| 1 | /*
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| 2 | * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
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| 3 | * (Royal Institute of Technology, Stockholm, Sweden).
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| 4 | * All rights reserved.
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| 5 | *
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| 6 | * Redistribution and use in source and binary forms, with or without
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| 7 | * modification, are permitted provided that the following conditions
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| 8 | * are met:
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| 9 | *
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| 10 | * 1. Redistributions of source code must retain the above copyright
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| 11 | * notice, this list of conditions and the following disclaimer.
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| 12 | *
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| 13 | * 2. Redistributions in binary form must reproduce the above copyright
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| 14 | * notice, this list of conditions and the following disclaimer in the
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| 15 | * documentation and/or other materials provided with the distribution.
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| 16 | *
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| 17 | * 3. Neither the name of the Institute nor the names of its contributors
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| 18 | * may be used to endorse or promote products derived from this software
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| 19 | * without specific prior written permission.
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| 20 | *
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| 21 | * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 31 | * SUCH DAMAGE.
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| 32 | */
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| 33 |
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| 34 | #include "krb5_locl.h"
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| 35 | #include <dirent.h>
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| 36 |
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| 37 | #ifndef _WIN32
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| 38 |
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| 39 | /* see if principal is mentioned in the filename access file, return
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| 40 | TRUE (in result) if so, FALSE otherwise */
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| 41 |
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| 42 | static krb5_error_code
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| 43 | check_one_file(krb5_context context,
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| 44 | const char *filename,
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| 45 | struct passwd *pwd,
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| 46 | krb5_principal principal,
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| 47 | krb5_boolean *result)
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| 48 | {
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| 49 | FILE *f;
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| 50 | char buf[BUFSIZ];
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| 51 | krb5_error_code ret;
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| 52 | struct stat st;
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| 53 |
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| 54 | *result = FALSE;
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| 55 |
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| 56 | f = fopen (filename, "r");
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| 57 | if (f == NULL)
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| 58 | return errno;
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| 59 | rk_cloexec_file(f);
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| 60 |
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| 61 | /* check type and mode of file */
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| 62 | if (fstat(fileno(f), &st) != 0) {
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| 63 | fclose (f);
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| 64 | return errno;
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| 65 | }
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| 66 | if (S_ISDIR(st.st_mode)) {
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| 67 | fclose (f);
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| 68 | return EISDIR;
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| 69 | }
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| 70 | if (st.st_uid != pwd->pw_uid && st.st_uid != 0) {
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| 71 | fclose (f);
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| 72 | return EACCES;
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| 73 | }
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| 74 | if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
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| 75 | fclose (f);
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| 76 | return EACCES;
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| 77 | }
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| 78 |
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| 79 | while (fgets (buf, sizeof(buf), f) != NULL) {
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| 80 | krb5_principal tmp;
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| 81 | char *newline = buf + strcspn(buf, "\n");
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| 82 |
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| 83 | if(*newline != '\n') {
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| 84 | int c;
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| 85 | c = fgetc(f);
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| 86 | if(c != EOF) {
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| 87 | while(c != EOF && c != '\n')
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| 88 | c = fgetc(f);
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| 89 | /* line was too long, so ignore it */
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| 90 | continue;
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| 91 | }
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| 92 | }
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| 93 | *newline = '\0';
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| 94 | ret = krb5_parse_name (context, buf, &tmp);
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| 95 | if (ret)
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| 96 | continue;
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| 97 | *result = krb5_principal_compare (context, principal, tmp);
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| 98 | krb5_free_principal (context, tmp);
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| 99 | if (*result) {
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| 100 | fclose (f);
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| 101 | return 0;
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| 102 | }
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| 103 | }
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| 104 | fclose (f);
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| 105 | return 0;
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| 106 | }
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| 107 |
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| 108 | static krb5_error_code
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| 109 | check_directory(krb5_context context,
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| 110 | const char *dirname,
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| 111 | struct passwd *pwd,
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| 112 | krb5_principal principal,
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| 113 | krb5_boolean *result)
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| 114 | {
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| 115 | DIR *d;
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| 116 | struct dirent *dent;
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| 117 | char filename[MAXPATHLEN];
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| 118 | krb5_error_code ret = 0;
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| 119 | struct stat st;
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| 120 |
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| 121 | *result = FALSE;
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| 122 |
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| 123 | if(lstat(dirname, &st) < 0)
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| 124 | return errno;
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| 125 |
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| 126 | if (!S_ISDIR(st.st_mode))
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| 127 | return ENOTDIR;
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| 128 |
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| 129 | if (st.st_uid != pwd->pw_uid && st.st_uid != 0)
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| 130 | return EACCES;
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| 131 | if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0)
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| 132 | return EACCES;
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| 133 |
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| 134 | if((d = opendir(dirname)) == NULL)
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| 135 | return errno;
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| 136 |
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| 137 | {
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| 138 | int fd;
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| 139 | struct stat st2;
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| 140 |
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| 141 | fd = dirfd(d);
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| 142 | if(fstat(fd, &st2) < 0) {
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| 143 | closedir(d);
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| 144 | return errno;
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| 145 | }
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| 146 | if(st.st_dev != st2.st_dev || st.st_ino != st2.st_ino) {
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| 147 | closedir(d);
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| 148 | return EACCES;
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| 149 | }
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| 150 | }
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| 151 |
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| 152 | while((dent = readdir(d)) != NULL) {
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| 153 | if(strcmp(dent->d_name, ".") == 0 ||
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| 154 | strcmp(dent->d_name, "..") == 0 ||
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| 155 | dent->d_name[0] == '#' || /* emacs autosave */
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| 156 | dent->d_name[strlen(dent->d_name) - 1] == '~') /* emacs backup */
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| 157 | continue;
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| 158 | snprintf(filename, sizeof(filename), "%s/%s", dirname, dent->d_name);
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| 159 | ret = check_one_file(context, filename, pwd, principal, result);
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| 160 | if(ret == 0 && *result == TRUE)
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| 161 | break;
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| 162 | ret = 0; /* don't propagate errors upstream */
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| 163 | }
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| 164 | closedir(d);
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| 165 | return ret;
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| 166 | }
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| 167 |
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| 168 | #endif /* !_WIN32 */
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| 169 |
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| 170 | static krb5_boolean
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| 171 | match_local_principals(krb5_context context,
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| 172 | krb5_principal principal,
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| 173 | const char *luser)
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| 174 | {
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| 175 | krb5_error_code ret;
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| 176 | krb5_realm *realms, *r;
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| 177 | krb5_boolean result = FALSE;
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| 178 |
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| 179 | /* multi-component principals can never match */
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| 180 | if(krb5_principal_get_comp_string(context, principal, 1) != NULL)
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| 181 | return FALSE;
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| 182 |
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| 183 | ret = krb5_get_default_realms (context, &realms);
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| 184 | if (ret)
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| 185 | return FALSE;
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| 186 |
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| 187 | for (r = realms; *r != NULL; ++r) {
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| 188 | if(strcmp(krb5_principal_get_realm(context, principal),
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| 189 | *r) != 0)
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| 190 | continue;
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| 191 | if(strcmp(krb5_principal_get_comp_string(context, principal, 0),
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| 192 | luser) == 0) {
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| 193 | result = TRUE;
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| 194 | break;
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| 195 | }
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| 196 | }
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| 197 | krb5_free_host_realm (context, realms);
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| 198 | return result;
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| 199 | }
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| 200 |
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| 201 | /**
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| 202 | * This function takes the name of a local user and checks if
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| 203 | * principal is allowed to log in as that user.
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| 204 | *
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| 205 | * The user may have a ~/.k5login file listing principals that are
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| 206 | * allowed to login as that user. If that file does not exist, all
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| 207 | * principals with a first component identical to the username, and a
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| 208 | * realm considered local, are allowed access.
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| 209 | *
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| 210 | * The .k5login file must contain one principal per line, be owned by
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| 211 | * user and not be writable by group or other (but must be readable by
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| 212 | * anyone).
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| 213 | *
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| 214 | * Note that if the file exists, no implicit access rights are given
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| 215 | * to user@@LOCALREALM.
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| 216 | *
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| 217 | * Optionally, a set of files may be put in ~/.k5login.d (a
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| 218 | * directory), in which case they will all be checked in the same
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| 219 | * manner as .k5login. The files may be called anything, but files
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| 220 | * starting with a hash (#) , or ending with a tilde (~) are
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| 221 | * ignored. Subdirectories are not traversed. Note that this directory
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| 222 | * may not be checked by other Kerberos implementations.
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| 223 | *
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| 224 | * If no configuration file exists, match user against local domains,
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| 225 | * ie luser@@LOCAL-REALMS-IN-CONFIGURATION-FILES.
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| 226 | *
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| 227 | * @param context Kerberos 5 context.
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| 228 | * @param principal principal to check if allowed to login
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| 229 | * @param luser local user id
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| 230 | *
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| 231 | * @return returns TRUE if access should be granted, FALSE otherwise.
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| 232 | *
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| 233 | * @ingroup krb5_support
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| 234 | */
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| 235 |
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| 236 | KRB5_LIB_FUNCTION krb5_boolean KRB5_LIB_CALL
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| 237 | krb5_kuserok (krb5_context context,
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| 238 | krb5_principal principal,
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| 239 | const char *luser)
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| 240 | {
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| 241 | #ifndef _WIN32
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| 242 | char *buf;
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| 243 | size_t buflen;
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| 244 | struct passwd *pwd = NULL;
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| 245 | char *profile_dir = NULL;
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| 246 | krb5_error_code ret;
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| 247 | krb5_boolean result = FALSE;
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| 248 |
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| 249 | krb5_boolean found_file = FALSE;
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| 250 |
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| 251 | #ifdef POSIX_GETPWNAM_R
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| 252 | char pwbuf[2048];
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| 253 | struct passwd pw;
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| 254 |
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| 255 | if(getpwnam_r(luser, &pw, pwbuf, sizeof(pwbuf), &pwd) != 0)
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| 256 | return FALSE;
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| 257 | #else
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| 258 | pwd = getpwnam (luser);
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| 259 | #endif
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| 260 | if (pwd == NULL)
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| 261 | return FALSE;
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| 262 | profile_dir = pwd->pw_dir;
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| 263 |
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| 264 | #define KLOGIN "/.k5login"
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| 265 | buflen = strlen(profile_dir) + sizeof(KLOGIN) + 2; /* 2 for .d */
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| 266 | buf = malloc(buflen);
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| 267 | if(buf == NULL)
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| 268 | return FALSE;
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| 269 | /* check user's ~/.k5login */
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| 270 | strlcpy(buf, profile_dir, buflen);
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| 271 | strlcat(buf, KLOGIN, buflen);
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| 272 | ret = check_one_file(context, buf, pwd, principal, &result);
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| 273 |
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| 274 | if(ret == 0 && result == TRUE) {
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| 275 | free(buf);
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| 276 | return TRUE;
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| 277 | }
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| 278 |
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| 279 | if(ret != ENOENT)
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| 280 | found_file = TRUE;
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| 281 |
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| 282 | strlcat(buf, ".d", buflen);
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| 283 | ret = check_directory(context, buf, pwd, principal, &result);
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| 284 | free(buf);
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| 285 | if(ret == 0 && result == TRUE)
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| 286 | return TRUE;
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| 287 |
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| 288 | if(ret != ENOENT && ret != ENOTDIR)
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| 289 | found_file = TRUE;
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| 290 |
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| 291 | /* finally if no files exist, allow all principals matching
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| 292 | <localuser>@<LOCALREALM> */
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| 293 | if(found_file == FALSE)
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| 294 | return match_local_principals(context, principal, luser);
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| 295 |
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| 296 | return FALSE;
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| 297 | #else
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| 298 | /* The .k5login file may be on a remote profile and we don't have
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| 299 | access to the profile until we have a token handle for the
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| 300 | user's credentials. */
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| 301 | return match_local_principals(context, principal, luser);
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| 302 | #endif
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| 303 | }
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