dnsparser.c File Reference

helper library to parse DNS packets. More...

#include "platform.h"
#include "gnunet_util_lib.h"

Include dependency graph for dnsparser.c:

Go to the source code of this file.

Functions
int	GNUNET_DNSPARSER_check_label (const char *label)
	Check if a label in UTF-8 format can be coded into valid IDNA. More...
int	GNUNET_DNSPARSER_check_name (const char *name)
	Check if a label in UTF-8 format can be coded into valid IDNA. More...
void	GNUNET_DNSPARSER_free_soa (struct GNUNET_DNSPARSER_SoaRecord *soa)
	Free SOA information record. More...
void	GNUNET_DNSPARSER_free_cert (struct GNUNET_DNSPARSER_CertRecord *cert)
	Free CERT information record. More...
void	GNUNET_DNSPARSER_free_srv (struct GNUNET_DNSPARSER_SrvRecord *srv)
	Free SRV information record. More...
void	GNUNET_DNSPARSER_free_mx (struct GNUNET_DNSPARSER_MxRecord *mx)
	Free MX information record. More...
void	GNUNET_DNSPARSER_free_record (struct GNUNET_DNSPARSER_Record *r)
	Free the given DNS record. More...
static char *	parse_name (const char *udp_payload, size_t udp_payload_length, size_t *off, unsigned int depth)
	Parse name inside of a DNS query or record. More...
char *	GNUNET_DNSPARSER_parse_name (const char *udp_payload, size_t udp_payload_length, size_t *off)
	Parse name inside of a DNS query or record. More...
int	GNUNET_DNSPARSER_parse_query (const char *udp_payload, size_t udp_payload_length, size_t *off, struct GNUNET_DNSPARSER_Query *q)
	Parse a DNS query entry. More...
struct GNUNET_DNSPARSER_SoaRecord *	GNUNET_DNSPARSER_parse_soa (const char *udp_payload, size_t udp_payload_length, size_t *off)
	Parse a DNS SOA record. More...
struct GNUNET_DNSPARSER_MxRecord *	GNUNET_DNSPARSER_parse_mx (const char *udp_payload, size_t udp_payload_length, size_t *off)
	Parse a DNS MX record. More...
struct GNUNET_DNSPARSER_SrvRecord *	GNUNET_DNSPARSER_parse_srv (const char *udp_payload, size_t udp_payload_length, size_t *off)
	Parse a DNS SRV record. More...
struct GNUNET_DNSPARSER_CertRecord *	GNUNET_DNSPARSER_parse_cert (const char *udp_payload, size_t udp_payload_length, size_t *off)
	Parse a DNS CERT record. More...
int	GNUNET_DNSPARSER_parse_record (const char *udp_payload, size_t udp_payload_length, size_t *off, struct GNUNET_DNSPARSER_Record *r)
	Parse a DNS record entry. More...
struct GNUNET_DNSPARSER_Packet *	GNUNET_DNSPARSER_parse (const char *udp_payload, size_t udp_payload_length)
	Parse a UDP payload of a DNS packet in to a nice struct for further processing and manipulation. More...
struct GNUNET_DNSPARSER_Record *	GNUNET_DNSPARSER_duplicate_record (const struct GNUNET_DNSPARSER_Record *r)
	Duplicate (deep-copy) the given DNS record. More...
struct GNUNET_DNSPARSER_SoaRecord *	GNUNET_DNSPARSER_duplicate_soa_record (const struct GNUNET_DNSPARSER_SoaRecord *r)
	Duplicate (deep-copy) the given DNS record. More...
struct GNUNET_DNSPARSER_CertRecord *	GNUNET_DNSPARSER_duplicate_cert_record (const struct GNUNET_DNSPARSER_CertRecord *r)
	Duplicate (deep-copy) the given DNS record. More...
struct GNUNET_DNSPARSER_MxRecord *	GNUNET_DNSPARSER_duplicate_mx_record (const struct GNUNET_DNSPARSER_MxRecord *r)
	Duplicate (deep-copy) the given DNS record. More...
struct GNUNET_DNSPARSER_SrvRecord *	GNUNET_DNSPARSER_duplicate_srv_record (const struct GNUNET_DNSPARSER_SrvRecord *r)
	Duplicate (deep-copy) the given DNS record. More...
void	GNUNET_DNSPARSER_free_packet (struct GNUNET_DNSPARSER_Packet *p)
	Free memory taken by a packet. More...
int	GNUNET_DNSPARSER_builder_add_name (char *dst, size_t dst_len, size_t *off, const char *name)
	Add a DNS name to the UDP packet at the given location, converting the name to IDNA notation as necessary. More...
int	GNUNET_DNSPARSER_builder_add_query (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_Query *query)
	Add a DNS query to the UDP packet at the given location. More...
int	GNUNET_DNSPARSER_builder_add_mx (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_MxRecord *mx)
	Add an MX record to the UDP packet at the given location. More...
int	GNUNET_DNSPARSER_builder_add_cert (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_CertRecord *cert)
	Add a CERT record to the UDP packet at the given location. More...
int	GNUNET_DNSPARSER_builder_add_soa (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_SoaRecord *soa)
	Add an SOA record to the UDP packet at the given location. More...
int	GNUNET_DNSPARSER_builder_add_srv (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_SrvRecord *srv)
	Add an SRV record to the UDP packet at the given location. More...
static int	add_record (char *dst, size_t dst_len, size_t *off, const struct GNUNET_DNSPARSER_Record *record)
	Add a DNS record to the UDP packet at the given location. More...
int	GNUNET_DNSPARSER_pack (const struct GNUNET_DNSPARSER_Packet *p, uint16_t max, char **buf, size_t *buf_length)
	Given a DNS packet p, generate the corresponding UDP payload. More...
char *	GNUNET_DNSPARSER_bin_to_hex (const void *data, size_t data_size)
	Convert a block of binary data to HEX. More...
size_t	GNUNET_DNSPARSER_hex_to_bin (const char *hex, void *data)
	Convert a HEX string to block of binary data. More...

Detailed Description

helper library to parse DNS packets.

Author

Philipp Toelke

Christian Grothoff

Definition in file dnsparser.c.

Function Documentation

parse_name()

static char* parse_name ( const char *  udp_payload, size_t  udp_payload_length, size_t *  off, unsigned int  depth  )

static

Parse name inside of a DNS query or record.

Parameters

udp_payload	entire UDP payload
udp_payload_length	length of udp_payload
off	pointer to the offset of the name to parse in the udp_payload (to be incremented by the size of the name)
depth	current depth of our recursion (to prevent stack overflow)

Returns

name as 0-terminated C string on success, NULL if the payload is malformed

Definition at line 214 of file dnsparser.c.

{
  const uint8_t *input = (const uint8_t *) udp_payload;
  char *ret;
  char *tmp;
  char *xstr;
  uint8_t len;
  size_t xoff;
  char *utf8;
  Idna_rc rc;
 
  ret = GNUNET_strdup ("");
  while (1)
  {
    if (*off >= udp_payload_length)
    {
      GNUNET_break_op (0);
      goto error;
    }
    len = input[*off];
    if (0 == len)
    {
      (*off)++;
      break;
    }
    if (len < 64)
    {
      if (*off + 1 + len > udp_payload_length)
      {
        GNUNET_break_op (0);
        goto error;
      }
      GNUNET_asprintf (&tmp, "%.*s", (int) len, &udp_payload[*off + 1]);
      if (IDNA_SUCCESS !=
          (rc = idna_to_unicode_8z8z (tmp, &utf8, IDNA_ALLOW_UNASSIGNED)))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    _ ("Failed to convert DNS IDNA name `%s' to UTF-8: %s\n"),
                    tmp,
                    idna_strerror (rc));
        GNUNET_free (tmp);
        GNUNET_asprintf (&tmp,
                         "%s%.*s.",
                         ret,
                         (int) len,
                         &udp_payload[*off + 1]);
      }
      else
      {
        GNUNET_free (tmp);
        GNUNET_asprintf (&tmp, "%s%s.", ret, utf8);
        free (utf8);
      }
      GNUNET_free (ret);
      ret = tmp;
      *off += 1 + len;
    }
    else if ((64 | 128) == (len & (64 | 128)))
    {
      if (depth > 32)
      {
        GNUNET_break_op (0);
        goto error;       /* hard bound on stack to prevent "infinite" recursion, disallow! */
      }
      /* pointer to string */
      if (*off + 1 > udp_payload_length)
      {
        GNUNET_break_op (0);
        goto error;
      }
      xoff = ((len - (64 | 128)) << 8) + input[*off + 1];
      xstr = parse_name (udp_payload, udp_payload_length, &xoff, depth + 1);
      if (NULL == xstr)
      {
        GNUNET_break_op (0);
        goto error;
      }
      GNUNET_asprintf (&tmp, "%s%s.", ret, xstr);
      GNUNET_free (ret);
      GNUNET_free (xstr);
      ret = tmp;
      if (strlen (ret) > udp_payload_length)
      {
        GNUNET_break_op (0);
        goto error;       /* we are looping (building an infinite string) */
      }
      *off += 2;
      /* pointers always terminate names */
      break;
    }
    else
    {
      /* neither pointer nor inline string, not supported... */
      GNUNET_break_op (0);
      goto error;
    }
  }
  if (0 < strlen (ret))
    ret[strlen (ret) - 1] = '\0'; /* eat tailing '.' */
  return ret;
error:
  GNUNET_break_op (0);
  GNUNET_free (ret);
  return NULL;
}

References _, GNUNET_asprintf(), GNUNET_break_op, GNUNET_ERROR_TYPE_INFO, GNUNET_free, GNUNET_log, GNUNET_strdup, len, and ret.

Referenced by GNUNET_DNSPARSER_parse_name().

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add_record()

static int add_record ( char *  dst, size_t  dst_len, size_t *  off, const struct GNUNET_DNSPARSER_Record *  record  )

static

Add a DNS record to the UDP packet at the given location.

Parameters

dst	where to write the query
dst_len	number of bytes in dst
off	pointer to offset where to write the query (increment by bytes used) must not be changed if there is an error
record	record to write

Returns

GNUNET_SYSERR if record is invalid GNUNET_NO if record did not fit GNUNET_OK if record was added to dst

Definition at line 1156 of file dnsparser.c.

{
  int ret;
  size_t start;
  size_t pos;
  struct GNUNET_TUN_DnsRecordLine rl;
 
  start = *off;
  ret = GNUNET_DNSPARSER_builder_add_name (dst,
                                           dst_len
                                           - sizeof(
                                             struct GNUNET_TUN_DnsRecordLine),
                                           off,
                                           record->name);
  if (GNUNET_OK != ret)
    return ret;
  /* '*off' is now the position where we will need to write the record line */
 
  pos = *off + sizeof(struct GNUNET_TUN_DnsRecordLine);
  switch (record->type)
  {
  case GNUNET_DNSPARSER_TYPE_MX:
    ret = GNUNET_DNSPARSER_builder_add_mx (dst, dst_len, &pos, record->data.mx);
    break;
 
  case GNUNET_DNSPARSER_TYPE_CERT:
    ret =
      GNUNET_DNSPARSER_builder_add_cert (dst, dst_len, &pos, record->data.cert);
    break;
 
  case GNUNET_DNSPARSER_TYPE_SOA:
    ret =
      GNUNET_DNSPARSER_builder_add_soa (dst, dst_len, &pos, record->data.soa);
    break;
 
  case GNUNET_DNSPARSER_TYPE_NS:
  case GNUNET_DNSPARSER_TYPE_CNAME:
  case GNUNET_DNSPARSER_TYPE_PTR:
    ret = GNUNET_DNSPARSER_builder_add_name (dst,
                                             dst_len,
                                             &pos,
                                             record->data.hostname);
    break;
 
  case GNUNET_DNSPARSER_TYPE_SRV:
    ret =
      GNUNET_DNSPARSER_builder_add_srv (dst, dst_len, &pos, record->data.srv);
    break;
 
  default:
    if (pos + record->data.raw.data_len > dst_len)
    {
      ret = GNUNET_NO;
      break;
    }
    GNUNET_memcpy (&dst[pos], record->data.raw.data, record->data.raw.data_len);
    pos += record->data.raw.data_len;
    ret = GNUNET_OK;
    break;
  }
  if (GNUNET_OK != ret)
  {
    *off = start;
    return GNUNET_NO;
  }
 
  if (pos - (*off + sizeof(struct GNUNET_TUN_DnsRecordLine)) > UINT16_MAX)
  {
    /* record data too long */
    *off = start;
    return GNUNET_NO;
  }
  rl.type = htons (record->type);
  rl.dns_traffic_class = htons (record->dns_traffic_class);
  rl.ttl = htonl (
    GNUNET_TIME_absolute_get_remaining (record->expiration_time).rel_value_us
    / 1000LL / 1000LL); /* in seconds */
  rl.data_len = htons (
    (uint16_t) (pos - (*off + sizeof(struct GNUNET_TUN_DnsRecordLine))));
  GNUNET_memcpy (&dst[*off], &rl, sizeof(struct GNUNET_TUN_DnsRecordLine));
  *off = pos;
  return GNUNET_OK;
}

References GNUNET_TUN_DnsRecordLine::data_len, GNUNET_TUN_DnsRecordLine::dns_traffic_class, GNUNET_DNSPARSER_builder_add_cert(), GNUNET_DNSPARSER_builder_add_mx(), GNUNET_DNSPARSER_builder_add_name(), GNUNET_DNSPARSER_builder_add_soa(), GNUNET_DNSPARSER_builder_add_srv(), GNUNET_DNSPARSER_TYPE_CERT, GNUNET_DNSPARSER_TYPE_CNAME, GNUNET_DNSPARSER_TYPE_MX, GNUNET_DNSPARSER_TYPE_NS, GNUNET_DNSPARSER_TYPE_PTR, GNUNET_DNSPARSER_TYPE_SOA, GNUNET_DNSPARSER_TYPE_SRV, GNUNET_memcpy, GNUNET_NO, GNUNET_OK, GNUNET_TIME_absolute_get_remaining(), record(), GNUNET_TIME_Relative::rel_value_us, ret, start, GNUNET_TUN_DnsRecordLine::ttl, and GNUNET_TUN_DnsRecordLine::type.

Referenced by GNUNET_DNSPARSER_pack().

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