index : cgit

-- Unit checks for the two auth filters, run under a standalone Lua by
-- t0505-auth.sh with the script path as the first argument and the variant,
-- inline or file, as the second. The scripts take luaossl and luaposix at
-- load, so the harness meets both with deterministic stand-ins, which keeps
-- every check about this script's own logic, the cookie layout, the expiry
-- and field rules, the redirect vetting and the action flows, rather than
-- about OpenSSL. The signing secret is pinned by replacing get_secret, and
-- the accounts and access lists are filled through each variant's own
-- channel, its commented-out examples switched on for the inline script and
-- fixture files reached through a redirected io.open for the file one. Both
-- variants carry the same data so the flow checks read identically for the
-- two.

local test_directory = arg[0]:match("^(.*)/") or "."
local h = dofile(test_directory .. "/harness.lua")

local script = arg[1]
local variant = arg[2]

h.stub_auth_modules()

-- The password behind every test account, stored as what the harness crypt
-- stand-in returns for it so a login with it verifies and any other fails.
local password = "open sesame"
local stored_hash = "$6$rounds=300000$testsalt$" .. password

if variant == "file" then
	local users_file = io.open("auth-users", "w")
	users_file:write("Alice:" .. stored_hash .. "\r\n")
	users_file:write("not a parsable line\n")
	users_file:close()
	local groups_file = io.open("auth-groups", "w")
	groups_file:write("devs:Alice, bob\n")
	groups_file:write("others:carol\n")
	groups_file:close()
	local repos_file = io.open("auth-repos", "w")
	repos_file:write("secret-repo:devs\n")
	repos_file:write("empty-repo:ghosts\n")
	repos_file:write("bare-repo:\n")
	repos_file:close()
	h.redirect_file("/etc/cgit-auth/users", "auth-users")
	h.redirect_file("/etc/cgit-auth/groups", "auth-groups")
	h.redirect_file("/etc/cgit-auth/repos", "auth-repos")
end

if variant == "inline" then
	h.load_with(script, {
		{ "local protected_repos = {\n", "local protected_repos = {\n" ..
			"\t[\"secret-repo\"] = { alice = true, Bob = true },\n" ..
			"\t[\"empty-repo\"] = {},\n" ..
			"\t[\"bare-repo\"] = {},\n" },
		{ "local users = {\n", "local users = {\n" ..
			"\tAlice = \"" .. stored_hash .. "\",\n" },
	})
else
	h.load(script)
end

function get_secret()
	return string.rep("0123456789abcdef", 4)
end

-- crypt is watched through its stand-in module, so a check can see whether
-- a login spent it and on which hash.
local unistd = require("posix.unistd")
local real_crypt = unistd.crypt
local crypt_settings = {}
unistd.crypt = function(trypass, setting)
	crypt_settings[#crypt_settings + 1] = setting
	return real_crypt(trypass, setting)
end

-- The lookups themselves, which are the part the two variants do not share.

local hash = account_hash("ALICE")
h.equals("an account is found whatever its case", hash, stored_hash)
h.equals("an unknown account is not", account_hash("nobody"), nil)
local _, stand_in = account_hash("nobody")
h.equals("it brings another account's hash to spend instead", stand_in, stored_hash)
h.equals("a nil user is not", account_hash(nil), nil)

local userset = repo_userset("secret-repo")
h.check("a protected repository lists its users",
	userset ~= nil and userset.alice and userset.bob)
h.equals("an unlisted repository is public", repo_userset("unlisted"), nil)
h.equals("the repository name matches case exactly", repo_userset("Secret-Repo"), nil)
local empty = repo_userset("empty-repo")
h.check("a protected repository with no members denies as an empty set",
	empty ~= nil and next(empty) == nil)
local bare = repo_userset("bare-repo")
h.check("a protected repository with no groups at all denies too",
	bare ~= nil and next(bare) == nil)

if variant == "file" then
	h.redirect_file("/etc/cgit-auth/users", "auth-users-missing")
	h.equals("a missing users file turns every login down", account_hash("alice"), nil)
	h.redirect_file("/etc/cgit-auth/users", "auth-users")
	-- Without the repos file nothing tells a protected repository from a
	-- public one, so every repository is refused while the index stays up.
	h.redirect_file("/etc/cgit-auth/repos", "auth-repos-missing")
	local refused = repo_userset("unlisted")
	h.check("a missing repos file refuses every repository",
		refused ~= nil and next(refused) == nil)
	h.equals("the index stays public all the same", repo_userset(nil), nil)
	h.redirect_file("/etc/cgit-auth/repos", "auth-repos")
end

-- The url and cookie helpers.

h.equals("decode handles escapes and plus", url_decode("%41+b"), "A b")
h.equals("encode escapes what is not a word", url_encode("a b|c"), "a+b%7Cc")
local tricky = "x&=?|"
h.equals("decode inverts encode", url_decode(url_encode(tricky)), tricky)

local params = parse_query("u=a&p=b=c&x=%41")
h.equals("a query splits on ampersands", params.u, "a")
h.equals("a value keeps its own equals signs", params.p, "b=c")
h.equals("a value is decoded", params.x, "A")

h.equals("a cookie is found among others",
	get_cookie("foo=1; cgitauth=abc; bar=2", "cgitauth"), "abc")
h.equals("a lone cookie is found", get_cookie("cgitauth=abc", "cgitauth"), "abc")
h.equals("no header yields no cookie", get_cookie(nil, "cgitauth"), nil)
h.equals("a longer name does not match", get_cookie("xcgitauth=z", "cgitauth"), nil)
h.equals("a magic character in the name is taken literally", get_cookie("a-b=z", "a-b"), "z")
h.equals("spaces around a pair are ignored", get_cookie(" foo=1 ;  cgitauth=abc ", "cgitauth"), "abc")
h.equals("a value keeps its own equals signs", get_cookie("cgitauth=a=b", "cgitauth"), "a=b")

-- The Cookie header is the visitor's to write, so a run of spaces in it
-- must not cost the square of its length.
local started = os.clock()
get_cookie("a=" .. string.rep(" ", 20000) .. "b", "cgitauth")
h.equals("a long run of spaces is read quickly",
	get_cookie(string.rep(" ", 20000) .. "cgitauth=abc", "cgitauth"), "abc")
h.check("and in linear time", os.clock() - started < 0.5)

h.check("equal strings compare equal", constant_equals("abc", "abc"))
h.check("differing strings do not", not constant_equals("abc", "abd"))
h.check("differing lengths do not", not constant_equals("a", "ab"))
h.check("non strings do not", not constant_equals(nil, "a"))

h.check("a local path is a safe redirect", is_safe_redirect("/x"))
h.check("a scheme relative target is not", not is_safe_redirect("//evil"))
h.check("a backslash variant is not", not is_safe_redirect("/\\evil"))
h.check("a missing target is not", not is_safe_redirect(nil))

h.equals("control characters are stripped from header values", strip_controls("a\r\nb"), "ab")

-- Signing and verification.

local now = os.time()

local cookie = secure_value("username", "alice", now + 3600)
h.equals("a signed value verifies and comes back", validate_value("username", cookie), "alice")

cookie = secure_value("username", "a|b", now + 3600)
h.equals("a value holding the separator survives the round trip", validate_value("username", cookie), "a|b")

cookie = secure_value("username", "a\nb", now + 3600)
h.equals("a signed control character is still rejected on the way out",
	validate_value("username", cookie), nil)

cookie = secure_value("redirect", "/repo/?a=b", 0)
h.equals("an expiration of zero never expires", validate_value("redirect", cookie), "/repo/?a=b")

cookie = secure_value("username", "alice", now - 10)
h.equals("an expired value is rejected", validate_value("username", cookie), nil)

cookie = secure_value("username", "alice", now + 3600)
local flipped = cookie:sub(1, -2) .. (cookie:sub(-1) == "0" and "1" or "0")
h.equals("a tampered signature is rejected", validate_value("username", flipped), nil)

h.equals("a value signed for one field does not serve another", validate_value("redirect", cookie), nil)

h.equals("no cookie does not verify", validate_value("username", nil), nil)
h.equals("a tiny cookie does not verify", validate_value("username", "ab"), nil)
h.equals("a leading separator does not verify", validate_value("username", "|x|1|s|sig"), nil)
h.equals("an unsigned cookie does not verify",
	validate_value("username", "username|alice|123|salt"), nil)
h.equals("an exponent spelling of the expiry does not verify",
	validate_value("username", "username|alice|1e9|salt|beef"), nil)
h.equals("an empty value signs to nothing", secure_value("username", "", 1), "")

-- The headers the filter writes itself.

h.reset()
set_cookie("cgitauth", "value")
local out = h.output()
h.contains("a session cookie carries the hardening attributes", out,
	"Set-Cookie: cgitauth=value; HttpOnly; SameSite=Lax; Path=/; Secure; " ..
	"Max-Age=604800\n")

h.reset()
set_cookie("cgitauth", "")
h.contains("an empty value clears the cookie instead", h.output(),
	"Set-Cookie: cgitauth=; HttpOnly; SameSite=Lax; Path=/; Secure; " ..
	"Max-Age=0\n")

h.reset()
redirect_to("/x\r\nX-Evil: 1")
out = h.output()
h.contains("a newline cannot split the location header", out,
	"Location: /xX-Evil: 1\n")
h.excludes("no carriage return slips through", out, "\r")

-- The three actions, driven the way cgit drives them, an open carrying the
-- request, a write only for the posted form and the answer read off the
-- close.

local function run_action(action, opts)
	opts = opts or {}
	h.reset()
	filter_open(action, opts.cookie or "", opts.method or "GET", "", "",
		"/", "example.org", "on", opts.repo or "", "summary",
		opts.url or "/repo/", "/?p=login")
	if opts.body then
		filter_write(opts.body)
	end
	local ret = filter_close()
	return h.output(), ret
end

local ret

out, ret = run_action("authenticate-cookie", { repo = "unlisted" })
h.equals("a public repository needs no cookie", ret, 1)

out, ret = run_action("authenticate-cookie", { repo = "secret-repo" })
h.equals("a protected repository turns a bare request away", ret, 0)

local session = secure_value("username", "Alice", now + 3600)
out, ret = run_action("authenticate-cookie", { repo = "secret-repo", cookie = "cgitauth=" .. session })
h.equals("a signed session for a member is let through", ret, 1)

out, ret = run_action("authenticate-cookie", { repo = "empty-repo", cookie = "cgitauth=" .. session })
h.equals("a memberless repository denies even a valid session", ret, 0)

local outsider = secure_value("username", "carol", now + 3600)
out, ret = run_action("authenticate-cookie", { repo = "secret-repo", cookie = "cgitauth=" .. outsider })
h.equals("a signed session for an outsider is turned away", ret, 0)

local forged = session:sub(1, -2) .. (session:sub(-1) == "0" and "1" or "0")
out, ret = run_action("authenticate-cookie", { repo = "secret-repo", cookie = "cgitauth=" .. forged })
h.equals("a forged session is turned away", ret, 0)

out, ret = run_action("no-such-action", {})
h.equals("an unknown action denies rather than raising", ret, 0)

out, ret = run_action("body", { url = "/repo/log/?q=x" })
h.contains("the login form posts to the login url", out, "<form method='post' action='/?p=login'>")
local token = out:match("name='redirect' value='([^']*)'")
h.equals("the form carries a signed way back", token and validate_value("redirect", token), "/repo/log/?q=x")

out, ret = run_action("body", { url = "//evil.example/x" })
token = out:match("name='redirect' value='([^']*)'")
h.equals("an unsafe destination is swapped for the login page",
	token and validate_value("redirect", token), "/?p=login")

local way_back = secure_value("redirect", "/repo/", 0)

out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=" .. url_encode(password) .. "&redirect=" .. url_encode(way_back),
})
h.contains("a good login redirects back", out, "Status: 302")
h.contains("to where the form said", out, "Location: /repo/\n")
local granted = out:match("Set%-Cookie: cgitauth=([^;]*);")
h.equals("and grants a session that verifies", granted and validate_value("username", granted), "Alice")

out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=wrong&redirect=" .. url_encode(way_back),
})
h.contains("a bad password redirects the same way", out, "Status: 302")
h.contains("but clears the session cookie", out, "Set-Cookie: cgitauth=; ")

out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=nobody&password=x&redirect=" .. url_encode(way_back),
})
h.contains("an unknown user is told nothing different", out, "Set-Cookie: cgitauth=; ")

-- A failed login for a name with no account spends crypt on a configured
-- hash, the same work a real check costs, so timing tells nothing.
crypt_settings = {}
run_action("authenticate-post", {
	method = "POST",
	body = "username=nobody&password=x&redirect=" .. url_encode(way_back),
})
h.equals("a missing account spends crypt on a configured hash", crypt_settings[1], stored_hash)

if variant == "file" then
	h.redirect_file("/etc/cgit-auth/users", "auth-users-missing")
	crypt_settings = {}
	run_action("authenticate-post", {
		method = "POST",
		body = "username=nobody&password=x&redirect=" .. url_encode(way_back),
	})
	h.equals("with no accounts at all nothing is spent", #crypt_settings, 0)
	h.redirect_file("/etc/cgit-auth/users", "auth-users")
end

-- crypt's work grows with the password, so one past the cap is turned down
-- before crypt sees it.
crypt_settings = {}
out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=" .. string.rep("a", 257) .. "&redirect=" .. url_encode(way_back),
})
h.contains("an overlong password is turned down", out, "Set-Cookie: cgitauth=; ")
h.equals("without spending crypt on it", #crypt_settings, 0)
run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=" .. string.rep("a", 256) .. "&redirect=" .. url_encode(way_back),
})
h.equals("a password at the cap is still checked", #crypt_settings, 1)

out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=" .. url_encode(password),
})
h.contains("a post without the signed token is not served", out, "Status: 404")

local hijack = secure_value("redirect", "//evil.example/", 0)
out, ret = run_action("authenticate-post", {
	method = "POST",
	body = "username=Alice&password=" .. url_encode(password) .. "&redirect=" .. url_encode(hijack),
})
h.contains("even a signed unsafe destination is not followed", out, "Status: 404")

-- The libraries load only once a request needs one, so with every one of
-- them gone a public repository is still served, while a protected one
-- fails closed instead of reaching its content.
for _, name in ipairs({ "openssl.rand", "openssl.hmac", "posix.sys.stat", "posix.unistd" }) do
	package.loaded[name] = nil
	h.preload_failure(name)
end
out, ret = run_action("authenticate-cookie", { repo = "unlisted" })
h.equals("without the libraries a public repository is served", ret, 1)
h.check("while a protected one fails closed", not pcall(run_action,
	"authenticate-cookie", { repo = "secret-repo", cookie = "cgitauth=" .. session }))
h.check("and so does its login form", not pcall(run_action, "body", {}))

h.finish()