src/hash.c: Add thread safe initialization of SipHash seed

2 files changed, 112 insertions, 0 deletions

diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..4b397bd
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,104 @@
+#include "config.h"
+
+#include <assert.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <siphashbs.h>
+
+#include "hash.h"
+#include "logerr.h"
+#include "random.h"
+
+
+
+static volatile bool
+INITIALIZED = false;
+
+static uint8_t
+SIPHASH_KEY[SIPHASH_KEY_LENGTH];
+
+static pthread_mutex_t
+SEED_MUTEX = PTHREAD_MUTEX_INITIALIZER;
+
+
+
+static int
+unsafe_init(void) {
+	int rc = -1;
+
+	if (urandom_bytes(SIPHASH_KEY_LENGTH, &SIPHASH_KEY)) {
+		logerr("urandom_bytes()");
+		goto out;
+	}
+
+	rc = 0;
+out:
+	return rc;
+}
+
+static int
+safe_init(void) {
+	int rc = -1;
+
+	bool lock_acquired = false;
+
+	if (INITIALIZED == true) {
+		rc = 0;
+		goto out;
+	}
+
+	const int ret1 = pthread_mutex_lock(&SEED_MUTEX);
+	if (ret1) {
+		logerr("pthread_mutex_lock(): %s", strerror(ret1));
+		goto out;
+	}
+	lock_acquired = true;
+
+	if (INITIALIZED == true) {
+		rc = 0;
+		goto out;
+	}
+
+	if (unsafe_init()) {
+		logerr("unsafe_init()");
+		goto out;
+	}
+
+	INITIALIZED = true;
+
+	rc = 0;
+out:
+	if (lock_acquired) {
+		const int ret2 = pthread_mutex_unlock(&SEED_MUTEX);
+		if (ret2) {
+			logerr("pthread_mutex_unlock(): %s", strerror(ret2));
+			rc = -1;
+		}
+	}
+	return rc;
+}
+
+static void
+ensure_initialized(void) {
+	assert((safe_init() == 0) && "Failed to initialized the hash seed");
+}
+
+int
+hash_init(void) {
+	return safe_init();
+}
+
+void
+hash(
+	const size_t inlen,
+	const void *const restrict in,
+	uint8_t out[HASH_OUTPUT_LENGTH]
+) {
+	ensure_initialized();
+	siphashbs(SIPHASH_KEY, inlen, in, out);
+}
diff --git a/src/hash.h b/src/hash.h
new file mode 100644
index 0000000..4831c4b
--- /dev/null
+++ b/src/hash.h
@@ -0,0 +1,8 @@
+#define HASH_OUTPUT_LENGTH 16U
+
+void
+hash(
+	const size_t inlen,
+	const void *const restrict in,
+	uint8_t out[HASH_OUTPUT_LENGTH]
+);