From 58f6eb7b8bbd6e22994f4b147b6c2fc9c7d1daa0 Mon Sep 17 00:00:00 2001
From: Daniel-Constantin Mierla <miconda@gmail.com>
Date: Mon, 7 Oct 2019 14:57:06 +0200
Subject: [PATCH] tls: add cryptorand (fortuna) engine for PRNG if libssl
 v1.1.0+

- set it to be the default PRNG with libssl v1.1.0+
---
 src/modules/tls/tls_mod.c  |  7 +++++--
 src/modules/tls/tls_rand.c | 42 ++++++++++++++++++++++++++++++++++++++
 src/modules/tls/tls_rand.h |  1 +
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/modules/tls/tls_mod.c b/src/modules/tls/tls_mod.c
index 75d8aa8fd20..424fad8a08c 100644
--- a/src/modules/tls/tls_mod.c
+++ b/src/modules/tls/tls_mod.c
@@ -453,6 +453,9 @@ int ksr_rand_engine_param(modparam_t type, void* val)
 	} else if(reng->len == 8 && strncasecmp(reng->s, "fastrand", 8) == 0) {
 		LM_DBG("setting fastrand random engine\n");
 		RAND_set_rand_method(RAND_ksr_fastrand_method());
+	} else if (reng->len == 10 && strncasecmp(reng->s, "cryptorand", 10) == 0) {
+		LM_DBG("setting cryptorand random engine\n");
+		RAND_set_rand_method(RAND_ksr_cryptorand_method());
 	}
 #endif
 	return 0;
@@ -563,8 +566,8 @@ int mod_register(char *path, int *dlflags, void *p1, void *p2)
 	register_tls_hooks(&tls_h);
 
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
-	LM_DBG("setting fastrand random engine\n");
-	RAND_set_rand_method(RAND_ksr_fastrand_method());
+	LM_DBG("setting cryptorand random engine\n");
+	RAND_set_rand_method(RAND_ksr_cryptorand_method());
 #endif
 
 	sr_kemi_modules_add(sr_kemi_tls_exports);
diff --git a/src/modules/tls/tls_rand.c b/src/modules/tls/tls_rand.c
index bc80f658c34..3cb2e8a7123 100644
--- a/src/modules/tls/tls_rand.c
+++ b/src/modules/tls/tls_rand.c
@@ -129,4 +129,46 @@ const RAND_METHOD *RAND_ksr_fastrand_method(void)
     return &_ksr_fastrand_method;
 }
 
+
+/*
+ * Implementation with Fortuna cryptographic PRNG.
+ * We are not strictly implementing the OpenSSL API here - we will
+ * not return an error if the PRNG has not been seeded with enough
+ * randomness to ensure an unpredictable byte sequence.
+ */
+static int ksr_cryptorand_bytes(unsigned char *outdata, int size)
+{
+	if (size < 0) {
+		return 0;
+	} else if (size == 0) {
+		return 1;
+	}
+
+	sr_get_pseudo_random_bytes(outdata, size);
+	return 1;
+}
+
+static int ksr_cryptorand_status(void)
+{
+    return 1;
+}
+
+/*
+ * We don't have a dedicated function for pseudo-random
+ * bytes, just use the secure version as well for it.
+ */
+const RAND_METHOD _ksr_cryptorand_method = {
+    NULL,
+    ksr_cryptorand_bytes,
+    NULL,
+    NULL,
+    ksr_cryptorand_bytes,
+    ksr_cryptorand_status
+};
+
+const RAND_METHOD *RAND_ksr_cryptorand_method(void)
+{
+    return &_ksr_cryptorand_method;
+}
+
 #endif /* OPENSSL_VERSION_NUMBER >= 0x10100000L */
diff --git a/src/modules/tls/tls_rand.h b/src/modules/tls/tls_rand.h
index d1a3f0d37f8..c73d36b8d94 100644
--- a/src/modules/tls/tls_rand.h
+++ b/src/modules/tls/tls_rand.h
@@ -27,6 +27,7 @@
 
 const RAND_METHOD *RAND_ksr_krand_method(void);
 const RAND_METHOD *RAND_ksr_fastrand_method(void);
+const RAND_METHOD *RAND_ksr_cryptorand_method(void);
 
 #endif /* OPENSSL_VERSION_NUMBER >= 0x10100000L */
 #endif