Packet Signing via XEdDSA (#10478)

* Test commit for XEdDSA support * Update to Crypto lib in Meshtatic org * Generate a new node identity on key generation (#7628) * Generate a new node identity on key generation * Fixes * Fixes * Fixes * Messed up * Fixes * Update src/modules/AdminModule.cpp Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update src/mesh/NodeDB.cpp Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Figured it out! * Cleanup * Update src/mesh/NodeDB.h Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update src/mesh/NodeDB.cpp Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update src/modules/AdminModule.cpp Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update crypto commit hash * Some fixes for xeddsa pr (#9610) * fix: add null check for getMeshNode() in NodeInfoModule getMeshNode() can return nullptr for unknown nodes. Dereferencing without a check crashes the firmware when receiving NodeInfo from a node not yet in the database. * fix: enforce XEdDSA signature verification and prevent stripping Previously, failed signature verification still allowed the packet through, making signatures purely cosmetic. Now: - Failed verification drops the packet (DECODE_FAILURE) - Successfully verified nodes get HAS_XEDDSA_SIGNED bitfield set - Unsigned packets from previously-signing nodes are rejected - Log levels reduced from WARN/ERROR to DEBUG/WARN as appropriate * fix: include packet metadata in XEdDSA signature The signature now covers [fromNode | packetId | portnum | payload] instead of just the payload bytes. This prevents: - Replay attacks (different packetId fails verification) - Reattribution (different fromNode fails verification) - Portnum redirection (different portnum fails verification) Also adds a key initialization check to xeddsa_sign (returns false if XEdDSA keys are all zeros) and checks the return value in the encode path. * fix: handle existing key pair in AdminModule security config When a user provides both a valid private key and public key via admin config, the crypto engine's DH private key and owner public key were never loaded. DMs and XEdDSA signing would silently break. Add an else branch to load both keys into the crypto engine. * perf: cache Ed25519 public key conversion in xeddsa_verify curve_to_ed_pub() performs field element parsing, inversion, and multiplication on every call. Since packets from the same node tend to arrive in bursts, a single-entry cache avoids repeating this expensive conversion for consecutive packets from one sender. * fix: skip identity cleanup when node number is unchanged createNewIdentity() was called on every generateCryptoKeyPair(), including normal boots where the same key is regenerated. This caused unnecessary NodeDB writes and old-node cleanup logic to run when the node number hadn't actually changed. Also fixes only zeroing byte[0] of the old node's public key instead of clearing the entire array. * fix: replace hardcoded 120 with derived XEDDSA_SIGNATURE_SIZE constant The payload size check for XEdDSA signing used a magic number (120). Replace with a derivation from DATA_PAYLOAD_LEN and XEDDSA_SIGNATURE_SIZE so the limit adjusts automatically if constants change. This also increases the max signable payload from 120 to 169 bytes, which is still safe since the actual encoded size is checked after pb_encode. * fix: add const qualifiers to XEdDSA verify and curve_to_ed_pub inputs pubKey, payload, and signature parameters in xeddsa_verify are input-only and should not be modified. Same for curve_pubkey in curve_to_ed_pub. * chore: remove commented-out old Crypto dependency in portduino.ini * Leave out the admin module change for now --------- Co-authored-by: Jonathan Bennett <jbennett@incomsystems.biz> * trunk * protobuf re-update * Protobufs * Merge resolution fix * Put XEDDSA on the right bit * NodeDB update to new nodeInfoLite accessors, etc * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Refine unsigned packet rejection logic in Router (#10534) * use hardware random to fill the first 32 signature bytes with entropy prior to signing. * Add XEdDSA packet-signing policy tests and update dependencies for macos * Minor fixes * integrate XEdDSA support and update dependencies across multiple modules --------- Co-authored-by: Ben Meadors <benmmeadors@gmail.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Wessel <github@weebl.me> Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: thebentern <9000580+thebentern@users.noreply.github.com>
2026-06-13 06:45:56 -05:00
parent 07a87a8254
commit 8267bb22bd
20 changed files with 852 additions and 64 deletions
@@ -12,10 +12,18 @@
 #include <Curve25519.h>
 #include <RNG.h>
 #include <SHA256.h>
-#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN)
-#if !defined(ARCH_STM32WL)
-#define CryptRNG RNG
+
+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+#include "XEdDSA.h"
+#include <Ed25519.h>
+
+#ifndef NUM_LIMBS_256BIT
+#define NUM_LIMBS_BITS(n) (((n) + sizeof(limb_t) * 8 - 1) / (8 * sizeof(limb_t)))
+#define NUM_LIMBS_256BIT NUM_LIMBS_BITS(256)
 #endif
+#endif
+
+#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN)

 /**
 * Create a public/private key pair with Curve25519.
@@ -46,6 +54,9 @@ void CryptoEngine::generateKeyPair(uint8_t *pubKey, uint8_t *privKey)
    Curve25519::dh1(public_key, private_key);
    memcpy(pubKey, public_key, sizeof(public_key));
    memcpy(privKey, private_key, sizeof(private_key));
+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+    XEdDSA::priv_curve_to_ed_keys(private_key, xeddsa_private_key, xeddsa_public_key);
+#endif
 }

 /**
@@ -65,6 +76,9 @@ bool CryptoEngine::regeneratePublicKey(uint8_t *pubKey, uint8_t *privKey)
        }
        memcpy(private_key, privKey, sizeof(private_key));
        memcpy(public_key, pubKey, sizeof(public_key));
+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+        XEdDSA::priv_curve_to_ed_keys(private_key, xeddsa_private_key, xeddsa_public_key);
+#endif
    } else {
        LOG_WARN("X25519 key generation failed due to blank private key");
        return false;
@@ -72,6 +86,97 @@ bool CryptoEngine::regeneratePublicKey(uint8_t *pubKey, uint8_t *privKey)
    return true;
 }

+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+/**
+ * Build a signing buffer that covers packet metadata and payload:
+ *   [fromNode(4) | packetId(4) | portnum(4) | payload(N)]
+ * This prevents replay, reattribution, and portnum redirection attacks.
+ */
+static size_t buildSigningBuffer(uint8_t *buf, size_t bufSize, uint32_t fromNode, uint32_t packetId, uint32_t portnum,
+                                 const uint8_t *payload, size_t payloadLen)
+{
+    const size_t headerLen = sizeof(uint32_t) * 3;
+    size_t totalLen = headerLen + payloadLen;
+    if (totalLen > bufSize)
+        return 0;
+    // May need endian conversion for oddball platforms.
+    memcpy(buf, &fromNode, sizeof(uint32_t));
+    memcpy(buf + sizeof(uint32_t), &packetId, sizeof(uint32_t));
+    memcpy(buf + sizeof(uint32_t) * 2, &portnum, sizeof(uint32_t));
+    memcpy(buf + headerLen, payload, payloadLen);
+    return totalLen;
+}
+
+bool CryptoEngine::xeddsa_sign(uint32_t fromNode, uint32_t packetId, uint32_t portnum, const uint8_t *payload, size_t payloadLen,
+                               uint8_t *signature)
+{
+    if (memfll(xeddsa_private_key, 0, sizeof(xeddsa_private_key)))
+        return false;
+    uint8_t sigBuf[MAX_BLOCKSIZE];
+    size_t sigLen = buildSigningBuffer(sigBuf, sizeof(sigBuf), fromNode, packetId, portnum, payload, payloadLen);
+    if (sigLen == 0)
+        return false;
+    // the XEdDSA::sign function requires at least the first 32 bytes of signature to be pre-filled with randomness
+    HardwareRNG::fill(signature, 32);
+    XEdDSA::sign(signature, xeddsa_private_key, xeddsa_public_key, sigBuf, sigLen);
+    return true;
+}
+
+bool CryptoEngine::xeddsa_verify(const uint8_t *pubKey, uint32_t fromNode, uint32_t packetId, uint32_t portnum,
+                                 const uint8_t *payload, size_t payloadLen, const uint8_t *signature)
+{
+    // Use cached Ed25519 key if the Curve25519 key matches, avoiding expensive field inversion
+    if (memcmp(pubKey, cached_curve_pubkey, 32) != 0) {
+        curve_to_ed_pub(pubKey, cached_ed_pubkey);
+        memcpy(cached_curve_pubkey, pubKey, 32);
+    }
+    uint8_t sigBuf[MAX_BLOCKSIZE];
+    size_t sigLen = buildSigningBuffer(sigBuf, sizeof(sigBuf), fromNode, packetId, portnum, payload, payloadLen);
+    if (sigLen == 0)
+        return false;
+    return XEdDSA::verify(signature, cached_ed_pubkey, sigBuf, sigLen);
+}
+
+void CryptoEngine::curve_to_ed_pub(const uint8_t *curve_pubkey, uint8_t *ed_pubkey)
+{
+
+    // Apply the birational map defined in RFC 7748, section 4.1 "Curve25519" to calculate an Ed25519 public
+    // key from a Curve25519 public key. Because the serialization format of Curve25519 public keys only
+    // contains the u coordinate, the x coordinate of the corresponding Ed25519 public key can't be uniquely
+    // calculated as defined by the birational map. The x coordinate is represented in the serialization
+    // format of Ed25519 public keys only in a single sign bit. XEdDSA always normalizes the Ed25519 public
+    // key to a sign bit of zero (the signer negates its key pair when needed), so this function clears the
+    // sign bit unconditionally below instead of taking it as an input.
+    fe u, y;
+    fe one;
+    fe u_minus_one, u_plus_one, u_plus_one_inv;
+
+    // Parse the Curve25519 public key input as a field element containing the u coordinate. RFC 7748,
+    // section 5 "The X25519 and X448 Functions", mandates that the most significant bit of the Curve25519
+    // public key has to be zeroized. This is handled by fe_frombytes internally.
+    fe_frombytes(u, curve_pubkey);
+
+    // Calculate the parameters (u - 1) and (u + 1)
+    fe_1(one);
+    fe_sub(u_minus_one, u, one);
+    fe_add(u_plus_one, u, one);
+
+    // Invert u + 1
+    fe_invert(u_plus_one_inv, u_plus_one);
+
+    // Calculate y = (u - 1) * inv(u + 1) (mod p)
+    fe_mul(y, u_minus_one, u_plus_one_inv);
+
+    // Serialize the field element containing the y coordinate to the Ed25519 public key output
+    fe_tobytes(ed_pubkey, y);
+
+    // Set the sign bit to zero
+    ed_pubkey[31] &= 0x7f;
+
+    // need to convert the pubkey y = ( u - 1) * inv( u + 1) (mod p).
+}
+#endif
+
 bool CryptoEngine::ensurePkiKeys(meshtastic_Config_SecurityConfig &security, meshtastic_User &user)
 {
    if (user.is_licensed) {
@@ -23,6 +23,7 @@ struct CryptoKey {

 #define MAX_BLOCKSIZE 256
 #define TEST_CURVE25519_FIELD_OPS // Exposes Curve25519::isWeakPoint() for testing keys
+#define XEDDSA_SIGNATURE_SIZE 64

 class CryptoEngine
 {
@@ -37,7 +38,12 @@ class CryptoEngine
    virtual void generateKeyPair(uint8_t *pubKey, uint8_t *privKey);
    virtual bool regeneratePublicKey(uint8_t *pubKey, uint8_t *privKey);
    virtual bool ensurePkiKeys(meshtastic_Config_SecurityConfig &security, meshtastic_User &user);
-
+#endif
+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+    bool xeddsa_sign(uint32_t fromNode, uint32_t packetId, uint32_t portnum, const uint8_t *payload, size_t payloadLen,
+                     uint8_t *signature);
+    bool xeddsa_verify(const uint8_t *pubKey, uint32_t fromNode, uint32_t packetId, uint32_t portnum, const uint8_t *payload,
+                       size_t payloadLen, const uint8_t *signature);
 #endif
    void setDHPrivateKey(uint8_t *_private_key);
    // The remotePublic key parameter takes the public_key bytes container from
@@ -85,6 +91,14 @@ class CryptoEngine
 #if !(MESHTASTIC_EXCLUDE_PKI)
    uint8_t shared_key[32] = {0};
    uint8_t private_key[32] = {0};
+#if !(MESHTASTIC_EXCLUDE_XEDDSA)
+    uint8_t xeddsa_public_key[32] = {0};
+    uint8_t xeddsa_private_key[32] = {0};
+    void curve_to_ed_pub(const uint8_t *curve_pubkey, uint8_t *ed_pubkey);
+    // Single-entry cache for curve_to_ed_pub conversion (avoids expensive field inversion per packet)
+    uint8_t cached_curve_pubkey[32] = {0};
+    uint8_t cached_ed_pubkey[32] = {0};
+#endif
 #endif
    /**
     * Init our 128 bit nonce for a new packet
@@ -448,8 +448,6 @@ NodeDB::NodeDB()

    // likewise - we always want the app requirements to come from the running appload
    myNodeInfo.min_app_version = 30200; // format is Mmmss (where M is 1+the numeric major number. i.e. 30200 means 2.2.00
-    // Note! We do this after loading saved settings, so that if somehow an invalid nodenum was stored in preferences we won't
-    // keep using that nodenum forever. Crummy guess at our nodenum (but we will check against the nodedb to avoid conflicts)
    pickNewNodeNum();

    // Set our board type so we can share it with others
@@ -469,31 +467,18 @@ NodeDB::NodeDB()
    }

 #if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN || MESHTASTIC_EXCLUDE_PKI)
-
-    if (!owner.is_licensed && config.lora.region != meshtastic_Config_LoRaConfig_RegionCode_UNSET) {
-        bool keygenSuccess = false;
-        keyIsLowEntropy = checkLowEntropyPublicKey(config.security.public_key);
-        if (config.security.private_key.size == 32 && !keyIsLowEntropy) {
-            if (crypto->regeneratePublicKey(config.security.public_key.bytes, config.security.private_key.bytes)) {
-                keygenSuccess = true;
-            }
-        } else {
-            crypto->generateKeyPair(config.security.public_key.bytes, config.security.private_key.bytes);
-            keygenSuccess = true;
-        }
-        if (keygenSuccess) {
-            config.security.public_key.size = 32;
-            config.security.private_key.size = 32;
-            owner.public_key.size = 32;
-            memcpy(owner.public_key.bytes, config.security.public_key.bytes, 32);
-        }
-    }
+    // Generate crypto keys if needed using consolidated function
+    // Set my node num uint32 value to bytes from the public key (if we have one)
+    // Generate identity and crypto keys if needed; this will create a new identity if one does not exist
+    generateCryptoKeyPair(nullptr);
 #elif !(MESHTASTIC_EXCLUDE_PKI)
    // Calculate Curve25519 public and private keys
    if (config.security.private_key.size == 32 && config.security.public_key.size == 32) {
        owner.public_key.size = config.security.public_key.size;
        memcpy(owner.public_key.bytes, config.security.public_key.bytes, config.security.public_key.size);
        crypto->setDHPrivateKey(config.security.private_key.bytes);
+        // Set my node num uint32 value to bytes from the new public key
+        myNodeInfo.my_node_num = crc32Buffer(config.security.public_key.bytes, config.security.public_key.size);
    }
 #endif
    // Include our owner in the node db under our nodenum
@@ -3059,6 +3044,99 @@ bool NodeDB::checkLowEntropyPublicKey(const meshtastic_Config_SecurityConfig_pub
 }
 #endif

+bool NodeDB::generateCryptoKeyPair(const uint8_t *privateKey)
+{
+#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN || MESHTASTIC_EXCLUDE_PKI)
+    // Only generate keys for non-licensed users and if LoRa region is set
+    if (owner.is_licensed || config.lora.region == meshtastic_Config_LoRaConfig_RegionCode_UNSET) {
+        return false;
+    }
+
+    bool keygenSuccess = false;
+    // Record whether the stored key is a known compromised/low-entropy key so main.cpp can warn the
+    // user. A detected low-entropy key is regenerated below, but the flag stays set so the
+    // "Compromised keys were detected and regenerated" notification still fires.
+    keyIsLowEntropy = checkLowEntropyPublicKey(config.security.public_key);
+
+    // If a specific private key was provided, use it
+    if (privateKey != nullptr) {
+        LOG_INFO("Using provided private key for PKI");
+        memcpy(config.security.private_key.bytes, privateKey, 32);
+        config.security.private_key.size = 32;
+        config.security.public_key.size = 32;
+
+        // Generate public key from the provided private key
+        if (crypto->regeneratePublicKey(config.security.public_key.bytes, config.security.private_key.bytes)) {
+            keygenSuccess = true;
+        } else {
+            LOG_ERROR("Failed to generate public key from provided private key");
+            return false;
+        }
+    }
+    // Try to regenerate public key from existing private key if it's valid and not low entropy
+    else if (config.security.private_key.size == 32 && !keyIsLowEntropy) {
+        config.security.public_key.size = 32;
+        LOG_DEBUG("Regenerate PKI public key from existing private key");
+        if (crypto->regeneratePublicKey(config.security.public_key.bytes, config.security.private_key.bytes)) {
+            keygenSuccess = true;
+        }
+    } else {
+        // Generate a new key pair
+        LOG_INFO("Generate new PKI keys");
+        config.security.public_key.size = 32;
+        config.security.private_key.size = 32;
+        crypto->generateKeyPair(config.security.public_key.bytes, config.security.private_key.bytes);
+        keygenSuccess = true;
+    }
+
+    // Update sizes and copy to owner if successful
+    if (keygenSuccess) {
+        owner.public_key.size = 32;
+        memcpy(owner.public_key.bytes, config.security.public_key.bytes, 32);
+
+        // Set the DH private key for crypto operations
+        LOG_DEBUG("Set DH private key for crypto operations");
+        crypto->setDHPrivateKey(config.security.private_key.bytes);
+
+        // Conditionally create new identity based on parameter
+        createNewIdentity();
+    }
+    return keygenSuccess;
+#else
+    return false;
+#endif
+}
+
+bool NodeDB::createNewIdentity()
+{
+    uint32_t oldNodeNum = getNodeNum();
+    uint32_t newNodeNum = crc32Buffer(config.security.public_key.bytes, config.security.public_key.size);
+
+    // If the key hasn't changed, nothing to do
+    if (newNodeNum == oldNodeNum)
+        return false;
+
+    // Retire the old node entry
+    meshtastic_NodeInfoLite *node = getMeshNode(oldNodeNum);
+    if (node != NULL) {
+        LOG_DEBUG("Old node num %u is now %u", oldNodeNum, newNodeNum);
+        nodeInfoLiteSetBit(node, NODEINFO_BITFIELD_IS_IGNORED_MASK, true);
+        node->public_key.size = 0;
+        memset(node->public_key.bytes, 0, sizeof(node->public_key.bytes));
+    }
+
+    // Drop satellite-store entries (position/telemetry/environment/status) keyed by the retired
+    // node number so stale data isn't left attached to the old identity.
+    eraseNodeSatellites(oldNodeNum);
+
+    myNodeInfo.my_node_num = newNodeNum;
+
+    meshtastic_NodeInfoLite *info = getOrCreateMeshNode(getNodeNum());
+    TypeConversions::CopyUserToNodeInfoLite(info, owner);
+
+    return true;
+}
+
 bool NodeDB::backupPreferences(meshtastic_AdminMessage_BackupLocation location)
 {
    bool success = false;
@@ -376,6 +376,12 @@ class NodeDB
    bool checkLowEntropyPublicKey(const meshtastic_Config_SecurityConfig_public_key_t &keyToTest);
 #endif

+    /// Consolidate crypto key generation logic used across multiple modules
+    /// @param privateKey Optional 32-byte private key to use. If nullptr, generates new random keys.
+    bool generateCryptoKeyPair(const uint8_t *privateKey = nullptr);
+
+    bool createNewIdentity();
+
    bool backupPreferences(meshtastic_AdminMessage_BackupLocation location);
    bool restorePreferences(meshtastic_AdminMessage_BackupLocation location,
                            int restoreWhat = SEGMENT_CONFIG | SEGMENT_MODULECONFIG | SEGMENT_DEVICESTATE | SEGMENT_CHANNELS);
@@ -519,7 +525,9 @@ extern uint32_t error_address;
 #define NODEINFO_BITFIELD_IS_UNMESSAGABLE_MASK (1u << NODEINFO_BITFIELD_IS_UNMESSAGABLE_SHIFT)
 #define NODEINFO_BITFIELD_HAS_IS_UNMESSAGABLE_SHIFT 8
 #define NODEINFO_BITFIELD_HAS_IS_UNMESSAGABLE_MASK (1u << NODEINFO_BITFIELD_HAS_IS_UNMESSAGABLE_SHIFT)
-// Bits 9..31 reserved for future single-bit flags.
+#define NODEINFO_BITFIELD_HAS_XEDDSA_SIGNED_SHIFT 9
+#define NODEINFO_BITFIELD_HAS_XEDDSA_SIGNED_MASK (1u << NODEINFO_BITFIELD_HAS_XEDDSA_SIGNED_SHIFT)
+// Bits 10..31 reserved for future single-bit flags.

 // Convenience accessors so call sites read like the old struct fields.
 inline bool nodeInfoLiteHasUser(const meshtastic_NodeInfoLite *n)
@@ -558,6 +566,10 @@ inline bool nodeInfoLiteIsKeyManuallyVerified(const meshtastic_NodeInfoLite *n)
 {
    return n && (n->bitfield & NODEINFO_BITFIELD_IS_KEY_MANUALLY_VERIFIED_MASK);
 }
+inline bool nodeInfoLiteHasXeddsaSigned(const meshtastic_NodeInfoLite *n)
+{
+    return n && (n->bitfield & NODEINFO_BITFIELD_HAS_XEDDSA_SIGNED_MASK);
+}

 inline void nodeInfoLiteSetBit(meshtastic_NodeInfoLite *n, uint32_t mask, bool value)
 {
@@ -559,6 +559,38 @@ DecodeState perhapsDecode(meshtastic_MeshPacket *p)
        if (p->decoded.has_bitfield)
            p->decoded.want_response |= p->decoded.bitfield & BITFIELD_WANT_RESPONSE_MASK;

+#if !(MESHTASTIC_EXCLUDE_PKI) && !(MESHTASTIC_EXCLUDE_XEDDSA)
+        if (p->decoded.xeddsa_signature.size == XEDDSA_SIGNATURE_SIZE) {
+            meshtastic_NodeInfoLite *node = nodeDB->getMeshNode(p->from);
+            if (node && node->public_key.size == 32) {
+                p->xeddsa_signed =
+                    crypto->xeddsa_verify(node->public_key.bytes, p->from, p->id, p->decoded.portnum, p->decoded.payload.bytes,
+                                          p->decoded.payload.size, p->decoded.xeddsa_signature.bytes);
+                if (p->xeddsa_signed) {
+                    // Mark this node as a signer so future unsigned packets from it are rejected
+                    nodeInfoLiteSetBit(node, NODEINFO_BITFIELD_HAS_XEDDSA_SIGNED_MASK, true);
+                    LOG_DEBUG("Verified XEdDSA signature from 0x%08x", p->from);
+                } else {
+                    LOG_WARN("XEdDSA signature verification failed from 0x%08x, dropping", p->from);
+                    return DecodeState::DECODE_FAILURE;
+                }
+            } else {
+                LOG_DEBUG("No public key for 0x%08x, cannot verify XEdDSA signature", p->from);
+            }
+        } else {
+            // Unsigned packet — only reject the class of packet a signing node always signs:
+            // an unencrypted broadcast small enough to also carry a signature (see perhapsEncode()).
+            // Unicast packets and oversized broadcasts are never signed, so they must not be
+            // hard-failed here even if this node has signed before.
+            const meshtastic_NodeInfoLite *node = nodeDB->getMeshNode(p->from);
+            if (node && nodeInfoLiteHasXeddsaSigned(node) && isBroadcast(p->to) &&
+                p->decoded.payload.size + XEDDSA_SIGNATURE_SIZE < meshtastic_Constants_DATA_PAYLOAD_LEN) {
+                LOG_WARN("Dropping unsigned broadcast from 0x%08x that previously signed", p->from);
+                return DecodeState::DECODE_FAILURE;
+            }
+        }
+#endif
+
        /* Not actually ever used.
        // Decompress if needed. jm
        if (p->decoded.portnum == meshtastic_PortNum_TEXT_MESSAGE_COMPRESSED_APP) {
@@ -629,6 +661,18 @@ meshtastic_Routing_Error perhapsEncode(meshtastic_MeshPacket *p)
            p->decoded.has_bitfield = true;
            p->decoded.bitfield |= (config.lora.config_ok_to_mqtt << BITFIELD_OK_TO_MQTT_SHIFT);
            p->decoded.bitfield |= (p->decoded.want_response << BITFIELD_WANT_RESPONSE_SHIFT);
+#if !(MESHTASTIC_EXCLUDE_PKI) && !(MESHTASTIC_EXCLUDE_XEDDSA)
+            // Sign broadcast packets if payload + signature fits within the max Data payload.
+            // The actual encoded size is checked after pb_encode (TOO_LARGE).
+            if (!p->pki_encrypted && isBroadcast(p->to) &&
+                p->decoded.payload.size + XEDDSA_SIGNATURE_SIZE < meshtastic_Constants_DATA_PAYLOAD_LEN) {
+                if (crypto->xeddsa_sign(p->from, p->id, p->decoded.portnum, p->decoded.payload.bytes, p->decoded.payload.size,
+                                        p->decoded.xeddsa_signature.bytes)) {
+                    p->decoded.xeddsa_signature.size = XEDDSA_SIGNATURE_SIZE;
+                    LOG_DEBUG("XEdDSA signed packet 0x%08x", p->id);
+                }
+            }
+#endif
        }

        size_t numbytes = pb_encode_to_bytes(bytes, sizeof(bytes), &meshtastic_Data_msg, &p->decoded);
@@ -18,6 +18,7 @@ meshtastic_NodeInfo TypeConversions::ConvertToNodeInfo(const meshtastic_NodeInfo
    info.is_ignored = nodeInfoLiteIsIgnored(lite);
    info.is_key_manually_verified = nodeInfoLiteIsKeyManuallyVerified(lite);
    info.is_muted = nodeInfoLiteIsMuted(lite);
+    info.has_xeddsa_signed = nodeInfoLiteHasXeddsaSigned(lite);

    if (lite->has_hops_away) {
        info.has_hops_away = true;