From f63695609c88a3f76129499bb49fb82e8155fb32 Mon Sep 17 00:00:00 2001
From: ellie timoney <ellie@fastmail.com>
Date: Wed, 19 May 2021 14:01:41 +1000
Subject: [PATCH] hash: use a seed when hashing

Part of CVE-2021-33582
---
 lib/hash.c | 9 ++++++---
 lib/hash.h | 5 +++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/lib/hash.c b/lib/hash.c
index cf85d9d2ca..1b025b21b5 100644
--- a/lib/hash.c
+++ b/lib/hash.c
@@ -48,6 +48,9 @@ hash_table *construct_hash_table(hash_table *table, size_t size, int use_mpool)
 	  fatal("construct_hash_table called without a size", EC_TEMPFAIL);
 
       table->size  = size;
+      do {
+        table->seed = rand();
+      } while (table->seed == 0);
 
       /* Allocate the table -- different for using memory pools and not */
       if(use_mpool) {
@@ -76,7 +79,7 @@ hash_table *construct_hash_table(hash_table *table, size_t size, int use_mpool)
 
 void *hash_insert(const char *key, void *data, hash_table *table)
 {
-      unsigned val = strhash(key) % table->size;
+      unsigned val = strhash_seeded(table->seed, key) % table->size;
       bucket *ptr, *newptr;
       bucket **prev;
 
@@ -163,7 +166,7 @@ void *hash_lookup(const char *key, hash_table *table)
       if (!table->size)
           return NULL;
 
-      val = strhash(key) % table->size;
+      val = strhash_seeded(table->seed, key) % table->size;
 
       if (!(table->table)[val])
             return NULL;
@@ -187,7 +190,7 @@ void *hash_lookup(const char *key, hash_table *table)
  * since it will leak memory until you get rid of the entire hash table */
 void *hash_del(char *key, hash_table *table)
 {
-      unsigned val = strhash(key) % table->size;
+      unsigned val = strhash_seeded(table->seed, key) % table->size;
       bucket *ptr, *last = NULL;
 
       if (!(table->table)[val])
diff --git a/lib/hash.h b/lib/hash.h
index 77d0dc8a33..c3bc1dc2f5 100644
--- a/lib/hash.h
+++ b/lib/hash.h
@@ -5,9 +5,13 @@
 #define HASH__H
 
 #include <stddef.h>           /* For size_t     */
+#include <stdint.h>
+
 #include "strhash.h"
 #include "mpool.h"
 
+#define HASH_TABLE_INITIALIZER {0, 0, NULL, NULL}
+
 /*
 ** A hash table consists of an array of these buckets.  Each bucket
 ** holds a copy of the key, a pointer to the data associated with the
@@ -32,6 +36,7 @@ typedef struct bucket {
 
 typedef struct hash_table {
     size_t size;
+    uint32_t seed;
     bucket **table;
     struct mpool *pool;
 } hash_table;