260 lines
8.1 KiB
Lua
260 lines
8.1 KiB
Lua
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local cjson_safe = require 'cjson.safe'
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local basexx = require 'basexx'
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local digest = require 'openssl.digest'
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local hmac = require 'openssl.hmac'
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local pkey = require 'openssl.pkey'
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-- Generates an RSA signature of the data.
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-- @param data The data to be signed.
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-- @param key The private signing key in PEM format.
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-- @param algo The digest algorithm to user when generating the signature: sha256, sha384, or sha512.
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-- @return The signature or nil and an error message.
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local function signRS (data, key, algo)
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local privkey = pkey.new(key)
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if privkey == nil then
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return nil, 'Not a private PEM key'
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else
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local datadigest = digest.new(algo):update(data)
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return privkey:sign(datadigest)
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end
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end
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-- Verifies an RSA signature on the data.
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-- @param data The signed data.
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-- @param signature The signature to be verified.
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-- @param key The public key of the signer.
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-- @param algo The digest algorithm to user when generating the signature: sha256, sha384, or sha512.
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-- @return True if the signature is valid, false otherwise. Also returns false if the key is invalid.
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local function verifyRS (data, signature, key, algo)
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local pubkey = pkey.new(key)
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if pubkey == nil then
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return false
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end
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local datadigest = digest.new(algo):update(data)
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return pubkey:verify(signature, datadigest)
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end
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local alg_sign = {
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['HS256'] = function(data, key) return hmac.new(key, 'sha256'):final(data) end,
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['HS384'] = function(data, key) return hmac.new(key, 'sha384'):final(data) end,
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['HS512'] = function(data, key) return hmac.new(key, 'sha512'):final(data) end,
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['RS256'] = function(data, key) return signRS(data, key, 'sha256') end,
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['RS384'] = function(data, key) return signRS(data, key, 'sha384') end,
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['RS512'] = function(data, key) return signRS(data, key, 'sha512') end
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}
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local alg_verify = {
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['HS256'] = function(data, signature, key) return signature == alg_sign['HS256'](data, key) end,
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['HS384'] = function(data, signature, key) return signature == alg_sign['HS384'](data, key) end,
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['HS512'] = function(data, signature, key) return signature == alg_sign['HS512'](data, key) end,
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['RS256'] = function(data, signature, key) return verifyRS(data, signature, key, 'sha256') end,
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['RS384'] = function(data, signature, key) return verifyRS(data, signature, key, 'sha384') end,
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['RS512'] = function(data, signature, key) return verifyRS(data, signature, key, 'sha512') end
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}
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-- Splits a token into segments, separated by '.'.
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-- @param token The full token to be split.
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-- @return A table of segments.
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local function split_token(token)
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local segments={}
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for str in string.gmatch(token, "([^\\.]+)") do
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table.insert(segments, str)
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end
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return segments
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end
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-- Parses a JWT token into it's header, body, and signature.
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-- @param token The JWT token to be parsed.
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-- @return A JSON header and body represented as a table, and a signature.
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local function parse_token(token)
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local segments=split_token(token)
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if #segments ~= 3 then
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return nil, nil, nil, "Invalid token"
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end
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local header, err = cjson_safe.decode(basexx.from_url64(segments[1]))
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if err then
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return nil, nil, nil, "Invalid header"
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end
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local body, err = cjson_safe.decode(basexx.from_url64(segments[2]))
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if err then
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return nil, nil, nil, "Invalid body"
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end
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local sig, err = basexx.from_url64(segments[3])
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if err then
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return nil, nil, nil, "Invalid signature"
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end
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return header, body, sig
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end
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-- Removes the signature from a JWT token.
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-- @param token A JWT token.
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-- @return The token without its signature.
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local function strip_signature(token)
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local segments=split_token(token)
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if #segments ~= 3 then
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return nil, nil, nil, "Invalid token"
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end
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table.remove(segments)
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return table.concat(segments, ".")
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end
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-- Verifies that a claim is in a list of allowed claims. Allowed claims can be exact values, or the
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-- catch all wildcard '*'.
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-- @param claim The claim to be verified.
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-- @param acceptedClaims A table of accepted claims.
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-- @return True if the claim was allowed, false otherwise.
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local function verify_claim(claim, acceptedClaims)
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for i, accepted in ipairs(acceptedClaims) do
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if accepted == '*' then
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return true;
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end
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if claim == accepted then
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return true;
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end
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end
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return false;
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end
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local M = {}
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-- Encodes the data into a signed JWT token.
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-- @param data The data the put in the body of the JWT token.
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-- @param key The key to use for signing the JWT token.
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-- @param alg The signature algorithm to use: HS256, HS384, HS512, RS256, RS384, or RS512.
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-- @param header Additional values to put in the JWT header.
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-- @param The resulting JWT token, or nil and an error message.
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function M.encode(data, key, alg, header)
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if type(data) ~= 'table' then return nil, "Argument #1 must be table" end
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if type(key) ~= 'string' then return nil, "Argument #2 must be string" end
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alg = alg or "HS256"
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if not alg_sign[alg] then
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return nil, "Algorithm not supported"
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end
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header = header or {}
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header['typ'] = 'JWT'
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header['alg'] = alg
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local headerEncoded, err = cjson_safe.encode(header)
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if headerEncoded == nil then
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return nil, err
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end
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local dataEncoded, err = cjson_safe.encode(data)
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if dataEncoded == nil then
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return nil, err
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end
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local segments = {
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basexx.to_url64(headerEncoded),
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basexx.to_url64(dataEncoded)
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}
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local signing_input = table.concat(segments, ".")
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local signature, error = alg_sign[alg](signing_input, key)
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if signature == nil then
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return nil, error
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end
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segments[#segments+1] = basexx.to_url64(signature)
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return table.concat(segments, ".")
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end
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-- Verify that the token is valid, and if it is return the decoded JSON payload data.
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-- @param token The token to verify.
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-- @param expectedAlgo The signature algorithm the caller expects the token to be signed with:
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-- HS256, HS384, HS512, RS256, RS384, or RS512.
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-- @param key The verification key used for the signature.
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-- @param acceptedIssuers Optional table of accepted issuers. If not nil, the 'iss' claim will be
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-- checked against this list.
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-- @param acceptedAudiences Optional table of accepted audiences. If not nil, the 'aud' claim will
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-- be checked against this list.
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-- @return A table representing the JSON body of the token, or nil and an error message.
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function M.verify(token, expectedAlgo, key, acceptedIssuers, acceptedAudiences)
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if type(token) ~= 'string' then return nil, "token argument must be string" end
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if type(expectedAlgo) ~= 'string' then return nil, "algorithm argument must be string" end
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if type(key) ~= 'string' then return nil, "key argument must be string" end
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if acceptedIssuers ~= nil and type(acceptedIssuers) ~= 'table' then
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return nil, "acceptedIssuers argument must be table"
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end
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if acceptedAudiences ~= nil and type(acceptedAudiences) ~= 'table' then
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return nil, "acceptedAudiences argument must be table"
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end
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if not alg_verify[expectedAlgo] then
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return nil, "Algorithm not supported"
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end
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local header, body, sig, err = parse_token(token)
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if err ~= nil then
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return nil, err
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end
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-- Validate header
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if not header.typ or header.typ ~= "JWT" then
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return nil, "Invalid typ"
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end
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if not header.alg or header.alg ~= expectedAlgo then
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return nil, "Invalid or incorrect alg"
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end
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-- Validate signature
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if not alg_verify[expectedAlgo](strip_signature(token), sig, key) then
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return nil, 'Invalid signature'
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end
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-- Validate body
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if body.exp and type(body.exp) ~= "number" then
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return nil, "exp must be number"
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end
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if body.nbf and type(body.nbf) ~= "number" then
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return nil, "nbf must be number"
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end
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if body.exp and os.time() >= body.exp then
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return nil, "Not acceptable by exp"
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end
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if body.nbf and os.time() < body.nbf then
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return nil, "Not acceptable by nbf"
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end
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if acceptedIssuers ~= nil then
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local issClaim = body.iss;
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if issClaim == nil then
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return nil, "'iss' claim is missing";
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end
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if not verify_claim(issClaim, acceptedIssuers) then
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return nil, "invalid 'iss' claim";
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end
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end
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if acceptedAudiences ~= nil then
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local audClaim = body.aud;
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if audClaim == nil then
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return nil, "'aud' claim is missing";
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end
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if not verify_claim(audClaim, acceptedAudiences) then
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return nil, "invalid 'aud' claim";
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end
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end
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return body
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end
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return M
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