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Diffstat (limited to 'custom/extensions/auth-inline.lua')
| -rw-r--r-- | custom/extensions/auth-inline.lua | 528 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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diff --git a/custom/extensions/auth-inline.lua b/custom/extensions/auth-inline.lua new file mode 100644 index 0000000..168a444 --- /dev/null +++ b/custom/extensions/auth-inline.lua @@ -0,0 +1,528 @@ +-- cgit auth-filter that gates repositories behind a login form and a signed +-- session cookie. +-- +-- This is the INLINE variant. The user accounts and the per-repository access +-- lists are written directly in this script, in the two tables in the +-- CONFIGURATION block below. Edit them here and reload. This suits a small +-- fixed set of users that rarely changes. +-- +-- The companion auth-file.lua behaves identically but reads its accounts and +-- access lists from files on disk instead, which suits larger or externally +-- managed user sets. +-- +-- Enable it in cgitrc with +-- auth-filter=lua:/path/to/auth-inline.lua +-- +-- SUPPORTED LUA +-- +-- Lua 5.1, 5.2, 5.3, 5.4 and LuaJIT. Lua 5.5 is not supported, because luaossl +-- has no 5.5 build. Match the runtime to the Lua that cgit is built against. +-- +-- HTTPS IS RECOMMENDED +-- +-- Serve cgit over HTTPS. Terminate TLS at the web server in front of cgit. The +-- session cookie is marked Secure by default, so a browser only sends it back +-- over HTTPS. If you genuinely run cgit over plain HTTP with no TLS anywhere, +-- set cookie_insecure below, otherwise the cookie is never returned and login +-- appears to loop. +-- +-- DEPENDENCIES +-- +-- luaossl OpenSSL binding, provides openssl.rand and openssl.hmac +-- <https://github.com/wahern/luaossl> +-- luaposix POSIX binding, provides posix.sys.stat and posix.unistd +-- <https://github.com/luaposix/luaposix> +-- +-- The reliable cross-platform install is LuaRocks, matched to your Lua +-- version. luaossl also needs the OpenSSL development headers present. +-- +-- # Debian and Ubuntu +-- sudo apt install luarocks libssl-dev +-- sudo luarocks --lua-version 5.1 install luaossl +-- sudo luarocks --lua-version 5.1 install luaposix +-- +-- # Fedora +-- sudo dnf install luarocks openssl-devel +-- sudo luarocks --lua-version 5.1 install luaossl luaposix +-- +-- # Alpine +-- sudo apk add luarocks openssl-dev +-- sudo luarocks-5.1 install luaossl luaposix +-- +-- # macOS with Homebrew +-- brew install luarocks openssl +-- luarocks install luaossl OPENSSL_DIR="$(brew --prefix openssl)" +-- luarocks install luaposix +-- +-- Some distributions also package these, for example lua-luaossl and lua-posix +-- on Debian. If you use a distribution package, make sure it is built for the +-- same Lua version as cgit. +-- +-- SECURITY NOTES +-- +-- The cookie carries only a username with no server-side session store, so +-- deleting an account does not revoke a cookie already issued until it +-- expires, and instances that share a secret file accept each other's cookies. +-- The login form carries no CSRF token. Both are acceptable for gating read +-- access to a git browser. Weigh them before guarding anything more sensitive. + +local sysstat = require("posix.sys.stat") +local unistd = require("posix.unistd") +local rand = require("openssl.rand") +local hmac = require("openssl.hmac") + +-- +-- ========================= CONFIGURATION ========================= +-- Edit the values in this block. Nothing below it needs changing for +-- ordinary use. +-- + +-- Protected repositories and the users allowed into each. A repository listed +-- here is protected. One not listed is public. Keys and user names are matched +-- case-insensitively. REPLACE THE EXAMPLES BELOW, they are commented out so an +-- unedited copy protects nothing and grants no accounts. +local protected_repos = { + -- ["secret-repo"] = { alice = true, bob = true }, + -- ["another"] = { alice = true }, +} + +-- Accounts as name = hash. Generate a hash with +-- mkpasswd -m sha-512 -R 300000 +-- REPLACE THE EXAMPLES BELOW. The commented lines are not real credentials and +-- must not be deployed as-is. +local users = { + -- alice = "$6$rounds=300000$REPLACE_THIS_SALT$REPLACE_THIS_HASH", + -- bob = "$6$rounds=300000$REPLACE_THIS_SALT$REPLACE_THIS_HASH", +} + +-- Where the cookie-signing secret is stored. It is created on first use. It +-- must be persistent and writable by cgit. Prefer a path OUTSIDE the cache +-- root, because pruning the cache would delete a secret kept inside it and +-- invalidate every live session. This file should not be world-readable. +local secret_filename = "/var/cache/cgit/auth-secret" + +-- How long a login stays valid, in seconds. Default one week. +local session_seconds = 7 * 24 * 60 * 60 + +-- Name of the session cookie. +local cookie_name = "cgitauth" + +-- Path the cookie is scoped to. "/" covers the whole host. Set it to the cgit +-- root to scope the cookie more tightly. +local cookie_path = "/" + +-- Leave false so the cookie is marked Secure and only travels over HTTPS. Set +-- it true ONLY if cgit is served over plain HTTP with no TLS anywhere, see the +-- HTTPS note in the header. +local cookie_insecure = false + +-- +-- ================================================================= +-- + +-- A throwaway hash of the documented shape, used only to spend the same work +-- on a missing account as on a present one, so a failed login does not reveal +-- by timing whether the username exists. +local dummy_hash = "$6$rounds=300000$0000000000000000$" + +-- Module state shared across the open, write and close calls of one request. +local action, http, cgit, post + +-- +-- +-- Account and access-list storage. This is the ONLY part that differs from +-- auth-file.lua. Swap these two functions to change where accounts live. +-- +-- + +-- Fold the configured tables to lowercased user names once, so lookups match +-- case-insensitively the same way auth-file.lua does. Repository names keep +-- their case. +do + local folded = {} + for name, hash in pairs(users) do + folded[tostring(name):lower()] = hash + end + users = folded + for repo, set in pairs(protected_repos) do + local fs = {} + for name, allowed in pairs(set) do + fs[tostring(name):lower()] = allowed + end + protected_repos[repo] = fs + end +end + +-- Return the stored password hash for a user, or nil. +function account_hash(user) + if user == nil then + return nil + end + return users[user:lower()] +end + +-- Return the set of users allowed to access a repository, keyed by lowercased +-- user name, or nil if the repository is not protected. +function repo_userset(repo) + if repo == nil then + return nil + end + return protected_repos[repo] +end + +-- +-- +-- Utility functions based on keplerproject/wsapi. +-- +-- + +function url_decode(str) + if not str then + return "" + end + str = string.gsub(str, "+", " ") + str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end) + str = string.gsub(str, "\r\n", "\n") + return str +end + +function url_encode(str) + if not str then + return "" + end + str = string.gsub(str, "\n", "\r\n") + str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end) + str = string.gsub(str, " ", "+") + return str +end + +-- Parse an application/x-www-form-urlencoded body. A value may itself contain +-- '=', for example a base64 password, so the value runs to the next '&'. +function parse_qs(qs) + local tab = {} + for key, val in string.gmatch(qs or "", "([^&=]+)=([^&]*)") do + tab[url_decode(key)] = url_decode(val) + end + return tab +end + +-- Return the value of the named cookie, or nil. The stored token was already +-- url-encoded by secure_value, so it is returned verbatim, which keeps the +-- write path (set_cookie) and the read path symmetric. Decoding it here would +-- break the signature check for any value carrying a percent escape. +function get_cookie(cookies, name) + cookies = string.gsub(";" .. (cookies or "") .. ";", "%s*;%s*", ";") + return string.match(cookies, ";" .. name .. "=(.-);") +end + +function tohex(b) + local x = "" + for i = 1, #b do + x = x .. string.format("%.2x", string.byte(b, i)) + end + return x +end + +-- +-- +-- Cookie construction and validation helpers. +-- +-- + +local secret = nil + +-- Load the cookie-signing secret, creating it on first use. Failures raise, +-- which cgit turns into a request error, so a broken secret denies rather than +-- signs with nothing. +function get_secret() + if secret ~= nil then + return secret + end + local secret_file = io.open(secret_filename, "r") + if secret_file == nil then + local old_umask = sysstat.umask(63) + local temporary_filename = secret_filename .. ".tmp." .. tohex(rand.bytes(16)) + local temporary_file = io.open(temporary_filename, "w") + if temporary_file == nil then + sysstat.umask(old_umask) + error("cgit auth: cannot create secret file " .. secret_filename) + end + local wrote = temporary_file:write(tohex(rand.bytes(32))) + local closed = temporary_file:close() + if not wrote or not closed then + os.remove(temporary_filename) + sysstat.umask(old_umask) + error("cgit auth: failed writing secret file " .. secret_filename) + end + unistd.link(temporary_filename, secret_filename) -- Intentionally fails if another worker won the race. + unistd.unlink(temporary_filename) + sysstat.umask(old_umask) + secret_file = io.open(secret_filename, "r") + end + if secret_file == nil then + error("cgit auth: cannot read secret file " .. secret_filename) + end + secret = secret_file:read("*l") + secret_file:close() + if secret == nil or secret:len() ~= 64 then + secret = nil + error("cgit auth: secret file " .. secret_filename .. " is malformed, expected 64 hex characters") + end + return secret +end + +-- A redirect target is unsafe if a browser would read it as another origin. +-- The only such form cgit can be tricked into signing is a scheme-relative +-- "//host" or "/\host". Everything else stays on this host. +function is_safe_redirect(url) + if type(url) ~= "string" then + return false + end + local head = url:sub(1, 2) + if head == "//" or head == "/\\" then + return false + end + return true +end + +-- Return the value carried by a signed cookie, or nil if it does not verify. +function validate_value(expected_field, cookie) + local i = 0 + local value = "" + local field = "" + local expiration = 0 + local salt = "" + local chmac = "" + + if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then + return nil + end + + for component in string.gmatch(cookie, "[^|]+") do + if i == 0 then + field = component + elseif i == 1 then + value = component + elseif i == 2 then + -- The expiration must be a plain integer. Rejecting other forms + -- keeps the signed bytes canonical, since tonumber and tostring of + -- "1e9" or "100.0" differ across Lua versions. + if not string.match(component, "^%d+$") then + return nil + end + expiration = tonumber(component) + elseif i == 3 then + salt = component + elseif i == 4 then + chmac = component + else + break + end + i = i + 1 + end + + if chmac == nil or chmac:len() == 0 then + return nil + end + + -- Compare the HMAC without short-circuiting on the first mismatch. + if not constant_equals(chmac, tohex(hmac.new(get_secret(), "sha256"):final(field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt))) then + return nil + end + + -- An expiration of 0 never expires and is used for the redirect token. + if expiration ~= 0 and expiration <= os.time() then + return nil + end + + if url_decode(field) ~= expected_field then + return nil + end + + local decoded = url_decode(value) + -- Reject values carrying control characters so a signed value cannot + -- smuggle CR or LF into a response header. + if decoded:find("%c") then + return nil + end + return decoded +end + +function secure_value(field, value, expiration) + if value == nil or value:len() <= 0 then + return "" + end + + local salt = tohex(rand.bytes(16)) + value = url_encode(value) + field = url_encode(field) + local authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt + authstr = authstr .. "|" .. tohex(hmac.new(get_secret(), "sha256"):final(authstr)) + return authstr +end + +-- Strip control characters that could split an HTTP response header. +function strip_ctl(s) + return (string.gsub(s or "", "%c", "")) +end + +-- Compare two strings in time that does not depend on how many leading bytes +-- match, so a mismatch position is not revealed by timing. +function constant_equals(a, b) + if type(a) ~= "string" or type(b) ~= "string" or #a ~= #b then + return false + end + local diff = 0 + for i = 1, #a do + local d = a:byte(i) - b:byte(i) + diff = diff + d * d + end + return diff == 0 +end + +function set_cookie(cookie, value) + local attrs = "; HttpOnly; SameSite=Lax; Path=" .. cookie_path + if not cookie_insecure then + attrs = attrs .. "; Secure" + end + if value == "" then + attrs = attrs .. "; Max-Age=0" + elseif session_seconds > 0 then + attrs = attrs .. "; Max-Age=" .. tostring(session_seconds) + end + html("Set-Cookie: " .. cookie .. "=" .. strip_ctl(value) .. attrs .. "\n") +end + +function redirect_to(url) + html("Status: 302 Redirect\n") + html("Cache-Control: no-cache, no-store\n") + html("Location: " .. strip_ctl(url) .. "\n") +end + +function not_found() + html("Status: 404 Not Found\n") + html("Cache-Control: no-cache, no-store\n\n") +end + +-- +-- +-- Authentication actions. Identical to auth-inline.lua from here down. +-- +-- + +-- Sets HTTP cookie headers based on post and sets up redirection. +function authenticate_post() + local redirect = validate_value("redirect", post["redirect"]) + + if redirect == nil or not is_safe_redirect(redirect) then + not_found() + return 0 + end + + redirect_to(redirect) + + local username = post["username"] + local password = post["password"] + local ok = false + if username ~= nil and password ~= nil then + local hash = account_hash(username) + if hash == nil then + -- Spend the work anyway, see dummy_hash. + unistd.crypt(password, dummy_hash) + elseif constant_equals(hash, unistd.crypt(password, hash)) then + ok = true + end + end + + if ok then + set_cookie(cookie_name, secure_value("username", username, os.time() + session_seconds)) + else + set_cookie(cookie_name, "") + end + + html("\n") + return 0 +end + +-- Returns 1 if the cookie is valid and 0 if it is not. +function authenticate_cookie() + local accepted_users = repo_userset(cgit["repo"]) + if accepted_users == nil then + -- The repository is not protected. + return 1 + end + + local username = validate_value("username", get_cookie(http["cookie"], cookie_name)) + if username == nil or not accepted_users[username:lower()] then + return 0 + end + return 1 +end + +-- Prints the html for the login form. +function body() + local target = cgit["url"] + if not is_safe_redirect(target) then + target = cgit["login"] + end + + html("<h2>Authentication Required</h2>") + html("<form method='post' action='") + html_attr(cgit["login"]) + html("'>") + html("<input type='hidden' name='redirect' value='") + html_attr(secure_value("redirect", target, 0)) + html("' />") + html("<table>") + html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>") + html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>") + html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>") + html("</table></form>") + + return 0 +end + +-- +-- +-- Wrapper around the filter API, exposing the http, cgit and post tables to +-- the functions above. +-- +-- + +local actions = {} +actions["authenticate-post"] = authenticate_post +actions["authenticate-cookie"] = authenticate_cookie +actions["body"] = body + +function filter_open(...) + action = actions[select(1, ...)] + + post = {} + + http = {} + http["cookie"] = select(2, ...) + http["method"] = select(3, ...) + http["query"] = select(4, ...) + http["referer"] = select(5, ...) + http["path"] = select(6, ...) + http["host"] = select(7, ...) + http["https"] = select(8, ...) + + cgit = {} + cgit["repo"] = select(9, ...) + cgit["page"] = select(10, ...) + cgit["url"] = select(11, ...) + cgit["login"] = select(12, ...) +end + +function filter_close() + if action == nil then + -- Unknown action, deny rather than raise. + return 0 + end + return action() +end + +function filter_write(str) + post = parse_qs(str) +end |