| -rw-r--r-- | cgit.c | 22 | ||||
| -rw-r--r-- | cgitrc.5.txt | 3 | ||||
| -rw-r--r-- | filters/simple-authentication.lua | 200 |
3 files changed, 94 insertions, 131 deletions
@@ -614,19 +614,22 @@ static inline void open_auth_filter(struct cgit_context *ctx, const char *functi ctx->qry.url ? ctx->qry.url : ""); } -/* We intentionally keep this rather small, instead of looping and - * feeding it to the filter a couple bytes at a time. This way, the - * filter itself does not need to handle any denial of service or - * buffer bloat issues. If this winds up being too small, people - * will complain on the mailing list, and we'll increase it as needed. */ #define MAX_AUTHENTICATION_POST_BYTES 4096 -/* The filter is expected to spit out "Status: " and all headers. */ static inline void authenticate_post(struct cgit_context *ctx) { - char buffer[MAX_AUTHENTICATION_POST_BYTES]; - int len; + if (ctx->env.http_referer && strlen(ctx->env.http_referer) > 0) { + html("Status: 302 Redirect\n"); + html("Cache-Control: no-cache, no-store\n"); + htmlf("Location: %s\n", ctx->env.http_referer); + } else { + html("Status: 501 Missing Referer\n"); + html("Cache-Control: no-cache, no-store\n\n"); + exit(0); + } open_auth_filter(ctx, "authenticate-post"); + char buffer[MAX_AUTHENTICATION_POST_BYTES]; + int len; len = ctx->env.content_length; if (len > MAX_AUTHENTICATION_POST_BYTES) len = MAX_AUTHENTICATION_POST_BYTES; @@ -634,7 +637,10 @@ static inline void authenticate_post(struct cgit_context *ctx) die_errno("Could not read POST from stdin"); if (write(STDOUT_FILENO, buffer, len) < 0) die_errno("Could not write POST to stdout"); + /* The filter may now spit out a Set-Cookie: ... */ cgit_close_filter(ctx->cfg.auth_filter); + + html("\n"); exit(0); } diff --git a/cgitrc.5.txt b/cgitrc.5.txt index 682d8bb..c45dbd3 100644 --- a/cgitrc.5.txt +++ b/cgitrc.5.txt @@ -662,8 +662,7 @@ auth filter:: the http cookie and return a 0 if it is invalid or 1 if it is invalid, in the exit code / close function. If the filter action is "authenticate-post", this filter receives POST'd parameters on - standard input, and should write a complete CGI request, preferably - with a 302 redirect, and write to output one or more "Set-Cookie" + standard input, and should write to output one or more "Set-Cookie" HTTP headers, each followed by a newline. Please see `filters/simple-authentication.lua` for a clear example diff --git a/filters/simple-authentication.lua b/filters/simple-authentication.lua index 5935d08..4cd4983 100644 --- a/filters/simple-authentication.lua +++ b/filters/simple-authentication.lua @@ -33,28 +33,15 @@ local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM" -- -- --- Sets HTTP cookie headers based on post and sets up redirection. +-- Sets HTTP cookie headers based on post function authenticate_post() local password = users[post["username"]] - local redirect = validate_value(post["redirect"]) - - if redirect == nil then - not_found() - return 0 - end - - redirect_to(redirect) - - -- TODO: Implement time invariant string comparison function to mitigate timing attack. + -- TODO: Implement time invariant string comparison function to mitigate against timing attack. if password == nil or password ~= post["password"] then - set_cookie("cgitauth", "") + construct_cookie("", "cgitauth") else - -- One week expiration time - local username = secure_value(post["username"], os.time() + 604800) - set_cookie("cgitauth", username) + construct_cookie(post["username"], "cgitauth") end - - html("\n") return 0 end @@ -67,8 +54,8 @@ function authenticate_cookie() return 1 end - local username = validate_value(get_cookie(http["cookie"], "cgitauth")) - if username == nil or not accepted_users[username:lower()] then + local username = validate_cookie(get_cookie(http["cookie"], "cgitauth")) + if username == nil or not accepted_users[username] then return 0 else return 1 @@ -81,9 +68,6 @@ function body() html("<form method='post' action='") html_attr(cgit["login"]) html("'>") - html("<input type='hidden' name='redirect' value='") - html_attr(secure_value(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>") @@ -94,10 +78,81 @@ function body() end +-- +-- +-- Cookie construction and validation helpers. +-- +-- + +local crypto = require("crypto") + +-- Returns username of cookie if cookie is valid. Otherwise returns nil. +function validate_cookie(cookie) + local i = 0 + local username = "" + local expiration = 0 + local salt = "" + local hmac = "" + + if cookie:len() < 3 or cookie:sub(1, 1) == "|" then + return nil + end + + for component in string.gmatch(cookie, "[^|]+") do + if i == 0 then + username = component + elseif i == 1 then + expiration = tonumber(component) + if expiration == nil then + expiration = 0 + end + elseif i == 2 then + salt = component + elseif i == 3 then + hmac = component + else + break + end + i = i + 1 + end + + if hmac == nil or hmac:len() == 0 then + return nil + end + + -- TODO: implement time invariant comparison to prevent against timing attack. + if hmac ~= crypto.hmac.digest("sha1", username .. "|" .. tostring(expiration) .. "|" .. salt, secret) then + return nil + end + + if expiration <= os.time() then + return nil + end + + return username:lower() +end + +function construct_cookie(username, cookie) + local authstr = "" + if username:len() > 0 then + -- One week expiration time + local expiration = os.time() + 604800 + local salt = crypto.hex(crypto.rand.bytes(16)) + + authstr = username .. "|" .. tostring(expiration) .. "|" .. salt + authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret) + end + + html("Set-Cookie: " .. cookie .. "=" .. authstr .. "; HttpOnly") + if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then + html("; secure") + end + html("\n") +end -- -- --- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions. +-- Wrapper around filter API follows below, exposing the http table, the cgit table, and the post table to the above functions. -- -- @@ -142,7 +197,7 @@ end -- -- --- Utility functions based on keplerproject/wsapi. +-- Utility functions follow below, based on keplerproject/wsapi. -- -- @@ -156,16 +211,6 @@ function url_decode(str) 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 @@ -178,90 +223,3 @@ 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 crypto = require("crypto") - --- Returns value of cookie if cookie is valid. Otherwise returns nil. -function validate_value(cookie) - local i = 0 - local value = "" - 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 - value = component - elseif i == 1 then - expiration = tonumber(component) - if expiration == nil then - expiration = 0 - end - elseif i == 2 then - salt = component - elseif i == 3 then - hmac = component - else - break - end - i = i + 1 - end - - if hmac == nil or hmac:len() == 0 then - return nil - end - - -- TODO: implement time invariant comparison to prevent against timing attack. - if hmac ~= crypto.hmac.digest("sha1", value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then - return nil - end - - if expiration ~= 0 and expiration <= os.time() then - return nil - end - - return url_decode(value) -end - -function secure_value(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) - authstr = value .. "|" .. tostring(expiration) .. "|" .. salt - authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, 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 |