prosody
53e0ae770917
util/jwt.lua

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util/jwt.lua @ 12180:53e0ae770917

util.xml: Do not allow doctypes, comments or processing instructions Yes. This is as bad as it sounds. CVE pending. In Prosody itself, this only affects mod_websocket, which uses util.xml to parse the <open/> frame, thus allowing unauthenticated remote DoS using Billion Laughs. However, third-party modules using util.xml may also be affected by this. This commit installs handlers which disallow the use of doctype declarations and processing instructions without any escape hatch. It, by default, also introduces such a handler for comments, however, there is a way to enable comments nontheless. This is because util.xml is used to parse human-facing data, where comments are generally a desirable feature, and also because comments are generally harmless.
author Jonas Schäfer <jonas@wielicki.name>
date Mon, 10 Jan 2022 18:23:54 +0100
parent 11561:d2f33b8fdc96
child 12696:27a72982e331
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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c4ded3be7cc0 util.jwt: Basic JSON Web Token library supporting HS256 tokens
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1 local s_gsub = string.gsub;
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2 local json = require "util.json";
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3 local hashes = require "util.hashes";
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4 local base64_encode = require "util.encodings".base64.encode;
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5 local base64_decode = require "util.encodings".base64.decode;
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d2f33b8fdc96 util.jwt: Use constant-time comparison with expected signature
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6 local secure_equals = require "util.hashes".equals;
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7
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8 local b64url_rep = { ["+"] = "-", ["/"] = "_", ["="] = "", ["-"] = "+", ["_"] = "/" };
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9 local function b64url(data)
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10 return (s_gsub(base64_encode(data), "[+/=]", b64url_rep));
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11 end
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12 local function unb64url(data)
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13 return base64_decode(s_gsub(data, "[-_]", b64url_rep).."==");
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14 end
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15
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16 local static_header = b64url('{"alg":"HS256","typ":"JWT"}') .. '.';
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17
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18 local function sign(key, payload)
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19 local encoded_payload = json.encode(payload);
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20 local signed = static_header .. b64url(encoded_payload);
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21 local signature = hashes.hmac_sha256(key, signed);
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22 return signed .. "." .. b64url(signature);
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23 end
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24
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25 local jwt_pattern = "^(([A-Za-z0-9-_]+)%.([A-Za-z0-9-_]+))%.([A-Za-z0-9-_]+)$"
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26 local function verify(key, blob)
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27 local signed, bheader, bpayload, signature = string.match(blob, jwt_pattern);
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28 if not signed then
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29 return nil, "invalid-encoding";
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30 end
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31 local header = json.decode(unb64url(bheader));
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32 if not header or type(header) ~= "table" then
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33 return nil, "invalid-header";
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34 elseif header.alg ~= "HS256" then
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35 return nil, "unsupported-algorithm";
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36 end
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37 if not secure_equals(b64url(hashes.hmac_sha256(key, signed)), signature) then
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38 return false, "signature-mismatch";
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39 end
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40 local payload, err = json.decode(unb64url(bpayload));
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41 if err ~= nil then
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42 return nil, "json-decode-error";
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43 end
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44 return true, payload;
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45 end
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46
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47 return {
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48 sign = sign;
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49 verify = verify;
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50 };
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51