From 62d2ae721c68e95e13f56e98fae9b801b2584366 Mon Sep 17 00:00:00 2001
From: xnumad <34810600+xnumad@users.noreply.github.com>
Date: Thu, 8 Feb 2024 12:16:53 +0100
Subject: [PATCH] IDGEN

---
 .../gnrc/network_layer/ipv6/nib/_nib-slaac.c  | 57 +++++++++++++++++++
 .../gnrc/network_layer/ipv6/nib/_nib-slaac.h  | 15 +++++
 2 files changed, 72 insertions(+)

diff --git a/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c b/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c
index c3c53f3e0c227..3bafee297d69e 100644
--- a/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c
+++ b/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c
@@ -109,6 +109,63 @@ bool _iid_is_iana_reserved(const eui64_t *iid)
            || (iid->uint32[0].u32 == htonl(0x02005eff) && iid->uint8[4] == 0xfe)
            || (iid->uint32[0].u32 == htonl(0xfdffffff) && iid->uint16[2].u16 == htons(0xffff) && iid->uint8[6] == 0xff && (iid->uint8[7] & 0x80));
 }
+
+uint8_t _ipv6_get_rfc7217_iid(eui64_t *iid, const gnrc_netif_t *netif, const ipv6_addr_t *pfx,
+                              const uint8_t dad_ctr)
+{
+#ifndef STABLE_PRIVACY_SECRET_KEY
+#error "Stable privacy requires a secret_key, this should have been configured by sys/net/gnrc/Makefile.dep"
+#endif
+    const uint8_t secret_key[16] = { STABLE_PRIVACY_SECRET_KEY };
+    //SHOULD be of at least 128 bits - https://datatracker.ietf.org/doc/html/rfc7217
+
+    uint8_t digest[SHA256_DIGEST_LENGTH];
+
+    {
+        sha256_context_t c;
+        sha256_init(&c);
+        sha256_update(&c, pfx, sizeof(*pfx));
+
+#if GNRC_NETIF_L2ADDR_MAXLEN > 0
+        if (netif->flags & GNRC_NETIF_FLAGS_HAS_L2ADDR) {
+            sha256_update(&c, &netif->l2addr, netif->l2addr_len);
+        } else
+#endif
+            sha256_update(&c, &netif->pid, sizeof(netif->pid));
+
+        sha256_update(&c, &dad_ctr, sizeof(dad_ctr));
+        sha256_update(&c, secret_key, sizeof(secret_key));
+        sha256_final(&c, digest);
+    }
+
+    assert(iid->uint64.u64 == 0);
+    assert(sizeof(digest) >= sizeof(*iid)); //as bits: 256 >= 64 //digest is large enough
+
+    //copy digest into IID
+    //RFC 7217 says "starting from the least significant bit",
+    //i.e. in reverse order
+    for (uint8_t i = 0; i < sizeof(*iid); i++) { //for each of the 8 bytes
+        for (int j = 0; j < 8; j++) { //for each of the 8 bits _within byte_
+            if ((digest[(sizeof(digest)-1)-i])&(1<<j)) { //is 1 //reverse order
+                iid->uint8[i] |= 1 << ((8-1)-j); //set 1 //precondition: *iid = 0
+            }
+        }
+    }
+
+    /* "The resulting Interface Identifier SHOULD be compared against
+     * the reserved IPv6 Interface Identifiers"
+     * - https://datatracker.ietf.org/doc/html/rfc7217#section-5 */
+    if (_iid_is_iana_reserved(iid)) {
+        if (!stable_privacy_should_retry_idgen(&dad_ctr,
+                                               "IANA reserved IID generated")) {
+            return -1;
+        }
+        (iid)->uint64.u64 = 0; //gnrc_netif_ipv6_get_iid @pre
+        return _ipv6_get_rfc7217_iid(iid, netif, pfx, dad_ctr);
+    }
+
+    return dad_ctr;
+}
 #endif
 
 #if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC)
diff --git a/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.h b/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.h
index a305e76fd855e..44a4fd998e8f6 100644
--- a/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.h
+++ b/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.h
@@ -103,6 +103,21 @@ void _auto_configure_addr(gnrc_netif_t *netif, const ipv6_addr_t *pfx,
  * @return whether the IID is IANA reserved
  */
 bool _iid_is_iana_reserved(const eui64_t *iid);
+
+/**
+ * @brief
+ * @pre @p iid is all 0 bits (iid->uint64.u64 == 0)
+ * @param[out] iid
+ * @param[in] netif The network interface to use as source for IID generation.
+ * ("Net_iface" in rfc7217)
+ * @param[in] pfx The prefix for which the IID is to be generated.
+ * ("Prefix" in rfc7217)
+ * @param[in] dad_ctr ("DAD_Counter" in rfc7217)
+ * @return new value of DAD_Counter, to be stored associated with the address
+ * @return -1 if failed, because retry limit reached
+ */
+uint8_t _ipv6_get_rfc7217_iid(eui64_t *iid, const gnrc_netif_t *netif, const ipv6_addr_t *pfx,
+                              uint8_t dad_ctr);
 #endif
 
 #if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC) || defined(DOXYGEN)