/src/samba/lib/util/asn1.c

Source
/*
   Unix SMB/CIFS implementation.
   simple ASN1 routines
   Copyright (C) Andrew Tridgell 2001

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/locale.h"
#include "lib/util/asn1.h"
#include "lib/util/debug.h"
#include "lib/util/samba_util.h"
#include "lib/util/smb_strtox.h"

struct nesting {
  off_t start;
  size_t taglen; /* for parsing */
  struct nesting *next;
};


struct asn1_data {
  uint8_t *data;
  size_t length;
  off_t ofs;
  struct nesting *nesting;
  bool has_error;
  unsigned depth;
  unsigned max_depth;
};

/* allocate an asn1 structure */
struct asn1_data *asn1_init(TALLOC_CTX *mem_ctx, unsigned max_depth)
{
  struct asn1_data *ret = talloc_zero(mem_ctx, struct asn1_data);
  if (ret == NULL) {
    DBG_ERR("asn1_init failed! out of memory\n");
    return ret;
  }
  ret->max_depth = max_depth;
  return ret;
}

/* free an asn1 structure */
void asn1_free(struct asn1_data *data)
{
  talloc_free(data);
}

bool asn1_has_error(const struct asn1_data *data)
{
  return data->has_error;
}

void asn1_set_error(struct asn1_data *data)
{
  data->has_error = true;
}

bool asn1_has_nesting(const struct asn1_data *data)
{
  return data->nesting != NULL;
}

off_t asn1_current_ofs(const struct asn1_data *data)
{
  return data->ofs;
}

/* write to the ASN1 buffer, advancing the buffer pointer */
bool asn1_write(struct asn1_data *data, const void *p, int _len)
{
  size_t len, ofs, newlen;

  if (data->has_error) return false;

  if (_len < 0) {
    goto error;
  }
  len = _len;

  if (data->ofs < 0) {
    goto error;
  }
  ofs = data->ofs;

  newlen = ofs + len;
  if (newlen < ofs) {
    goto error;
  }

  if (data->length < newlen) {
    uint8_t *newp;
    newp = talloc_realloc(data, data->data, uint8_t, newlen);
    if (!newp) {
      goto error;
    }
    data->data = newp;
    data->length = newlen;
  }
  if (len > 0) {
    memcpy(data->data + data->ofs, p, len);
    data->ofs += len;
  }
  return true;
error:
  data->has_error = true;
  return false;
}

/* useful fn for writing a uint8_t */
bool asn1_write_uint8(struct asn1_data *data, uint8_t v)
{
  return asn1_write(data, &v, 1);
}

/* push a tag onto the asn1 data buffer. Used for nested structures */
bool asn1_push_tag(struct asn1_data *data, uint8_t tag)
{
  struct nesting *nesting;

  if (!asn1_write_uint8(data, tag)) {
    return false;
  }
  nesting = talloc(data, struct nesting);
  if (!nesting) {
    data->has_error = true;
    return false;
  }

  nesting->start = data->ofs;
  nesting->next = data->nesting;
  data->nesting = nesting;
  return asn1_write_uint8(data, 0xff);
}

/* pop a tag */
bool asn1_pop_tag(struct asn1_data *data)
{
  struct nesting *nesting;
  size_t len;

  if (data->has_error) {
    return false;
  }

  nesting = data->nesting;

  if (!nesting) {
    data->has_error = true;
    return false;
  }
  len = data->ofs - (nesting->start+1);
  /* yes, this is ugly. We don't know in advance how many bytes the length
     of a tag will take, so we assumed 1 byte. If we were wrong then we
     need to correct our mistake */
  if (len > 0xFFFFFF) {
    data->data[nesting->start] = 0x84;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    memmove(data->data+nesting->start+5, data->data+nesting->start+1, len);
    data->data[nesting->start+1] = (len>>24) & 0xFF;
    data->data[nesting->start+2] = (len>>16) & 0xFF;
    data->data[nesting->start+3] = (len>>8) & 0xFF;
    data->data[nesting->start+4] = len&0xff;
  } else if (len > 0xFFFF) {
    data->data[nesting->start] = 0x83;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    memmove(data->data+nesting->start+4, data->data+nesting->start+1, len);
    data->data[nesting->start+1] = (len>>16) & 0xFF;
    data->data[nesting->start+2] = (len>>8) & 0xFF;
    data->data[nesting->start+3] = len&0xff;
  } else if (len > 255) {
    data->data[nesting->start] = 0x82;
    if (!asn1_write_uint8(data, 0)) return false;
    if (!asn1_write_uint8(data, 0)) return false;
    memmove(data->data+nesting->start+3, data->data+nesting->start+1, len);
    data->data[nesting->start+1] = len>>8;
    data->data[nesting->start+2] = len&0xff;
  } else if (len > 127) {
    data->data[nesting->start] = 0x81;
    if (!asn1_write_uint8(data, 0)) return false;
    memmove(data->data+nesting->start+2, data->data+nesting->start+1, len);
    data->data[nesting->start+1] = len;
  } else {
    data->data[nesting->start] = len;
  }

  data->nesting = nesting->next;
  talloc_free(nesting);
  return true;
}

/* "i" is the one's complement representation, as is the normal result of an
 * implicit signed->unsigned conversion */

static bool push_int_bigendian(struct asn1_data *data, unsigned int i, bool negative)
{
  uint8_t lowest = i & 0xFF;

  i = i >> 8;
  if (i != 0)
    if (!push_int_bigendian(data, i, negative))
      return false;

  if (data->nesting->start+1 == data->ofs) {

    /* We did not write anything yet, looking at the highest
     * valued byte */

    if (negative) {
      /* Don't write leading 0xff's */
      if (lowest == 0xFF)
        return true;

      if ((lowest & 0x80) == 0) {
        /* The only exception for a leading 0xff is if
         * the highest bit is 0, which would indicate
         * a positive value */
        if (!asn1_write_uint8(data, 0xff))
          return false;
      }
    } else {
      if (lowest & 0x80) {
        /* The highest bit of a positive integer is 1,
         * this would indicate a negative number. Push
         * a 0 to indicate a positive one */
        if (!asn1_write_uint8(data, 0))
          return false;
      }
    }
  }

  return asn1_write_uint8(data, lowest);
}

/* write an Integer without the tag framing. Needed for example for the LDAP
 * Abandon Operation */

bool asn1_write_implicit_Integer(struct asn1_data *data, int i)
{
  if (data->has_error) {
    return false;
  }

  if (i == -1) {
    /* -1 is special as it consists of all-0xff bytes. In
                    push_int_bigendian this is the only case that is not
                    properly handled, as all 0xff bytes would be handled as
                    leading ones to be ignored. */
    return asn1_write_uint8(data, 0xff);
  } else {
    return push_int_bigendian(data, i, i<0);
  }
}


/* write an integer */
bool asn1_write_Integer(struct asn1_data *data, int i)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_INTEGER);
  ok = ok && asn1_write_implicit_Integer(data, i);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

/* write a BIT STRING */
bool asn1_write_BitString(struct asn1_data *data, const void *p, size_t length, uint8_t padding)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_BIT_STRING);
  ok = ok && asn1_write_uint8(data, padding);
  ok = ok && asn1_write(data, p, length);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

bool ber_write_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB *blob, const char *OID)
{
  unsigned long int v, v2;
  const char *p = (const char *)OID;
  char *newp;
  int i;
  int error = 0;

  if (!isdigit(*p)) return false;
  v = smb_strtoul(p, &newp, 10, &error, SMB_STR_STANDARD);
  if (newp[0] != '.' || error != 0) {
    return false;
  }
  p = newp + 1;

  if (!isdigit(*p)) return false;
  v2 = smb_strtoul(p, &newp, 10, &error, SMB_STR_STANDARD);
  if (newp[0] != '.' || error != 0) {
    return false;
  }
  p = newp + 1;

  /*the ber representation can't use more space than the string one */
  *blob = data_blob_talloc(mem_ctx, NULL, strlen(OID));
  if (!blob->data) return false;

  blob->data[0] = 40*v + v2;

  i = 1;
  while (*p) {
    if (!isdigit(*p)) return false;
    v = smb_strtoul(p, &newp, 10, &error, SMB_STR_STANDARD);
    if (newp[0] == '.' || error != 0) {
      p = newp + 1;
      if (!*p) {
        /* empty last component */
        data_blob_free(blob);
        return false;
      }
    } else if (newp[0] == '\0') {
      p = newp;
    } else {
      data_blob_free(blob);
      return false;
    }
    if (v >= (1<<28)) blob->data[i++] = (0x80 | ((v>>28)&0x7f));
    if (v >= (1<<21)) blob->data[i++] = (0x80 | ((v>>21)&0x7f));
    if (v >= (1<<14)) blob->data[i++] = (0x80 | ((v>>14)&0x7f));
    if (v >= (1<<7)) blob->data[i++] = (0x80 | ((v>>7)&0x7f));
    blob->data[i++] = (v&0x7f);
  }

  blob->length = i;

  return true;
}

/**
 * Serialize partial OID string.
 * Partial OIDs are in the form:
 *   1:2.5.6:0x81
 *   1:2.5.6:0x8182
 */
bool ber_write_partial_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB *blob, const char *partial_oid)
{
  TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
  char *oid = talloc_strdup(tmp_ctx, partial_oid);
  char *p;

  /* truncate partial part so ber_write_OID_String() works */
  p = strchr(oid, ':');
  if (p) {
    *p = '\0';
    p++;
  }

  if (!ber_write_OID_String(mem_ctx, blob, oid)) {
    talloc_free(tmp_ctx);
    return false;
  }

  /* Add partially encoded sub-identifier */
  if (p) {
    DATA_BLOB tmp_blob = strhex_to_data_blob(tmp_ctx, p);
    if (!data_blob_append(mem_ctx, blob, tmp_blob.data,
              tmp_blob.length)) {
      talloc_free(tmp_ctx);
      return false;
    }
  }

  talloc_free(tmp_ctx);

  return true;
}

/* write an object ID to a ASN1 buffer */
bool asn1_write_OID(struct asn1_data *data, const char *OID)
{
  DATA_BLOB blob;

  if (!asn1_push_tag(data, ASN1_OID)) return false;

  if (!ber_write_OID_String(NULL, &blob, OID)) {
    data->has_error = true;
    return false;
  }

  if (!asn1_write(data, blob.data, blob.length)) {
    data_blob_free(&blob);
    data->has_error = true;
    return false;
  }
  data_blob_free(&blob);
  return asn1_pop_tag(data);
}

/* write an octet string */
bool asn1_write_OctetString(struct asn1_data *data, const void *p, size_t length)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_OCTET_STRING);
  ok = ok && asn1_write(data, p, length);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

/* write a LDAP string */
bool asn1_write_LDAPString(struct asn1_data *data, const char *s)
{
  return asn1_write(data, s, strlen(s));
}

/* write a LDAP string from a DATA_BLOB */
bool asn1_write_DATA_BLOB_LDAPString(struct asn1_data *data, const DATA_BLOB *s)
{
  return asn1_write(data, s->data, s->length);
}

/* write a general string */
bool asn1_write_GeneralString(struct asn1_data *data, const char *s)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_GENERAL_STRING);
  ok = ok && asn1_write_LDAPString(data, s);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

bool asn1_write_ContextSimple(struct asn1_data *data, uint8_t num, DATA_BLOB *blob)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_CONTEXT_SIMPLE(num));
  ok = ok && asn1_write(data, blob->data, blob->length);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

/* write a BOOLEAN */
bool asn1_write_BOOLEAN(struct asn1_data *data, bool v)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_BOOLEAN);
  ok = ok && asn1_write_uint8(data, v ? 0xFF : 0);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

bool asn1_read_BOOLEAN(struct asn1_data *data, bool *v)
{
  uint8_t tmp = 0;
  if (!asn1_start_tag(data, ASN1_BOOLEAN)) return false;
  *v = false;
  if (!asn1_read_uint8(data, &tmp)) return false;
  if (tmp == 0xFF) {
    *v = true;
  }
  return asn1_end_tag(data);
}

/* write a BOOLEAN in a simple context */
bool asn1_write_BOOLEAN_context(struct asn1_data *data, bool v, int context)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_CONTEXT_SIMPLE(context));
  ok = ok && asn1_write_uint8(data, v ? 0xFF : 0);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

bool asn1_read_BOOLEAN_context(struct asn1_data *data, bool *v, int context)
{
  uint8_t tmp = 0;
  if (!asn1_start_tag(data, ASN1_CONTEXT_SIMPLE(context))) return false;
  *v = false;
  if (!asn1_read_uint8(data, &tmp)) return false;
  if (tmp == 0xFF) {
    *v = true;
  }
  return asn1_end_tag(data);
}

/* check a BOOLEAN */
bool asn1_check_BOOLEAN(struct asn1_data *data, bool v)
{
  uint8_t b = 0;

  if (!asn1_read_uint8(data, &b)) return false;
  if (b != ASN1_BOOLEAN) {
    data->has_error = true;
    return false;
  }
  if (!asn1_read_uint8(data, &b)) return false;
  if (b != v) {
    data->has_error = true;
    return false;
  }
  return !data->has_error;
}


/* load a struct asn1_data structure with a lump of data, ready to be parsed */
bool asn1_load(struct asn1_data *data, DATA_BLOB blob)
{
  /*
   * Save the maximum depth
   */
  unsigned max_depth = data->max_depth;

  *data = (struct asn1_data){
    .data = talloc_memdup(data, blob.data, blob.length),
    .length = blob.length,
    .max_depth = max_depth,
  };

  if (data->data == NULL) {
    data->has_error = true;
    return false;
  }

  return true;
}

/* Peek into an ASN1 buffer, not advancing the pointer */
static bool asn1_peek(struct asn1_data *data, void *p, int len)
{
  size_t ofs, end;

  if (data->has_error)
    return false;

  if (len < 0) {
    return false;
  }

  if (data->ofs < 0) {
    data->has_error = true;
    return false;
  }
  ofs = data->ofs;

  end = ofs + len;
  if (end < ofs) {
    return false;
  }

  if (end > data->length) {
    /* we need to mark the buffer as consumed, so the caller knows
       this was an out of data error, and not a decode error */
    data->ofs = data->length;
    return false;
  }

  memcpy(p, data->data + data->ofs, len);
  return true;
}

/* read from a ASN1 buffer, advancing the buffer pointer */
bool asn1_read(struct asn1_data *data, void *p, int len)
{
  if (!asn1_peek(data, p, len)) {
    data->has_error = true;
    return false;
  }

  data->ofs += len;
  return true;
}

/* read a uint8_t from a ASN1 buffer */
bool asn1_read_uint8(struct asn1_data *data, uint8_t *v)
{
  return asn1_read(data, v, 1);
}

bool asn1_peek_uint8(struct asn1_data *data, uint8_t *v)
{
  return asn1_peek(data, v, 1);
}

bool asn1_peek_tag(struct asn1_data *data, uint8_t tag)
{
  uint8_t b;

  if (asn1_tag_remaining(data) <= 0) {
    return false;
  }

  if (!asn1_peek_uint8(data, &b))
    return false;

  return (b == tag);
}

/*
 * just get the needed size the tag would consume
 */
static bool asn1_peek_tag_needed_size(struct asn1_data *data, uint8_t tag,
              size_t *size)
{
  off_t start_ofs = data->ofs;
  uint8_t b;
  size_t taglen = 0;

  if (data->has_error) {
    return false;
  }

  if (!asn1_read_uint8(data, &b)) {
    data->ofs = start_ofs;
    data->has_error = false;
    return false;
  }

  if (b != tag) {
    data->ofs = start_ofs;
    data->has_error = false;
    return false;
  }

  if (!asn1_read_uint8(data, &b)) {
    data->ofs = start_ofs;
    data->has_error = false;
    return false;
  }

  if (b & 0x80) {
    int n = b & 0x7f;
    if (!asn1_read_uint8(data, &b)) {
      data->ofs = start_ofs;
      data->has_error = false;
      return false;
    }
    if (n > 4) {
      /*
       * We should not allow more than 4 bytes
       * for the encoding of the tag length.
       *
       * Otherwise we'd overflow the taglen
       * variable on 32 bit systems.
       */
      data->ofs = start_ofs;
      data->has_error = false;
      return false;
    }
    taglen = b;
    while (n > 1) {
      size_t tmp_taglen;

      if (!asn1_read_uint8(data, &b)) {
        data->ofs = start_ofs;
        data->has_error = false;
        return false;
      }

      tmp_taglen = (taglen << 8) | b;

      if ((tmp_taglen >> 8) != taglen) {
        /* overflow */
        data->ofs = start_ofs;
        data->has_error = false;
        return false;
      }
      taglen = tmp_taglen;

      n--;
    }
  } else {
    taglen = b;
  }

  *size = (data->ofs - start_ofs) + taglen;

  data->ofs = start_ofs;
  data->has_error = false;
  return true;
}

/* start reading a nested asn1 structure */
bool asn1_start_tag(struct asn1_data *data, uint8_t tag)
{
  uint8_t b;
  struct nesting *nesting;

  /*
   * Check the depth of the parse tree and prevent it from growing
   * too large.
   */
  data->depth++;
  if (data->depth > data->max_depth) {
    data->has_error = true;
    return false;
  }

  if (!asn1_read_uint8(data, &b))
    return false;

  if (b != tag) {
    data->has_error = true;
    return false;
  }
  nesting = talloc(data, struct nesting);
  if (!nesting) {
    data->has_error = true;
    return false;
  }

  if (!asn1_read_uint8(data, &b)) {
    return false;
  }

  if (b & 0x80) {
    int n = b & 0x7f;
    if (!asn1_read_uint8(data, &b))
      return false;
    nesting->taglen = b;
    while (n > 1) {
      size_t taglen;

      if (!asn1_read_uint8(data, &b))
        return false;

      taglen = (nesting->taglen << 8) | b;

      if ((taglen >> 8) != nesting->taglen) {
        /* overflow */
        data->has_error = true;
        return false;
      }
      nesting->taglen = taglen;

      n--;
    }
  } else {
    nesting->taglen = b;
  }
  nesting->start = data->ofs;
  nesting->next = data->nesting;
  data->nesting = nesting;
  if (asn1_tag_remaining(data) == -1) {
    return false;
  }
  return !data->has_error;
}

/* stop reading a tag */
bool asn1_end_tag(struct asn1_data *data)
{
  struct nesting *nesting;

  if (data->depth == 0) {
    smb_panic("Unbalanced ASN.1 Tag nesting");
  }
  data->depth--;
  /* make sure we read it all */
  if (asn1_tag_remaining(data) != 0) {
    data->has_error = true;
    return false;
  }

  nesting = data->nesting;

  if (!nesting) {
    data->has_error = true;
    return false;
  }

  data->nesting = nesting->next;
  talloc_free(nesting);
  return true;
}

/* work out how many bytes are left in this nested tag */
int asn1_tag_remaining(struct asn1_data *data)
{
  size_t consumed, remaining_tag, remaining_data;
  if (data->has_error) {
    return -1;
  }

  if (!data->nesting) {
    goto error;
  }

  if (data->ofs < data->nesting->start) {
    goto error;
  }
  consumed = data->ofs - data->nesting->start;

  if (data->nesting->taglen < consumed) {
    goto error;
  }
  remaining_tag = data->nesting->taglen - consumed;

  if ((data->ofs < 0) || (data->length < (size_t)data->ofs)) {
    goto error;
  }
  remaining_data = data->length - data->ofs;

  if (remaining_tag > remaining_data) {
    goto error;
  }
  if (remaining_tag > INT_MAX) {
    goto error;
  }
  return remaining_tag;
error:
  data->has_error = true;
  return -1;
}

/**
 * Internal implementation for reading binary OIDs
 * Reading is done as far in the buffer as valid OID
 * till buffer ends or not valid sub-identifier is found.
 */
static bool _ber_read_OID_String_impl(TALLOC_CTX *mem_ctx, DATA_BLOB blob,
              char **OID, size_t *bytes_eaten)
{
  size_t i;
  uint8_t *b;
  unsigned int v;
  char *tmp_oid = NULL;

  if (blob.length < 2) return false;

  b = blob.data;

  tmp_oid = talloc_asprintf(mem_ctx, "%u.%u", b[0]/40, b[0]%40);

  if (bytes_eaten != NULL) {
    *bytes_eaten = 0;
  }

  for(i = 1, v = 0; i < blob.length; i++) {
    v = (v<<7) | (b[i]&0x7f);
    if ( ! (b[i] & 0x80)) {
      talloc_asprintf_addbuf(&tmp_oid, ".%u",  v);
      v = 0;
      if (bytes_eaten)
        *bytes_eaten = i+1;
    }
  }

  if (tmp_oid == NULL) {
    goto nomem;
  }

  *OID = tmp_oid;
  return true;

nomem:
  return false;
}

/* read an object ID from a data blob */
bool ber_read_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB blob, char **OID)
{
  size_t bytes_eaten;

  if (!_ber_read_OID_String_impl(mem_ctx, blob, OID, &bytes_eaten))
    return false;

  return (bytes_eaten == blob.length);
}

/**
 * Deserialize partial OID string.
 * Partial OIDs are in the form:
 *   1:2.5.6:0x81
 *   1:2.5.6:0x8182
 */
bool ber_read_partial_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB blob,
         char **partial_oid)
{
  size_t bytes_left;
  size_t bytes_eaten;
  char *identifier = NULL;
  char *tmp_oid = NULL;

  if (!_ber_read_OID_String_impl(mem_ctx, blob, &tmp_oid, &bytes_eaten))
    return false;

  if (bytes_eaten < blob.length) {
    bytes_left = blob.length - bytes_eaten;
    identifier = hex_encode_talloc(mem_ctx, &blob.data[bytes_eaten], bytes_left);
    if (!identifier)  goto nomem;

    *partial_oid = talloc_asprintf_append_buffer(tmp_oid, ":0x%s", identifier);
    if (!*partial_oid)  goto nomem;
    TALLOC_FREE(identifier);
  } else {
    *partial_oid = tmp_oid;
  }

  return true;

nomem:
  TALLOC_FREE(identifier);
  TALLOC_FREE(tmp_oid);
  return false;
}

/* read an object ID from a ASN1 buffer */
bool asn1_read_OID(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **OID)
{
  DATA_BLOB blob;
  int len;

  if (!asn1_start_tag(data, ASN1_OID)) return false;

  len = asn1_tag_remaining(data);
  if (len < 0) {
    data->has_error = true;
    return false;
  }

  blob = data_blob(NULL, len);
  if (!blob.data) {
    data->has_error = true;
    return false;
  }

  if (!asn1_read(data, blob.data, len)) {
    data_blob_free(&blob);
    return false;
  }

  if (!asn1_end_tag(data)) {
    data_blob_free(&blob);
    return false;
  }

  if (!ber_read_OID_String(mem_ctx, blob, OID)) {
    data->has_error = true;
    data_blob_free(&blob);
    return false;
  }

  data_blob_free(&blob);
  return true;
}

/* check that the next object ID is correct */
bool asn1_check_OID(struct asn1_data *data, const char *OID)
{
  char *id;

  if (!asn1_read_OID(data, data, &id)) return false;

  if (strcmp(id, OID) != 0) {
    talloc_free(id);
    data->has_error = true;
    return false;
  }
  talloc_free(id);
  return true;
}

/* read a LDAPString from a ASN1 buffer */
bool asn1_read_LDAPString(struct asn1_data *data,
        TALLOC_CTX *mem_ctx,
        char **_s)
{
  int len;
  char *s = NULL;
  bool ok;

  len = asn1_tag_remaining(data);
  if (len < 0) {
    data->has_error = true;
    return false;
  }
  s = talloc_array(mem_ctx, char, len + 1);
  if (s == NULL) {
    data->has_error = true;
    return false;
  }
  s[len] = 0;

  ok = asn1_read(data, s, len);
  if (!ok) {
    TALLOC_FREE(s);
    return false;
  }

  *_s = s;
  return true;
}


/* read a GeneralString from a ASN1 buffer */
bool asn1_read_GeneralString(struct asn1_data *data,
           TALLOC_CTX *mem_ctx,
           char **_s)
{
  char *s = NULL;
  bool ok = false;

  if (!asn1_start_tag(data, ASN1_GENERAL_STRING)) return false;
  if (!asn1_read_LDAPString(data, mem_ctx, &s)) return false;

  ok = asn1_end_tag(data);
  if (!ok) {
    TALLOC_FREE(s);
    return false;
  }

  *_s = s;
  return true;
}


static bool asn1_read_blob_tag(struct asn1_data *data, TALLOC_CTX *mem_ctx,
             uint8_t tag, DATA_BLOB *blob)
{
  int len;
  ZERO_STRUCTP(blob);
  if (!asn1_start_tag(data, tag)) return false;
  len = asn1_tag_remaining(data);
  if (len < 0) {
    data->has_error = true;
    return false;
  }
  *blob = data_blob_talloc(mem_ctx, NULL, len+1);
  if (!blob->data || blob->length < (unsigned)len) {
    data->has_error = true;
    return false;
  }
  if (!asn1_read(data, blob->data, len)) goto err;
  if (!asn1_end_tag(data)) goto err;
  blob->length--;
  blob->data[len] = 0;
  return true;

  err:

  data_blob_free(blob);
  return false;
}

/* read a octet string blob */
bool asn1_read_OctetString(struct asn1_data *data, TALLOC_CTX *mem_ctx, DATA_BLOB *blob)
{
  return asn1_read_blob_tag(data, mem_ctx, ASN1_OCTET_STRING, blob);
}

bool asn1_read_ContextSimple(struct asn1_data *data, TALLOC_CTX *mem_ctx, uint8_t num,
           DATA_BLOB *blob)
{
  return asn1_read_blob_tag(data, mem_ctx, ASN1_CONTEXT_SIMPLE(num), blob);
}

/* read an integer without tag*/
bool asn1_read_implicit_Integer(struct asn1_data *data, int *i)
{
  uint8_t b;
  uint32_t x = 0;
  bool first_byte = true;

  *i = 0;

  while (!data->has_error && asn1_tag_remaining(data)>0) {
    if (!asn1_read_uint8(data, &b)) return false;
    if (first_byte) {
      if (b & 0x80) {
        /* Number is negative. */
        x = (uint32_t)-1;
      }
      first_byte = false;
    }
    x = (x << 8) + b;
  }
  *i = (int)x;

  return !data->has_error;
}

/* read an integer */
bool asn1_read_Integer(struct asn1_data *data, int *i)
{
  *i = 0;

  if (!asn1_start_tag(data, ASN1_INTEGER)) return false;
  if (!asn1_read_implicit_Integer(data, i)) return false;
  return asn1_end_tag(data);
}

/* read a BIT STRING */
bool asn1_read_BitString(struct asn1_data *data, TALLOC_CTX *mem_ctx, DATA_BLOB *blob, uint8_t *padding)
{
  int len;
  ZERO_STRUCTP(blob);
  if (!asn1_start_tag(data, ASN1_BIT_STRING)) return false;
  len = asn1_tag_remaining(data);
  if (len < 0) {
    data->has_error = true;
    return false;
  }
  if (!asn1_read_uint8(data, padding)) return false;

  *blob = data_blob_talloc(mem_ctx, NULL, len+1);
  if (!blob->data || blob->length < (unsigned)len) {
    data->has_error = true;
    return false;
  }
  if (asn1_read(data, blob->data, len - 1)) {
    blob->length--;
    blob->data[len] = 0;
    asn1_end_tag(data);
  }

  if (data->has_error) {
    data_blob_free(blob);
    *padding = 0;
    return false;
  }
  return true;
}

/* read a non-negative enumerated value */
bool asn1_read_enumerated(struct asn1_data *data, int *v)
{
  unsigned int val_will_wrap = (0xFFU << ((sizeof(int)*8)-8));
  *v = 0;

  if (!asn1_start_tag(data, ASN1_ENUMERATED)) return false;
  while (!data->has_error && asn1_tag_remaining(data)>0) {
    uint8_t b;
    if (!asn1_read_uint8(data, &b)) {
      return false;
    }
    if (*v & val_will_wrap) {
      /*
       * There is something already in
       * the top byte of the int. If we
       * shift left by 8 it's going to
       * wrap. Prevent this.
       */
      data->has_error = true;
      return false;
    }
    /*
     * To please/fool the Undefined Behaviour Sanitizer we cast to
     * unsigned for the left shift.
     */
    *v = ((unsigned int)*v << 8) + b;
    if (*v < 0) {
      /* ASN1_ENUMERATED can't be -ve. */
      data->has_error = true;
      return false;
    }
  }
  return asn1_end_tag(data);
}

/* write an enumerated value to the stream */
bool asn1_write_enumerated(struct asn1_data *data, uint8_t v)
{
  bool ok = !asn1_has_error(data);
  ok = ok && asn1_push_tag(data, ASN1_ENUMERATED);
  ok = ok && asn1_write_uint8(data, v);
  ok = ok && asn1_pop_tag(data);
  return ok;
}

/*
  Get us the data just written without copying
*/
bool asn1_blob(const struct asn1_data *asn1, DATA_BLOB *blob)
{
  if (asn1->has_error) {
    return false;
  }
  if (asn1->nesting != NULL) {
    return false;
  }
  blob->data = asn1->data;
  blob->length = asn1->length;
  return true;
}

bool asn1_extract_blob(struct asn1_data *asn1, TALLOC_CTX *mem_ctx,
           DATA_BLOB *pblob)
{
  DATA_BLOB blob;

  if (!asn1_blob(asn1, &blob)) {
    return false;
  }

  *pblob = (DATA_BLOB){
    .length = blob.length,
    .data = talloc_move(mem_ctx, &blob.data),
  };

  /*
   * Stop access from here on
   */
  asn1->has_error = true;

  return true;
}

/*
  Fill in an asn1 struct without making a copy
*/
void asn1_load_nocopy(struct asn1_data *data, uint8_t *buf, size_t len)
{
  /*
   * Save max_depth
   */
  unsigned max_depth = data->max_depth;

  *data = (struct asn1_data) {
    .data = buf,
    .length = len,
    .max_depth = max_depth,
  };
}

int asn1_peek_full_tag(DATA_BLOB blob, uint8_t tag, size_t *packet_size)
{
  struct asn1_data asn1 = {};
  size_t size;
  bool ok;

  asn1_load_nocopy(&asn1, blob.data, blob.length);

  ok = asn1_peek_tag_needed_size(&asn1, tag, &size);
  if (!ok) {
    return EMSGSIZE;
  }

  if (size > blob.length) {
    *packet_size = size;
    return EAGAIN;
  }

  *packet_size = size;
  return 0;
}

/*
 * Get the length of the ASN.1 data
 */
size_t asn1_get_length(const struct asn1_data *asn1) {
  return asn1->length;
}

Coverage Report

Created: 2026-09-03 07:24