一般在项目中，我们为了保证接口的安全，都会使用签名验证。而生成签名，则需要对排序后的字符串进行md5加密。
然而在微信小程序中，没有自带的md5加密函数，于是我便在百度上寻找了以下代码：
/*
* A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
* Digest Algorithm, as defined in RFC 1321.
* Version 1.1 Copyright (C) Paul Johnston 1999 - 2002.
* Code also contributed by Greg Holt
* See http://pajhome.org.uk/site/legal.html for details.
*/
/*
* Add integers, wrapping at 2^32. This uses 16-bit operations internally
* to work around bugs in some JS interpreters.
*/
function safe_add(x, y) {
var lsw = (x & 0xFFFF) + (y & 0xFFFF)
var msw = (x >> 16) + (y >> 16) + (lsw >> 16)
return (msw << 16) | (lsw & 0xFFFF)
}
/*
* Bitwise rotate a 32-bit number to the left.
*/
function rol(num, cnt) {
return (num << cnt) | (num >>> (32 - cnt))
}
/*
* These functions implement the four basic operations the algorithm uses.
*/
function cmn(q, a, b, x, s, t) {
return safe_add(rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b)
}
function ff(a, b, c, d, x, s, t) {
return cmn((b & c) | ((~b) & d), a, b, x, s, t)
}
function gg(a, b, c, d, x, s, t) {
return cmn((b & d) | (c & (~d)), a, b, x, s, t)
}
function hh(a, b, c, d, x, s, t) {
return cmn(b ^ c ^ d, a, b, x, s, t)
}
function ii(a, b, c, d, x, s, t) {
return cmn(c ^ (b | (~d)), a, b, x, s, t)
}
/*
* Calculate the MD5 of an array of little-endian words, producing an array
* of little-endian words.
*/
function coreMD5(x) {
var a = 1732584193
var b = -271733879
var c = -1732584194
var d = 271733878
for (var i = 0; i < x.length; i += 16) {
var olda = a
var oldb = b
var oldc = c
var oldd = d
a = ff(a, b, c, d, x[i + 0], 7, -680876936)
d = ff(d, a, b, c, x[i + 1], 12, -389564586)
c = ff(c, d, a, b, x[i + 2], 17, 606105819)
b = ff(b, c, d, a, x[i + 3], 22, -1044525330)
a = ff(a, b, c, d, x[i + 4], 7, -176418897)
d = ff(d, a, b, c, x[i + 5], 12, 1200080426)
c = ff(c, d, a, b, x[i + 6], 17, -1473231341)
b = ff(b, c, d, a, x[i + 7], 22, -45705983)
a = ff(a, b, c, d, x[i + 8], 7, 1770035416)
d = ff(d, a, b, c, x[i + 9], 12, -1958414417)
c = ff(c, d, a, b, x[i + 10], 17, -42063)
b = ff(b, c, d, a, x[i + 11], 22, -1990404162)
a = ff(a, b, c, d, x[i + 12], 7, 1804603682)
d = ff(d, a, b, c, x[i + 13], 12, -40341101)
c = ff(c, d, a, b, x[i + 14], 17, -1502002290)
b = ff(b, c, d, a, x[i + 15], 22, 1236535329)
a = gg(a, b, c, d, x[i + 1], 5, -165796510)
d = gg(d, a, b, c, x[i + 6], 9, -1069501632)
c = gg(c, d, a, b, x[i + 11], 14, 643717713)
b = gg(b, c, d, a, x[i + 0], 20, -373897302)
a = gg(a, b, c, d, x[i + 5], 5, -701558691)
d = gg(d, a, b, c, x[i + 10], 9, 38016083)
c = gg(c, d, a, b, x[i + 15], 14, -660478335)
b = gg(b, c, d, a, x[i + 4], 20, -405537848)
a = gg(a, b, c, d, x[i + 9], 5, 568446438)
d = gg(d, a, b, c, x[i + 14], 9, -1019803690)
c = gg(c, d, a, b, x[i + 3], 14, -187363961)
b = gg(b, c, d, a, x[i + 8], 20, 1163531501)
a = gg(a, b, c, d, x[i + 13], 5, -1444681467)
d = gg(d, a, b, c, x[i + 2], 9, -51403784)
c = gg(c, d, a, b, x[i + 7], 14, 1735328473)
b = gg(b, c, d, a, x[i + 12], 20, -1926607734)
a = hh(a, b, c, d, x[i + 5], 4, -378558)
d = hh(d, a, b, c, x[i + 8], 11, -2022574463)
c = hh(c, d, a, b, x[i + 11], 16, 1839030562)
b = hh(b, c, d, a, x[i + 14], 23, -35309556)
a = hh(a, b, c, d, x[i + 1], 4, -1530992060)
d = hh(d, a, b, c, x[i + 4], 11, 1272893353)
c = hh(c, d, a, b, x[i + 7], 16, -155497632)
b = hh(b, c, d, a, x[i + 10], 23, -1094730640)
a = hh(a, b, c, d, x[i + 13], 4, 681279174)
d = hh(d, a, b, c, x[i + 0], 11, -358537222)
c = hh(c, d, a, b, x[i + 3], 16, -722521979)
b = hh(b, c, d, a, x[i + 6], 23, 76029189)
a = hh(a, b, c, d, x[i + 9], 4, -640364487)
d = hh(d, a, b, c, x[i + 12], 11, -421815835)
c = hh(c, d, a, b, x[i + 15], 16, 530742520)
b = hh(b, c, d, a, x[i + 2], 23, -995338651)
a = ii(a, b, c, d, x[i + 0], 6, -198630844)
d = ii(d, a, b, c, x[i + 7], 10, 1126891415)
c = ii(c, d, a, b, x[i + 14], 15, -1416354905)
b = ii(b, c, d, a, x[i + 5], 21, -57434055)
a = ii(a, b, c, d, x[i + 12], 6, 1700485571)
d = ii(d, a, b, c, x[i + 3], 10, -1894986606)
c = ii(c, d, a, b, x[i + 10], 15, -1051523)
b = ii(b, c, d, a, x[i + 1], 21, -2054922799)
a = ii(a, b, c, d, x[i + 8], 6, 1873313359)
d = ii(d, a, b, c, x[i + 15], 10, -30611744)
c = ii(c, d, a, b, x[i + 6], 15, -1560198380)
b = ii(b, c, d, a, x[i + 13], 21, 1309151649)
a = ii(a, b, c, d, x[i + 4], 6, -145523070)
d = ii(d, a, b, c, x[i + 11], 10, -1120210379)
c = ii(c, d, a, b, x[i + 2], 15, 718787259)
b = ii(b, c, d, a, x[i + 9], 21, -343485551)
a = safe_add(a, olda)
b = safe_add(b, oldb)
c = safe_add(c, oldc)
d = safe_add(d, oldd)
}
return [a, b, c, d]
}
/*
* Convert an array of little-endian words to a hex string.
*/
function binl2hex(binarray) {
var hex_tab = "0123456789abcdef"
var str = ""
for (var i = 0; i < binarray.length * 4; i++) {
str += hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8 + 4)) & 0xF) +
hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8)) & 0xF)
}
return str
}
/*
* Convert an array of little-endian words to a base64 encoded string.
*/
function binl2b64(binarray) {
var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
var str = ""
for (var i = 0; i < binarray.length * 32; i += 6) {
str += tab.charAt(((binarray[i >> 5] << (i % 32)) & 0x3F) |
((binarray[i >> 5 + 1] >> (32 - i % 32)) & 0x3F))
}
return str
}
/*
* Convert an 8-bit character string to a sequence of 16-word blocks, stored
* as an array, and append appropriate padding for MD4/5 calculation.
* If any of the characters are >255, the high byte is silently ignored.
*/
function str2binl(str) {
var nblk = ((str.length + 8) >> 6) + 1 // number of 16-word blocks
var blks = new Array(nblk * 16)
for (var i = 0; i < nblk * 16; i++) blks[i] = 0
for (var i = 0; i < str.length; i++)
blks[i >> 2] |= (str.charCodeAt(i) & 0xFF) << ((i % 4) * 8)
blks[i >> 2] |= 0x80 << ((i % 4) * 8)
blks[nblk * 16 - 2] = str.length * 8
return blks
}
/*
* Convert a wide-character string to a sequence of 16-word blocks, stored as
* an array, and append appropriate padding for MD4/5 calculation.
*/
function strw2binl(str) {
var nblk = ((str.length + 4) >> 5) + 1 // number of 16-word blocks
var blks = new Array(nblk * 16)
for (var i = 0; i < nblk * 16; i++) blks[i] = 0
for (var i = 0; i < str.length; i++)
blks[i >> 1] |= str.charCodeAt(i) << ((i % 2) * 16)
blks[i >> 1] |= 0x80 << ((i % 2) * 16)
blks[nblk * 16 - 2] = str.length * 16
return blks
}
/*
* External interface
*/
function hexMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
function hexMD5w(str) { return binl2hex(coreMD5(strw2binl(str))) }
function b64MD5(str) { return binl2b64(coreMD5(str2binl(str))) }
function b64MD5w(str) { return binl2b64(coreMD5(strw2binl(str))) }
/* Backward compatibility */
function calcMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
module.exports = {
hexMD5: hexMD5
}
在使用的过程中，正常的数字以及字母参数都没有出现问题，当涉及的业务需要传递值为中文字符串的参数时，会出现签名错误的问题，即前端和后端在同参数下生成的签名不一样。
一开始我通过将字符串进行url转译后再传给后台的方法来保证签名一致，不过当要后台根据参数插入数据的时候，发现插入的字符串都是url编码，于是我又开始从源头寻找问题的解决办法。
最开始的时候我以为是微信js的编码默认不是utf-8，实际通过对字符串url转译发现和在线utf-8转url的编码是一样的，而且时候也想到，如果编码格式和后台不一样，那么前端转译成的url编码在后台解码后生成的字符肯定是乱码，这才让我想到是md5加密代码的问题。而后，在百度上又寻找了一份优化后的md5加密代码，使用后发现完美解决了当前问题。
以下代码适用于微信小程序中对中文字符串进行md5加密
var rotateLeft = function (lValue, iShiftBits) {
return (lValue << iShiftBits) | (lValue >>> (32 - iShiftBits));
}
var addUnsigned = function (lX, lY) {
var lX4, lY4, lX8, lY8, lResult;
lX8 = (lX & 0x80000000);
lY8 = (lY & 0x80000000);
lX4 = (lX & 0x40000000);
lY4 = (lY & 0x40000000);
lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);
if (lX4 & lY4) return (lResult ^ 0x80000000 ^ lX8 ^ lY8);
if (lX4 | lY4) {
if (lResult & 0x40000000) return (lResult ^ 0xC0000000 ^ lX8 ^ lY8);
else return (lResult ^ 0x40000000 ^ lX8 ^ lY8);
} else {
return (lResult ^ lX8 ^ lY8);
}
}
var F = function (x, y, z) {
return (x & y) | ((~x) & z);
}
var G = function (x, y, z) {
return (x & z) | (y & (~z));
}
var H = function (x, y, z) {
return (x ^ y ^ z);
}
var I = function (x, y, z) {
return (y ^ (x | (~z)));
}
var FF = function (a, b, c, d, x, s, ac) {
a = addUnsigned(a, addUnsigned(addUnsigned(F(b, c, d), x), ac));
return addUnsigned(rotateLeft(a, s), b);
};
var GG = function (a, b, c, d, x, s, ac) {
a = addUnsigned(a, addUnsigned(addUnsigned(G(b, c, d), x), ac));
return addUnsigned(rotateLeft(a, s), b);
};
var HH = function (a, b, c, d, x, s, ac) {
a = addUnsigned(a, addUnsigned(addUnsigned(H(b, c, d), x), ac));
return addUnsigned(rotateLeft(a, s), b);
};
var II = function (a, b, c, d, x, s, ac) {
a = addUnsigned(a, addUnsigned(addUnsigned(I(b, c, d), x), ac));
return addUnsigned(rotateLeft(a, s), b);
};
var convertToWordArray = function (string) {
var lWordCount;
var lMessageLength = string.length;
var lNumberOfWordsTempOne = lMessageLength + 8;
var lNumberOfWordsTempTwo = (lNumberOfWordsTempOne - (lNumberOfWordsTempOne % 64)) / 64;
var lNumberOfWords = (lNumberOfWordsTempTwo + 1) * 16;
var lWordArray = Array(lNumberOfWords - 1);
var lBytePosition = 0;
var lByteCount = 0;
while (lByteCount < lMessageLength) {
lWordCount = (lByteCount - (lByteCount % 4)) / 4;
lBytePosition = (lByteCount % 4) * 8;
lWordArray[lWordCount] = (lWordArray[lWordCount] | (string.charCodeAt(lByteCount) << lBytePosition));
lByteCount++;
}
lWordCount = (lByteCount - (lByteCount % 4)) / 4;
lBytePosition = (lByteCount % 4) * 8;
lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80 << lBytePosition);
lWordArray[lNumberOfWords - 2] = lMessageLength << 3;
lWordArray[lNumberOfWords - 1] = lMessageLength >>> 29;
return lWordArray;
};
var wordToHex = function (lValue) {
var WordToHexValue = "",
WordToHexValueTemp = "",
lByte, lCount;
for (lCount = 0; lCount <= 3; lCount++) {
lByte = (lValue >>> (lCount * 8)) & 255;
WordToHexValueTemp = "0" + lByte.toString(16);
WordToHexValue = WordToHexValue + WordToHexValueTemp.substr(WordToHexValueTemp.length - 2, 2);
}
return WordToHexValue;
};
var uTF8Encode = function (string) {
string = string.replace(/\x0d\x0a/g, "\x0a");
var output = "";
for (var n = 0; n < string.length; n++) {
var c = string.charCodeAt(n);
if (c < 128) {
output += String.fromCharCode(c);
} else if ((c > 127) && (c < 2048)) {
output += String.fromCharCode((c >> 6) | 192);
output += String.fromCharCode((c & 63) | 128);
} else {
output += String.fromCharCode((c >> 12) | 224);
output += String.fromCharCode(((c >> 6) & 63) | 128);
output += String.fromCharCode((c & 63) | 128);
}
}
return output;
};
function md5(string) {
var x = Array();
var k, AA, BB, CC, DD, a, b, c, d;
var S11 = 7,
S12 = 12,
S13 = 17,
S14 = 22;
var S21 = 5,
S22 = 9,
S23 = 14,
S24 = 20;
var S31 = 4,
S32 = 11,
S33 = 16,
S34 = 23;
var S41 = 6,
S42 = 10,
S43 = 15,
S44 = 21;
string = uTF8Encode(string);
x = convertToWordArray(string);
a = 0x67452301;
b = 0xEFCDAB89;
c = 0x98BADCFE;
d = 0x10325476;
for (k = 0; k < x.length; k += 16) {
AA = a;
BB = b;
CC = c;
DD = d;
a = FF(a, b, c, d, x[k + 0], S11, 0xD76AA478);
d = FF(d, a, b, c, x[k + 1], S12, 0xE8C7B756);
c = FF(c, d, a, b, x[k + 2], S13, 0x242070DB);
b = FF(b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);
a = FF(a, b, c, d, x[k + 4], S11, 0xF57C0FAF);
d = FF(d, a, b, c, x[k + 5], S12, 0x4787C62A);
c = FF(c, d, a, b, x[k + 6], S13, 0xA8304613);
b = FF(b, c, d, a, x[k + 7], S14, 0xFD469501);
a = FF(a, b, c, d, x[k + 8], S11, 0x698098D8);
d = FF(d, a, b, c, x[k + 9], S12, 0x8B44F7AF);
c = FF(c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);
b = FF(b, c, d, a, x[k + 11], S14, 0x895CD7BE);
a = FF(a, b, c, d, x[k + 12], S11, 0x6B901122);
d = FF(d, a, b, c, x[k + 13], S12, 0xFD987193);
c = FF(c, d, a, b, x[k + 14], S13, 0xA679438E);
b = FF(b, c, d, a, x[k + 15], S14, 0x49B40821);
a = GG(a, b, c, d, x[k + 1], S21, 0xF61E2562);
d = GG(d, a, b, c, x[k + 6], S22, 0xC040B340);
c = GG(c, d, a, b, x[k + 11], S23, 0x265E5A51);
b = GG(b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);
a = GG(a, b, c, d, x[k + 5], S21, 0xD62F105D);
d = GG(d, a, b, c, x[k + 10], S22, 0x2441453);
c = GG(c, d, a, b, x[k + 15], S23, 0xD8A1E681);
b = GG(b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);
a = GG(a, b, c, d, x[k + 9], S21, 0x21E1CDE6);
d = GG(d, a, b, c, x[k + 14], S22, 0xC33707D6);
c = GG(c, d, a, b, x[k + 3], S23, 0xF4D50D87);
b = GG(b, c, d, a, x[k + 8], S24, 0x455A14ED);
a = GG(a, b, c, d, x[k + 13], S21, 0xA9E3E905);
d = GG(d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);
c = GG(c, d, a, b, x[k + 7], S23, 0x676F02D9);
b = GG(b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);
a = HH(a, b, c, d, x[k + 5], S31, 0xFFFA3942);
d = HH(d, a, b, c, x[k + 8], S32, 0x8771F681);
c = HH(c, d, a, b, x[k + 11], S33, 0x6D9D6122);
b = HH(b, c, d, a, x[k + 14], S34, 0xFDE5380C);
a = HH(a, b, c, d, x[k + 1], S31, 0xA4BEEA44);
d = HH(d, a, b, c, x[k + 4], S32, 0x4BDECFA9);
c = HH(c, d, a, b, x[k + 7], S33, 0xF6BB4B60);
b = HH(b, c, d, a, x[k + 10], S34, 0xBEBFBC70);
a = HH(a, b, c, d, x[k + 13], S31, 0x289B7EC6);
d = HH(d, a, b, c, x[k + 0], S32, 0xEAA127FA);
c = HH(c, d, a, b, x[k + 3], S33, 0xD4EF3085);
b = HH(b, c, d, a, x[k + 6], S34, 0x4881D05);
a = HH(a, b, c, d, x[k + 9], S31, 0xD9D4D039);
d = HH(d, a, b, c, x[k + 12], S32, 0xE6DB99E5);
c = HH(c, d, a, b, x[k + 15], S33, 0x1FA27CF8);
b = HH(b, c, d, a, x[k + 2], S34, 0xC4AC5665);
a = II(a, b, c, d, x[k + 0], S41, 0xF4292244);
d = II(d, a, b, c, x[k + 7], S42, 0x432AFF97);
c = II(c, d, a, b, x[k + 14], S43, 0xAB9423A7);
b = II(b, c, d, a, x[k + 5], S44, 0xFC93A039);
a = II(a, b, c, d, x[k + 12], S41, 0x655B59C3);
d = II(d, a, b, c, x[k + 3], S42, 0x8F0CCC92);
c = II(c, d, a, b, x[k + 10], S43, 0xFFEFF47D);
b = II(b, c, d, a, x[k + 1], S44, 0x85845DD1);
a = II(a, b, c, d, x[k + 8], S41, 0x6FA87E4F);
d = II(d, a, b, c, x[k + 15], S42, 0xFE2CE6E0);
c = II(c, d, a, b, x[k + 6], S43, 0xA3014314);
b = II(b, c, d, a, x[k + 13], S44, 0x4E0811A1);
a = II(a, b, c, d, x[k + 4], S41, 0xF7537E82);
d = II(d, a, b, c, x[k + 11], S42, 0xBD3AF235);
c = II(c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);
b = II(b, c, d, a, x[k + 9], S44, 0xEB86D391);
a = addUnsigned(a, AA);
b = addUnsigned(b, BB);
c = addUnsigned(c, CC);
d = addUnsigned(d, DD);
}
var tempValue = wordToHex(a) + wordToHex(b) + wordToHex(c) + wordToHex(d);
return tempValue.toLowerCase();
}
module.exports.md5 = md5