Use the HWRNG for generating DUIDs and IAIDs.

Before these were generated from a freshly seeded PRNG which reduces the
state space of possible DUIDs and skews the distribution of both DUIDs
and IAIDs as a function of the PRNG choice.

None of this really matters much in practice, but do things right.

duiaid.c

@@ -1,4 +1,4 @@
-// Copyright 2014-2018 Nicholas J. Kain <njkain at gmail dot com>
+// Copyright 2014-2022 Nicholas J. Kain <njkain at gmail dot com>
 // SPDX-License-Identifier: MIT
 #include <string.h>
 #include <stdlib.h>
@@ -11,7 +11,7 @@
 #include <limits.h>
 #include <errno.h>
 #include "nk/log.h"
-#include "nk/random.h"
+#include "nk/hwrng.h"
 #include "nk/io.h"
 #include "duiaid.h"
 #include "ndhc.h"
@@ -90,8 +90,7 @@ static int open_iaidfile_write(const uint8_t hwaddr[static 6],
 // RFC6355 specifies a RFC4122 UUID, but I simply use a 128-byte random
 // value, as the complexity of RFC4122 UUID generation is completely
 // unwarranted for DHCPv4.
-static size_t generate_duid(struct nk_random_state *s,
-                            char *dest, size_t dlen)
+static size_t generate_duid(char *dest, size_t dlen)
 {
     const size_t tlen = sizeof(uint16_t) + 4 * sizeof(uint32_t);
     if (dlen < tlen)
@@ -102,32 +101,27 @@ static size_t generate_duid(struct nk_random_state *s,
     memcpy(dest+off, &typefield, sizeof typefield);
     off += sizeof typefield;
 
-    for (size_t i = 0; i < 4; ++i) {
-        uint32_t r32 = nk_random_u32(s);
-        memcpy(dest+off, &r32, sizeof r32);
-        off += sizeof r32;
-    }
+    nk_hwrng_bytes(dest+off, sizeof(uint32_t) * 4);
+    off += sizeof(uint32_t) * 4;
+
     return off;
 }
 
 // RFC6355 specifies the IAID as a 32-bit value that uniquely identifies
 // a hardware link for a given host.
-static size_t generate_iaid(struct nk_random_state *s,
-                            char *dest, size_t dlen)
+static size_t generate_iaid(char *dest, size_t dlen)
 {
     if (dlen < sizeof(uint32_t))
         suicide("%s: dlen < %zu", __func__, sizeof(uint32_t));
     size_t off = 0;
 
-    uint32_t r32 = nk_random_u32(s);
-    memcpy(dest+off, &r32, sizeof r32);
-    off += sizeof r32;
+    nk_hwrng_bytes(dest+off, sizeof(uint32_t));
+    off += sizeof(uint32_t);
     return off;
 }
 
 // Failures are all fatal.
-void get_clientid(struct client_state_t *cs,
-                  struct client_config_t *cc)
+void get_clientid(struct client_config_t *cc)
 {
     if (cc->clientid_len > 0)
         return;
@@ -138,7 +132,7 @@ void get_clientid(struct client_state_t *cs,
 
     int fd = open_iaidfile_read(cc->arp, sizeof cc->arp);
     if (fd < 0) {
-        iaid_len = generate_iaid(&cs->rnd_state, iaid, sizeof iaid);
+        iaid_len = generate_iaid(iaid, sizeof iaid);
         fd = open_iaidfile_write(cc->arp, sizeof cc->arp);
         ssize_t r = safe_write(fd, iaid, iaid_len);
         if (r < 0 || (size_t)r != iaid_len)
@@ -155,7 +149,7 @@ void get_clientid(struct client_state_t *cs,
 
     fd = open_duidfile_read();
     if (fd < 0) {
-        duid_len = generate_duid(&cs->rnd_state, duid, sizeof duid);
+        duid_len = generate_duid(duid, sizeof duid);
         fd = open_duidfile_write();
         ssize_t r = safe_write(fd, duid, duid_len);
         if (r < 0 || (size_t)r != duid_len)

duiaid.h

@@ -1,11 +1,11 @@
-// Copyright 2014-2018 Nicholas J. Kain <njkain at gmail dot com>
+// Copyright 2014-2022 Nicholas J. Kain <njkain at gmail dot com>
 // SPDX-License-Identifier: MIT
 #ifndef NJK_NDHC_DUIAID_H_
 #define NJK_NDHC_DUIAID_H_
 
 #include "ndhc.h"
 
-void get_clientid(struct client_state_t *cs, struct client_config_t *cc);
+void get_clientid(struct client_config_t *cc);
 
 #endif
 

ndhc.c

@@ -567,7 +567,7 @@ int main(int argc, char *argv[])
     if (nl_getifdata() < 0)
         suicide("failed to get interface MAC or index");
 
-    get_clientid(&cs, &client_config);
+    get_clientid(&client_config);
 
     switch (perform_ifup()) {
     case 1: case 0: break;

nk/hwrng.c

@@ -95,7 +95,7 @@ static bool nk_get_urandom(char *seed, size_t len)
     return ret;
 }
 
-void nk_get_hwrng(void *seed, size_t len)
+void nk_hwrng_bytes(void *seed, size_t len)
 {
     char *s = (char *)seed;
     if (nk_getrandom(s, len))

nk/hwrng.h

@@ -1,11 +1,10 @@
-// Copyright 2016 Nicholas J. Kain <njkain at gmail dot com>
+// Copyright 2016-2022 Nicholas J. Kain <njkain at gmail dot com>
 // SPDX-License-Identifier: MIT
 #ifndef NCMLIB_HWCRNG__
 #define NCMLIB_HWCRNG__
 
 #include <stddef.h>
-
-void nk_get_hwrng(void *seed, size_t len);
+void nk_hwrng_bytes(void *seed, size_t len);
 
 #endif
 

nk/random.c

@@ -8,7 +8,7 @@
 
 void nk_random_init(struct nk_random_state *s)
 {
-    nk_get_hwrng(s->seed, sizeof(uint64_t) * 2);
+    nk_hwrng_bytes(s->seed, sizeof(uint64_t) * 2);
     s->seed[2] = 2000001;
     s->seed[3] = 0;
     for (size_t i = 0; i < 14; ++i) nk_random_u64(s);