luci-base: further hash calculation signedness bugfixes

 - cbi.js: make sure to treat single bytes as signed char when
   handling end cases

 - template_lmo.c: make sure to treat single bytes as signed
   char when handling end cases, avoids hash miscalculations
   on ARM

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 17 insertions, 8 deletions

diff --git a/modules/luci-base/htdocs/luci-static/resources/cbi.js b/modules/luci-base/htdocs/luci-static/resources/cbi.js
index 0e95906812..1607b9af65 100644
--- a/modules/luci-base/htdocs/luci-static/resources/cbi.js
+++ b/modules/luci-base/htdocs/luci-static/resources/cbi.js
@@ -15,6 +15,15 @@ var cbi_d = [];
 var cbi_t = [];
 var cbi_strings = { path: {}, label: {} };
 
+function s8(bytes, off) {
+	var n = bytes[off];
+	return (n > 0x7F) ? (n - 256) >>> 0 : n;
+}
+
+function u16(bytes, off) {
+	return ((bytes[off + 1] << 8) + bytes[off]) >>> 0;
+}
+
 function sfh(s) {
 	if (s === null || s.length === 0)
 		return null;
@@ -48,8 +57,8 @@ function sfh(s) {
 	    off = 0, tmp;
 
 	while (len--) {
-		hash += ((bytes[off + 1] << 8) + bytes[off]) >>> 0;
-		tmp   = ((((bytes[off + 3] << 8) + bytes[off + 2]) << 11) ^ hash) >>> 0;
+		hash += u16(bytes, off);
+		tmp   = ((u16(bytes, off + 2) << 11) ^ hash) >>> 0;
 		hash  = ((hash << 16) ^ tmp) >>> 0;
 		hash += hash >>> 11;
 		off  += 4;
@@ -57,20 +66,20 @@ function sfh(s) {
 
 	switch ((bytes.length & 3) >>> 0) {
 	case 3:
-		hash += ((bytes[off + 1] << 8) + bytes[off]) >>> 0;
+		hash += u16(bytes, off);
 		hash  = (hash ^ (hash << 16)) >>> 0;
-		hash  = (hash ^ (bytes[off + 2] << 18)) >>> 0;
+		hash  = (hash ^ (s8(bytes, off + 2) << 18)) >>> 0;
 		hash += hash >>> 11;
 		break;
 
 	case 2:
-		hash += ((bytes[off + 1] << 8) + bytes[off]) >>> 0;
+		hash += u16(bytes, off);
 		hash  = (hash ^ (hash << 11)) >>> 0;
 		hash += hash >>> 17;
 		break;
 
 	case 1:
-		hash += bytes[off];
+		hash += s8(bytes, off);
 		hash  = (hash ^ (hash << 10)) >>> 0;
 		hash += hash >>> 1;
 		break;
diff --git a/modules/luci-base/src/template_lmo.c b/modules/luci-base/src/template_lmo.c
index cd4c609a74..f7a118c9bb 100644
--- a/modules/luci-base/src/template_lmo.c
+++ b/modules/luci-base/src/template_lmo.c
@@ -46,14 +46,14 @@ uint32_t sfh_hash(const char *data, int len)
 	switch (rem) {
 		case 3: hash += sfh_get16(data);
 			hash ^= hash << 16;
-			hash ^= data[sizeof(uint16_t)] << 18;
+			hash ^= (signed char)data[sizeof(uint16_t)] << 18;
 			hash += hash >> 11;
 			break;
 		case 2: hash += sfh_get16(data);
 			hash ^= hash << 11;
 			hash += hash >> 17;
 			break;
-		case 1: hash += *data;
+		case 1: hash += (signed char)*data;
 			hash ^= hash << 10;
 			hash += hash >> 1;
 	}