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 static struct afb_cred *current;
  33
  34 static struct afb_cred *mkcred(uid_t uid, gid_t gid, pid_t pid, const char *label, size_t size)
  35 {
  36         struct afb_cred *cred;
  37         char *dest;
  38
  39         cred = malloc(1 + size + sizeof *cred);
  40         if (!cred)
  41                 errno = ENOMEM;
  42         else {
  43                 cred->refcount = 1;
  44                 cred->uid = uid;
  45                 cred->gid = gid;
  46                 cred->pid = pid;
  47                 dest = (char*)(&cred[1]);
  48                 memcpy(dest, label, size);
  49                 dest[size] = 0;
  50                 cred->label = dest;
  51                 cred->id = dest;
  52                 dest = strrchr(dest, ':');
  53                 if (dest && dest[1])
  54                         cred->id = &dest[1];
  55         }
  56         return cred;
  57 }
  58
  59 static struct afb_cred *mkcurrent()
  60 {
  61         char label[MAX_LABEL_LENGTH];
  62         int fd;
  63         ssize_t rc;
  64
  65         fd = open("/proc/self/attr/current", O_RDONLY);
  66         if (fd < 0)
  67                 rc = 0;
  68         else {
  69                 rc = read(fd, label, sizeof label);
  70                 if (rc < 0)
  71                         rc = 0;
  72                 close(fd);
  73         }
  74
  75         return mkcred(getuid(), getgid(), getpid(), label, (size_t)rc);
  76 }
  77
  78 struct afb_cred *afb_cred_create(uid_t uid, gid_t gid, pid_t pid, const char *label)
  79 {
  80         label = label ? : "";
  81         return mkcred(uid, gid, pid, label, strlen(label));
  82 }
  83
  84 struct afb_cred *afb_cred_create_for_socket(int fd)
  85 {
  86         int rc;
  87         socklen_t length;
  88         struct ucred ucred;
  89         char label[MAX_LABEL_LENGTH];
  90
  91         /* get the credentials */
  92         length = (socklen_t)(sizeof ucred);
  93         rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &length);
  94         if (rc < 0 || length != (socklen_t)(sizeof ucred)) {
  95                 if (!rc)
  96                         errno = EINVAL;
  97                 return NULL;
  98         }
  99
 100         /* get the security label */
 101         length = (socklen_t)(sizeof label);
 102         rc = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, label, &length);
 103         if (rc < 0 || length > (socklen_t)(sizeof label)) {
 104                 if (!rc)
 105                         errno = EINVAL;
 106                 return NULL;
 107         }
 108
 109         /* makes the result */
 110         return mkcred(ucred.uid, ucred.gid, ucred.pid, label, (size_t)length);
 111 }
 112
 113 struct afb_cred *afb_cred_addref(struct afb_cred *cred)
 114 {
 115         if (cred)
 116                 __atomic_add_fetch(&cred->refcount, 1, __ATOMIC_RELAXED);
 117         return cred;
 118 }
 119
 120 void afb_cred_unref(struct afb_cred *cred)
 121 {
 122         if (cred && !__atomic_sub_fetch(&cred->refcount, 1, __ATOMIC_RELAXED)) {
 123                 if (cred != current)
 124                         free(cred);
 125                 else
 126                         cred->refcount = 1;
 127         }
 128 }
 129
 130 struct afb_cred *afb_cred_current()
 131 {
 132         if (!current)
 133                 current = mkcurrent();
 134         return afb_cred_addref(current);
 135 }
 136