src/afb-cred.c

   1 /*
   2  * Copyright (C) 2017 "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 <unistd.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <sys/types.h>
  26 #include <sys/socket.h>
  27
  28 #include "afb-cred.h"
  29
  30 #define MAX_LABEL_LENGTH  1024
  31
  32 #if !defined(DEFAULT_PEERSEC_LABEL)
  33 #  define DEFAULT_PEERSEC_LABEL "NoLabel"
  34 #endif
  35 #if !defined(DEFAULT_PEERCRED_UID)
  36 #  define DEFAULT_PEERCRED_UID 99 /* nobody */
  37 #endif
  38 #if !defined(DEFAULT_PEERCRED_GID)
  39 #  define DEFAULT_PEERCRED_GID 99 /* nobody */
  40 #endif
  41 #if !defined(DEFAULT_PEERCRED_PID)
  42 #  define DEFAULT_PEERCRED_PID 0  /* no process */
  43 #endif
  44
  45 static struct afb_cred *current;
  46
  47 static struct afb_cred *mkcred(uid_t uid, gid_t gid, pid_t pid, const char *label, size_t size)
  48 {
  49         struct afb_cred *cred;
  50         char *dest, user[64];
  51         size_t i;
  52         uid_t u;
  53
  54         i = 0;
  55         u = uid;
  56         do {
  57                 user[i++] = (char)('0' + u % 10);
  58                 u = u / 10;
  59         } while(u && i < sizeof user);
  60
  61         cred = malloc(2 + i + size + sizeof *cred);
  62         if (!cred)
  63                 errno = ENOMEM;
  64         else {
  65                 cred->refcount = 1;
  66                 cred->uid = uid;
  67                 cred->gid = gid;
  68                 cred->pid = pid;
  69                 dest = (char*)(&cred[1]);
  70                 cred->user = dest;
  71                 while(i)
  72                         *dest++ = user[--i];
  73                 *dest++ = 0;
  74                 cred->label = dest;
  75                 cred->id = dest;
  76                 memcpy(dest, label, size);
  77                 dest[size] = 0;
  78                 dest = strrchr(dest, ':');
  79                 if (dest)
  80                         cred->id = &dest[1];
  81         }
  82         return cred;
  83 }
  84
  85 static struct afb_cred *mkcurrent()
  86 {
  87         char label[MAX_LABEL_LENGTH];
  88         int fd;
  89         ssize_t rc;
  90
  91         fd = open("/proc/self/attr/current", O_RDONLY);
  92         if (fd < 0)
  93                 rc = 0;
  94         else {
  95                 rc = read(fd, label, sizeof label);
  96                 if (rc < 0)
  97                         rc = 0;
  98                 close(fd);
  99         }
 100
 101         return mkcred(getuid(), getgid(), getpid(), label, (size_t)rc);
 102 }
 103
 104 struct afb_cred *afb_cred_create(uid_t uid, gid_t gid, pid_t pid, const char *label)
 105 {
 106         label = label ? : DEFAULT_PEERSEC_LABEL;
 107         return mkcred(uid, gid, pid, label, strlen(label));
 108 }
 109
 110 struct afb_cred *afb_cred_create_for_socket(int fd)
 111 {
 112         int rc;
 113         socklen_t length;
 114         struct ucred ucred;
 115         char label[MAX_LABEL_LENGTH];
 116
 117         /* get the credentials */
 118         length = (socklen_t)(sizeof ucred);
 119         rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &length);
 120         if (rc < 0 || length != (socklen_t)(sizeof ucred)) {
 121 #if !defined(NO_DEFAULT_PEERCRED)
 122                 if (!rc)
 123                         errno = EINVAL;
 124                 return NULL;
 125 #else
 126                 ucred.uid = DEFAULT_PEERCRED_UID;
 127                 ucred.gid = DEFAULT_PEERCRED_GID;
 128                 ucred.pid = DEFAULT_PEERCRED_PID;
 129 #endif
 130         }
 131
 132         /* get the security label */
 133         length = (socklen_t)(sizeof label);
 134         rc = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, label, &length);
 135         if (rc < 0 || length > (socklen_t)(sizeof label)) {
 136 #if !defined(NO_DEFAULT_PEERSEC)
 137                 length = (socklen_t)strlen(DEFAULT_PEERSEC_LABEL);
 138                 strcpy (label, DEFAULT_PEERSEC_LABEL);
 139 #else
 140                 if (!rc)
 141                         errno = EINVAL;
 142                 return NULL;
 143 #endif
 144         }
 145
 146         /* makes the result */
 147         return mkcred(ucred.uid, ucred.gid, ucred.pid, label, (size_t)length);
 148 }
 149
 150 struct afb_cred *afb_cred_addref(struct afb_cred *cred)
 151 {
 152         if (cred)
 153                 __atomic_add_fetch(&cred->refcount, 1, __ATOMIC_RELAXED);
 154         return cred;
 155 }
 156
 157 void afb_cred_unref(struct afb_cred *cred)
 158 {
 159         if (cred && !__atomic_sub_fetch(&cred->refcount, 1, __ATOMIC_RELAXED)) {
 160                 if (cred != current)
 161                         free(cred);
 162                 else
 163                         cred->refcount = 1;
 164         }
 165 }
 166
 167 struct afb_cred *afb_cred_current()
 168 {
 169         if (!current)
 170                 current = mkcurrent();
 171         return afb_cred_addref(current);
 172 }
 173