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twister-seeder
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working DNS

pull/1/head
Pieter Wuille 13 years ago
parent
7721f9c1a3
commit
e93ffbf4df
1 changed files with 153 additions and 46 deletions
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  1. 193
      dns.c

193
dns.c
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@ -26,32 +26,51 @@ typedef enum { @@ -26,32 +26,51 @@ typedef enum {
} dns_type;
int port = 53;
char *host = "seedbeta.bitcoin.sipa.be";
int datattl = 60;
char *host = "seedtest.bitcoin.sipa.be";
char *ns = "vps.sipa.be";
// 0: ok
// -1: premature end of input
// -2: unsufficient space in output
int parse_name(const unsigned char **inpos, const unsigned char *inend, char *buf, size_t bufsize) {
// -1: premature end of input, forward reference, component > 63 char
// -2: insufficient space in output
int parse_name(const unsigned char **inpos, const unsigned char *inend, const unsigned char *inbuf, char *buf, size_t bufsize) {
size_t bufused = 0;
int init = 1;
do {
if (*inpos == inend)
return -1;
int octet = *(inpos++);
// read length of next component
int octet = *((*inpos)++);
if (octet == 0) {
buf[bufused] = 0;
return 0;
}
// add dot in output
if (!init) {
if (bufused == bufsize-1)
return -2;
buf[bufused++] = '.';
} else
init = 0;
// handle references
if ((octet & 0xC0) == 0xC0) {
if (*inpos == inend)
return -1;
int ref = ((octet - 0xC0) << 8) + *((*inpos)++);
if (ref < 0 || ref >= (*inpos)-inbuf) return -1;
const unsigned char *newbuf = inbuf + ref;
return parse_name(&newbuf, *inpos, inbuf, buf+bufused, bufsize-bufused);
}
if (octet > 63) return -1;
// copy data
while (octet) {
if (*inpos == inend)
return -1;
if (bufused == bufsize-1)
return -2;
octet--;
buf[bufused++] = *(inpos++);
buf[bufused++] = *((*inpos)++);
}
if (bufused == bufsize-1)
return -2;
buf[bufused++] = '.';
} while(1);
}
@ -59,7 +78,7 @@ int parse_name(const unsigned char **inpos, const unsigned char *inend, char *bu @@ -59,7 +78,7 @@ int parse_name(const unsigned char **inpos, const unsigned char *inend, char *bu
// -1: component > 63 characters
// -2: insufficent space in output
// -3: two subsequent dots
int write_name(unsigned char** outpos, unsigned char *outend, char *name) {
int write_name(unsigned char** outpos, unsigned char *outend, char *name, int offset) {
while (*name != 0) {
char *dot = strchr(name, '.');
char *fin = dot;
@ -67,36 +86,76 @@ int write_name(unsigned char** outpos, unsigned char *outend, char *name) { @@ -67,36 +86,76 @@ int write_name(unsigned char** outpos, unsigned char *outend, char *name) {
if (fin - name > 63) return -1;
if (fin == name) return -3;
if (outend - *outpos < fin - name + 2) return -2;
*(outpos++) = fin - name;
*((*outpos)++) = fin - name;
memcpy(*outpos, name, fin - name);
outpos += fin - name;
*outpos += fin - name;
if (!dot) break;
name = dot + 1;
}
if (offset < 0) {
// no reference
if (outend == *outpos) return -2;
*(outpos++) = 0;
*((*outpos)++) = 0;
} else {
if (outend - *outpos < 2) return -2;
*((*outpos)++) = (offset >> 8) | 0xC0;
*((*outpos)++) = offset & 0xFF;
}
return 0;
}
int write_record_a(unsigned char** outpos, unsigned char *outend, char *name, int cls, int ttl, uint32_t ip) {
int write_record(unsigned char** outpos, unsigned char *outend, char *name, int offset, int typ, int cls, int ttl) {
unsigned char *oldpos = *outpos;
int error = 0;
// name
if (write_name(outpos, outend, name)) goto error;
if (outend - *outpos < 14) goto error;
int ret = write_name(outpos, outend, name, offset);
if (ret) { error = ret; goto error; }
if (outend - *outpos < 8) { error = -4; goto error; }
// type
*(outpos++) = TYPE_A >> 8; *(outpos++) = TYPE_A & 0xFF;
*((*outpos)++) = typ >> 8; *((*outpos)++) = typ & 0xFF;
// class
*(outpos++) = cls >> 8; *(outpos++) = cls & 0xFF;
*((*outpos)++) = cls >> 8; *((*outpos)++) = cls & 0xFF;
// ttl
*(outpos++) = (ttl >> 24) & 0xFF; *(outpos++) = (ttl >> 16) & 0xFF; *(outpos++) = (ttl >> 8) & 0xFF; *(outpos++) = ttl & 0xFF;
*((*outpos)++) = (ttl >> 24) & 0xFF; *((*outpos)++) = (ttl >> 16) & 0xFF; *((*outpos)++) = (ttl >> 8) & 0xFF; *((*outpos)++) = ttl & 0xFF;
return 0;
error:
*outpos = oldpos;
return error;
}
int write_record_a(unsigned char** outpos, unsigned char *outend, char *name, int offset, int cls, int ttl, uint32_t ip) {
unsigned char *oldpos = *outpos;
int error = 0;
int ret = write_record(outpos, outend, name, offset, TYPE_A, cls, ttl);
if (ret) return ret;
if (outend - *outpos < 6) { error = -5; goto error; }
// rdlength
*(outpos++) = 0; *(outpos++) = 4;
*((*outpos)++) = 0; *((*outpos)++) = 4;
// rdata
*(outpos++) = (ip >> 24) & 0xFF; *(outpos++) = (ip >> 16) & 0xFF; *(outpos++) = (ip >> 8) & 0xFF; *(outpos++) = ttl & 0xFF;
*((*outpos)++) = (ip >> 24) & 0xFF; *((*outpos)++) = (ip >> 16) & 0xFF; *((*outpos)++) = (ip >> 8) & 0xFF; *((*outpos)++) = ttl & 0xFF;
return 0;
error:
*outpos = oldpos;
return -1;
return error;
}
int write_record_ns(unsigned char** outpos, unsigned char *outend, char *name, int offset, int cls, int ttl, char *ns) {
unsigned char *oldpos = *outpos;
int ret = write_record(outpos, outend, name, offset, TYPE_NS, cls, ttl);
if (ret) return ret;
int error = 0;
if (outend - *outpos < 2) { error = -5; goto error; }
(*outpos) += 2;
unsigned char *curpos = *outpos;
ret = write_name(outpos, outend, ns, -1);
if (ret) { error = ret; goto error; }
curpos[-2] = (*outpos - curpos) >> 8;
curpos[-1] = (*outpos - curpos) & 0xFF;
return 0;
error:
*outpos = oldpos;
return error;
}
ssize_t dnshandle(const unsigned char *inbuf, size_t insize, unsigned char* outbuf) {
@ -110,28 +169,31 @@ ssize_t dnshandle(const unsigned char *inbuf, size_t insize, unsigned char* outb @@ -110,28 +169,31 @@ ssize_t dnshandle(const unsigned char *inbuf, size_t insize, unsigned char* outb
outbuf[2] = inbuf[2];
outbuf[3] = inbuf[3];
// clear error
outbuf[3] &= ~240;
outbuf[3] &= ~15;
// check qr
if (inbuf[2] & 1) { error = 1; goto error; }
if (inbuf[2] & 128) { printf("Got response?\n"); error = 1; goto error; }
// check opcode
if (((inbuf[2] & 30) >> 1) != 0) { error = 4; goto error; }
if (((inbuf[2] & 120) >> 3) != 0) { printf("Opcode nonzero?\n"); error = 4; goto error; }
// check Z
if (((inbuf[3] & 14) >> 1) != 0) { error = 1; goto error; }
if (((inbuf[3] & 112) >> 4) != 0) { printf("Z nonzero?\n"); error = 1; goto error; }
// unset TC
outbuf[2] &= ~64;
outbuf[2] &= ~2;
// unset RA
outbuf[3] &= ~1;
outbuf[3] &= ~128;
// check questions
int nquestion = inbuf[4] << 8 + inbuf[5];
if (nquestion == 0) { error = 0; goto error; }
if (nquestion > 0) { error = 4; goto error; }
int nquestion = (inbuf[4] << 8) + inbuf[5];
if (nquestion == 0) { printf("No questions?\n"); error = 0; goto error; }
if (nquestion > 1) { printf("Multiple questions %i?\n", nquestion); error = 4; goto error; }
const unsigned char *inpos = inbuf + 12;
const unsigned char *inend = inbuf + insize;
char name[256];
int ret = parse_name(&inpos, inend, name, 256))
int offset = inpos - inbuf;
int ret = parse_name(&inpos, inend, inbuf, name, 256);
printf("got request for host='%s'\n", name);
if (ret == -1) { error = 1; goto error; }
if (ret == -2) { error = 5; goto error; }
if (strcmp(name, host)) { error = 0; goto error; }
int namel = strlen(name), hostl = strlen(host);
if (strcmp(name, host) && (namel<hostl+2 || name[namel-hostl-1]!='.' || strcmp(name+namel-hostl,host))) { error = 5; goto error; }
if (inend - inpos < 4) { error = 1; goto error; }
// copy question to output
memcpy(outbuf+12, inbuf+12, inpos+4 - (inbuf+12));
@ -140,26 +202,70 @@ ssize_t dnshandle(const unsigned char *inbuf, size_t insize, unsigned char* outb @@ -140,26 +202,70 @@ ssize_t dnshandle(const unsigned char *inbuf, size_t insize, unsigned char* outb
outbuf[6] = 0; outbuf[7] = 0;
outbuf[8] = 0; outbuf[9] = 0;
outbuf[10] = 0; outbuf[11] = 0;
// set qr
outbuf[2] |= 128;
int typ = inpos[0] << 8 + inpos[1];
int cls = inpos[2] << 8 + inpos[3];
int typ = (inpos[0] << 8) + inpos[1];
int cls = (inpos[2] << 8) + inpos[3];
inpos += 4;
unsigned char *outpos = outbuf+(inpos-inbuf);
unsigned char *outend = outbuf + BUFLEN;
printf("type=%i class=%i\n", typ, cls);
// calculate size of authority section
int auth_size = 0;
if (!((typ == TYPE_NS || typ == QTYPE_ANY) && (cls == CLASS_IN || cls == QCLASS_ANY))) {
// authority section will be necessary
unsigned char *oldpos = outpos;
write_record_ns(&oldpos, outend, "", offset, CLASS_IN, 0, ns);
auth_size = oldpos - outpos;
printf("Authority section will claim %i bytes\n", auth_size);
}
// Answer section
int have_ns = 0;
if ((typ == TYPE_NS || typ == QTYPE_ANY) && (cls == CLASS_IN || cls == QCLASS_ANY)) {
int ret2 = write_record_ns(&outpos, outend, "", offset, CLASS_IN, 30583, ns);
printf("wrote NS record: %i\n", ret2);
if (!ret2) { outbuf[7]++; have_ns++; }
}
if ((typ == TYPE_A || typ == QTYPE_ANY) && (cls == CLASS_IN || cls == QCLASS_ANY)) {
uint32_t ip = 0x01101102;
while (!write_record_a(&outpos, outend, host, CLASS_IN, 1, ip)) {
do {
int ret = write_record_a(&outpos, outend - auth_size, "", offset, CLASS_IN, datattl, ip);
printf("wrote A record: %i\n", ret);
if (!ret) {
ip += 0x01101102;
outbuf[7] ++;
outbuf[7]++;
} else
break;
} while(1);
}
// Authority section
if (!have_ns) {
int ret2 = write_record_ns(&outpos, outend, "", offset, CLASS_IN, 30583, ns);
printf("wrote NS record: %i\n", ret2);
if (!ret2) {
outbuf[9]++;
}
}
// set AA
outbuf[2] |= 32;
outbuf[2] |= 4;
return outpos - outbuf;
error:
// set error
outbuf[3] |= error << 4;
outbuf[3] |= error & 0xF;
// set counts
outbuf[4] = 0; outbuf[5] = 0;
outbuf[6] = 0; outbuf[7] = 0;
@ -170,7 +276,7 @@ error: @@ -170,7 +276,7 @@ error:
int dnsserver(void) {
struct sockaddr_in si_me, si_other;
int s, i, slen=sizeof(si_other);
socklen_t s, i, slen=sizeof(si_other);
unsigned char inbuf[BUFLEN], outbuf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
return -1;
@ -178,14 +284,15 @@ int dnsserver(void) { @@ -178,14 +284,15 @@ int dnsserver(void) {
si_me.sin_family = AF_INET;
si_me.sin_port = htons(port);
si_me.sin_addr.s_addr = INADDR_ANY;
if (bind(s, &si_me, sizeof(si_me))==-1)
if (bind(s, (struct sockaddr*)&si_me, sizeof(si_me))==-1)
return -2;
do {
ssize_t insize = recvfrom(s, inbuf, BUFLEN, 0, &si_other, &slen);
ssize_t insize = recvfrom(s, inbuf, BUFLEN, 0, (struct sockaddr*)&si_other, &slen);
printf("Got %i-byte request\n", insize);
if (insize > 0) {
ssize_t ret = dnshandle(inbuf, insize, outbuf);
if (ret > 0)
sendto(s, outbuf, ret, &si_other, &slen);
sendto(s, outbuf, ret, 0, (struct sockaddr*)&si_other, slen);
}
} while(1);
return 0;

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