auth-filters: add simple file-based authentication scheme

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 file changed, 352 insertions, 0 deletions

diff --git a/filters/file-authentication.lua b/filters/file-authentication.luanew file mode 100644index 0000000..6ee1e19--- /dev/null+++ b/filters/file-authentication.lua@@ -0,0 +1,352 @@+-- This script may be used with the auth-filter.+--+-- Requirements:+-- 	luacrypto >= 0.3+-- 	<http://mkottman.github.io/luacrypto/>+-- 	luaposix+-- 	<https://github.com/luaposix/luaposix>+--+local sysstat = require("posix.sys.stat")+local unistd = require("posix.unistd")+local crypto = require("crypto")+++-- This file should contain a series of lines in the form of:+--	username1:hash1+--	username2:hash2+--	username3:hash3+--	...+-- Hashes can be generated using something like `mkpasswd -m sha-512 -R 300000`.+-- This file should not be world-readable.+local users_filename = "/etc/cgit-auth/users"++-- This file should contain a series of lines in the form of:+-- 	groupname1:username1,username2,username3,...+--	...+local groups_filename = "/etc/cgit-auth/groups"++-- This file should contain a series of lines in the form of:+-- 	reponame1:groupname1,groupname2,groupname3,...+--	...+local repos_filename = "/etc/cgit-auth/repos"++-- Set this to a path this script can write to for storing a persistent+-- cookie secret, which should not be world-readable.+local secret_filename = "/var/cache/cgit/auth-secret"++--+--+-- Authentication functions follow below. Swap these out if you want different authentication semantics.+--+--++-- Looks up a hash for a given user.+function lookup_hash(user)+	local line+	for line in io.lines(users_filename) do+		local u, h = string.match(line, "(.-):(.+)")+		if u:lower() == user:lower() then+			return h+		end+	end+	return nil+end++-- Looks up users for a given repo.+function lookup_users(repo)+	local users = nil+	local groups = nil+	local line, group, user+	for line in io.lines(repos_filename) do+		local r, g = string.match(line, "(.-):(.+)")+		if r == repo then+			groups = { }+			for group in string.gmatch(g, "([^,]+)") do+				groups[group:lower()] = true+			end+			break+		end+	end+	if groups == nil then+		return nil+	end+	for line in io.lines(groups_filename) do+		local g, u = string.match(line, "(.-):(.+)")+		if groups[g:lower()] then+			if users == nil then+				users = { }+			end+			for user in string.gmatch(u, "([^,]+)") do+				users[user:lower()] = true+			end+		end+	end+	return users+end+++-- Sets HTTP cookie headers based on post and sets up redirection.+function authenticate_post()+	local hash = lookup_hash(post["username"])+	local redirect = validate_value("redirect", post["redirect"])++	if redirect == nil then+		not_found()+		return 0+	end++	redirect_to(redirect)++	if hash == nil or hash ~= unistd.crypt(post["password"], hash) then+		set_cookie("cgitauth", "")+	else+		-- One week expiration time+		local username = secure_value("username", post["username"], os.time() + 604800)+		set_cookie("cgitauth", username)+	end++	html("\n")+	return 0+end+++-- Returns 1 if the cookie is valid and 0 if it is not.+function authenticate_cookie()+	accepted_users = lookup_users(cgit["repo"])+	if accepted_users == nil then+		-- We return as valid if the repo is not protected.+		return 1+	end++	local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))+	if username == nil or not accepted_users[username:lower()] then+		return 0+	else+		return 1+	end+end++-- Prints the html for the login form.+function body()+	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", cgit["url"], 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 filter API, exposing the http table, the cgit table, and the post table to the above functions.+--+--++local actions = {}+actions["authenticate-post"] = authenticate_post+actions["authenticate-cookie"] = authenticate_cookie+actions["body"] = body++function filter_open(...)+	action = actions[select(1, ...)]++	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()+	return action()+end++function filter_write(str)+	post = parse_qs(str)+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++function parse_qs(qs)+	local tab = {}+	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do+		tab[url_decode(key)] = url_decode(val)+	end+	return tab+end++function get_cookie(cookies, name)+	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")+	return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))+end+++--+--+-- Cookie construction and validation helpers.+--+--++local secret = nil++-- Loads a secret from a file, creates a secret, or returns one from memory.+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." .. crypto.hex(crypto.rand.bytes(16))+		local temporary_file = io.open(temporary_filename, "w")+		if temporary_file == nil then+			os.exit(177)+		end+		temporary_file:write(crypto.hex(crypto.rand.bytes(32)))+		temporary_file:close()+		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.+		unistd.unlink(temporary_filename)+		sysstat.umask(old_umask)+		secret_file = io.open(secret_filename, "r")+	end+	if secret_file == nil then+		os.exit(177)+	end+	secret = secret_file:read()+	secret_file:close()+	if secret:len() ~= 64 then+		os.exit(177)+	end+	return secret+end++-- Returns value of cookie if cookie is valid. Otherwise returns nil.+function validate_value(expected_field, cookie)+	local i = 0+	local value = ""+	local field = ""+	local expiration = 0+	local salt = ""+	local hmac = ""++	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+			expiration = tonumber(component)+			if expiration == nil then+				expiration = -1+			end+		elseif i == 3 then+			salt = component+		elseif i == 4 then+			hmac = component+		else+			break+		end+		i = i + 1+	end++	if hmac == nil or hmac:len() == 0 then+		return nil+	end++	-- Lua hashes strings, so these comparisons are time invariant.+	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then+		return nil+	end++	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then+		return nil+	end++	if url_decode(field) ~= expected_field then+		return nil+	end++	return url_decode(value)+end++function secure_value(field, value, expiration)+	if value == nil or value:len() <= 0 then+		return ""+	end++	local authstr = ""+	local salt = crypto.hex(crypto.rand.bytes(16))+	value = url_encode(value)+	field = url_encode(field)+	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt+	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())+	return authstr+end++function set_cookie(cookie, value)+	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")+	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then+		html("; secure")+	end+	html("\n")+end++function redirect_to(url)+	html("Status: 302 Redirect\n")+	html("Cache-Control: no-cache, no-store\n")+	html("Location: " .. url .. "\n")+end++function not_found()+	html("Status: 404 Not Found\n")+	html("Cache-Control: no-cache, no-store\n\n")+end
diff --git a/filters/file-authentication.lua b/filters/file-authentication.lua
new file mode 100644
index 0000000..6ee1e19
--- /dev/null
+++ b/filters/file-authentication.lua
@@ -0,0 +1,352 @@
+-- This script may be used with the auth-filter.
+--
+-- Requirements:
+-- 	luacrypto >= 0.3
+-- 	<http://mkottman.github.io/luacrypto/>
+-- 	luaposix
+-- 	<https://github.com/luaposix/luaposix>
+--
+local sysstat = require("posix.sys.stat")
+local unistd = require("posix.unistd")
+local crypto = require("crypto")
+
+
+-- This file should contain a series of lines in the form of:
+--	username1:hash1
+--	username2:hash2
+--	username3:hash3
+--	...
+-- Hashes can be generated using something like `mkpasswd -m sha-512 -R 300000`.
+-- This file should not be world-readable.
+local users_filename = "/etc/cgit-auth/users"
+
+-- This file should contain a series of lines in the form of:
+-- 	groupname1:username1,username2,username3,...
+--	...
+local groups_filename = "/etc/cgit-auth/groups"
+
+-- This file should contain a series of lines in the form of:
+-- 	reponame1:groupname1,groupname2,groupname3,...
+--	...
+local repos_filename = "/etc/cgit-auth/repos"
+
+-- Set this to a path this script can write to for storing a persistent
+-- cookie secret, which should not be world-readable.
+local secret_filename = "/var/cache/cgit/auth-secret"
+
+--
+--
+-- Authentication functions follow below. Swap these out if you want different authentication semantics.
+--
+--
+
+-- Looks up a hash for a given user.
+function lookup_hash(user)
+	local line
+	for line in io.lines(users_filename) do
+		local u, h = string.match(line, "(.-):(.+)")
+		if u:lower() == user:lower() then
+			return h
+		end
+	end
+	return nil
+end
+
+-- Looks up users for a given repo.
+function lookup_users(repo)
+	local users = nil
+	local groups = nil
+	local line, group, user
+	for line in io.lines(repos_filename) do
+		local r, g = string.match(line, "(.-):(.+)")
+		if r == repo then
+			groups = { }
+			for group in string.gmatch(g, "([^,]+)") do
+				groups[group:lower()] = true
+			end
+			break
+		end
+	end
+	if groups == nil then
+		return nil
+	end
+	for line in io.lines(groups_filename) do
+		local g, u = string.match(line, "(.-):(.+)")
+		if groups[g:lower()] then
+			if users == nil then
+				users = { }
+			end
+			for user in string.gmatch(u, "([^,]+)") do
+				users[user:lower()] = true
+			end
+		end
+	end
+	return users
+end
+
+
+-- Sets HTTP cookie headers based on post and sets up redirection.
+function authenticate_post()
+	local hash = lookup_hash(post["username"])
+	local redirect = validate_value("redirect", post["redirect"])
+
+	if redirect == nil then
+		not_found()
+		return 0
+	end
+
+	redirect_to(redirect)
+
+	if hash == nil or hash ~= unistd.crypt(post["password"], hash) then
+		set_cookie("cgitauth", "")
+	else
+		-- One week expiration time
+		local username = secure_value("username", post["username"], os.time() + 604800)
+		set_cookie("cgitauth", username)
+	end
+
+	html("\n")
+	return 0
+end
+
+
+-- Returns 1 if the cookie is valid and 0 if it is not.
+function authenticate_cookie()
+	accepted_users = lookup_users(cgit["repo"])
+	if accepted_users == nil then
+		-- We return as valid if the repo is not protected.
+		return 1
+	end
+
+	local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
+	if username == nil or not accepted_users[username:lower()] then
+		return 0
+	else
+		return 1
+	end
+end
+
+-- Prints the html for the login form.
+function body()
+	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", cgit["url"], 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 filter API, exposing the http table, the cgit table, and the post table to the above functions.
+--
+--
+
+local actions = {}
+actions["authenticate-post"] = authenticate_post
+actions["authenticate-cookie"] = authenticate_cookie
+actions["body"] = body
+
+function filter_open(...)
+	action = actions[select(1, ...)]
+
+	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()
+	return action()
+end
+
+function filter_write(str)
+	post = parse_qs(str)
+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
+
+function parse_qs(qs)
+	local tab = {}
+	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
+		tab[url_decode(key)] = url_decode(val)
+	end
+	return tab
+end
+
+function get_cookie(cookies, name)
+	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
+	return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
+end
+
+
+--
+--
+-- Cookie construction and validation helpers.
+--
+--
+
+local secret = nil
+
+-- Loads a secret from a file, creates a secret, or returns one from memory.
+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." .. crypto.hex(crypto.rand.bytes(16))
+		local temporary_file = io.open(temporary_filename, "w")
+		if temporary_file == nil then
+			os.exit(177)
+		end
+		temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
+		temporary_file:close()
+		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
+		unistd.unlink(temporary_filename)
+		sysstat.umask(old_umask)
+		secret_file = io.open(secret_filename, "r")
+	end
+	if secret_file == nil then
+		os.exit(177)
+	end
+	secret = secret_file:read()
+	secret_file:close()
+	if secret:len() ~= 64 then
+		os.exit(177)
+	end
+	return secret
+end
+
+-- Returns value of cookie if cookie is valid. Otherwise returns nil.
+function validate_value(expected_field, cookie)
+	local i = 0
+	local value = ""
+	local field = ""
+	local expiration = 0
+	local salt = ""
+	local hmac = ""
+
+	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
+			expiration = tonumber(component)
+			if expiration == nil then
+				expiration = -1
+			end
+		elseif i == 3 then
+			salt = component
+		elseif i == 4 then
+			hmac = component
+		else
+			break
+		end
+		i = i + 1
+	end
+
+	if hmac == nil or hmac:len() == 0 then
+		return nil
+	end
+
+	-- Lua hashes strings, so these comparisons are time invariant.
+	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
+		return nil
+	end
+
+	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
+		return nil
+	end
+
+	if url_decode(field) ~= expected_field then
+		return nil
+	end
+
+	return url_decode(value)
+end
+
+function secure_value(field, value, expiration)
+	if value == nil or value:len() <= 0 then
+		return ""
+	end
+
+	local authstr = ""
+	local salt = crypto.hex(crypto.rand.bytes(16))
+	value = url_encode(value)
+	field = url_encode(field)
+	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
+	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
+	return authstr
+end
+
+function set_cookie(cookie, value)
+	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
+	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
+		html("; secure")
+	end
+	html("\n")
+end
+
+function redirect_to(url)
+	html("Status: 302 Redirect\n")
+	html("Cache-Control: no-cache, no-store\n")
+	html("Location: " .. url .. "\n")
+end
+
+function not_found()
+	html("Status: 404 Not Found\n")
+	html("Cache-Control: no-cache, no-store\n\n")
+end