mirror of
https://github.com/servalproject/serval-dna.git
synced 2025-01-31 08:25:22 +00:00
Move packet-related functions from dataformats.c to packetformats.c
So that dataformats.o can be linked into executables that don't have log.o.
This commit is contained in:
Andrew Bettison
parent
a3cdf17410
commit
1fbf7001d1
163
dataformats.c
163
dataformats.c
@ -105,166 +105,3 @@ int strn_is_did(const char *did, size_t *lenp)
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*lenp = i;
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return 1;
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}
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int extractDid(unsigned char *packet,int *ofs,char *did)
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{
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int d=0;
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int highP=1;
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int nybl;
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nybl=0;
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while(nybl!=0xf&&(*ofs<(OFS_SIDDIDFIELD+SIDDIDFIELD_LEN))&&(d<64))
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{
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if (highP) nybl=packet[*ofs]>>4; else nybl=packet[*ofs]&0xf;
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if (nybl<0xa) did[d++]='0'+nybl;
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else
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switch(nybl) {
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case 0xa: did[d++]='*'; break;
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case 0xb: did[d++]='#'; break;
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case 0xc: did[d++]='+'; break;
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}
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if (highP) highP=0; else { (*ofs)++; highP=1; }
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}
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if (d>63) return WHY("DID too long");
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did[d]=0;
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return 0;
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}
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int stowDid(unsigned char *packet,int *ofs,char *did)
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{
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int highP=1;
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int nybl;
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int d=0;
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int len=0;
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if (debug&DEBUG_PACKETFORMATS) printf("Packing DID \"%s\"\n",did);
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while(did[d]&&(d<DID_MAXSIZE))
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{
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switch(did[d])
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{
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case '0': case '1': case '2': case '3': case '4':
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case '5': case '6': case '7': case '8': case '9':
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nybl=did[d]-'0'; break;
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case '*': nybl=0xa; break;
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case '#': nybl=0xb; break;
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case '+': nybl=0xc; break;
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default:
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WHY("Illegal digits in DID number");
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return -1;
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}
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if (highP) { packet[*ofs]=nybl<<4; highP=0; }
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else {
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packet[(*ofs)++]|=nybl; highP=1;
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len++;
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}
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d++;
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}
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if (d>=DID_MAXSIZE)
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{
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WHY("DID number too long");
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return -1;
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}
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/* Append end of number code, filling the whole byte for fast and easy comparison */
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if (highP) packet[(*ofs)++]=0xff;
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else packet[(*ofs)++]|=0x0f;
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len++;
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/* Fill remainder of field with randomness to protect any encryption */
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for(;len<SID_SIZE;len++) packet[(*ofs)++]=random()&0xff;
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return 0;
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}
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int extractSid(const unsigned char *packet, int *ofs, char *sid)
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{
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(void) tohex(sid, packet + *ofs, SID_SIZE);
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*ofs += SID_SIZE;
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return 0;
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}
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int stowSid(unsigned char *packet, int ofs, const char *sid)
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{
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if (debug & DEBUG_PACKETFORMATS)
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printf("stowing SID \"%s\"\n", sid);
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if (strcasecmp(sid,"broadcast") == 0)
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memset(packet + ofs, 0xff, SID_SIZE);
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else if (fromhex(packet + ofs, sid, SID_SIZE) != SID_SIZE || sid[SID_STRLEN] != '\0')
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return WHY("invalid SID");
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return 0;
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}
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int packetGetID(unsigned char *packet,int len,char *did,char *sid)
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{
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int ofs=HEADERFIELDS_LEN;
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switch(packet[ofs])
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{
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case 0: /* DID */
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ofs++;
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if (extractDid(packet,&ofs,did)) return WHY("Could not decode DID");
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if (debug&DEBUG_PACKETFORMATS) DEBUGF("Decoded DID as %s", did);
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return 0;
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break;
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case 1: /* SID */
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ofs++;
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if (len<(OFS_SIDDIDFIELD+SID_SIZE)) return WHY("Packet too short");
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if (extractSid(packet,&ofs,sid)) return WHY("Could not decode SID");
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return 0;
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break;
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default: /* no idea */
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return WHY("Unknown ID key");
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break;
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}
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return WHY("Impossible event #1 just occurred");
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}
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/*
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One of the goals of our packet format is to make it very difficult to mount a known plain-text
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attack against the ciphered part of the packet.
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One defence is to make sure that no fixed fields are actually left zero.
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We accomplish this by filling "zero" fields with randomised data that meets a simple test condition.
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We have chosen to use the condition that if the modulo 256 sum of the bytes equals zero, then the packet
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is assumed to be zero/empty.
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The following two functions allow us to test this, and also to fill a field with safe "zero" data.
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*/
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int isFieldZeroP(unsigned char *packet,int start,int count)
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{
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int mod=0;
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int i;
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for(i=start;i<start+count;i++)
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{
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mod+=packet[i];
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mod&=0xff;
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}
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if (debug&DEBUG_PACKETFORMATS) {
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if (mod) DEBUGF("Field [%d,%d) is non-zero (mod=0x%02x)",start,start+count,mod);
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else DEBUGF("Field [%d,%d) is zero",start,start+count);
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}
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if (mod) return 0; else return 1;
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}
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int safeZeroField(unsigned char *packet,int start,int count)
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{
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int mod=0;
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int i;
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if (debug&DEBUG_PACKETFORMATS)
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DEBUGF("Known plain-text counter-measure: safe-zeroing [%d,%d)", start,start+count);
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for(i=start;i<(start+count-1);i++)
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{
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packet[i]=random()&0xff;
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mod+=packet[i];
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mod&=0xff;
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}
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/* set final byte so that modulo sum is zero */
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packet[i]=(0x100-mod)&0xff;
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return 0;
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}
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163
packetformats.c
163
packetformats.c
@ -18,6 +18,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include "serval.h"
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#include "str.h"
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int packetOk(struct overlay_interface *interface, unsigned char *packet, size_t len,
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unsigned char *transaction_id,int ttl,
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@ -40,3 +41,165 @@ int packetOk(struct overlay_interface *interface, unsigned char *packet, size_t
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return WHY("Packet type not recognised.");
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}
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int extractDid(unsigned char *packet,int *ofs,char *did)
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{
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int d=0;
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int highP=1;
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int nybl;
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nybl=0;
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while(nybl!=0xf&&(*ofs<(OFS_SIDDIDFIELD+SIDDIDFIELD_LEN))&&(d<64))
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{
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if (highP) nybl=packet[*ofs]>>4; else nybl=packet[*ofs]&0xf;
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if (nybl<0xa) did[d++]='0'+nybl;
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else
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switch(nybl) {
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case 0xa: did[d++]='*'; break;
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case 0xb: did[d++]='#'; break;
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case 0xc: did[d++]='+'; break;
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}
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if (highP) highP=0; else { (*ofs)++; highP=1; }
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}
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if (d>63) return WHY("DID too long");
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did[d]=0;
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return 0;
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}
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int stowDid(unsigned char *packet,int *ofs,char *did)
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{
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int highP=1;
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int nybl;
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int d=0;
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int len=0;
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if (debug&DEBUG_PACKETFORMATS) printf("Packing DID \"%s\"\n",did);
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while(did[d]&&(d<DID_MAXSIZE))
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{
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switch(did[d])
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{
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case '0': case '1': case '2': case '3': case '4':
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case '5': case '6': case '7': case '8': case '9':
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nybl=did[d]-'0'; break;
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case '*': nybl=0xa; break;
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case '#': nybl=0xb; break;
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case '+': nybl=0xc; break;
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default:
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WHY("Illegal digits in DID number");
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return -1;
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}
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if (highP) { packet[*ofs]=nybl<<4; highP=0; }
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else {
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packet[(*ofs)++]|=nybl; highP=1;
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len++;
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}
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d++;
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}
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if (d>=DID_MAXSIZE)
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{
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WHY("DID number too long");
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return -1;
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}
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/* Append end of number code, filling the whole byte for fast and easy comparison */
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if (highP) packet[(*ofs)++]=0xff;
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else packet[(*ofs)++]|=0x0f;
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len++;
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/* Fill remainder of field with randomness to protect any encryption */
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for(;len<SID_SIZE;len++) packet[(*ofs)++]=random()&0xff;
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return 0;
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}
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int extractSid(const unsigned char *packet, int *ofs, char *sid)
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{
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(void) tohex(sid, packet + *ofs, SID_SIZE);
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*ofs += SID_SIZE;
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return 0;
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}
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int stowSid(unsigned char *packet, int ofs, const char *sid)
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{
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if (debug & DEBUG_PACKETFORMATS)
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printf("stowing SID \"%s\"\n", sid);
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if (strcasecmp(sid,"broadcast") == 0)
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memset(packet + ofs, 0xff, SID_SIZE);
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else if (fromhex(packet + ofs, sid, SID_SIZE) != SID_SIZE || sid[SID_STRLEN] != '\0')
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return WHY("invalid SID");
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return 0;
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}
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int packetGetID(unsigned char *packet,int len,char *did,char *sid)
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{
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int ofs=HEADERFIELDS_LEN;
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switch(packet[ofs])
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{
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case 0: /* DID */
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ofs++;
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if (extractDid(packet,&ofs,did)) return WHY("Could not decode DID");
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if (debug&DEBUG_PACKETFORMATS) DEBUGF("Decoded DID as %s", did);
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return 0;
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break;
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case 1: /* SID */
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ofs++;
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if (len<(OFS_SIDDIDFIELD+SID_SIZE)) return WHY("Packet too short");
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if (extractSid(packet,&ofs,sid)) return WHY("Could not decode SID");
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return 0;
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break;
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default: /* no idea */
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return WHY("Unknown ID key");
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break;
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}
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return WHY("Impossible event #1 just occurred");
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}
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/*
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One of the goals of our packet format is to make it very difficult to mount a known plain-text
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attack against the ciphered part of the packet.
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One defence is to make sure that no fixed fields are actually left zero.
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We accomplish this by filling "zero" fields with randomised data that meets a simple test condition.
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We have chosen to use the condition that if the modulo 256 sum of the bytes equals zero, then the packet
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is assumed to be zero/empty.
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The following two functions allow us to test this, and also to fill a field with safe "zero" data.
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*/
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int isFieldZeroP(unsigned char *packet,int start,int count)
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{
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int mod=0;
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int i;
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for(i=start;i<start+count;i++)
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{
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mod+=packet[i];
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mod&=0xff;
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}
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if (debug&DEBUG_PACKETFORMATS) {
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if (mod) DEBUGF("Field [%d,%d) is non-zero (mod=0x%02x)",start,start+count,mod);
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else DEBUGF("Field [%d,%d) is zero",start,start+count);
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}
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if (mod) return 0; else return 1;
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}
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int safeZeroField(unsigned char *packet,int start,int count)
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{
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int mod=0;
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int i;
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if (debug&DEBUG_PACKETFORMATS)
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DEBUGF("Known plain-text counter-measure: safe-zeroing [%d,%d)", start,start+count);
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for(i=start;i<(start+count-1);i++)
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{
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packet[i]=random()&0xff;
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mod+=packet[i];
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mod&=0xff;
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}
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/* set final byte so that modulo sum is zero */
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packet[i]=(0x100-mod)&0xff;
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return 0;
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}
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