338 lines
8.7 KiB
C
338 lines
8.7 KiB
C
/*
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* Copyright (c) 2019 Kungliga Tekniska Högskolan
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* (Royal Institute of Technology, Stockholm, Sweden).
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* This plugin authorizes requested certificate SANs and EKUs by checking for
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* existence of files of the form:
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*
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*
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* /<path>/<princ>/<ext>-<value>
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*
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* where <path> is the value of:
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*
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* [kdc] simple_csr_authorizer_directory = PATH
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*
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* <princ> is a requesting client principal name with all characters other than
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* alphanumeric, '-', '_', and non-leading '.' URL-encoded.
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*
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* <ext> is one of:
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*
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* - pkinit (SAN)
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* - xmpt (SAN)
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* - emailt (SAN)
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* - ms-upt (SAN)
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* - dnsnamt (SAN)
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* - eku (EKU OID)
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*
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* and <value> is a display form of the SAN or EKU OID, with SANs URL-encoded
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* just like principal names (see above).
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*
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* OIDs are of the form "1.2.3.4.5".
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*
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* Only digitalSignature and nonRepudiation key usage values are permitted.
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*/
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#define _GNU_SOURCE 1
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <ctype.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <roken.h>
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#include <krb5.h>
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#include <hx509.h>
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#include <kdc.h>
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#include <common_plugin.h>
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#include <csr_authorizer_plugin.h>
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/*
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* string_encode_sz() and string_encode() encode a string to be safe for use as
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* a file name. They function very much like URL encoders, but '~' also gets
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* encoded, and '@', '-', '_', and non-leading '.' do not.
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*
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* A corresponding decoder is not needed.
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*/
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static size_t
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string_encode_sz(const char *in)
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{
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size_t sz = strlen(in);
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int first = 1;
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while (*in) {
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char c = *(in++);
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switch (c) {
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case '@':
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case '-':
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case '_':
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break;
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case '.':
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if (first)
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sz += 2;
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break;
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default:
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if (!isalnum(c))
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sz += 2;
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}
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first = 0;
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}
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return sz;
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}
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static char *
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string_encode(const char *in)
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{
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size_t len = strlen(in);
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size_t sz = string_encode_sz(in);
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size_t i, k;
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char *s;
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int first = 1;
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if ((s = malloc(sz + 1)) == NULL)
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return NULL;
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s[sz] = '\0';
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for (i = k = 0; i < len; i++, first = 0) {
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unsigned char c = ((const unsigned char *)in)[i];
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switch (c) {
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case '@':
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case '-':
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case '_':
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s[k++] = c;
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break;
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case '.':
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if (first) {
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s[k++] = '%';
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s[k++] = "0123456789abcdef"[(c&0xff)>>4];
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s[k++] = "0123456789abcdef"[(c&0x0f)];
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} else {
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s[k++] = c;
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}
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break;
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default:
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if (isalnum(c)) {
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s[k++] = c;
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} else {
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s[k++] = '%';
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s[k++] = "0123456789abcdef"[(c&0xff)>>4];
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s[k++] = "0123456789abcdef"[(c&0x0f)];
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}
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}
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}
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return s;
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}
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static KRB5_LIB_CALL krb5_error_code
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authorize(void *ctx,
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krb5_context context,
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const char *app,
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hx509_request csr,
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krb5_const_principal client,
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krb5_boolean *result)
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{
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krb5_error_code ret;
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hx509_context hx509ctx = NULL;
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KeyUsage ku;
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const char *d;
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size_t i;
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char *princ = NULL;
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char *s = NULL;
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if ((d = krb5_config_get_string(context, NULL, app ? app : "kdc",
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"simple_csr_authorizer_directory",
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NULL)) == NULL)
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return KRB5_PLUGIN_NO_HANDLE;
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if ((ret = hx509_context_init(&hx509ctx)))
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return ret;
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if ((ret = krb5_unparse_name(context, client, &princ)))
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goto out;
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s = string_encode(princ);
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free(princ);
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princ = NULL;
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if (s == NULL)
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goto enomem;
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princ = s;
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s = NULL;
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for (i = 0; ret == 0; i++) {
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hx509_san_type san_type;
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struct stat st;
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const char *prefix;
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char *san;
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char *p;
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ret = hx509_request_get_san(csr, i, &san_type, &s);
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if (ret)
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break;
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switch (san_type) {
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case HX509_SAN_TYPE_EMAIL:
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prefix = "email";
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break;
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case HX509_SAN_TYPE_DNSNAME:
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prefix = "dnsname";
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break;
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case HX509_SAN_TYPE_XMPP:
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prefix = "xmpp";
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break;
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case HX509_SAN_TYPE_PKINIT:
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prefix = "pkinit";
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break;
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case HX509_SAN_TYPE_MS_UPN:
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prefix = "ms-upn";
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break;
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default:
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ret = ENOTSUP;
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break;
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}
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if (ret)
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break;
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if ((san = string_encode(s)) == NULL ||
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asprintf(&p, "%s/%s/%s-%s", d, princ, prefix, san) == -1 ||
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p == NULL) {
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free(san);
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goto enomem;
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}
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ret = stat(p, &st) == -1 ? errno : 0;
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free(san);
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free(p);
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free(s);
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s = NULL;
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if (ret)
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goto skip;
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ret = hx509_request_authorize_san(csr, i);
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}
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if (ret == HX509_NO_ITEM)
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ret = 0;
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if (ret)
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goto out;
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for (i = 0; ret == 0; i++) {
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struct stat st;
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char *p;
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ret = hx509_request_get_eku(csr, i, &s);
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if (ret)
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break;
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if (asprintf(&p, "%s/%s/eku-%s", d, princ, s) == -1 || p == NULL)
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goto enomem;
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ret = stat(p, &st) == -1 ? errno : 0;
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free(p);
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free(s);
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s = NULL;
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if (ret)
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goto skip;
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ret = hx509_request_authorize_eku(csr, i);
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}
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if (ret == HX509_NO_ITEM)
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ret = 0;
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if (ret)
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goto out;
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ku = int2KeyUsage(0);
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ku.digitalSignature = 1;
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ku.nonRepudiation = 1;
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hx509_request_authorize_ku(csr, ku);
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*result = TRUE;
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ret = 0;
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goto out;
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skip:
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/* Allow another plugin to get a crack at this */
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ret = KRB5_PLUGIN_NO_HANDLE;
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goto out;
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enomem:
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ret = krb5_enomem(context);
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goto out;
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out:
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hx509_context_free(&hx509ctx);
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free(princ);
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free(s);
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return ret;
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}
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static KRB5_LIB_CALL krb5_error_code
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simple_csr_authorizer_init(krb5_context context, void **c)
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{
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*c = NULL;
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return 0;
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}
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static KRB5_LIB_CALL void
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simple_csr_authorizer_fini(void *c)
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{
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}
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static krb5plugin_csr_authorizer_ftable plug_desc =
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{ 1, simple_csr_authorizer_init, simple_csr_authorizer_fini, authorize };
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static krb5plugin_csr_authorizer_ftable *plugs[] = { &plug_desc };
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static uintptr_t
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simple_csr_authorizer_get_instance(const char *libname)
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{
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if (strcmp(libname, "krb5") == 0)
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return krb5_get_instance(libname);
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if (strcmp(libname, "kdc") == 0)
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return kdc_get_instance(libname);
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if (strcmp(libname, "hx509") == 0)
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return hx509_get_instance(libname);
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return 0;
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}
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krb5_plugin_load_ft kdc_csr_authorizer_plugin_load;
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krb5_error_code KRB5_CALLCONV
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kdc_csr_authorizer_plugin_load(heim_pcontext context,
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krb5_get_instance_func_t *get_instance,
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size_t *num_plugins,
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krb5_plugin_common_ftable_cp **plugins)
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{
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*get_instance = simple_csr_authorizer_get_instance;
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*num_plugins = sizeof(plugs) / sizeof(plugs[0]);
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*plugins = (krb5_plugin_common_ftable_cp *)plugs;
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return 0;
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}
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