src/afb-cred.c

   1 /*
   2  * Copyright (C) 2017-2019 "IoT.bzh"
   3  * Author: José Bollo <jose.bollo@iot.bzh>
   4  *
   5  * Licensed under the Apache License, Version 2.0 (the "License");
   6  * you may not use this file except in compliance with the License.
   7  * You may obtain a copy of the License at
   8  *
   9  *   http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  */
  17
  18 #define _GNU_SOURCE
  19
  20 #include <stdlib.h>
  21 #include <stdio.h>
  22 #include <stdint.h>
  23 #include <unistd.h>
  24 #include <string.h>
  25 #include <errno.h>
  26 #include <fcntl.h>
  27 #include <sys/types.h>
  28 #include <sys/socket.h>
  29
  30 #include "afb-cred.h"
  31 #include "afb-context.h"
  32 #include "afb-token.h"
  33 #include "verbose.h"
  34
  35
  36 #define MAX_LABEL_LENGTH  1024
  37
  38 #if !defined(NO_DEFAULT_PEERCRED) && !defined(ADD_DEFAULT_PEERCRED)
  39 #  define NO_DEFAULT_PEERCRED
  40 #endif
  41
  42 #if !defined(DEFAULT_PEERSEC_LABEL)
  43 #  define DEFAULT_PEERSEC_LABEL "NoLabel"
  44 #endif
  45 #if !defined(DEFAULT_PEERCRED_UID)
  46 #  define DEFAULT_PEERCRED_UID 99 /* nobody */
  47 #endif
  48 #if !defined(DEFAULT_PEERCRED_GID)
  49 #  define DEFAULT_PEERCRED_GID 99 /* nobody */
  50 #endif
  51 #if !defined(DEFAULT_PEERCRED_PID)
  52 #  define DEFAULT_PEERCRED_PID 0  /* no process */
  53 #endif
  54
  55 static char on_behalf_credential_permission[] = "urn:AGL:permission:*:partner:on-behalf-credentials";
  56 static char export_format[] = "%x:%x:%x-%s";
  57 static char import_format[] = "%x:%x:%x-%n";
  58
  59 static struct afb_cred *current;
  60
  61 static struct afb_cred *mkcred(uid_t uid, gid_t gid, pid_t pid, const char *label, size_t size)
  62 {
  63         struct afb_cred *cred;
  64         char *dest, user[64];
  65         size_t i;
  66         uid_t u;
  67
  68         i = 0;
  69         u = uid;
  70         do {
  71                 user[i++] = (char)('0' + u % 10);
  72                 u = u / 10;
  73         } while(u && i < sizeof user);
  74
  75         cred = malloc(2 + i + size + sizeof *cred);
  76         if (!cred)
  77                 errno = ENOMEM;
  78         else {
  79                 cred->refcount = 1;
  80                 cred->uid = uid;
  81                 cred->gid = gid;
  82                 cred->pid = pid;
  83                 cred->exported = NULL;
  84                 dest = (char*)(&cred[1]);
  85                 cred->user = dest;
  86                 while(i)
  87                         *dest++ = user[--i];
  88                 *dest++ = 0;
  89                 cred->label = dest;
  90                 cred->id = dest;
  91                 memcpy(dest, label, size);
  92                 dest[size] = 0;
  93                 dest = strrchr(dest, ':');
  94                 if (dest)
  95                         cred->id = &dest[1];
  96         }
  97         return cred;
  98 }
  99
 100 static struct afb_cred *mkcurrent()
 101 {
 102         char label[MAX_LABEL_LENGTH];
 103         int fd;
 104         ssize_t rc;
 105
 106         fd = open("/proc/self/attr/current", O_RDONLY);
 107         if (fd < 0)
 108                 rc = 0;
 109         else {
 110                 rc = read(fd, label, sizeof label);
 111                 if (rc < 0)
 112                         rc = 0;
 113                 close(fd);
 114         }
 115
 116         return mkcred(getuid(), getgid(), getpid(), label, (size_t)rc);
 117 }
 118
 119 struct afb_cred *afb_cred_create(uid_t uid, gid_t gid, pid_t pid, const char *label)
 120 {
 121         label = label ? : DEFAULT_PEERSEC_LABEL;
 122         return mkcred(uid, gid, pid, label, strlen(label));
 123 }
 124
 125 struct afb_cred *afb_cred_create_for_socket(int fd)
 126 {
 127         int rc;
 128         socklen_t length;
 129         struct ucred ucred;
 130         char label[MAX_LABEL_LENGTH];
 131
 132         /* get the credentials */
 133         length = (socklen_t)(sizeof ucred);
 134         rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &length);
 135         if (rc < 0 || length != (socklen_t)(sizeof ucred) || !~ucred.uid) {
 136 #if !defined(NO_DEFAULT_PEERCRED)
 137                 ucred.uid = DEFAULT_PEERCRED_UID;
 138                 ucred.gid = DEFAULT_PEERCRED_GID;
 139                 ucred.pid = DEFAULT_PEERCRED_PID;
 140 #else
 141                 if (!rc)
 142                         errno = EINVAL;
 143                 return NULL;
 144 #endif
 145         }
 146
 147         /* get the security label */
 148         length = (socklen_t)(sizeof label);
 149         rc = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, label, &length);
 150         if (rc < 0 || length > (socklen_t)(sizeof label)) {
 151 #if !defined(NO_DEFAULT_PEERSEC)
 152                 length = (socklen_t)strlen(DEFAULT_PEERSEC_LABEL);
 153                 strcpy (label, DEFAULT_PEERSEC_LABEL);
 154 #else
 155                 if (!rc)
 156                         errno = EINVAL;
 157                 return NULL;
 158 #endif
 159         }
 160
 161         /* makes the result */
 162         return mkcred(ucred.uid, ucred.gid, ucred.pid, label, (size_t)length);
 163 }
 164
 165 struct afb_cred *afb_cred_addref(struct afb_cred *cred)
 166 {
 167         if (cred)
 168                 __atomic_add_fetch(&cred->refcount, 1, __ATOMIC_RELAXED);
 169         return cred;
 170 }
 171
 172 void afb_cred_unref(struct afb_cred *cred)
 173 {
 174         if (cred && !__atomic_sub_fetch(&cred->refcount, 1, __ATOMIC_RELAXED)) {
 175                 if (cred == current)
 176                         cred->refcount = 1;
 177                 else {
 178                         free((void*)cred->exported);
 179                         free(cred);
 180                 }
 181         }
 182 }
 183
 184 struct afb_cred *afb_cred_current()
 185 {
 186         if (!current)
 187                 current = mkcurrent();
 188         return afb_cred_addref(current);
 189 }
 190
 191 const char *afb_cred_export(struct afb_cred *cred)
 192 {
 193         int rc;
 194
 195         if (!cred->exported) {
 196                 rc = asprintf((char**)&cred->exported,
 197                         export_format,
 198                                 (int)cred->uid,
 199                                 (int)cred->gid,
 200                                 (int)cred->pid,
 201                                 cred->label);
 202                 if (rc < 0) {
 203                         errno = ENOMEM;
 204                         cred->exported = NULL;
 205                 }
 206         }
 207         return cred->exported;
 208 }
 209
 210 struct afb_cred *afb_cred_import(const char *string)
 211 {
 212         struct afb_cred *cred;
 213         int rc, uid, gid, pid, pos;
 214
 215         rc = sscanf(string, import_format, &uid, &gid, &pid, &pos);
 216         if (rc == 3)
 217                 cred = afb_cred_create((uid_t)uid, (gid_t)gid, (pid_t)pid, &string[pos]);
 218         else {
 219                 errno = EINVAL;
 220                 cred = NULL;
 221         }
 222         return cred;
 223 }
 224
 225 struct afb_cred *afb_cred_mixed_on_behalf_import(struct afb_cred *cred, struct afb_context *context, const char *exported)
 226
 227 {
 228         struct afb_cred *imported;
 229         if (exported) {
 230                 if (afb_cred_has_permission(cred, on_behalf_credential_permission, context)) {
 231                         imported = afb_cred_import(exported);
 232                         if (imported)
 233                                 return imported;
 234                         ERROR("Can't import on behalf credentials: %m");
 235                 } else {
 236                         ERROR("On behalf credentials refused");
 237                 }
 238         }
 239         return afb_cred_addref(cred);
 240 }
 241
 242 /*********************************************************************************/
 243 static const char *token_of_context(struct afb_context *context)
 244 {
 245         return context && context->token ? afb_token_string(context->token) : "X";
 246 }
 247
 248 /*********************************************************************************/
 249 #ifdef BACKEND_PERMISSION_IS_CYNARA
 250
 251 #include <pthread.h>
 252 #include <cynara-client.h>
 253
 254 static cynara *handle;
 255 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 256
 257 int afb_cred_has_permission(struct afb_cred *cred, const char *permission, struct afb_context *context)
 258 {
 259         int rc;
 260
 261         if (!cred) {
 262                 /* case of permission for self */
 263                 return 1;
 264         }
 265         if (!permission) {
 266                 ERROR("Got a null permission!");
 267                 return 0;
 268         }
 269
 270         /* cynara isn't reentrant */
 271         pthread_mutex_lock(&mutex);
 272
 273         /* lazy initialisation */
 274         if (!handle) {
 275                 rc = cynara_initialize(&handle, NULL);
 276                 if (rc != CYNARA_API_SUCCESS) {
 277                         handle = NULL;
 278                         ERROR("cynara initialisation failed with code %d", rc);
 279                         return 0;
 280                 }
 281         }
 282
 283         /* query cynara permission */
 284         rc = cynara_check(handle, cred->label, token_of_context(context), cred->user, permission);
 285
 286         pthread_mutex_unlock(&mutex);
 287         return rc == CYNARA_API_ACCESS_ALLOWED;
 288 }
 289
 290 /*********************************************************************************/
 291 #else
 292 int afb_cred_has_permission(struct afb_cred *cred, const char *permission, struct afb_context *context)
 293 {
 294         WARNING("Granting permission %s by default of backend", permission ?: "(null)");
 295         return !!permission;
 296 }
 297 #endif
 298