[mod_secdownload] add required algorithm option; old behaviour available as "md5", new options "hmac-sha1" and "hmac-sha256"

Differential Revision: https://review.lighttpd.net/D7

From: Stefan Bühler <stbuehler@web.de>

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@3054 152afb58-edef-0310-8abb-c4023f1b3aa9

10 files changed, 678 insertions, 337 deletions

diff --git a/NEWS b/NEWS
index 23814cfe..7b113ac2 100644
--- a/NEWS
+++ b/NEWS
@@ -16,6 +16,7 @@ NEWS
   * [core] revert increase of temp file size back to 1MB, provide a configure option "server.upload-temp-file-size" instead (fixes #2680)
   * [core] add '~' to safe characters in ENCODING_REL_URI/ENCODING_REL_URI_PART encoding
   * [core] encode path with ENCODING_REL_URI in redirect to directory (fixes #2661, thx gstrauss)
+  * [mod_secdownload] add required algorithm option; old behaviour available as "md5", new options "hmac-sha1" and "hmac-sha256"
 
 - 1.4.37 - 2015-08-30
   * [mod_proxy] remove debug log line from error log (fixes #2659)
diff --git a/doc/outdated/secdownload.txt b/doc/outdated/secdownload.txt
index bf0a4815..21629983 100644
--- a/doc/outdated/secdownload.txt
+++ b/doc/outdated/secdownload.txt
@@ -144,4 +144,4 @@ secret have to match: ::
   secdownload.document-root   = "/home/www/servers/download-area/"
   secdownload.uri-prefix      = "/dl/"
   secdownload.timeout         = 120
-
+  secdownload.algorithm       = "md5"
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 6cb2f3c8..4f574d9f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -551,7 +551,7 @@ add_and_install_library(mod_redirect mod_redirect.c)
 add_and_install_library(mod_rewrite mod_rewrite.c)
 add_and_install_library(mod_rrdtool mod_rrdtool.c)
 add_and_install_library(mod_scgi mod_scgi.c)
-add_and_install_library(mod_secdownload mod_secure_download.c)
+add_and_install_library(mod_secdownload mod_secdownload.c)
 add_and_install_library(mod_setenv mod_setenv.c)
 add_and_install_library(mod_simple_vhost mod_simple_vhost.c)
 add_and_install_library(mod_ssi "mod_ssi_exprparser.c;mod_ssi_expr.c;mod_ssi.c")
diff --git a/src/Makefile.am b/src/Makefile.am
index 2ac8415b..a1f624ce 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -198,7 +198,7 @@ mod_ssi_la_LDFLAGS = -module -export-dynamic -avoid-version
 mod_ssi_la_LIBADD = $(common_libadd) $(PCRE_LIB)
 
 lib_LTLIBRARIES += mod_secdownload.la
-mod_secdownload_la_SOURCES = mod_secure_download.c
+mod_secdownload_la_SOURCES = mod_secdownload.c
 mod_secdownload_la_LDFLAGS = -module -export-dynamic -avoid-version
 mod_secdownload_la_LIBADD = $(common_libadd)
 
diff --git a/src/SConscript b/src/SConscript
index f7dc203f..3d873e8d 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -59,7 +59,7 @@ modules = {
 	'mod_usertrack' : { 'src' : [ 'mod_usertrack.c' ] },
 	'mod_proxy' : { 'src' : [ 'mod_proxy.c' ] },
 	'mod_userdir' : { 'src' : [ 'mod_userdir.c' ] },
-	'mod_secdownload' : { 'src' : [ 'mod_secure_download.c' ] },
+	'mod_secdownload' : { 'src' : [ 'mod_secdownload.c' ] },
 	'mod_accesslog' : { 'src' : [ 'mod_accesslog.c' ] },
 	'mod_simple_vhost' : { 'src' : [ 'mod_simple_vhost.c' ] },
 	'mod_evhost' : { 'src' : [ 'mod_evhost.c' ] },
diff --git a/src/mod_secdownload.c b/src/mod_secdownload.c
new file mode 100644
index 00000000..bbe293ff
--- /dev/null
+++ b/src/mod_secdownload.c
@@ -0,0 +1,536 @@
+#include "base.h"
+#include "log.h"
+#include "buffer.h"
+#include "base64.h"
+
+#include "plugin.h"
+
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if defined(USE_OPENSSL)
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#endif
+
+#include "md5.h"
+
+#define HASHLEN 16
+typedef unsigned char HASH[HASHLEN];
+#define HASHHEXLEN 32
+typedef char HASHHEX[HASHHEXLEN+1];
+
+/*
+ * mod_secdownload verifies a checksum associated with a timestamp
+ * and a path.
+ *
+ * It takes an URL of the form:
+ *   securl := <uri-prefix> <mac> <protected-path>
+ *   uri-prefix := '/' any*         # whatever was configured: must start with a '/')
+ *   mac := [a-zA-Z0-9_-]{mac_len}  # mac length depends on selected algorithm
+ *   protected-path := '/' <timestamp> <rel-path>
+ *   timestamp := [a-f0-9]{8}       # timestamp when the checksum was calculated
+ *                                  # to prevent access after timeout (active requests
+ *                                  # will finish successfully even after the timeout)
+ *   rel-path := '/' any*           # the protected path; changing the path breaks the
+ *                                  # checksum
+ *
+ * The timestamp is the `epoch` timestamp in hex, i.e. time in seconds
+ * since 00:00:00 UTC on 1 January 1970.
+ *
+ * mod_secdownload supports various MAC algorithms:
+ *
+ * # md5
+ * mac_len := 32 (and hex only)
+ * mac := md5-hex(<secrect><rel-path><timestamp>)   # lowercase hex
+ * perl example:
+    use Digest::MD5 qw(md5_hex);
+    my $secret = "verysecret";
+    my $rel_path = "/index.html"
+    my $xtime = sprintf("%08x", time);
+    my $url = '/'. md5_hex($secret . $rel_path . $xtime) . '/' . $xtime . $rel_path;
+ *
+ * # hmac-sha1
+ * mac_len := 27  (no base64 padding)
+ * mac := base64-url(hmac-sha1(<secret>, <protected-path>))
+ * perl example:
+    use Digest::SHA qw(hmac_sha1);
+    use MIME::Base64 qw(encode_base64url);
+    my $secret = "verysecret";
+    my $rel_path = "/index.html"
+    my $protected_path = '/' . sprintf("%08x", time) . $rel_path;
+    my $url = '/'. encode_base64url(hmac_sha1($protected_path, $secret)) . $protected_path;
+ *
+ * # hmac-256
+ * mac_len := 43  (no base64 padding)
+ * mac := base64-url(hmac-256(<secret>, <protected-path>))
+    use Digest::SHA qw(hmac_sha256);
+    use MIME::Base64 qw(encode_base64url);
+    my $secret = "verysecret";
+    my $rel_path = "/index.html"
+    my $protected_path = '/' . sprintf("%08x", time) . $rel_path;
+    my $url = '/'. encode_base64url(hmac_sha256($protected_path, $secret)) . $protected_path;
+ *
+ */
+
+/* plugin config for all request/connections */
+
+typedef enum {
+	SECDL_INVALID = 0,
+	SECDL_MD5 = 1,
+	SECDL_HMAC_SHA1 = 2,
+	SECDL_HMAC_SHA256 = 3,
+} secdl_algorithm;
+
+typedef struct {
+	buffer *doc_root;
+	buffer *secret;
+	buffer *uri_prefix;
+	secdl_algorithm algorithm;
+
+	unsigned int timeout;
+} plugin_config;
+
+typedef struct {
+	PLUGIN_DATA;
+
+	plugin_config **config_storage;
+
+	plugin_config conf;
+} plugin_data;
+
+static int const_time_memeq(const char *a, const char *b, size_t len) {
+	/* constant time memory compare, unless the compiler figures it out */
+	char diff = 0;
+	size_t i;
+	for (i = 0; i < len; ++i) {
+		diff |= (a[i] ^ b[i]);
+	}
+	return 0 == diff;
+}
+
+static const char* secdl_algorithm_names[] = {
+	"invalid",
+	"md5",
+	"hmac-sha1",
+	"hmac-sha256",
+};
+
+static secdl_algorithm algorithm_from_string(buffer *name) {
+	size_t ndx;
+
+	if (buffer_string_is_empty(name)) return SECDL_INVALID;
+
+	for (ndx = 1; ndx < sizeof(secdl_algorithm_names)/sizeof(secdl_algorithm_names[0]); ++ndx) {
+		if (0 == strcmp(secdl_algorithm_names[ndx], name->ptr)) return (secdl_algorithm)ndx;
+	}
+
+	return SECDL_INVALID;
+}
+
+static size_t secdl_algorithm_mac_length(secdl_algorithm alg) {
+	switch (alg) {
+	case SECDL_INVALID:
+		break;
+	case SECDL_MD5:
+		return 32;
+	case SECDL_HMAC_SHA1:
+		return 27;
+	case SECDL_HMAC_SHA256:
+		return 43;
+	}
+	return 0;
+}
+
+static int secdl_verify_mac(server *srv, plugin_config *config, const char* protected_path, const char* mac, size_t maclen) {
+	if (0 == maclen || secdl_algorithm_mac_length(config->algorithm) != maclen) return 0;
+
+	switch (config->algorithm) {
+	case SECDL_INVALID:
+		break;
+	case SECDL_MD5:
+		{
+			li_MD5_CTX Md5Ctx;
+			HASH HA1;
+			char hexmd5[32];
+			const char *ts_str;
+			const char *rel_uri;
+
+			/* legacy message:
+			 *   protected_path := '/' <timestamp-hex> <rel-path>
+			 *   timestamp-hex := [0-9a-f]{8}
+			 *   rel-path := '/' any*
+			 *   (the protected path was already verified)
+			 * message = <secret><rel-path><timestamp-hex>
+			 */
+			ts_str = protected_path + 1;
+			rel_uri = ts_str + 8;
+
+			li_MD5_Init(&Md5Ctx);
+			li_MD5_Update(&Md5Ctx, CONST_BUF_LEN(config->secret));
+			li_MD5_Update(&Md5Ctx, rel_uri, strlen(rel_uri));
+			li_MD5_Update(&Md5Ctx, ts_str, 8);
+			li_MD5_Final(HA1, &Md5Ctx);
+
+			li_tohex(hexmd5, (const char *)HA1, 16);
+
+			return (32 == maclen) && const_time_memeq(mac, hexmd5, 32);
+		}
+	case SECDL_HMAC_SHA1:
+#if defined(USE_OPENSSL)
+		{
+			unsigned char digest[20];
+			char base64_digest[27];
+
+			if (NULL == HMAC(
+					EVP_sha1(),
+					(unsigned char const*) CONST_BUF_LEN(config->secret),
+					(unsigned char const*) protected_path, strlen(protected_path),
+					digest, NULL)) {
+				log_error_write(srv, __FILE__, __LINE__, "s",
+					"hmac-sha1: HMAC() failed");
+				return 0;
+			}
+
+			li_to_base64_no_padding(base64_digest, 27, digest, 20, BASE64_URL);
+
+			return (27 == maclen) && const_time_memeq(mac, base64_digest, 27);
+		}
+#endif
+		break;
+	case SECDL_HMAC_SHA256:
+#if defined(USE_OPENSSL)
+		{
+			unsigned char digest[32];
+			char base64_digest[43];
+
+			if (NULL == HMAC(
+					EVP_sha256(),
+					(unsigned char const*) CONST_BUF_LEN(config->secret),
+					(unsigned char const*) protected_path, strlen(protected_path),
+					digest, NULL)) {
+				log_error_write(srv, __FILE__, __LINE__, "s",
+					"hmac-sha256: HMAC() failed");
+				return 0;
+			}
+
+			li_to_base64_no_padding(base64_digest, 43, digest, 32, BASE64_URL);
+
+			return (43 == maclen) && const_time_memeq(mac, base64_digest, 43);
+		}
+#endif
+		break;
+	}
+
+	return 0;
+}
+
+/* init the plugin data */
+INIT_FUNC(mod_secdownload_init) {
+	plugin_data *p;
+
+	p = calloc(1, sizeof(*p));
+
+	return p;
+}
+
+/* detroy the plugin data */
+FREE_FUNC(mod_secdownload_free) {
+	plugin_data *p = p_d;
+	UNUSED(srv);
+
+	if (!p) return HANDLER_GO_ON;
+
+	if (p->config_storage) {
+		size_t i;
+		for (i = 0; i < srv->config_context->used; i++) {
+			plugin_config *s = p->config_storage[i];
+
+			if (NULL == s) continue;
+
+			buffer_free(s->secret);
+			buffer_free(s->doc_root);
+			buffer_free(s->uri_prefix);
+
+			free(s);
+		}
+		free(p->config_storage);
+	}
+
+	free(p);
+
+	return HANDLER_GO_ON;
+}
+
+/* handle plugin config and check values */
+
+SETDEFAULTS_FUNC(mod_secdownload_set_defaults) {
+	plugin_data *p = p_d;
+	size_t i = 0;
+
+	config_values_t cv[] = {
+		{ "secdownload.secret",        NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 0 */
+		{ "secdownload.document-root", NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 1 */
+		{ "secdownload.uri-prefix",    NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 2 */
+		{ "secdownload.timeout",       NULL, T_CONFIG_INT,    T_CONFIG_SCOPE_CONNECTION }, /* 3 */
+		{ "secdownload.algorithm",     NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 4 */
+		{ NULL,                        NULL, T_CONFIG_UNSET,  T_CONFIG_SCOPE_UNSET      }
+	};
+
+	if (!p) return HANDLER_ERROR;
+
+	p->config_storage = calloc(1, srv->config_context->used * sizeof(plugin_config *));
+
+	for (i = 0; i < srv->config_context->used; i++) {
+		data_config const* config = (data_config const*)srv->config_context->data[i];
+		plugin_config *s;
+		buffer *algorithm = buffer_init();
+
+		s = calloc(1, sizeof(plugin_config));
+		s->secret        = buffer_init();
+		s->doc_root      = buffer_init();
+		s->uri_prefix    = buffer_init();
+		s->timeout       = 60;
+
+		cv[0].destination = s->secret;
+		cv[1].destination = s->doc_root;
+		cv[2].destination = s->uri_prefix;
+		cv[3].destination = &(s->timeout);
+		cv[4].destination = algorithm;
+
+		p->config_storage[i] = s;
+
+		if (0 != config_insert_values_global(srv, config->value, cv, i == 0 ? T_CONFIG_SCOPE_SERVER : T_CONFIG_SCOPE_CONNECTION)) {
+			buffer_free(algorithm);
+			return HANDLER_ERROR;
+		}
+
+		if (!buffer_is_empty(algorithm)) {
+			s->algorithm = algorithm_from_string(algorithm);
+			switch (s->algorithm) {
+			case SECDL_INVALID:
+				log_error_write(srv, __FILE__, __LINE__, "sb",
+					"invalid secdownload.algorithm:",
+					algorithm);
+				buffer_free(algorithm);
+				return HANDLER_ERROR;
+#if !defined(USE_OPENSSL)
+			case SECDL_HMAC_SHA1:
+			case SECDL_HMAC_SHA256:
+				log_error_write(srv, __FILE__, __LINE__, "sb",
+					"unsupported secdownload.algorithm:",
+					algorithm);
+				buffer_free(algorithm);
+				return HANDLER_ERROR;
+#endif
+			default:
+				break;
+			}
+		}
+
+		buffer_free(algorithm);
+	}
+
+	return HANDLER_GO_ON;
+}
+
+/**
+ * checks if the supplied string is a hex string
+ *
+ * @param str a possible hex string
+ * @return if the supplied string is a valid hex string 1 is returned otherwise 0
+ */
+
+static int is_hex_len(const char *str, size_t len) {
+	size_t i;
+
+	if (NULL == str) return 0;
+
+	for (i = 0; i < len && *str; i++, str++) {
+		/* illegal characters */
+		if (!((*str >= '0' && *str <= '9') ||
+		      (*str >= 'a' && *str <= 'f') ||
+		      (*str >= 'A' && *str <= 'F'))
+		    ) {
+			return 0;
+		}
+	}
+
+	return i == len;
+}
+
+/**
+ * checks if the supplied string is a base64 (modified URL) string
+ *
+ * @param str a possible base64 (modified URL) string
+ * @return if the supplied string is a valid base64 (modified URL) string 1 is returned otherwise 0
+ */
+
+static int is_base64_len(const char *str, size_t len) {
+	size_t i;
+
+	if (NULL == str) return 0;
+
+	for (i = 0; i < len && *str; i++, str++) {
+		/* illegal characters */
+		if (!((*str >= '0' && *str <= '9') ||
+		      (*str >= 'a' && *str <= 'z') ||
+		      (*str >= 'A' && *str <= 'Z') ||
+		      (*str == '-') || (*str == '_'))
+		    ) {
+			return 0;
+		}
+	}
+
+	return i == len;
+}
+
+#define PATCH(x) \
+	p->conf.x = s->x;
+static int mod_secdownload_patch_connection(server *srv, connection *con, plugin_data *p) {
+	size_t i, j;
+	plugin_config *s = p->config_storage[0];
+
+	PATCH(secret);
+	PATCH(doc_root);
+	PATCH(uri_prefix);
+	PATCH(timeout);
+	PATCH(algorithm);
+
+	/* skip the first, the global context */
+	for (i = 1; i < srv->config_context->used; i++) {
+		data_config *dc = (data_config *)srv->config_context->data[i];
+		s = p->config_storage[i];
+
+		/* condition didn't match */
+		if (!config_check_cond(srv, con, dc)) continue;
+
+		/* merge config */
+		for (j = 0; j < dc->value->used; j++) {
+			data_unset *du = dc->value->data[j];
+
+			if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.secret"))) {
+				PATCH(secret);
+			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.document-root"))) {
+				PATCH(doc_root);
+			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.uri-prefix"))) {
+				PATCH(uri_prefix);
+			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.timeout"))) {
+				PATCH(timeout);
+			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.algorithm"))) {
+				PATCH(algorithm);
+			}
+		}
+	}
+
+	return 0;
+}
+#undef PATCH
+
+
+URIHANDLER_FUNC(mod_secdownload_uri_handler) {
+	plugin_data *p = p_d;
+	const char *rel_uri, *ts_str, *mac_str, *protected_path;
+	time_t ts = 0;
+	size_t i, mac_len;
+
+	if (con->mode != DIRECT) return HANDLER_GO_ON;
+
+	if (buffer_is_empty(con->uri.path)) return HANDLER_GO_ON;
+
+	mod_secdownload_patch_connection(srv, con, p);
+
+	if (buffer_string_is_empty(p->conf.uri_prefix)) return HANDLER_GO_ON;
+
+	if (buffer_string_is_empty(p->conf.secret)) {
+		log_error_write(srv, __FILE__, __LINE__, "s",
+				"secdownload.secret has to be set");
+		con->http_status = 500;
+		return HANDLER_FINISHED;
+	}
+
+	if (buffer_string_is_empty(p->conf.doc_root)) {
+		log_error_write(srv, __FILE__, __LINE__, "s",
+				"secdownload.document-root has to be set");
+		con->http_status = 500;
+		return HANDLER_FINISHED;
+	}
+
+	if (SECDL_INVALID == p->conf.algorithm) {
+		log_error_write(srv, __FILE__, __LINE__, "s",
+				"secdownload.algorithm has to be set");
+		con->http_status = 500;
+		return HANDLER_FINISHED;
+	}
+
+	mac_len = secdl_algorithm_mac_length(p->conf.algorithm);
+
+	if (0 != strncmp(con->uri.path->ptr, p->conf.uri_prefix->ptr, buffer_string_length(p->conf.uri_prefix))) return HANDLER_GO_ON;
+
+	mac_str = con->uri.path->ptr + buffer_string_length(p->conf.uri_prefix);
+
+	if (!is_base64_len(mac_str, mac_len)) return HANDLER_GO_ON;
+
+	protected_path = mac_str + mac_len;
+	if (*protected_path != '/') return HANDLER_GO_ON;
+
+	ts_str = protected_path + 1;
+	if (!is_hex_len(ts_str, 8)) return HANDLER_GO_ON;
+	if (*(ts_str + 8) != '/') return HANDLER_GO_ON;
+
+	for (i = 0; i < 8; i++) {
+		ts = (ts << 4) + hex2int(ts_str[i]);
+	}
+
+	/* timed-out */
+	if ( (srv->cur_ts > ts && (unsigned int) (srv->cur_ts - ts) > p->conf.timeout) ||
+	     (srv->cur_ts < ts && (unsigned int) (ts - srv->cur_ts) > p->conf.timeout) ) {
+		/* "Gone" as the url will never be valid again instead of "408 - Timeout" where the request may be repeated */
+		con->http_status = 410;
+
+		return HANDLER_FINISHED;
+	}
+
+	rel_uri = ts_str + 8;
+
+	if (!secdl_verify_mac(srv, &p->conf, protected_path, mac_str, mac_len)) {
+		con->http_status = 403;
+
+		if (con->conf.log_request_handling) {
+			log_error_write(srv, __FILE__, __LINE__, "sb",
+				"mac invalid:",
+				con->uri.path);
+		}
+
+		return HANDLER_FINISHED;
+	}
+
+	/* starting with the last / we should have relative-path to the docroot
+	 */
+
+	buffer_copy_buffer(con->physical.doc_root, p->conf.doc_root);
+	buffer_copy_buffer(con->physical.basedir, p->conf.doc_root);
+	buffer_copy_string(con->physical.rel_path, rel_uri);
+	buffer_copy_buffer(con->physical.path, con->physical.doc_root);
+	buffer_append_string_buffer(con->physical.path, con->physical.rel_path);
+
+	return HANDLER_GO_ON;
+}
+
+/* this function is called at dlopen() time and inits the callbacks */
+
+int mod_secdownload_plugin_init(plugin *p);
+int mod_secdownload_plugin_init(plugin *p) {
+	p->version     = LIGHTTPD_VERSION_ID;
+	p->name        = buffer_init_string("secdownload");
+
+	p->init        = mod_secdownload_init;
+	p->handle_physical  = mod_secdownload_uri_handler;
+	p->set_defaults  = mod_secdownload_set_defaults;
+	p->cleanup     = mod_secdownload_free;
+
+	p->data        = NULL;
+
+	return 0;
+}
diff --git a/src/mod_secure_download.c b/src/mod_secure_download.c
deleted file mode 100644
index 3a41bbc4..00000000
--- a/src/mod_secure_download.c
+++ /dev/null
@@ -1,319 +0,0 @@
-#include "base.h"
-#include "log.h"
-#include "buffer.h"
-
-#include "plugin.h"
-
-#include <ctype.h>
-#include <stdlib.h>
-#include <string.h>
-
-#ifdef USE_OPENSSL
-#include <openssl/sha.h>
-#endif
-
-#include "md5.h"
-
-#define HASHLEN 16
-typedef unsigned char HASH[HASHLEN];
-#define HASHHEXLEN 32
-typedef char HASHHEX[HASHHEXLEN+1];
-#ifdef USE_OPENSSL
-#define IN const
-#else
-#define IN
-#endif
-#define OUT
-
-
-/* plugin config for all request/connections */
-
-typedef struct {
-	buffer *doc_root;
-	buffer *secret;
-	buffer *uri_prefix;
-
-	unsigned int timeout;
-} plugin_config;
-
-typedef struct {
-	PLUGIN_DATA;
-
-	buffer *md5;
-
-	plugin_config **config_storage;
-
-	plugin_config conf;
-} plugin_data;
-
-static int const_time_memeq(const char *a, const char *b, size_t len) {
-	/* constant time memory compare, unless the compiler figures it out */
-	char diff = 0;
-	size_t i;
-	for (i = 0; i < len; ++i) {
-		diff |= (a[i] ^ b[i]);
-	}
-	return 0 == diff;
-}
-
-/* init the plugin data */
-INIT_FUNC(mod_secdownload_init) {
-	plugin_data *p;
-
-	p = calloc(1, sizeof(*p));
-
-	p->md5 = buffer_init();
-
-	return p;
-}
-
-/* detroy the plugin data */
-FREE_FUNC(mod_secdownload_free) {
-	plugin_data *p = p_d;
-	UNUSED(srv);
-
-	if (!p) return HANDLER_GO_ON;
-
-	if (p->config_storage) {
-		size_t i;
-		for (i = 0; i < srv->config_context->used; i++) {
-			plugin_config *s = p->config_storage[i];
-
-			if (NULL == s) continue;
-
-			buffer_free(s->secret);
-			buffer_free(s->doc_root);
-			buffer_free(s->uri_prefix);
-
-			free(s);
-		}
-		free(p->config_storage);
-	}
-
-	buffer_free(p->md5);
-
-	free(p);
-
-	return HANDLER_GO_ON;
-}
-
-/* handle plugin config and check values */
-
-SETDEFAULTS_FUNC(mod_secdownload_set_defaults) {
-	plugin_data *p = p_d;
-	size_t i = 0;
-
-	config_values_t cv[] = {
-		{ "secdownload.secret",            NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION },       /* 0 */
-		{ "secdownload.document-root",     NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION },       /* 1 */
-		{ "secdownload.uri-prefix",        NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION },       /* 2 */
-		{ "secdownload.timeout",           NULL, T_CONFIG_INT, T_CONFIG_SCOPE_CONNECTION },        /* 3 */
-		{ NULL,                            NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET }
-	};
-
-	if (!p) return HANDLER_ERROR;
-
-	p->config_storage = calloc(1, srv->config_context->used * sizeof(plugin_config *));
-
-	for (i = 0; i < srv->config_context->used; i++) {
-		data_config const* config = (data_config const*)srv->config_context->data[i];
-		plugin_config *s;
-
-		s = calloc(1, sizeof(plugin_config));
-		s->secret        = buffer_init();
-		s->doc_root      = buffer_init();
-		s->uri_prefix    = buffer_init();
-		s->timeout       = 60;
-
-		cv[0].destination = s->secret;
-		cv[1].destination = s->doc_root;
-		cv[2].destination = s->uri_prefix;
-		cv[3].destination = &(s->timeout);
-
-		p->config_storage[i] = s;
-
-		if (0 != config_insert_values_global(srv, config->value, cv, i == 0 ? T_CONFIG_SCOPE_SERVER : T_CONFIG_SCOPE_CONNECTION)) {
-			return HANDLER_ERROR;
-		}
-	}
-
-	return HANDLER_GO_ON;
-}
-
-/**
- * checks if the supplied string is a MD5 string
- *
- * @param str a possible MD5 string
- * @return if the supplied string is a valid MD5 string 1 is returned otherwise 0
- */
-
-static int is_hex_len(const char *str, size_t len) {
-	size_t i;
-
-	if (NULL == str) return 0;
-
-	for (i = 0; i < len && *str; i++, str++) {
-		/* illegal characters */
-		if (!((*str >= '0' && *str <= '9') ||
-		      (*str >= 'a' && *str <= 'f') ||
-		      (*str >= 'A' && *str <= 'F'))
-		    ) {
-			return 0;
-		}
-	}
-
-	return i == len;
-}
-
-#define PATCH(x) \
-	p->conf.x = s->x;
-static int mod_secdownload_patch_connection(server *srv, connection *con, plugin_data *p) {
-	size_t i, j;
-	plugin_config *s = p->config_storage[0];
-
-	PATCH(secret);
-	PATCH(doc_root);
-	PATCH(uri_prefix);
-	PATCH(timeout);
-
-	/* skip the first, the global context */
-	for (i = 1; i < srv->config_context->used; i++) {
-		data_config *dc = (data_config *)srv->config_context->data[i];
-		s = p->config_storage[i];
-
-		/* condition didn't match */
-		if (!config_check_cond(srv, con, dc)) continue;
-
-		/* merge config */
-		for (j = 0; j < dc->value->used; j++) {
-			data_unset *du = dc->value->data[j];
-
-			if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.secret"))) {
-				PATCH(secret);
-			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.document-root"))) {
-				PATCH(doc_root);
-			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.uri-prefix"))) {
-				PATCH(uri_prefix);
-			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("secdownload.timeout"))) {
-				PATCH(timeout);
-			}
-		}
-	}
-
-	return 0;
-}
-#undef PATCH
-
-
-URIHANDLER_FUNC(mod_secdownload_uri_handler) {
-	plugin_data *p = p_d;
-	li_MD5_CTX Md5Ctx;
-	HASH HA1;
-	const char *rel_uri, *ts_str, *md5_str;
-	time_t ts = 0;
-	size_t i;
-
-	if (con->mode != DIRECT) return HANDLER_GO_ON;
-
-	if (buffer_is_empty(con->uri.path)) return HANDLER_GO_ON;
-
-	mod_secdownload_patch_connection(srv, con, p);
-
-	if (buffer_is_empty(p->conf.uri_prefix)) return HANDLER_GO_ON;
-
-	if (buffer_string_is_empty(p->conf.secret)) {
-		log_error_write(srv, __FILE__, __LINE__, "s",
-				"secdownload.secret has to be set");
-		return HANDLER_ERROR;
-	}
-
-	if (buffer_string_is_empty(p->conf.doc_root)) {
-		log_error_write(srv, __FILE__, __LINE__, "s",
-				"secdownload.document-root has to be set");
-		return HANDLER_ERROR;
-	}
-
-	/*
-	 *  /<uri-prefix>[a-f0-9]{32}/[a-f0-9]{8}/<rel-path>
-	 */
-
-	if (0 != strncmp(con->uri.path->ptr, p->conf.uri_prefix->ptr, buffer_string_length(p->conf.uri_prefix))) return HANDLER_GO_ON;
-
-	md5_str = con->uri.path->ptr + buffer_string_length(p->conf.uri_prefix);
-
-	if (!is_hex_len(md5_str, 32)) return HANDLER_GO_ON;
-	if (*(md5_str + 32) != '/') return HANDLER_GO_ON;
-
-	ts_str = md5_str + 32 + 1;
-
-	if (!is_hex_len(ts_str, 8)) return HANDLER_GO_ON;
-	if (*(ts_str + 8) != '/') return HANDLER_GO_ON;
-
-	for (i = 0; i < 8; i++) {
-		ts = (ts << 4) + hex2int(ts_str[i]);
-	}
-
-	/* timed-out */
-	if ( (srv->cur_ts > ts && (unsigned int) (srv->cur_ts - ts) > p->conf.timeout) ||
-	     (srv->cur_ts < ts && (unsigned int) (ts - srv->cur_ts) > p->conf.timeout) ) {
-		/* "Gone" as the url will never be valid again instead of "408 - Timeout" where the request may be repeated */
-		con->http_status = 410;
-
-		return HANDLER_FINISHED;
-	}
-
-	rel_uri = ts_str + 8;
-
-	/* checking MD5
-	 *
-	 * <secret><rel-path><timestamp-hex>
-	 */
-
-	buffer_copy_buffer(p->md5, p->conf.secret);
-	buffer_append_string(p->md5, rel_uri);
-	buffer_append_string_len(p->md5, ts_str, 8);
-
-	li_MD5_Init(&Md5Ctx);
-	li_MD5_Update(&Md5Ctx, CONST_BUF_LEN(p->md5));
-	li_MD5_Final(HA1, &Md5Ctx);
-
-	buffer_copy_string_hex(p->md5, (char *)HA1, 16);
-
-	if (!const_time_memeq(md5_str, p->md5->ptr, 32)) {
-		con->http_status = 403;
-
-		log_error_write(srv, __FILE__, __LINE__, "sss",
-				"md5 invalid:",
-				md5_str, p->md5->ptr);
-
-		return HANDLER_FINISHED;
-	}
-
-	/* starting with the last / we should have relative-path to the docroot
-	 */
-
-	buffer_copy_buffer(con->physical.doc_root, p->conf.doc_root);
-	buffer_copy_buffer(con->physical.basedir, p->conf.doc_root);
-	buffer_copy_string(con->physical.rel_path, rel_uri);
-	buffer_copy_buffer(con->physical.path, con->physical.doc_root);
-	buffer_append_string_buffer(con->physical.path, con->physical.rel_path);
-
-	return HANDLER_GO_ON;
-}
-
-/* this function is called at dlopen() time and inits the callbacks */
-
-int mod_secdownload_plugin_init(plugin *p);
-int mod_secdownload_plugin_init(plugin *p) {
-	p->version     = LIGHTTPD_VERSION_ID;
-	p->name        = buffer_init_string("secdownload");
-
-	p->init        = mod_secdownload_init;
-	p->handle_physical  = mod_secdownload_uri_handler;
-	p->set_defaults  = mod_secdownload_set_defaults;
-	p->cleanup     = mod_secdownload_free;
-
-	p->data        = NULL;
-
-	return 0;
-}
diff --git a/src/mod_userdir.c b/src/mod_userdir.c
index d2193d99..da2912d4 100644
--- a/src/mod_userdir.c
+++ b/src/mod_userdir.c
@@ -303,7 +303,7 @@ URIHANDLER_FUNC(mod_userdir_docroot_handler) {
 	 * for trailing '.', ' ' and '/' on windows
 	 * we assume that no docroot/physical handler changed this
 	 * (docroot should only set the docroot/server name, phyiscal should only change the phyiscal.path;
-	 *  the exception mod_secure_download doesn't work with userdir anyway)
+	 *  the exception mod_secdownload doesn't work with userdir anyway)
 	 */
 	buffer_append_slash(p->temp_path);
 	/* if no second '/' is found, we assume that it was stripped from the uri.path for the special handling
diff --git a/tests/lighttpd.conf b/tests/lighttpd.conf
index 83eee0e5..1893c5d4 100644
--- a/tests/lighttpd.conf
+++ b/tests/lighttpd.conf
@@ -170,6 +170,25 @@ $HTTP["host"] == "vvv.example.org" {
 	secdownload.document-root   = env.SRCDIR + "/tmp/lighttpd/servers/www.example.org/pages/"
 	secdownload.uri-prefix      = "/sec/"
 	secdownload.timeout         = 120
+	secdownload.algorithm       = "md5"
+}
+
+$HTTP["host"] == "vvv-sha1.example.org" {
+	server.document-root = env.SRCDIR + "/tmp/lighttpd/servers/www.example.org/pages/"
+	secdownload.secret          = "verysecret"
+	secdownload.document-root   = env.SRCDIR + "/tmp/lighttpd/servers/www.example.org/pages/"
+	secdownload.uri-prefix      = "/sec/"
+	secdownload.timeout         = 120
+	secdownload.algorithm       = "hmac-sha1"
+}
+
+$HTTP["host"] == "vvv-sha256.example.org" {
+	server.document-root = env.SRCDIR + "/tmp/lighttpd/servers/www.example.org/pages/"
+	secdownload.secret          = "verysecret"
+	secdownload.document-root   = env.SRCDIR + "/tmp/lighttpd/servers/www.example.org/pages/"
+	secdownload.uri-prefix      = "/sec/"
+	secdownload.timeout         = 120
+	secdownload.algorithm       = "hmac-sha256"
 }
 
 $HTTP["host"] == "zzz.example.org" {
diff --git a/tests/mod-secdownload.t b/tests/mod-secdownload.t
index c8cad385..96baf9d7 100755
--- a/tests/mod-secdownload.t
+++ b/tests/mod-secdownload.t
@@ -8,9 +8,11 @@ BEGIN {
 
 use strict;
 use IO::Socket;
-use Test::More tests => 7;
+use Test::More tests => 15;
 use LightyTest;
 use Digest::MD5 qw(md5_hex);
+use Digest::SHA qw(hmac_sha1 hmac_sha256);
+use MIME::Base64 qw(encode_base64url);
 
 my $tf = LightyTest->new();
 my $t;
@@ -18,9 +20,21 @@ my $t;
 ok($tf->start_proc == 0, "Starting lighttpd") or die();
 
 my $secret = "verysecret";
-my $f = "/index.html";
-my $thex = sprintf("%08x", time);
-my $m = md5_hex($secret.$f.$thex);
+my ($f, $thex, $m);
+
+$t->{REQUEST}  = ( <<EOF
+GET /index.html HTTP/1.0
+Host: www.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 200 } ];
+
+ok($tf->handle_http($t) == 0, 'skipping secdownload - direct access');
+
+## MD5
+$f = "/index.html";
+$thex = sprintf("%08x", time);
+$m = md5_hex($secret.$f.$thex);
 
 $t->{REQUEST}  = ( <<EOF
 GET /sec/$m/$thex$f HTTP/1.0
@@ -29,7 +43,7 @@ EOF
  );
 $t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 200 } ];
 
-ok($tf->handle_http($t) == 0, 'secdownload');
+ok($tf->handle_http($t) == 0, 'secdownload (md5)');
 
 $thex = sprintf("%08x", time - 1800);
 $m = md5_hex($secret.$f.$thex);
@@ -41,7 +55,7 @@ EOF
  );
 $t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 410 } ];
 
-ok($tf->handle_http($t) == 0, 'secdownload - gone (timeout)');
+ok($tf->handle_http($t) == 0, 'secdownload - gone (timeout) (md5)');
 
 $t->{REQUEST}  = ( <<EOF
 GET /sec$f HTTP/1.0
@@ -50,30 +64,120 @@ EOF
  );
 $t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
 
-ok($tf->handle_http($t) == 0, 'secdownload - direct access');
+ok($tf->handle_http($t) == 0, 'secdownload - direct access (md5)');
+
+$f = "/noexists";
+$thex = sprintf("%08x", time);
+$m = md5_hex($secret.$f.$thex);
 
 $t->{REQUEST}  = ( <<EOF
-GET $f HTTP/1.0
-Host: www.example.org
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - timeout (md5)');
+
+## HMAC-SHA1
+$f = "/index.html";
+$thex = sprintf("%08x", time);
+$m = encode_base64url(hmac_sha1("/$thex$f", $secret));
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv-sha1.example.org
 EOF
  );
 $t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 200 } ];
 
-ok($tf->handle_http($t) == 0, 'secdownload - conditional access');
+ok($tf->handle_http($t) == 0, 'secdownload (hmac-sha1)');
+
+$thex = sprintf("%08x", time - 1800);
+$m = encode_base64url(hmac_sha1("/$thex$f", $secret));
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv-sha1.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 410 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - gone (timeout) (hmac-sha1)');
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec$f HTTP/1.0
+Host: vvv-sha1.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - direct access (hmac-sha1)');
 
 
 $f = "/noexists";
 $thex = sprintf("%08x", time);
-$m = md5_hex($secret.$f.$thex);
+$m = encode_base64url(hmac_sha1("/$thex$f", $secret));
 
 $t->{REQUEST}  = ( <<EOF
 GET /sec/$m/$thex$f HTTP/1.0
-Host: vvv.example.org
+Host: vvv-sha1.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - timeout (hmac-sha1)');
+
+## HMAC-SHA256
+$f = "/index.html";
+$thex = sprintf("%08x", time);
+$m = encode_base64url(hmac_sha256("/$thex$f", $secret));
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv-sha256.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 200 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload (hmac-sha256)');
+
+$thex = sprintf("%08x", time - 1800);
+$m = encode_base64url(hmac_sha256("/$thex$f", $secret));
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv-sha256.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 410 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - gone (timeout) (hmac-sha256)');
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec$f HTTP/1.0
+Host: vvv-sha256.example.org
+EOF
+ );
+$t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
+
+ok($tf->handle_http($t) == 0, 'secdownload - direct access (hmac-sha256)');
+
+
+$f = "/noexists";
+$thex = sprintf("%08x", time);
+$m = encode_base64url(hmac_sha256("/$thex$f", $secret));
+
+$t->{REQUEST}  = ( <<EOF
+GET /sec/$m/$thex$f HTTP/1.0
+Host: vvv-sha256.example.org
 EOF
  );
 $t->{RESPONSE} = [ { 'HTTP-Protocol' => 'HTTP/1.0', 'HTTP-Status' => 404 } ];
 
-ok($tf->handle_http($t) == 0, 'secdownload - timeout');
+ok($tf->handle_http($t) == 0, 'secdownload - timeout (hmac-sha256)');
+
+## THE END
 
 ok($tf->stop_proc == 0, "Stopping lighttpd");