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POStuck implementing HMAC in javascript
 

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    <p>I've been trying to code HMAC algorithm in Javascript but have got to a point where I can not figure out what is going wrong. I'm at the point where you create the inner hash, but the returned value does not match that specified in the FIPS 198 document example A1 when using SHA1 (step 6).</p> <pre><code>/* function hmac (key, message) if (length(key) &gt; blocksize) then key = hash(key) // keys longer than blocksize are shortened end if if (length(key) &lt; blocksize) then key = key ∥ [0x00 * (blocksize - length(key))] // keys shorter than blocksize are zero-padded ('∥' is concatenation) end if o_key_pad = [0x5c * blocksize] ⊕ key // Where blocksize is that of the underlying hash function i_key_pad = [0x36 * blocksize] ⊕ key // Where ⊕ is exclusive or (XOR) return hash(o_key_pad ∥ hash(i_key_pad ∥ message)) // Where '∥' is concatenation end function */ /* STEPS Step 1 Table 1: The HMAC Algorithm STEP-BY-STEP DESCRIPTION If the length of K = B: set K0 = K. Go to step 4. Step 2 If the length of K &gt; B: hash K to obtain an L byte string, then append (B-L) zeros to create a B-byte string K0 (i.e., K0 = H(K) || 00...00). Go to step 4. Step 3 If the length of K &lt; B: append zeros to the end of K to create a B-byte string K0 (e.g., if K is 20 bytes in length and B = 64, then K will be appended with 44 zero bytes 0x00). Step 4 Exclusive-Or K0 with ipad to produce a B-byte string: K0 ̄ ipad. Step 5 Append the stream of data 'text' to the string resulting from step 4: (K0 ̄ ipad) || text. Step 6 Apply H to the stream generated in step 5: H((K0 ̄ ipad) || text). Step 7 Exclusive-Or K0 with opad: K0 ̄ opad. Step 8 Append the result from step 6 to step 7: (K0 ̄ opad) || H((K0 ̄ ipad) || text). Step 9 Apply H to the result from step 8: H((K0 ̄ opad )|| H((K0 ̄ ipad) || text)). Step 10 Select the leftmost t bytes of the result of step 9 as the MAC. */ /* FIPS PUB 198, The Keyed-Hash Message Authentication Code http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf A.1 SHA-1 with 64-Byte Key */ //Check sha1 hashers if ($u.sha1("test") !== CryptoJS.SHA1("test").toString()) { throw new Error("hasher output mismatch"); } var key = "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"; var k0 = "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"; var k0ipad = "36373435323330313e3f3c3d3a3b383926272425222320212e2f2c2d2a2b282916171415121310111e1f1c1d1a1b181906070405020300010e0f0c0d0a0b0809"; var k0opad = "5c5d5e5f58595a5b54555657505152534c4d4e4f48494a4b44454647404142437c7d7e7f78797a7b74757677707172736c6d6e6f68696a6b6465666760616263"; var ipt = "36373435323330313e3f3c3d3a3b383926272425222320212e2f2c2d2a2b282916171415121310111e1f1c1d1a1b181906070405020300010e0f0c0d0a0b080953616d706c65202331"; var h1 = "bcc2c68cabbbf1c3f5b05d8e7e73a4d27b7e1b20"; var message = "Sample #1"; var result = ""; function hmac(key, message) { key = key.replace(/\s*/g, ""); var swap = false, // for swap endianess length = key.length, blockSize = 64 * 2, // for sha 1 = 64, as hex * 2 ml = message.length, i = 0, o_key_pad = "", i_key_pad = "", ikeypmessage = "", hipt, temp1, temp2; // 1. If the length of K = B: set K0 = K. Go to step 4. if (length !== blockSize) { // 2. If the length of K &gt; B: hash K to obtain an L byte string, then append (B-L) // zeros to create a B-byte string K0 (i.e., K0 = H(K) || 00...00). Go to step 4. // Actually in code, goto step3 ri append zeros if (length &gt; blockSize) { key = $u.sha1(key); } // 3. If the length of K &lt; B: append zeros to the end of K to create a B-byte string K0 // (e.g., if K is 20 bytes in length and B = 64, then K will be appended with 44 // zero bytes 0x00). while (key.length &lt; blockSize) { key += "0"; i += 1; } } // check against the FIP198 example if (key !== k0) { console.log(key, k0); throw new Error("key and k0 mismatch"); } // 4. Exclusive-Or K0 with ipad to produce a B-byte string: K0 ̄ ipad. // 7. Exclusive-Or K0 with opad: K0 ̄ opad. i = 0; while (i &lt; blockSize) { temp1 = parseInt(key.slice(i, i + 2), 16); temp2 = (temp1 ^ 0x36).toString(16); i_key_pad += temp2.length &gt; 1 ? temp2 : "0" + temp2; temp2 = (temp1 ^ 0x5c).toString(16); o_key_pad += temp2.length &gt; 1 ? temp2 : "0" + temp2; i += 2; } if (i_key_pad !== k0ipad) { console.log(i_key_pad, k0ipad); throw new Error("i_key_pad and k0ipad mismatch"); } if (o_key_pad !== k0opad) { console.log(o_key_pad, k0opad); throw new Error("o_key_pad and k0opad mismatch"); } // 5. Append the stream of data 'text' to the string resulting from step 4: // (K0 ̄ ipad) || text. i = 0; temp1 = ""; while (i &lt; ml) { temp1 += message.charCodeAt(i).toString(16); i += 1; } ikeypmessage = i_key_pad + temp1; if (ikeypmessage !== ipt) { console.log(i_key_pad + temp1, ipt); throw new Error("i_key_pad + temp1 and ipt mismatch"); } // convert hex string to ucs2 string ml = ikeypmessage.length; temp1 = []; i = 0; while (i &lt; ml) { // for changinging endianess if (swap) { temp1[i &gt;&gt; 1] = ikeypmessage.charAt(i + 1) + ikeypmessage.charAt(i); } else { temp1[i &gt;&gt; 1] = ikeypmessage.slice(i, i + 2); } i += 2; } // for changinging endianess if (swap) { temp1.reverse(); } // convert byte to ucs2 string ml = temp1.length; temp2 = ""; i = 0; while (i &lt; ml) { temp2 += String.fromCharCode(parseInt(temp1[i], 16)); i += 1; } ikeypmessage = temp2; // This is the point where it goes bottom up // 6. Apply H to the stream generated in step 5: H((K0 ̄ ipad) || text). console.log(ikeypmessage); hipt = $u.sha1(ikeypmessage); if (hipt !== h1) { console.log(hipt, h1); throw new Error("hipt and h1 mismatch"); } } console.log(hmac(key, message)); </code></pre> <p>This code is available of <a href="http://jsfiddle.net/Xotic750/nfLd3/" rel="nofollow">jsfiddle</a> and if there is anyone that can give me a pointer as to where I am going wrong it would be much appreciated.</p> <p>I have tried converting from a hex string to a ucs2 string and changing endianess, all give me different results but none match the example.</p>
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    1. COOne basic thing to consider is that JavaScript strings use UTF-16 characters; the elements of a string aren't bytes, in other words.
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    2. COAh yes, I had forgotten about the possible multi byte string issue after the XORing. I will have to check that.
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    3. COI don't think this is the issue as all the characters in use should be single byte UCS2, all are below char code 256, correct me if I am wrong.
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