From 8127f4db30799d96b786509b74f49db4768cf6f1 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 5 May 2014 12:13:33 -0400
Subject: [PATCH 1/3] Use siphash on channel/circuit-id map too

Fixes ticket 11750.
---
 changes/bug11750     | 5 +++++
 src/or/circuitlist.c | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 changes/bug11750

diff --git a/changes/bug11750 b/changes/bug11750
new file mode 100644
index 0000000000..f779ac8fe0
--- /dev/null
+++ b/changes/bug11750
@@ -0,0 +1,5 @@
+  o Minor features (security):
+    - Apply the secure SipHash-2-4 function to the hash table mapping
+      circuit IDs and channels to circuits. We missed this one when we
+      were converting all the other hash functions to use SipHash back
+      in 0.2.5.3-alpha. Resolves ticket 11750.
diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c
index 90fc93f3a8..58fb22d8ce 100644
--- a/src/or/circuitlist.c
+++ b/src/or/circuitlist.c
@@ -76,7 +76,14 @@ chan_circid_entries_eq_(chan_circid_circuit_map_t *a,
 static INLINE unsigned int
 chan_circid_entry_hash_(chan_circid_circuit_map_t *a)
 {
-  return ((unsigned)a->circ_id) ^ (unsigned)(uintptr_t)(a->chan);
+  struct {
+    void *chan;
+    circid_t circid;
+  } s;
+  memset(&s, 0, sizeof(s));
+  s.chan = a->chan;
+  s.circid = a->circ_id;
+  return (unsigned) siphash24g(&s, sizeof(s));
 }
 
 /** Map from [chan,circid] to circuit. */

From 0ad607d6042e59e8d63a32ddd98a6673ed5f79db Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Tue, 6 May 2014 12:27:18 -0400
Subject: [PATCH 2/3] Faster chan_circid_entry_hash implementation

Since this is critical-path, let's tune the value we pass to
csiphash a little so it fits into one whole round.
---
 src/or/circuitlist.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c
index 58fb22d8ce..e5ed9c04fd 100644
--- a/src/or/circuitlist.c
+++ b/src/or/circuitlist.c
@@ -76,14 +76,15 @@ chan_circid_entries_eq_(chan_circid_circuit_map_t *a,
 static INLINE unsigned int
 chan_circid_entry_hash_(chan_circid_circuit_map_t *a)
 {
-  struct {
-    void *chan;
-    circid_t circid;
-  } s;
-  memset(&s, 0, sizeof(s));
-  s.chan = a->chan;
-  s.circid = a->circ_id;
-  return (unsigned) siphash24g(&s, sizeof(s));
+  /* Try to squeze the siphash input into 8 bytes to save any extra siphash
+   * rounds.  This hash function is in the critical path. */
+  uintptr_t chan = (uintptr_t) (void*) a->chan;
+  uint32_t array[2];
+  array[0] = a->circ_id;
+  /* The low bits of the channel pointer are uninteresting, since the channel
+   * is a pretty big structure. */
+  array[1] = (uint32_t) (chan >> 6);
+  return (unsigned) siphash24g(array, sizeof(array));
 }
 
 /** Map from [chan,circid] to circuit. */

From e9c1c3ff7f3123495493bad7aa77ef6194005c75 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Tue, 6 May 2014 12:55:39 -0400
Subject: [PATCH 3/3] Add a siphash benchmark.

---
 src/test/bench.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/test/bench.c b/src/test/bench.c
index c9cc101b72..a3fa7fe319 100644
--- a/src/test/bench.c
+++ b/src/test/bench.c
@@ -337,6 +337,30 @@ bench_dmap(void)
   smartlist_free(sl2);
 }
 
+static void
+bench_siphash(void)
+{
+  char buf[128];
+  int lens[] = { 7, 8, 15, 16, 20, 32, 111, 128, -1 };
+  int i, j;
+  uint64_t total;
+  uint64_t start, end;
+  const int N = 300000;
+  crypto_rand(buf, sizeof(buf));
+
+  for (i = 0; lens[i] > 0; ++i) {
+    total = 0;
+    reset_perftime();
+    start = perftime();
+    for (j = 0; j < N; ++j) {
+      total += siphash24g(buf, lens[i]);
+    }
+    end = perftime();
+    printf("siphash24g(%d): %.2f ns per call\n",
+           lens[i], NANOCOUNT(start,end,N));
+  }
+}
+
 static void
 bench_cell_ops(void)
 {
@@ -487,6 +511,7 @@ typedef struct benchmark_t {
 
 static struct benchmark_t benchmarks[] = {
   ENT(dmap),
+  ENT(siphash),
   ENT(aes),
   ENT(onion_TAP),
 #ifdef CURVE25519_ENABLED