DOMHDR.C

/* Domain header conversion routines
 * Copyright 1991 Phil Karn, KA9Q
 *
 * Additional support for the Domain Name Server
 * by Johan. K. Reinalda, WG7J,
 * based on previous work by Gerard v.d. Grinten, PA0GRI
 */
#include "global.h"
#include "mbuf.h"
#include "domain.h"
  
struct dict {
    struct dict *next;
    char *nm;          /* name already stored into reply buf */
    int16 nmoff;       /* offset to name in reply buf */
};
#define NULLDICT (struct dict *)0

static int dn_expand __ARGS((char *msg,char *compressed,char *full,int fullen));
static char *getq __ARGS((struct rr **rrpp,char *msg,char *cp));
static char *ntohrr __ARGS((struct rr **rrpp,char *msg,char *cp));
#ifdef DOMAINSERVER
static char *dn_compress __ARGS((char *msg,struct dict **dp,char *cp,char *name));
static char *htonrr __ARGS((char *msg,struct dict **dp,struct rr *rr,char *buffer));
static int16 clookup __ARGS((struct dict **dp,char *name,int16 offs));
#endif
  
int
ntohdomain(dhdr,bpp)
register struct dhdr *dhdr;
struct mbuf **bpp;
{
    int16 tmp,len;
    register int16 i;
    char *msg,*cp;
    struct rr **rrpp;
  
    len = len_p(*bpp);
    msg = mallocw(len);
    pullup(bpp,msg,len);
    memset((char *)dhdr,0,sizeof(struct dhdr));
  
    dhdr->id = get16(&msg[0]);
    tmp = get16(&msg[2]);
    if(tmp & 0x8000)
        dhdr->qr = 1;
    dhdr->opcode = (tmp >> 11) & 0xf;
    if(tmp & 0x0400)
        dhdr->aa = 1;
    if(tmp & 0x0200)
        dhdr->tc = 1;
    if(tmp & 0x0100)
        dhdr->rd = 1;
    if(tmp & 0x0080)
        dhdr->ra = 1;
    dhdr->rcode = tmp & 0xf;
    dhdr->qdcount = get16(&msg[4]);
    dhdr->ancount = get16(&msg[6]);
    dhdr->nscount = get16(&msg[8]);
    dhdr->arcount = get16(&msg[10]);
  
    /* Now parse the variable length sections */
    cp = &msg[12];
  
    /* Question section */
    rrpp = &dhdr->questions;
    for(i=0;i<dhdr->qdcount;i++){
        if((cp = getq(rrpp,msg,cp)) == NULLCHAR){
            free(msg);
            return -1;
        }
        (*rrpp)->source = RR_QUESTION;
        rrpp = &(*rrpp)->next;
    }
    *rrpp = NULLRR;
  
    /* Answer section */
    rrpp = &dhdr->answers;
    for(i=0;i<dhdr->ancount;i++){
        if((cp = ntohrr(rrpp,msg,cp)) == NULLCHAR){
            free(msg);
            return -1;
        }
        (*rrpp)->source = RR_ANSWER;
        rrpp = &(*rrpp)->next;
    }
    *rrpp = NULLRR;
  
    /* Name server (authority) section */
    rrpp = &dhdr->authority;
    for(i=0;i<dhdr->nscount;i++){
        if((cp = ntohrr(rrpp,msg,cp)) == NULLCHAR){
            free(msg);
            return -1;
        }
        (*rrpp)->source = RR_AUTHORITY;
        rrpp = &(*rrpp)->next;
    }
    *rrpp = NULLRR;
  
    /* Additional section */
    rrpp = &dhdr->additional;
    for(i=0;i<dhdr->arcount;i++){
        if((cp = ntohrr(rrpp,msg,cp)) == NULLCHAR){
            free(msg);
            return -1;
        }
        (*rrpp)->source = RR_ADDITIONAL;
        rrpp = &(*rrpp)->next;
    }
    *rrpp = NULLRR;
    free(msg);
    return 0;
}
static char *
getq(rrpp,msg,cp)
struct rr **rrpp;
char *msg;
char *cp;
{
    register struct rr *rrp;
    int len;
    char *name;
  
    *rrpp = rrp = (struct rr *)callocw(1,sizeof(struct rr));
    name = mallocw(512);
    len = dn_expand(msg,cp,name,512);
    if(len == -1){
        free(name);
        return NULLCHAR;
    }
    cp += len;
    rrp->name = strdup(name);
    rrp->type = get16(cp);
    cp += 2;
    rrp->class = get16(cp);
    cp += 2;
    rrp->ttl = 0;
    rrp->rdlength = 0;
    free(name);
    return cp;
}
/* Read a resource record from a domain message into a host structure */
static char *
ntohrr(rrpp,msg,cp)
struct rr **rrpp; /* Where to allocate resource record structure */
char *msg;      /* Pointer to beginning of domain message */
char *cp;       /* Pointer to start of encoded RR record */
{
    register struct rr *rrp;
    int len;
    char *name;
  
    *rrpp = rrp = (struct rr *)callocw(1,sizeof(struct rr));
    name = mallocw(512);
    if((len = dn_expand(msg,cp,name,512)) == -1){
        free(name);
        return NULLCHAR;
    }
    cp += len;
    rrp->name = strdup(name);
    rrp->type = get16(cp);
    cp += 2;
    rrp->class = get16(cp);
    cp+= 2;
    rrp->ttl = get32(cp);
    cp += 4;
    rrp->rdlength = get16(cp);
    cp += 2;
    switch(rrp->type){
        case TYPE_A:
        /* Just read the address directly into the structure */
            rrp->rdata.addr = get32(cp);
            cp += 4;
            break;
        case TYPE_CNAME:
        case TYPE_MB:
        case TYPE_MG:
        case TYPE_MR:
        case TYPE_NS:
        case TYPE_PTR:
        /* These types all consist of a single domain name;
         * convert it to ascii format
         */
            len = dn_expand(msg,cp,name,512);
            if(len == -1){
                free(name);
                return NULLCHAR;
            }
            rrp->rdata.name = strdup(name);
            rrp->rdlength = strlen(name);
            cp += len;
            break;
        case TYPE_HINFO:
            len = *cp++;
            rrp->rdata.hinfo.cpu = mallocw(len+1);
            memcpy( rrp->rdata.hinfo.cpu, cp, len );
            rrp->rdata.hinfo.cpu[len] = '\0';
            cp += len;
  
            len = *cp++;
            rrp->rdata.hinfo.os = mallocw(len+1);
            memcpy( rrp->rdata.hinfo.os, cp, len );
            rrp->rdata.hinfo.os[len] = '\0';
            cp += len;
            break;
        case TYPE_MX:
            rrp->rdata.mx.pref = get16(cp);
            cp += 2;
        /* Get domain name of exchanger */
            len = dn_expand(msg,cp,name,512);
            if(len == -1){
                free(name);
                return NULLCHAR;
            }
            rrp->rdata.mx.exch = strdup(name);
            cp += len;
            break;
        case TYPE_SOA:
        /* Get domain name of name server */
            len = dn_expand(msg,cp,name,512);
            if(len == -1){
                free(name);
                return NULLCHAR;
            }
            rrp->rdata.soa.mname = strdup(name);
            cp += len;
  
        /* Get domain name of responsible person */
            len = dn_expand(msg,cp,name,512);
            if(len == -1){
                free(name);
                return NULLCHAR;
            }
            rrp->rdata.soa.rname = strdup(name);
            cp += len;
  
            rrp->rdata.soa.serial = get32(cp);
            cp += 4;
            rrp->rdata.soa.refresh = get32(cp);
            cp += 4;
            rrp->rdata.soa.retry = get32(cp);
            cp += 4;
            rrp->rdata.soa.expire = get32(cp);
            cp += 4;
            rrp->rdata.soa.minimum = get32(cp);
            cp += 4;
            break;
        case TYPE_TXT:
        /* Just stash */
            rrp->rdata.data = mallocw(rrp->rdlength);
            memcpy(rrp->rdata.data,cp,rrp->rdlength);
            cp += rrp->rdlength;
            break;
        default:
        /* Ignore (note no data is retained, DESPITE rrp->rdlength) */
            cp += rrp->rdlength;
            break;
    }
    free(name);
    return cp;
}
  
/* Convert a compressed domain name to the human-readable form */
static int
dn_expand(msg,compressed,full,fullen)
char *msg;              /* Complete domain message */
char *compressed;       /* Pointer to compressed name */
char *full;             /* Pointer to result buffer */
int fullen;             /* Length of same */
{
    unsigned int slen;      /* Length of current segment */
    register char *cp;
    int clen = 0;   /* Total length of compressed name */
    int indirect = 0;       /* Set if indirection encountered */
    int nseg = 0;           /* Total number of segments in name */
  
    cp = compressed;
    for(;;){
        slen = uchar(*cp++);    /* Length of this segment */
        if(!indirect)
            clen++;
        if((slen & 0xc0) == 0xc0){
            if(!indirect)
                clen++;
            indirect = 1;
            /* Follow indirection */
            cp = &msg[((slen & 0x3f)<<8) + uchar(*cp)];
            slen = uchar(*cp++);
        }
        if(slen == 0)   /* zero length == all done */
            break;
        fullen -= slen + 1;
        if(fullen < 0)
            return -1;
        if(!indirect)
            clen += slen;
        while(slen-- != 0)
            *full++ = *cp++;
        *full++ = '.';
        nseg++;
    }
    if(nseg == 0){
        /* Root name; represent as single dot */
        *full++ = '.';
        fullen--;
    }
    *full++ = '\0';
    fullen--;
    return clen;    /* Length of compressed message */
}
  
  
  
#ifdef DOMAINSERVER
  
/* Most of this code is based on the DNS server in PA0GRI's 910828
 * Ported to the current NOS code by Johan. K. Reinalda, WG7J
 * for version and bug/feature info, see domain.c
 */

/* Search name dictionary, returning offset code, or inserting if not found */
static int16
clookup(dp,name,offs)
struct dict **dp;
char *name;
int16 offs;
{
    struct dict *p;

    for (p = *dp; p; p=p->next) {
        if (!strcmp(name,p->nm))
            return p->nmoff;
    }
    if ((p = (struct dict *)malloc(sizeof(struct dict)))!=NULLDICT) {
        p->next = *dp;  /* add to head of list */
        p->nm = strdup(name);
        p->nmoff = (offs & 0x3FFF) | 0xC000;
        *dp = p;
    }
    return 0;
}

static char *
dn_compress(msg,dp,cp,name)
char *msg;
struct dict **dp;
char *cp;
char *name;
{
    int len,dlen;
    int16 ccode;
    char *cp1;
    dlen = strlen(name);
    for(;;){
        /* Look for next dot */
        cp1 = strchr(name,'.');
        if(cp1 != NULLCHAR)
            len = (int)(cp1-name); /* More to come */
        else
            len = dlen;     /* Last component */
        *cp++ = len;            /* Write length of component */
        if(len == 0)
            return cp;
        if((ccode=clookup(dp,name,(int16)(cp-msg-1)))!=0) { /* name is in dictionary? */
            cp = put16(cp-1,ccode);  /* yes, use indirect reference */
            return cp;
        }
        /* Copy component up to (but not including) dot */
        strncpy(cp,name,len);
        cp += len;
        if(cp1 == NULLCHAR){
            *cp++ = 0;      /* Last one; write null and finish */
            return cp;
        }
        name += len+1;
        dlen -= len+1;
    }
}
  
/* Translate a resource record from host format to network format */
static char *
htonrr(msg,dp,rr,buffer)
struct dict **dp;
struct rr *rr;
char *msg,*buffer;
{
    struct rr *rrp;
    char *cp, *p;
    int i, len;
  
    cp = buffer;
    for(rrp = rr; rrp != NULLRR; rrp = rrp->next) {
#ifdef notdef
        i = strlen(rrp->name);
        if(rrp->name[i-1] != '.'
        && rrp->origin != NULLCHAR) {
            p = mallocw(i + strlen(rrp->origin) + 2);
            sprintf(p,"%s.%s",rrp->name,rrp->origin);
            cp = dn_compress(msg,dp,cp,p);
            free(p);  /* this is why I do a strdup() in clookup .. n5knx */
        } else
#endif
            cp = dn_compress(msg,dp,cp,rrp->name);
        cp = put16(cp,rrp->type);
        cp = put16(cp,rrp->class);
        cp = put32(cp,rrp->ttl);
#ifdef notdef
    /* The length doesn't seem to be right for all types ! */
        cp = put16(cp,rrp->rdlength);
#endif
        p = cp;     /* This is where the length goes ! */
        cp += 2;    /* Save the space for lenght field */
  
        switch(rrp->type) {
            case TYPE_A:
                cp = put32(cp,rrp->rdata.addr);
                break;
            case TYPE_SOA:
                cp = dn_compress(msg,dp,cp,rrp->rdata.soa.mname);
                cp = dn_compress(msg,dp,cp,rrp->rdata.soa.rname);
                cp = put32(cp,rrp->rdata.soa.serial);
                cp = put32(cp,rrp->rdata.soa.refresh);
                cp = put32(cp,rrp->rdata.soa.retry);
                cp = put32(cp,rrp->rdata.soa.expire);
                cp = put32(cp,rrp->rdata.soa.minimum);
                break;
            case TYPE_HINFO:
                *cp++ = len = strlen(rrp->rdata.hinfo.cpu);
                strncpy(cp,rrp->rdata.hinfo.cpu,len);
                cp += len;
                *cp++ = len = strlen(rrp->rdata.hinfo.os);
                strncpy(cp,rrp->rdata.hinfo.os,len);
                cp += len;
                break;
            case TYPE_MX:
                cp = put16(cp,rrp->rdata.mx.pref);
                cp = dn_compress(msg,dp,cp,rrp->rdata.mx.exch);
                break;
            case TYPE_CNAME:
            case TYPE_MB:
            case TYPE_MG:
            case TYPE_MR:
            case TYPE_NS:
            case TYPE_PTR:
                cp = dn_compress(msg,dp,cp,rrp->rdata.data);
                break;
            case TYPE_TXT:
                cp = put16(cp,rrp->rdlength);
                for(i=0 ; i < rrp->rdlength ; i++)
                    *cp++ = rrp->rdata.data[i];
                break;
#if 0
            case TYPE_MINFO:    /* Unsupported type */
                cp = dn_compress(msg,dp,cp,rrp->rdata.minfo.rmailbx);
                cp = dn_compress(msg,dp,cp,rrp->rdata.minfo.emailbx);
            case TYPE_MD:       /* Unsupported type */
            case TYPE_MF:       /* Unsupported type */
            case TYPE_NULL:     /* Unsupported type */
            case TYPE_WKS:      /* Unsupported type */
                cp = dn_compress(msg,dp,cp,rrp->rdata.data);
                break;
#else
/* Fall into default handler, ie, store nothing in the data portion
   for these unsupported types.
   Note what we do here MUST agree with what ntohrr() does, or we'll
   end up dn_compress'ing NULLPTR->data!
*/
#endif
/*          default:  recall no data was stored in ntohrr() */
        }
    /* Calculate the lenght of the RR */
        len = (int) (cp - p - 2);
        put16(p,len);       /* and set it */
    }
    return cp;
}
  
int
htondomain(dhdr,buffer,buflen)
struct dhdr *dhdr;
char *buffer;   /* Area for query */
int16 buflen;   /* Length of same */
{
    char *cp;
    struct rr *rrp;
    struct dict *dp = NULLDICT;
    struct dict *p,*pn;
    int16 parameter;
    int i, count;
  
    cp = buffer;
    cp = put16(cp,dhdr->id);
    if(dhdr->qr)
        parameter = 0x8000;
    else
        parameter = 0;
    parameter |= (dhdr->opcode & 0x0f) << 11;
    if(dhdr->aa)
        parameter |= DOM_AUTHORITY;
    if(dhdr->tc)
        parameter |= DOM_TRUNC;
    if(dhdr->rd)
        parameter |= DOM_DORECURSE;
    if(dhdr->ra)
        parameter |= DOM_CANRECURSE;
    parameter |= (dhdr->rcode & 0x0f);
    cp = put16(cp,parameter);
    cp = put16(cp,dhdr->qdcount);
    cp = put16(cp,dhdr->ancount);
    cp = put16(cp,dhdr->nscount);
    cp = put16(cp,dhdr->arcount);
    if((count = dhdr->qdcount) > 0) {
        rrp = dhdr->questions;
        for(i = 0; i < count; i++) {
            cp = dn_compress(buffer,&dp,cp,rrp->name);
            cp = put16(cp,rrp->type);
            cp = put16(cp,rrp->class);
            rrp = rrp->next;
        }
    }

    if(dhdr->ancount > 0)
        cp = htonrr(buffer,&dp,dhdr->answers,cp);

    if(dhdr->nscount > 0)
        cp = htonrr(buffer,&dp,dhdr->authority,cp);

    if(dhdr->arcount > 0)
        cp = htonrr(buffer,&dp,dhdr->additional,cp);

    for(p=dp; p; p=pn) {
#ifdef DICTTRACE
        log(-1,"dict: %4x %s", p->nmoff, p->nm);
#endif
        pn=p->next;
        free(p->nm);
        free(p);
    }

    return (int)(cp - buffer);
}
  
  
#endif /* DOMAINSERVER */