local switch: Implement shared-secret feature

This allows for a “shared secret” to be entered for a network switch,
segmenting traffic so that multiple people could use the feature
simultaneously without accidentally entering into or interfering with
each other's networks.

Takes a string specified in the configuration file (using the
net_%02i_secret key) and hashes it through SHA3-256 to prepend to each
data packet.  This hash is used to compare packets on reception and
allow or discard them.
This commit is contained in:
Mike Swanson
2026-02-09 19:06:45 -08:00
parent ad235874c7
commit f3d22bbef3
4 changed files with 538 additions and 4 deletions

View File

@@ -98,6 +98,7 @@ typedef struct netcard_conf_t {
char host_dev_name[128];
uint32_t link_state;
uint8_t switch_group;
char secret[256];
uint8_t promisc_mode;
char slirp_net[16];
char nrs_hostname[128];

481
src/include/shathree.h Normal file
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@@ -0,0 +1,481 @@
/*
** This code is from SQLite
** (https://sqlite.org/src/info/2025-02-27T21:17:55z), at file path
** ext/misc/shathree.c. The SQLite functions have been removed, but
** it is the same code written by D. Richard Hipp.
*/
#ifndef SHATHREE_H
/*
** 2017-03-08
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*/
#include <assert.h>
#include <string.h>
#include <stdarg.h>
/******************************************************************************
** The Hash Engine
*/
/*
** Macros to determine whether the machine is big or little endian,
** and whether or not that determination is run-time or compile-time.
**
** For best performance, an attempt is made to guess at the byte-order
** using C-preprocessor macros. If that is unsuccessful, or if
** -DSHA3_BYTEORDER=0 is set, then byte-order is determined
** at run-time.
*/
#ifndef SHA3_BYTEORDER
# if defined(i386) || defined(__i386__) || defined(_M_IX86) || \
defined(__x86_64) || defined(__x86_64__) || defined(_M_X64) || \
defined(_M_AMD64) || defined(_M_ARM) || defined(__x86) || \
defined(__arm__)
# define SHA3_BYTEORDER 1234
# elif defined(sparc) || defined(__ppc__)
# define SHA3_BYTEORDER 4321
# else
# define SHA3_BYTEORDER 0
# endif
#endif
#define u64 uint64_t
/*
** State structure for a SHA3 hash in progress
*/
typedef struct SHA3Context SHA3Context;
struct SHA3Context {
union {
u64 s[25]; /* Keccak state. 5x5 lines of 64 bits each */
unsigned char x[1600]; /* ... or 1600 bytes */
} u;
unsigned nRate; /* Bytes of input accepted per Keccak iteration */
unsigned nLoaded; /* Input bytes loaded into u.x[] so far this cycle */
unsigned ixMask; /* Insert next input into u.x[nLoaded^ixMask]. */
unsigned iSize; /* 224, 256, 358, or 512 */
};
/*
** A single step of the Keccak mixing function for a 1600-bit state
*/
static void KeccakF1600Step(SHA3Context *p){
int i;
u64 b0, b1, b2, b3, b4;
u64 c0, c1, c2, c3, c4;
u64 d0, d1, d2, d3, d4;
static const u64 RC[] = {
0x0000000000000001ULL, 0x0000000000008082ULL,
0x800000000000808aULL, 0x8000000080008000ULL,
0x000000000000808bULL, 0x0000000080000001ULL,
0x8000000080008081ULL, 0x8000000000008009ULL,
0x000000000000008aULL, 0x0000000000000088ULL,
0x0000000080008009ULL, 0x000000008000000aULL,
0x000000008000808bULL, 0x800000000000008bULL,
0x8000000000008089ULL, 0x8000000000008003ULL,
0x8000000000008002ULL, 0x8000000000000080ULL,
0x000000000000800aULL, 0x800000008000000aULL,
0x8000000080008081ULL, 0x8000000000008080ULL,
0x0000000080000001ULL, 0x8000000080008008ULL
};
# define a00 (p->u.s[0])
# define a01 (p->u.s[1])
# define a02 (p->u.s[2])
# define a03 (p->u.s[3])
# define a04 (p->u.s[4])
# define a10 (p->u.s[5])
# define a11 (p->u.s[6])
# define a12 (p->u.s[7])
# define a13 (p->u.s[8])
# define a14 (p->u.s[9])
# define a20 (p->u.s[10])
# define a21 (p->u.s[11])
# define a22 (p->u.s[12])
# define a23 (p->u.s[13])
# define a24 (p->u.s[14])
# define a30 (p->u.s[15])
# define a31 (p->u.s[16])
# define a32 (p->u.s[17])
# define a33 (p->u.s[18])
# define a34 (p->u.s[19])
# define a40 (p->u.s[20])
# define a41 (p->u.s[21])
# define a42 (p->u.s[22])
# define a43 (p->u.s[23])
# define a44 (p->u.s[24])
# define ROL64(a,x) ((a<<x)|(a>>(64-x)))
for(i=0; i<24; i+=4){
c0 = a00^a10^a20^a30^a40;
c1 = a01^a11^a21^a31^a41;
c2 = a02^a12^a22^a32^a42;
c3 = a03^a13^a23^a33^a43;
c4 = a04^a14^a24^a34^a44;
d0 = c4^ROL64(c1, 1);
d1 = c0^ROL64(c2, 1);
d2 = c1^ROL64(c3, 1);
d3 = c2^ROL64(c4, 1);
d4 = c3^ROL64(c0, 1);
b0 = (a00^d0);
b1 = ROL64((a11^d1), 44);
b2 = ROL64((a22^d2), 43);
b3 = ROL64((a33^d3), 21);
b4 = ROL64((a44^d4), 14);
a00 = b0 ^((~b1)& b2 );
a00 ^= RC[i];
a11 = b1 ^((~b2)& b3 );
a22 = b2 ^((~b3)& b4 );
a33 = b3 ^((~b4)& b0 );
a44 = b4 ^((~b0)& b1 );
b2 = ROL64((a20^d0), 3);
b3 = ROL64((a31^d1), 45);
b4 = ROL64((a42^d2), 61);
b0 = ROL64((a03^d3), 28);
b1 = ROL64((a14^d4), 20);
a20 = b0 ^((~b1)& b2 );
a31 = b1 ^((~b2)& b3 );
a42 = b2 ^((~b3)& b4 );
a03 = b3 ^((~b4)& b0 );
a14 = b4 ^((~b0)& b1 );
b4 = ROL64((a40^d0), 18);
b0 = ROL64((a01^d1), 1);
b1 = ROL64((a12^d2), 6);
b2 = ROL64((a23^d3), 25);
b3 = ROL64((a34^d4), 8);
a40 = b0 ^((~b1)& b2 );
a01 = b1 ^((~b2)& b3 );
a12 = b2 ^((~b3)& b4 );
a23 = b3 ^((~b4)& b0 );
a34 = b4 ^((~b0)& b1 );
b1 = ROL64((a10^d0), 36);
b2 = ROL64((a21^d1), 10);
b3 = ROL64((a32^d2), 15);
b4 = ROL64((a43^d3), 56);
b0 = ROL64((a04^d4), 27);
a10 = b0 ^((~b1)& b2 );
a21 = b1 ^((~b2)& b3 );
a32 = b2 ^((~b3)& b4 );
a43 = b3 ^((~b4)& b0 );
a04 = b4 ^((~b0)& b1 );
b3 = ROL64((a30^d0), 41);
b4 = ROL64((a41^d1), 2);
b0 = ROL64((a02^d2), 62);
b1 = ROL64((a13^d3), 55);
b2 = ROL64((a24^d4), 39);
a30 = b0 ^((~b1)& b2 );
a41 = b1 ^((~b2)& b3 );
a02 = b2 ^((~b3)& b4 );
a13 = b3 ^((~b4)& b0 );
a24 = b4 ^((~b0)& b1 );
c0 = a00^a20^a40^a10^a30;
c1 = a11^a31^a01^a21^a41;
c2 = a22^a42^a12^a32^a02;
c3 = a33^a03^a23^a43^a13;
c4 = a44^a14^a34^a04^a24;
d0 = c4^ROL64(c1, 1);
d1 = c0^ROL64(c2, 1);
d2 = c1^ROL64(c3, 1);
d3 = c2^ROL64(c4, 1);
d4 = c3^ROL64(c0, 1);
b0 = (a00^d0);
b1 = ROL64((a31^d1), 44);
b2 = ROL64((a12^d2), 43);
b3 = ROL64((a43^d3), 21);
b4 = ROL64((a24^d4), 14);
a00 = b0 ^((~b1)& b2 );
a00 ^= RC[i+1];
a31 = b1 ^((~b2)& b3 );
a12 = b2 ^((~b3)& b4 );
a43 = b3 ^((~b4)& b0 );
a24 = b4 ^((~b0)& b1 );
b2 = ROL64((a40^d0), 3);
b3 = ROL64((a21^d1), 45);
b4 = ROL64((a02^d2), 61);
b0 = ROL64((a33^d3), 28);
b1 = ROL64((a14^d4), 20);
a40 = b0 ^((~b1)& b2 );
a21 = b1 ^((~b2)& b3 );
a02 = b2 ^((~b3)& b4 );
a33 = b3 ^((~b4)& b0 );
a14 = b4 ^((~b0)& b1 );
b4 = ROL64((a30^d0), 18);
b0 = ROL64((a11^d1), 1);
b1 = ROL64((a42^d2), 6);
b2 = ROL64((a23^d3), 25);
b3 = ROL64((a04^d4), 8);
a30 = b0 ^((~b1)& b2 );
a11 = b1 ^((~b2)& b3 );
a42 = b2 ^((~b3)& b4 );
a23 = b3 ^((~b4)& b0 );
a04 = b4 ^((~b0)& b1 );
b1 = ROL64((a20^d0), 36);
b2 = ROL64((a01^d1), 10);
b3 = ROL64((a32^d2), 15);
b4 = ROL64((a13^d3), 56);
b0 = ROL64((a44^d4), 27);
a20 = b0 ^((~b1)& b2 );
a01 = b1 ^((~b2)& b3 );
a32 = b2 ^((~b3)& b4 );
a13 = b3 ^((~b4)& b0 );
a44 = b4 ^((~b0)& b1 );
b3 = ROL64((a10^d0), 41);
b4 = ROL64((a41^d1), 2);
b0 = ROL64((a22^d2), 62);
b1 = ROL64((a03^d3), 55);
b2 = ROL64((a34^d4), 39);
a10 = b0 ^((~b1)& b2 );
a41 = b1 ^((~b2)& b3 );
a22 = b2 ^((~b3)& b4 );
a03 = b3 ^((~b4)& b0 );
a34 = b4 ^((~b0)& b1 );
c0 = a00^a40^a30^a20^a10;
c1 = a31^a21^a11^a01^a41;
c2 = a12^a02^a42^a32^a22;
c3 = a43^a33^a23^a13^a03;
c4 = a24^a14^a04^a44^a34;
d0 = c4^ROL64(c1, 1);
d1 = c0^ROL64(c2, 1);
d2 = c1^ROL64(c3, 1);
d3 = c2^ROL64(c4, 1);
d4 = c3^ROL64(c0, 1);
b0 = (a00^d0);
b1 = ROL64((a21^d1), 44);
b2 = ROL64((a42^d2), 43);
b3 = ROL64((a13^d3), 21);
b4 = ROL64((a34^d4), 14);
a00 = b0 ^((~b1)& b2 );
a00 ^= RC[i+2];
a21 = b1 ^((~b2)& b3 );
a42 = b2 ^((~b3)& b4 );
a13 = b3 ^((~b4)& b0 );
a34 = b4 ^((~b0)& b1 );
b2 = ROL64((a30^d0), 3);
b3 = ROL64((a01^d1), 45);
b4 = ROL64((a22^d2), 61);
b0 = ROL64((a43^d3), 28);
b1 = ROL64((a14^d4), 20);
a30 = b0 ^((~b1)& b2 );
a01 = b1 ^((~b2)& b3 );
a22 = b2 ^((~b3)& b4 );
a43 = b3 ^((~b4)& b0 );
a14 = b4 ^((~b0)& b1 );
b4 = ROL64((a10^d0), 18);
b0 = ROL64((a31^d1), 1);
b1 = ROL64((a02^d2), 6);
b2 = ROL64((a23^d3), 25);
b3 = ROL64((a44^d4), 8);
a10 = b0 ^((~b1)& b2 );
a31 = b1 ^((~b2)& b3 );
a02 = b2 ^((~b3)& b4 );
a23 = b3 ^((~b4)& b0 );
a44 = b4 ^((~b0)& b1 );
b1 = ROL64((a40^d0), 36);
b2 = ROL64((a11^d1), 10);
b3 = ROL64((a32^d2), 15);
b4 = ROL64((a03^d3), 56);
b0 = ROL64((a24^d4), 27);
a40 = b0 ^((~b1)& b2 );
a11 = b1 ^((~b2)& b3 );
a32 = b2 ^((~b3)& b4 );
a03 = b3 ^((~b4)& b0 );
a24 = b4 ^((~b0)& b1 );
b3 = ROL64((a20^d0), 41);
b4 = ROL64((a41^d1), 2);
b0 = ROL64((a12^d2), 62);
b1 = ROL64((a33^d3), 55);
b2 = ROL64((a04^d4), 39);
a20 = b0 ^((~b1)& b2 );
a41 = b1 ^((~b2)& b3 );
a12 = b2 ^((~b3)& b4 );
a33 = b3 ^((~b4)& b0 );
a04 = b4 ^((~b0)& b1 );
c0 = a00^a30^a10^a40^a20;
c1 = a21^a01^a31^a11^a41;
c2 = a42^a22^a02^a32^a12;
c3 = a13^a43^a23^a03^a33;
c4 = a34^a14^a44^a24^a04;
d0 = c4^ROL64(c1, 1);
d1 = c0^ROL64(c2, 1);
d2 = c1^ROL64(c3, 1);
d3 = c2^ROL64(c4, 1);
d4 = c3^ROL64(c0, 1);
b0 = (a00^d0);
b1 = ROL64((a01^d1), 44);
b2 = ROL64((a02^d2), 43);
b3 = ROL64((a03^d3), 21);
b4 = ROL64((a04^d4), 14);
a00 = b0 ^((~b1)& b2 );
a00 ^= RC[i+3];
a01 = b1 ^((~b2)& b3 );
a02 = b2 ^((~b3)& b4 );
a03 = b3 ^((~b4)& b0 );
a04 = b4 ^((~b0)& b1 );
b2 = ROL64((a10^d0), 3);
b3 = ROL64((a11^d1), 45);
b4 = ROL64((a12^d2), 61);
b0 = ROL64((a13^d3), 28);
b1 = ROL64((a14^d4), 20);
a10 = b0 ^((~b1)& b2 );
a11 = b1 ^((~b2)& b3 );
a12 = b2 ^((~b3)& b4 );
a13 = b3 ^((~b4)& b0 );
a14 = b4 ^((~b0)& b1 );
b4 = ROL64((a20^d0), 18);
b0 = ROL64((a21^d1), 1);
b1 = ROL64((a22^d2), 6);
b2 = ROL64((a23^d3), 25);
b3 = ROL64((a24^d4), 8);
a20 = b0 ^((~b1)& b2 );
a21 = b1 ^((~b2)& b3 );
a22 = b2 ^((~b3)& b4 );
a23 = b3 ^((~b4)& b0 );
a24 = b4 ^((~b0)& b1 );
b1 = ROL64((a30^d0), 36);
b2 = ROL64((a31^d1), 10);
b3 = ROL64((a32^d2), 15);
b4 = ROL64((a33^d3), 56);
b0 = ROL64((a34^d4), 27);
a30 = b0 ^((~b1)& b2 );
a31 = b1 ^((~b2)& b3 );
a32 = b2 ^((~b3)& b4 );
a33 = b3 ^((~b4)& b0 );
a34 = b4 ^((~b0)& b1 );
b3 = ROL64((a40^d0), 41);
b4 = ROL64((a41^d1), 2);
b0 = ROL64((a42^d2), 62);
b1 = ROL64((a43^d3), 55);
b2 = ROL64((a44^d4), 39);
a40 = b0 ^((~b1)& b2 );
a41 = b1 ^((~b2)& b3 );
a42 = b2 ^((~b3)& b4 );
a43 = b3 ^((~b4)& b0 );
a44 = b4 ^((~b0)& b1 );
}
}
/*
** Initialize a new hash. iSize determines the size of the hash
** in bits and should be one of 224, 256, 384, or 512. Or iSize
** can be zero to use the default hash size of 256 bits.
*/
static void SHA3Init(SHA3Context *p, int iSize){
memset(p, 0, sizeof(*p));
p->iSize = iSize;
if( iSize>=128 && iSize<=512 ){
p->nRate = (1600 - ((iSize + 31)&~31)*2)/8;
}else{
p->nRate = (1600 - 2*256)/8;
}
#if SHA3_BYTEORDER==1234
/* Known to be little-endian at compile-time. No-op */
#elif SHA3_BYTEORDER==4321
p->ixMask = 7; /* Big-endian */
#else
{
static unsigned int one = 1;
if( 1==*(unsigned char*)&one ){
/* Little endian. No byte swapping. */
p->ixMask = 0;
}else{
/* Big endian. Byte swap. */
p->ixMask = 7;
}
}
#endif
}
/*
** Make consecutive calls to the SHA3Update function to add new content
** to the hash
*/
static void SHA3Update(
SHA3Context *p,
const unsigned char *aData,
unsigned int nData
){
unsigned int i = 0;
if( aData==0 ) return;
#if SHA3_BYTEORDER==1234
if( (p->nLoaded % 8)==0 && ((aData - (const unsigned char*)0)&7)==0 ){
for(; i+7<nData; i+=8){
p->u.s[p->nLoaded/8] ^= *(u64*)&aData[i];
p->nLoaded += 8;
if( p->nLoaded>=p->nRate ){
KeccakF1600Step(p);
p->nLoaded = 0;
}
}
}
#endif
for(; i<nData; i++){
#if SHA3_BYTEORDER==1234
p->u.x[p->nLoaded] ^= aData[i];
#elif SHA3_BYTEORDER==4321
p->u.x[p->nLoaded^0x07] ^= aData[i];
#else
p->u.x[p->nLoaded^p->ixMask] ^= aData[i];
#endif
p->nLoaded++;
if( p->nLoaded==p->nRate ){
KeccakF1600Step(p);
p->nLoaded = 0;
}
}
}
/*
** After all content has been added, invoke SHA3Final() to compute
** the final hash. The function returns a pointer to the binary
** hash value.
*/
static unsigned char *SHA3Final(SHA3Context *p){
unsigned int i;
if( p->nLoaded==p->nRate-1 ){
const unsigned char c1 = 0x86;
SHA3Update(p, &c1, 1);
}else{
const unsigned char c2 = 0x06;
const unsigned char c3 = 0x80;
SHA3Update(p, &c2, 1);
p->nLoaded = p->nRate - 1;
SHA3Update(p, &c3, 1);
}
for(i=0; i<p->nRate; i++){
p->u.x[i+p->nRate] = p->u.x[i^p->ixMask];
}
return &p->u.x[p->nRate];
}
#endif