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auth-filters: add simple file-based authentication scheme
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld
parent
82856923bf
commit
77b6f83344
352
filters/file-authentication.lua
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352
filters/file-authentication.lua
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@ -0,0 +1,352 @@
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-- This script may be used with the auth-filter.
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--
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-- Requirements:
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-- luacrypto >= 0.3
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-- <http://mkottman.github.io/luacrypto/>
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-- luaposix
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-- <https://github.com/luaposix/luaposix>
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--
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local sysstat = require("posix.sys.stat")
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local unistd = require("posix.unistd")
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local crypto = require("crypto")
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-- This file should contain a series of lines in the form of:
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-- username1:hash1
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-- username2:hash2
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-- username3:hash3
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-- ...
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-- Hashes can be generated using something like `mkpasswd -m sha-512 -R 300000`.
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-- This file should not be world-readable.
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local users_filename = "/etc/cgit-auth/users"
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-- This file should contain a series of lines in the form of:
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-- groupname1:username1,username2,username3,...
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-- ...
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local groups_filename = "/etc/cgit-auth/groups"
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-- This file should contain a series of lines in the form of:
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-- reponame1:groupname1,groupname2,groupname3,...
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-- ...
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local repos_filename = "/etc/cgit-auth/repos"
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-- Set this to a path this script can write to for storing a persistent
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-- cookie secret, which should not be world-readable.
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local secret_filename = "/var/cache/cgit/auth-secret"
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--
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--
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-- Authentication functions follow below. Swap these out if you want different authentication semantics.
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--
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--
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-- Looks up a hash for a given user.
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function lookup_hash(user)
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local line
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for line in io.lines(users_filename) do
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local u, h = string.match(line, "(.-):(.+)")
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if u:lower() == user:lower() then
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return h
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end
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end
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return nil
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end
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-- Looks up users for a given repo.
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function lookup_users(repo)
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local users = nil
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local groups = nil
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local line, group, user
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for line in io.lines(repos_filename) do
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local r, g = string.match(line, "(.-):(.+)")
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if r == repo then
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groups = { }
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for group in string.gmatch(g, "([^,]+)") do
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groups[group:lower()] = true
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end
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break
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end
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end
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if groups == nil then
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return nil
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end
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for line in io.lines(groups_filename) do
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local g, u = string.match(line, "(.-):(.+)")
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if groups[g:lower()] then
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if users == nil then
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users = { }
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end
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for user in string.gmatch(u, "([^,]+)") do
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users[user:lower()] = true
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end
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end
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end
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return users
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end
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-- Sets HTTP cookie headers based on post and sets up redirection.
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function authenticate_post()
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local hash = lookup_hash(post["username"])
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local redirect = validate_value("redirect", post["redirect"])
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if redirect == nil then
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not_found()
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return 0
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end
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redirect_to(redirect)
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if hash == nil or hash ~= unistd.crypt(post["password"], hash) then
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set_cookie("cgitauth", "")
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else
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-- One week expiration time
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local username = secure_value("username", post["username"], os.time() + 604800)
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set_cookie("cgitauth", username)
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end
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html("\n")
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return 0
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end
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-- Returns 1 if the cookie is valid and 0 if it is not.
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function authenticate_cookie()
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accepted_users = lookup_users(cgit["repo"])
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if accepted_users == nil then
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-- We return as valid if the repo is not protected.
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return 1
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end
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local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
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if username == nil or not accepted_users[username:lower()] then
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return 0
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else
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return 1
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end
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end
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-- Prints the html for the login form.
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function body()
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html("<h2>Authentication Required</h2>")
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html("<form method='post' action='")
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html_attr(cgit["login"])
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html("'>")
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html("<input type='hidden' name='redirect' value='")
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html_attr(secure_value("redirect", cgit["url"], 0))
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html("' />")
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html("<table>")
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html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
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html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
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html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
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html("</table></form>")
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return 0
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end
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--
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--
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-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
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--
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--
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local actions = {}
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actions["authenticate-post"] = authenticate_post
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actions["authenticate-cookie"] = authenticate_cookie
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actions["body"] = body
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function filter_open(...)
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action = actions[select(1, ...)]
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http = {}
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http["cookie"] = select(2, ...)
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http["method"] = select(3, ...)
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http["query"] = select(4, ...)
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http["referer"] = select(5, ...)
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http["path"] = select(6, ...)
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http["host"] = select(7, ...)
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http["https"] = select(8, ...)
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cgit = {}
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cgit["repo"] = select(9, ...)
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cgit["page"] = select(10, ...)
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cgit["url"] = select(11, ...)
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cgit["login"] = select(12, ...)
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end
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function filter_close()
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return action()
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end
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function filter_write(str)
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post = parse_qs(str)
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end
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--
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--
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-- Utility functions based on keplerproject/wsapi.
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--
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--
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function url_decode(str)
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if not str then
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return ""
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end
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str = string.gsub(str, "+", " ")
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str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
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str = string.gsub(str, "\r\n", "\n")
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return str
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end
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function url_encode(str)
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if not str then
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return ""
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end
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str = string.gsub(str, "\n", "\r\n")
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str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
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str = string.gsub(str, " ", "+")
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return str
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end
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function parse_qs(qs)
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local tab = {}
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for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
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tab[url_decode(key)] = url_decode(val)
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end
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return tab
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end
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function get_cookie(cookies, name)
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cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
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return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
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end
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--
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--
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-- Cookie construction and validation helpers.
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--
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--
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local secret = nil
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-- Loads a secret from a file, creates a secret, or returns one from memory.
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function get_secret()
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if secret ~= nil then
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return secret
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end
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local secret_file = io.open(secret_filename, "r")
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if secret_file == nil then
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local old_umask = sysstat.umask(63)
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local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
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local temporary_file = io.open(temporary_filename, "w")
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if temporary_file == nil then
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os.exit(177)
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end
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temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
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temporary_file:close()
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unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
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unistd.unlink(temporary_filename)
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sysstat.umask(old_umask)
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secret_file = io.open(secret_filename, "r")
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end
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if secret_file == nil then
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os.exit(177)
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end
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secret = secret_file:read()
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secret_file:close()
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if secret:len() ~= 64 then
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os.exit(177)
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end
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return secret
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end
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-- Returns value of cookie if cookie is valid. Otherwise returns nil.
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function validate_value(expected_field, cookie)
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local i = 0
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local value = ""
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local field = ""
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local expiration = 0
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local salt = ""
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local hmac = ""
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if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
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return nil
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end
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for component in string.gmatch(cookie, "[^|]+") do
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if i == 0 then
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field = component
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elseif i == 1 then
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value = component
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elseif i == 2 then
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expiration = tonumber(component)
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if expiration == nil then
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expiration = -1
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end
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elseif i == 3 then
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salt = component
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elseif i == 4 then
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hmac = component
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else
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break
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end
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i = i + 1
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end
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if hmac == nil or hmac:len() == 0 then
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return nil
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end
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-- Lua hashes strings, so these comparisons are time invariant.
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if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
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return nil
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end
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if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
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return nil
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end
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if url_decode(field) ~= expected_field then
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return nil
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end
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return url_decode(value)
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end
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function secure_value(field, value, expiration)
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if value == nil or value:len() <= 0 then
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return ""
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end
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local authstr = ""
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local salt = crypto.hex(crypto.rand.bytes(16))
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value = url_encode(value)
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field = url_encode(field)
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authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
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authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
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return authstr
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end
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function set_cookie(cookie, value)
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html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
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if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
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html("; secure")
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end
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html("\n")
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end
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function redirect_to(url)
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html("Status: 302 Redirect\n")
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html("Cache-Control: no-cache, no-store\n")
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html("Location: " .. url .. "\n")
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end
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function not_found()
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html("Status: 404 Not Found\n")
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html("Cache-Control: no-cache, no-store\n\n")
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end
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