/src/libressl/crypto/x509/x509_constraints.c

Source (jump to first uncovered line)
/* $OpenBSD: x509_constraints.c,v 1.28 2022/06/27 15:03:11 beck Exp $ */
/*
 * Copyright (c) 2020 Bob Beck <beck@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>

#include <openssl/safestack.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>

#include "x509_internal.h"

/* RFC 2821 section 4.5.3.1 */
#define LOCAL_PART_MAX_LEN 64
#define DOMAIN_PART_MAX_LEN 255

struct x509_constraints_name *
x509_constraints_name_new(void)
{
  return (calloc(1, sizeof(struct x509_constraints_name)));
}

void
x509_constraints_name_clear(struct x509_constraints_name *name)
{
  free(name->name);
  free(name->local);
  free(name->der);
  memset(name, 0, sizeof(*name));
}

void
x509_constraints_name_free(struct x509_constraints_name *name)
{
  if (name == NULL)
    return;
  x509_constraints_name_clear(name);
  free(name);
}

struct x509_constraints_name *
x509_constraints_name_dup(struct x509_constraints_name *name)
{
  struct x509_constraints_name *new;

  if ((new = x509_constraints_name_new()) == NULL)
    goto err;
  new->type = name->type;
  new->af = name->af;
  new->der_len = name->der_len;
  if (name->der_len > 0) {
    if ((new->der = malloc(name->der_len)) == NULL)
      goto err;
    memcpy(new->der, name->der, name->der_len);
  }
  if (name->name != NULL && (new->name = strdup(name->name)) == NULL)
    goto err;
  if (name->local != NULL && (new->local = strdup(name->local)) == NULL)
    goto err;
  memcpy(new->address, name->address, sizeof(name->address));
  return new;
 err:
  x509_constraints_name_free(new);
  return NULL;
}

struct x509_constraints_names *
x509_constraints_names_new(size_t names_max)
{
  struct x509_constraints_names *new;

  if ((new = calloc(1, sizeof(struct x509_constraints_names))) == NULL)
    return NULL;

  new->names_max = names_max;

  return new;
}

void
x509_constraints_names_clear(struct x509_constraints_names *names)
{
  size_t i;

  for (i = 0; i < names->names_count; i++)
    x509_constraints_name_free(names->names[i]);
  free(names->names);
  memset(names, 0, sizeof(*names));
}

void
x509_constraints_names_free(struct x509_constraints_names *names)
{
  if (names == NULL)
    return;

  x509_constraints_names_clear(names);
  free(names);
}

int
x509_constraints_names_add(struct x509_constraints_names *names,
    struct x509_constraints_name *name)
{
  if (names->names_count >= names->names_max)
    return 0;
  if (names->names_count == names->names_len) {
    struct x509_constraints_name **tmp;
    if ((tmp = recallocarray(names->names, names->names_len,
        names->names_len + 32, sizeof(*tmp))) == NULL)
      return 0;
    names->names_len += 32;
    names->names = tmp;
  }
  names->names[names->names_count] = name;
  names->names_count++;
  return 1;
}

struct x509_constraints_names *
x509_constraints_names_dup(struct x509_constraints_names *names)
{
  struct x509_constraints_names *new = NULL;
  struct x509_constraints_name *name = NULL;
  size_t i;

  if (names == NULL)
    return NULL;

  if ((new = x509_constraints_names_new(names->names_max)) == NULL)
    goto err;

  for (i = 0; i < names->names_count; i++) {
    if ((name = x509_constraints_name_dup(names->names[i])) == NULL)
      goto err;
    if (!x509_constraints_names_add(new, name))
      goto err;
  }

  return new;
 err:
  x509_constraints_names_free(new);
  x509_constraints_name_free(name);
  return NULL;
}


/*
 * Validate that the name contains only a hostname consisting of RFC
 * 5890 compliant A-labels (see RFC 6066 section 3). This is more
 * permissive to allow for a leading '.'  for a subdomain based
 * constraint, as well as allowing for '_' which is commonly accepted
 * by nonconformant DNS implementaitons.
 *
 * if "wildcards" is set it allows '*' to occur in the string at the end of a
 * component.
 */
static int
x509_constraints_valid_domain_internal(uint8_t *name, size_t len, int wildcards)
{
  uint8_t prev, c = 0;
  int component = 0;
  int first;
  size_t i;

  if (len > DOMAIN_PART_MAX_LEN)
    return 0;

  for (i = 0; i < len; i++) {
    prev = c;
    c = name[i];

    first = (i == 0);

    /* Everything has to be ASCII, with no NUL byte */
    if (!isascii(c) || c == '\0')
      return 0;
    /* It must be alphanumeric, a '-', '.', '_' or '*' */
    if (!isalnum(c) && c != '-' && c != '.' && c != '_' && c != '*')
      return 0;

    /* if it is a '*', fail if not wildcards */
    if (!wildcards && c == '*')
      return 0;

    /* '-' must not start a component or be at the end. */
    if (c == '-' && (component == 0 || i == len - 1))
      return 0;

    /*
     * '.' must not be at the end. It may be first overall
     * but must not otherwise start a component.
     */
    if (c == '.' && ((component == 0 && !first) || i == len - 1))
      return 0;

    if (c == '.') {
      /* Components can not end with a dash. */
      if (prev == '-')
        return 0;
      /* Start new component */
      component = 0;
      continue;
    }
    /*
     * Wildcards can only occur at the end of a component.
     * c*.com is valid, c*c.com is not.
     */
    if (prev == '*')
      return 0;

    /* Components must be 63 chars or less. */
    if (++component > 63)
      return 0;
  }
  return 1;
}

int
x509_constraints_valid_domain(uint8_t *name, size_t len)
{
  if (len == 0)
    return 0;
  /*
   * A domain may not be less than two characters, so you can't
   * have a require subdomain name with less than that.
   */
  if (len < 3 && name[0] == '.')
    return 0;
  return x509_constraints_valid_domain_internal(name, len, 0);
}

int
x509_constraints_valid_host(uint8_t *name, size_t len)
{
  struct sockaddr_in sin4;
  struct sockaddr_in6 sin6;

  if (len == 0)
    return 0;
  if (name[0] == '.') /* leading . not allowed in a host name*/
    return 0;
  if (inet_pton(AF_INET, name, &sin4) == 1)
    return 0;
  if (inet_pton(AF_INET6, name, &sin6) == 1)
    return 0;
  return x509_constraints_valid_domain_internal(name, len, 0);
}

int
x509_constraints_valid_sandns(uint8_t *name, size_t len)
{
  if (len == 0)
    return 0;

  if (name[0] == '.') /* leading . not allowed in a SAN DNS name */
    return 0;
  /*
   * A domain may not be less than two characters, so you
   * can't wildcard a single domain of less than that
   */
  if (len < 4 && name[0] == '*')
    return 0;
  /*
   * A wildcard may only be followed by a '.'
   */
  if (len >= 4 && name[0] == '*' && name[1] != '.')
    return 0;

  return x509_constraints_valid_domain_internal(name, len, 1);
}

static inline int
local_part_ok(char c)
{
  return (('0' <= c && c <= '9') || ('a' <= c && c <= 'z') ||
      ('A' <= c && c <= 'Z') || c == '!' || c == '#' || c == '$' ||
      c == '%' || c == '&' || c == '\'' || c == '*' || c == '+' ||
      c == '-' || c == '/' || c == '=' || c == '?' ||  c == '^' ||
      c == '_' || c == '`' || c == '{' || c == '|' || c == '}' ||
      c == '~' || c == '.');
}

/*
 * Parse "candidate" as an RFC 2821 mailbox.
 * Returns 0 if candidate is not a valid mailbox or if an error occurs.
 * Returns 1 if candidate is a mailbox and adds newly allocated
 * local and domain parts of the mailbox to "name->local" and name->name"
 */
int
x509_constraints_parse_mailbox(uint8_t *candidate, size_t len,
    struct x509_constraints_name *name)
{
  char working[DOMAIN_PART_MAX_LEN + 1] = { 0 };
  char *candidate_local = NULL;
  char *candidate_domain = NULL;
  size_t i, wi = 0;
  int accept = 0;
  int quoted = 0;

  if (candidate == NULL)
    return 0;

  /* It can't be bigger than the local part, domain part and the '@' */
  if (len > LOCAL_PART_MAX_LEN + DOMAIN_PART_MAX_LEN + 1)
    return 0;

  for (i = 0; i < len; i++) {
    char c = candidate[i];
    /* non ascii, cr, lf, or nul is never allowed */
    if (!isascii(c) || c == '\r' || c == '\n' || c == '\0')
      goto bad;
    if (i == 0) {
      /* local part is quoted part */
      if (c == '"')
        quoted = 1;
      /* can not start with a . */
      if (c == '.')
        goto bad;
    }
    if (accept) {
      if (wi >= DOMAIN_PART_MAX_LEN)
        goto bad;
      working[wi++] = c;
      accept = 0;
      continue;
    }
    if (candidate_local != NULL) {
      /* We are looking for the domain part */
      if (wi >= DOMAIN_PART_MAX_LEN)
        goto bad;
      working[wi++] = c;
      if (i == len - 1) {
        if (wi == 0)
          goto bad;
        if (candidate_domain != NULL)
          goto bad;
        candidate_domain = strdup(working);
        if (candidate_domain == NULL)
          goto bad;
      }
      continue;
    }
    /* We are looking for the local part */
    if (wi >= LOCAL_PART_MAX_LEN)
      break;

    if (quoted) {
      if (c == '\\') {
        accept = 1;
        continue;
      }
      if (c == '"' && i != 0) {
        /* end the quoted part. @ must be next */
        if (i + 1 == len || candidate[i + 1] != '@')
          goto bad;
        quoted = 0;
      }
      /*
       * XXX Go strangely permits sp but forbids ht
       * mimic that for now
       */
      if (c == 9)
        goto bad;
      if (wi >= LOCAL_PART_MAX_LEN)
        goto bad;
      working[wi++] = c;
      continue; /* all's good inside our quoted string */
    }
    if (c == '@') {
      if (wi == 0)
        goto bad;
      if (candidate_local != NULL)
        goto bad;
      candidate_local = strdup(working);
      if (candidate_local == NULL)
        goto bad;
      memset(working, 0, sizeof(working));
      wi = 0;
      continue;
    }
    if (c == '\\') {
      /*
       * RFC 3936 hints these can happen outside of
       * quotend string. don't include the \ but
       * next character must be ok.
       */
      if (i + 1 == len)
        goto bad;
      if (!local_part_ok(candidate[i + 1]))
        goto bad;
      accept = 1;
    }
    if (!local_part_ok(c))
      goto bad;
    if (wi >= LOCAL_PART_MAX_LEN)
      goto bad;
    working[wi++] = c;
  }
  if (candidate_local == NULL || candidate_domain == NULL)
    goto bad;
  if (!x509_constraints_valid_host(candidate_domain,
      strlen(candidate_domain)))
    goto bad;

  if (name != NULL) {
    name->local = candidate_local;
    name->name = candidate_domain;
    name->type = GEN_EMAIL;
  } else {
    free(candidate_local);
    free(candidate_domain);
  }
  return 1;
 bad:
  free(candidate_local);
  free(candidate_domain);
  return 0;
}

int
x509_constraints_valid_domain_constraint(uint8_t *constraint, size_t len)
{
  if (len == 0)
    return 1; /* empty constraints match */

  /*
   * A domain may not be less than two characters, so you
   * can't match a single domain of less than that
   */
  if (len < 3 && constraint[0] == '.')
    return 0;
  return x509_constraints_valid_domain_internal(constraint, len, 0);
}

/*
 * Extract the host part of a URI. On failure to parse a valid host part of the
 * URI, 0 is returned indicating an invalid URI. If the host part parses as
 * valid, or is not present, 1 is returned indicating a possibly valid URI.
 *
 * In the case of a valid URI, *hostpart will be set to a copy of the host part
 * of the URI, or the empty string if no URI is present. If memory allocation
 * fails *hostpart will be set to NULL, even though we returned 1. It is the
 * caller's responsibility to indicate an error for memory allocation failure,
 * and the callers responsibility to free *hostpart.
 *
 * RFC 3986:
 * the authority part of a uri starts with // and is terminated with
 * the next '/', '?', '#' or end of the URI.
 *
 * The authority itself contains [userinfo '@'] host [: port]
 *
 * so the host starts at the start or after the '@', and ends
 * with end of URI, '/', '?', "#', or ':'.
 */
int
x509_constraints_uri_host(uint8_t *uri, size_t len, char **hostpart)
{
  size_t i, hostlen = 0;
  uint8_t *authority = NULL;
  char *host = NULL;

  /*
   * Find first '//'. there must be at least a '//' and
   * something else.
   */
  if (len < 3)
    return 0;
  for (i = 0; i < len - 1; i++) {
    if (!isascii(uri[i]))
      return 0;
    if (uri[i] == '/' && uri[i + 1] == '/') {
      authority = uri + i + 2;
      break;
    }
  }
  if (authority == NULL) {
    /*
     * There is no authority, so no host part in this
     * URI. This might be ok or might not, but it must
     * fail if we run into a name constraint later, so
     * we indicate that we have a URI with an empty
     * host part, and succeed.
     */
    *hostpart = strdup("");
    return 1;
  }
  for (i = authority - uri; i < len; i++) {
    if (!isascii(uri[i]))
      return 0;
    /* it has a userinfo part */
    if (uri[i] == '@') {
      hostlen = 0;
      /* it can only have one */
      if (host != NULL)
        break;
      /* start after the userinfo part */
      host = uri + i + 1;
      continue;
    }
    /* did we find the end? */
    if (uri[i] == ':' || uri[i] == '/' || uri[i] == '?' ||
        uri[i] == '#')
      break;
    hostlen++;
  }
  if (hostlen == 0)
    return 0;
  if (host == NULL)
    host = authority;
  if (!x509_constraints_valid_host(host, hostlen))
    return 0;
  if (hostpart != NULL)
    *hostpart = strndup(host, hostlen);
  return 1;
}

int
x509_constraints_sandns(char *sandns, size_t dlen, char *constraint, size_t len)
{
  char *suffix;

  if (len == 0)
    return 1; /* an empty constraint matches everything */

  /* match the end of the domain */
  if (dlen < len)
    return 0;
  suffix = sandns + (dlen - len);
  return (strncasecmp(suffix, constraint, len) == 0);
}

/*
 * Validate a pre-validated domain of length dlen against a pre-validated
 * constraint of length len.
 *
 * returns 1 if the domain and constraint match.
 * returns 0 otherwise.
 *
 * an empty constraint matches everyting.
 * constraint will be matched against the domain as a suffix if it
 * starts with a '.'.
 * domain will be matched against the constraint as a suffix if it
 * starts with a '.'.
 */
int
x509_constraints_domain(char *domain, size_t dlen, char *constraint, size_t len)
{
  if (len == 0)
    return 1; /* an empty constraint matches everything */

  if (constraint[0] == '.') {
    /* match the end of the domain */
    char *suffix;
    if (dlen < len)
      return 0;
    suffix = domain + (dlen - len);
    return (strncasecmp(suffix, constraint, len) == 0);
  }
  if (domain[0] == '.') {
    /* match the end of the constraint */
    char *suffix;
    if (len < dlen)
      return 0;
    suffix = constraint + (len - dlen);
    return (strncasecmp(suffix, domain, dlen) == 0);
  }
  /* otherwise we must exactly match the constraint */
  if (dlen != len)
    return 0;
  return (strncasecmp(domain, constraint, len) == 0);
}

int
x509_constraints_uri(uint8_t *uri, size_t ulen, uint8_t *constraint, size_t len,
    int *error)
{
  int ret = 0;
  char *hostpart = NULL;

  if (!x509_constraints_uri_host(uri, ulen, &hostpart)) {
    *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
    goto err;
  }
  if (hostpart == NULL) {
    *error = X509_V_ERR_OUT_OF_MEM;
    goto err;
  }
  if (!x509_constraints_valid_domain_constraint(constraint, len)) {
    *error = X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX;
    goto err;
  }
  ret = x509_constraints_domain(hostpart, strlen(hostpart), constraint,
      len);
 err:
  free(hostpart);
  return ret;
}

/*
 * Verify a validated address of size alen with a validated contraint
 * of size constraint_len. returns 1 if matching, 0 if not.
 * Addresses are assumed to be pre-validated for a length of 4 and 8
 * respectively for ipv4 addreses and constraints, and a length of
 * 16 and 32 respectively for ipv6 address constraints by the caller.
 */
int
x509_constraints_ipaddr(uint8_t *address, size_t alen, uint8_t *constraint,
    size_t len)
{
  uint8_t *mask;
  size_t i;

  if (alen * 2 != len)
    return 0;

  mask = constraint + alen;
  for (i = 0; i < alen; i++) {
    if ((address[i] & mask[i]) != (constraint[i] & mask[i]))
      return 0;
  }
  return 1;
}

/*
 * Verify a canonicalized der encoded constraint dirname
 * a canonicalized der encoded constraint.
 */
int
x509_constraints_dirname(uint8_t *dirname, size_t dlen,
    uint8_t *constraint, size_t len)
{
  /*
   * The constraint must be a prefix in DER format, so it can't be
   * longer than the name it is checked against.
   */
  if (len > dlen)
    return 0;
  return (memcmp(constraint, dirname, len) == 0);
}

/*
 * De-obfuscate a GENERAL_NAME into useful bytes for a name or constraint.
 */
int
x509_constraints_general_to_bytes(GENERAL_NAME *name, uint8_t **bytes,
    size_t *len)
{
  *bytes = NULL;
  *len = 0;

  if (name->type == GEN_DNS) {
    ASN1_IA5STRING *aname = name->d.dNSName;

    *bytes = aname->data;
    *len = aname->length;

    return name->type;
  }
  if (name->type == GEN_EMAIL) {
    ASN1_IA5STRING *aname = name->d.rfc822Name;

    *bytes = aname->data;
    *len = aname->length;

    return name->type;
  }
  if (name->type == GEN_URI) {
    ASN1_IA5STRING *aname = name->d.uniformResourceIdentifier;

    *bytes = aname->data;
    *len = aname->length;

    return name->type;
  }
  if (name->type == GEN_DIRNAME) {
    X509_NAME *dname = name->d.directoryName;

    if (!dname->modified || i2d_X509_NAME(dname, NULL) >= 0) {
      *bytes = dname->canon_enc;
      *len = dname->canon_enclen;

      return name->type;
    }
  }
  if (name->type == GEN_IPADD) {
    *bytes = name->d.ip->data;
    *len = name->d.ip->length;

    return name->type;
  }

  return 0;
}


/*
 * Extract the relevant names for constraint checking from "cert",
 * validate them, and add them to the list of cert names for "chain".
 * returns 1 on success sets error and returns 0 on failure.
 */
int
x509_constraints_extract_names(struct x509_constraints_names *names,
    X509 *cert, int is_leaf, int *error)
{
  struct x509_constraints_name *vname = NULL;
  X509_NAME *subject_name;
  GENERAL_NAME *name;
  ssize_t i = 0;
  int name_type, include_cn = is_leaf, include_email = is_leaf;

  /* first grab the altnames */
  while ((name = sk_GENERAL_NAME_value(cert->altname, i++)) != NULL) {
    uint8_t *bytes = NULL;
    size_t len = 0;

    if ((vname = x509_constraints_name_new()) == NULL) {
      *error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }

    name_type = x509_constraints_general_to_bytes(name, &bytes,
        &len);
    switch(name_type) {
    case GEN_DNS:
      if (!x509_constraints_valid_sandns(bytes, len)) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      if ((vname->name = strndup(bytes, len)) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      vname->type = GEN_DNS;
      include_cn = 0; /* don't use cn from subject */
      break;
    case GEN_EMAIL:
      if (!x509_constraints_parse_mailbox(bytes, len,
          vname)) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      vname->type = GEN_EMAIL;
      include_email = 0; /* don't use email from subject */
      break;
    case GEN_URI:
      if (!x509_constraints_uri_host(bytes, len, &vname->name)) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      if (vname->name == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      vname->type = GEN_URI;
      break;
    case GEN_DIRNAME:
      if (len == 0) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      if (bytes == NULL || ((vname->der = malloc(len)) ==
          NULL)) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      memcpy(vname->der, bytes, len);
      vname->der_len = len;
      vname->type = GEN_DIRNAME;
      break;
    case GEN_IPADD:
      if (len == 4)
        vname->af = AF_INET;
      if (len == 16)
        vname->af = AF_INET6;
      if (vname->af != AF_INET && vname->af != AF_INET6) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      memcpy(vname->address, bytes, len);
      vname->type = GEN_IPADD;
      break;
    default:
      /* Ignore this name */
      x509_constraints_name_free(vname);
      vname = NULL;
      continue;
    }
    if (!x509_constraints_names_add(names, vname)) {
      *error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    vname = NULL;
  }

  x509_constraints_name_free(vname);
  vname = NULL;

  subject_name = X509_get_subject_name(cert);
  if (X509_NAME_entry_count(subject_name) > 0) {
    X509_NAME_ENTRY *email;
    X509_NAME_ENTRY *cn;
    /*
     * This cert has a non-empty subject, so we must add
     * the subject as a dirname to be compared against
     * any dirname constraints
     */
    if ((subject_name->modified &&
        i2d_X509_NAME(subject_name, NULL) < 0) ||
        (vname = x509_constraints_name_new()) == NULL ||
        (vname->der = malloc(subject_name->canon_enclen)) == NULL) {
      *error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }

    memcpy(vname->der, subject_name->canon_enc,
        subject_name->canon_enclen);
    vname->der_len = subject_name->canon_enclen;
    vname->type = GEN_DIRNAME;
    if (!x509_constraints_names_add(names, vname)) {
      *error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    vname = NULL;
    /*
     * Get any email addresses from the subject line, and
     * add them as mbox names to be compared against any
     * email constraints
     */
    while (include_email &&
        (i = X509_NAME_get_index_by_NID(subject_name,
        NID_pkcs9_emailAddress, i)) >= 0) {
      ASN1_STRING *aname;
      if ((email = X509_NAME_get_entry(subject_name, i)) == NULL ||
          (aname = X509_NAME_ENTRY_get_data(email)) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if ((vname = x509_constraints_name_new()) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if (!x509_constraints_parse_mailbox(aname->data,
          aname->length, vname)) {
        *error = X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
        goto err;
      }
      vname->type = GEN_EMAIL;
      if (!x509_constraints_names_add(names, vname)) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      vname = NULL;
    }
    /*
     * Include the CN as a hostname to be checked againt
     * name constraints if it looks like a hostname.
     */
    while (include_cn &&
        (i = X509_NAME_get_index_by_NID(subject_name,
        NID_commonName, i)) >= 0) {
      ASN1_STRING *aname;
      if ((cn = X509_NAME_get_entry(subject_name, i)) == NULL ||
          (aname = X509_NAME_ENTRY_get_data(cn)) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if (!x509_constraints_valid_host(aname->data,
          aname->length))
        continue; /* ignore it if not a hostname */
      if ((vname = x509_constraints_name_new()) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if ((vname->name = strndup(aname->data,
          aname->length)) == NULL) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      vname->type = GEN_DNS;
      if (!x509_constraints_names_add(names, vname)) {
        *error = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      vname = NULL;
    }
  }
  return 1;
 err:
  x509_constraints_name_free(vname);
  return 0;
}

/*
 * Validate a constraint in a general name, putting the relevant data
 * into "name" if valid. returns 0, and sets error if the constraint is
 * not valid. returns 1 if the constraint validated. name->type will be
 * set to a valid type if there is constraint data in name, or unmodified
 * if the GENERAL_NAME had a valid type but was ignored.
 */
int
x509_constraints_validate(GENERAL_NAME *constraint,
    struct x509_constraints_name **out_name, int *out_error)
{
  uint8_t *bytes = NULL;
  size_t len = 0;
  struct x509_constraints_name *name;
  int error = X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX;
  int name_type;

  if (out_name == NULL || *out_name != NULL)
    return 0;

  if (out_error != NULL)
    *out_error = 0;

  if ((name = x509_constraints_name_new()) == NULL) {
    error = X509_V_ERR_OUT_OF_MEM;
    goto err;
  }

  name_type = x509_constraints_general_to_bytes(constraint, &bytes, &len);
  switch (name_type) {
  case GEN_DIRNAME:
    if (len == 0)
      goto err; /* XXX The RFCs are delightfully vague */
    if (bytes == NULL || (name->der = malloc(len)) == NULL) {
      error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    memcpy(name->der, bytes, len);
    name->der_len = len;
    name->type = GEN_DIRNAME;
    break;
  case GEN_DNS:
    if (!x509_constraints_valid_domain_constraint(bytes, len))
      goto err;
    if ((name->name = strndup(bytes, len)) == NULL) {
      error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    name->type = GEN_DNS;
    break;
  case GEN_EMAIL:
    if (len > 0 && memchr(bytes + 1, '@', len - 1) != NULL) {
      if (!x509_constraints_parse_mailbox(bytes, len, name))
        goto err;
      break;
    }
    /*
     * Mail constraints of the form @domain.com are accepted by
     * OpenSSL and Microsoft.
     */
    if (len > 0 && bytes[0] == '@') {
      bytes++;
      len--;
    }
    if (!x509_constraints_valid_domain_constraint(bytes, len))
      goto err;
    if ((name->name = strndup(bytes, len)) == NULL) {
      error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    name->type = GEN_EMAIL;
    break;
  case GEN_IPADD:
    /* Constraints are ip then mask */
    if (len == 8)
      name->af = AF_INET;
    else if (len == 32)
      name->af = AF_INET6;
    else
      goto err;
    memcpy(&name->address[0], bytes, len);
    name->type = GEN_IPADD;
    break;
  case GEN_URI:
    if (!x509_constraints_valid_domain_constraint(bytes, len))
      goto err;
    if ((name->name = strndup(bytes, len)) == NULL) {
      error = X509_V_ERR_OUT_OF_MEM;
      goto err;
    }
    name->type = GEN_URI;
    break;
  default:
    break;
  }

  *out_name = name;

  return 1;

 err:
  x509_constraints_name_free(name);
  if (out_error != NULL)
    *out_error = error;

  return 0;
}

int
x509_constraints_extract_constraints(X509 *cert,
    struct x509_constraints_names *permitted,
    struct x509_constraints_names *excluded,
    int *error)
{
  struct x509_constraints_name *vname = NULL;
  NAME_CONSTRAINTS *nc = cert->nc;
  GENERAL_SUBTREE *subtree;
  int i;

  if (nc == NULL)
    return 1;

  for (i = 0; i < sk_GENERAL_SUBTREE_num(nc->permittedSubtrees); i++) {

    subtree = sk_GENERAL_SUBTREE_value(nc->permittedSubtrees, i);
    if (subtree->minimum || subtree->maximum) {
      *error = X509_V_ERR_SUBTREE_MINMAX;
      return 0;
    }
    if (!x509_constraints_validate(subtree->base, &vname, error))
      return 0;
    if (vname->type == 0) {
      x509_constraints_name_free(vname);
      vname = NULL;
      continue;
    }
    if (!x509_constraints_names_add(permitted, vname)) {
      x509_constraints_name_free(vname);
      vname = NULL;
      *error = X509_V_ERR_OUT_OF_MEM;
      return 0;
    }
    vname = NULL;
  }

  for (i = 0; i < sk_GENERAL_SUBTREE_num(nc->excludedSubtrees); i++) {
    subtree = sk_GENERAL_SUBTREE_value(nc->excludedSubtrees, i);
    if (subtree->minimum || subtree->maximum) {
      *error = X509_V_ERR_SUBTREE_MINMAX;
      return 0;
    }
    if (!x509_constraints_validate(subtree->base, &vname, error))
      return 0;
    if (vname->type == 0) {
      x509_constraints_name_free(vname);
      vname = NULL;
      continue;
    }
    if (!x509_constraints_names_add(excluded, vname)) {
      x509_constraints_name_free(vname);
      vname = NULL;
      *error = X509_V_ERR_OUT_OF_MEM;
      return 0;
    }
    vname = NULL;
  }

  return 1;
}

/*
 * Match a validated name in "name" against a validated constraint in
 * "constraint" return 1 if then name matches, 0 otherwise.
 */
int
x509_constraints_match(struct x509_constraints_name *name,
    struct x509_constraints_name *constraint)
{
  if (name->type != constraint->type)
    return 0;
  if (name->type == GEN_DNS)
    return x509_constraints_sandns(name->name, strlen(name->name),
        constraint->name, strlen(constraint->name));
  if (name->type == GEN_URI)
    return x509_constraints_domain(name->name, strlen(name->name),
        constraint->name, strlen(constraint->name));
  if (name->type == GEN_IPADD) {
    size_t nlen = name->af == AF_INET ? 4 : 16;
    size_t clen = name->af == AF_INET ? 8 : 32;
    if (name->af != AF_INET && name->af != AF_INET6)
      return 0;
    if (constraint->af != AF_INET && constraint->af != AF_INET6)
      return 0;
    if (name->af != constraint->af)
      return 0;
    return x509_constraints_ipaddr(name->address, nlen,
        constraint->address, clen);
  }
  if (name->type == GEN_EMAIL) {
    if (constraint->local) {
      /* mailbox local and domain parts must exactly match */
      return (strcmp(name->local, constraint->local) == 0 &&
          strcmp(name->name, constraint->name) == 0);
    }
    /* otherwise match the constraint to the domain part */
    return x509_constraints_domain(name->name, strlen(name->name),
        constraint->name, strlen(constraint->name));
  }
  if (name->type == GEN_DIRNAME)
    return x509_constraints_dirname(name->der, name->der_len,
        constraint->der, constraint->der_len);
  return 0;
}

/*
 * Make sure every name in names does not match any excluded
 * constraints, and does match at least one permitted constraint if
 * any are present. Returns 1 if ok, 0, and sets error if not.
 */
int
x509_constraints_check(struct x509_constraints_names *names,
    struct x509_constraints_names *permitted,
    struct x509_constraints_names *excluded, int *error)
{
  size_t i, j;

  for (i = 0; i < names->names_count; i++) {
    int permitted_seen = 0;
    int permitted_matched = 0;

    for (j = 0; j < excluded->names_count; j++) {
      if (x509_constraints_match(names->names[i],
          excluded->names[j])) {
        *error = X509_V_ERR_EXCLUDED_VIOLATION;
        return 0;
      }
    }
    for (j = 0; j < permitted->names_count; j++) {
      if (permitted->names[j]->type == names->names[i]->type)
        permitted_seen++;
      if (x509_constraints_match(names->names[i],
          permitted->names[j])) {
        permitted_matched++;
        break;
      }
    }
    if (permitted_seen && !permitted_matched) {
      *error = X509_V_ERR_PERMITTED_VIOLATION;
      return 0;
    }
  }
  return 1;
}

/*
 * Walk a validated chain of X509 certs, starting at the leaf, and
 * validate the name constraints in the chain. Intended for use with
 * the legacy X509 validtion code in x509_vfy.c
 *
 * returns 1 if the constraints are ok, 0 otherwise, setting error and
 * depth
 */
int
x509_constraints_chain(STACK_OF(X509) *chain, int *error, int *depth)
{
  int chain_length, verify_err = X509_V_ERR_UNSPECIFIED, i = 0;
  struct x509_constraints_names *names = NULL;
  struct x509_constraints_names *excluded = NULL;
  struct x509_constraints_names *permitted = NULL;
  size_t constraints_count = 0;
  X509 *cert;

  if (chain == NULL || (chain_length = sk_X509_num(chain)) == 0)
    goto err;
  if (chain_length == 1)
    return 1;
  if ((names = x509_constraints_names_new(
      X509_VERIFY_MAX_CHAIN_NAMES)) == NULL) {
    verify_err = X509_V_ERR_OUT_OF_MEM;
    goto err;
  }

  if ((cert = sk_X509_value(chain, 0)) == NULL)
    goto err;
  if (!x509_constraints_extract_names(names, cert, 1, &verify_err))
    goto err;
  for (i = 1; i < chain_length; i++) {
    if ((cert = sk_X509_value(chain, i)) == NULL)
      goto err;
    if (cert->nc != NULL) {
      if ((permitted = x509_constraints_names_new(
          X509_VERIFY_MAX_CHAIN_CONSTRAINTS)) == NULL) {
        verify_err = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if ((excluded = x509_constraints_names_new(
          X509_VERIFY_MAX_CHAIN_CONSTRAINTS)) == NULL) {
        verify_err = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if (!x509_constraints_extract_constraints(cert,
          permitted, excluded, &verify_err))
        goto err;
      constraints_count += permitted->names_count;
      constraints_count += excluded->names_count;
      if (constraints_count >
          X509_VERIFY_MAX_CHAIN_CONSTRAINTS) {
        verify_err = X509_V_ERR_OUT_OF_MEM;
        goto err;
      }
      if (!x509_constraints_check(names, permitted, excluded,
          &verify_err))
        goto err;
      x509_constraints_names_free(excluded);
      excluded = NULL;
      x509_constraints_names_free(permitted);
      permitted = NULL;
    }
    if (!x509_constraints_extract_names(names, cert, 0,
        &verify_err))
      goto err;
  }

  x509_constraints_names_free(names);
  return 1;

 err:
  *error = verify_err;
  *depth = i;
  x509_constraints_names_free(excluded);
  x509_constraints_names_free(permitted);
  x509_constraints_names_free(names);
  return 0;
}

Coverage Report

Created: 2022-08-24 06:30