116 lines
3.8 KiB
JavaScript
116 lines
3.8 KiB
JavaScript
/** @fileOverview CBC mode implementation
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*
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* @author Emily Stark
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* @author Mike Hamburg
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* @author Dan Boneh
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*/
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/** @namespace
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* Dangerous: CBC mode with PKCS#5 padding.
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*
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* @author Emily Stark
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* @author Mike Hamburg
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* @author Dan Boneh
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*/
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if (sjcl.beware === undefined) {
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sjcl.beware = {};
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}
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sjcl.beware["CBC mode is dangerous because it doesn't protect message integrity."
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] = function() {
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sjcl.mode.cbc = {
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/** The name of the mode.
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* @constant
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*/
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name: "cbc",
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/** Encrypt in CBC mode with PKCS#5 padding.
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* @param {Object} prp The block cipher. It must have a block size of 16 bytes.
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* @param {bitArray} plaintext The plaintext data.
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* @param {bitArray} iv The initialization value.
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* @param {bitArray} [adata=[]] The authenticated data. Must be empty.
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* @return The encrypted data, an array of bytes.
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* @throws {sjcl.exception.invalid} if the IV isn't exactly 128 bits, or if any adata is specified.
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*/
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encrypt: function(prp, plaintext, iv, adata) {
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if (adata && adata.length) {
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throw new sjcl.exception.invalid("cbc can't authenticate data");
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}
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if (sjcl.bitArray.bitLength(iv) !== 128) {
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throw new sjcl.exception.invalid("cbc iv must be 128 bits");
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}
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var i,
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w = sjcl.bitArray,
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xor = w._xor4,
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bl = w.bitLength(plaintext),
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bp = 0,
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output = [];
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if (bl&7) {
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throw new sjcl.exception.invalid("pkcs#5 padding only works for multiples of a byte");
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}
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for (i=0; bp+128 <= bl; i+=4, bp+=128) {
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/* Encrypt a non-final block */
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iv = prp.encrypt(xor(iv, plaintext.slice(i,i+4)));
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output.splice(i,0,iv[0],iv[1],iv[2],iv[3]);
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}
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/* Construct the pad. */
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bl = (16 - ((bl >> 3) & 15)) * 0x1010101;
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/* Pad and encrypt. */
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iv = prp.encrypt(xor(iv,w.concat(plaintext,[bl,bl,bl,bl]).slice(i,i+4)));
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output.splice(i,0,iv[0],iv[1],iv[2],iv[3]);
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return output;
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},
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/** Decrypt in CBC mode.
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* @param {Object} prp The block cipher. It must have a block size of 16 bytes.
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* @param {bitArray} ciphertext The ciphertext data.
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* @param {bitArray} iv The initialization value.
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* @param {bitArray} [adata=[]] The authenticated data. It must be empty.
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* @return The decrypted data, an array of bytes.
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* @throws {sjcl.exception.invalid} if the IV isn't exactly 128 bits, or if any adata is specified.
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* @throws {sjcl.exception.corrupt} if if the message is corrupt.
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*/
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decrypt: function(prp, ciphertext, iv, adata) {
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if (adata && adata.length) {
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throw new sjcl.exception.invalid("cbc can't authenticate data");
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}
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if (sjcl.bitArray.bitLength(iv) !== 128) {
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throw new sjcl.exception.invalid("cbc iv must be 128 bits");
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}
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if ((sjcl.bitArray.bitLength(ciphertext) & 127) || !ciphertext.length) {
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throw new sjcl.exception.corrupt("cbc ciphertext must be a positive multiple of the block size");
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}
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var i,
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w = sjcl.bitArray,
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xor = w._xor4,
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bi, bo,
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output = [];
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adata = adata || [];
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for (i=0; i<ciphertext.length; i+=4) {
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bi = ciphertext.slice(i,i+4);
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bo = xor(iv,prp.decrypt(bi));
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output.splice(i,0,bo[0],bo[1],bo[2],bo[3]);
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iv = bi;
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}
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/* check and remove the pad */
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bi = output[i-1] & 255;
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if (bi == 0 || bi > 16) {
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throw new sjcl.exception.corrupt("pkcs#5 padding corrupt");
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}
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bo = bi * 0x1010101;
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if (!w.equal(w.bitSlice([bo,bo,bo,bo], 0, bi*8),
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w.bitSlice(output, output.length*32 - bi*8, output.length*32))) {
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throw new sjcl.exception.corrupt("pkcs#5 padding corrupt");
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}
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return w.bitSlice(output, 0, output.length*32 - bi*8);
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}
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};
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};
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