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Just a bit of security hygiene. (#4313)

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* Make sure to call randomSeed() on esp32

* Randomize the top 22 bits of the Message ID

* Make it clear that we are not calling randomSeed() on purpose

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
This commit is contained in:
Jonathan Bennett
2024-07-23 11:52:14 -05:00
committed by GitHub
parent e27375d331
commit 300c3d32aa
2 changed files with 12 additions and 7 deletions
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15
src/mesh/Router.cpp
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@@ -92,22 +92,23 @@ void Router::enqueueReceivedMessage(meshtastic_MeshPacket *p)
// FIXME, move this someplace better
PacketId generatePacketId()
{
static uint32_t i; // Note: trying to keep this in noinit didn't help for working across reboots
static uint32_t rollingPacketId; // Note: trying to keep this in noinit didn't help for working across reboots
static bool didInit = false;
uint32_t numPacketId = UINT32_MAX;
if (!didInit) {
didInit = true;
// pick a random initial sequence number at boot (to prevent repeated reboots always starting at 0)
// Note: we mask the high order bit to ensure that we never pass a 'negative' number to random
i = random(numPacketId & 0x7fffffff);
LOG_DEBUG("Initial packet id %u, numPacketId %u\n", i, numPacketId);
rollingPacketId = random(UINT32_MAX & 0x7fffffff);
LOG_DEBUG("Initial packet id %u\n", rollingPacketId);
}
i++;
PacketId id = (i % numPacketId) + 1; // return number between 1 and numPacketId (ie - never zero)
rollingPacketId++;
rollingPacketId &= UINT32_MAX >> 22; // Mask out the top 22 bits
PacketId id = rollingPacketId | random(UINT32_MAX & 0x7fffffff) << 10; // top 22 bits
LOG_DEBUG("Partially randomized packet id %u\n", id);
return id;
}