length; i += 1) {
        const param = param_list[i]
        let value = req[param]
        if (typeof value !== "string") value = ""
        let new_value = Buffer.from(value, "utf-8").toString("base64")
        if (i > 0) payload += "&"
        payload += `${param}=${new_value}`
    }

    // console.log(payload)
    const data_buffer = Buffer.from(payload, 'utf-8')
    const key_obj = {
        key: local_private_key,
        padding: crypto.constants.RSA_PKCS1_PSS_PADDING,
        saltLength: crypto.constants.RSA_PSS_SALTLEN_DIGEST // salt长度，需与SHA256结果长度(32)一致
    }

    const sig_buffer = ss_buffer = crypto.sign(
        'RSA-SHA256',
        data_buffer,
        key_obj
    )
    const sig = sig_buffer.toString('base64')
    return sig
}

const ctx = getCtx()
const req = getReq()

let res = getSignature(ctx, req)
console.log(res)