include/net/scm.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_NET_SCM_H
   3 #define __LINUX_NET_SCM_H
   4
   5 #include <linux/limits.h>
   6 #include <linux/net.h>
   7 #include <linux/cred.h>
   8 #include <linux/security.h>
   9 #include <linux/pid.h>
  10 #include <linux/nsproxy.h>
  11
  12 /* Well, we should have at least one descriptor open
  13  * to accept passed FDs 8)
  14  */
  15 #define SCM_MAX_FD      253
  16
  17 struct scm_creds {
  18         u32     pid;
  19         kuid_t  uid;
  20         kgid_t  gid;
  21 };
  22
  23 struct scm_fp_list {
  24         short                   count;
  25         short                   max;
  26         struct user_struct      *user;
  27         struct file             *fp[SCM_MAX_FD];
  28 };
  29
  30 struct scm_cookie {
  31         struct pid              *pid;           /* Skb credentials */
  32         struct scm_fp_list      *fp;            /* Passed files         */
  33         struct scm_creds        creds;          /* Skb credentials      */
  34 #ifdef CONFIG_SECURITY_NETWORK
  35         u32                     secid;          /* Passed security ID   */
  36 #endif
  37 };
  38
  39 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm);
  40 void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm);
  41 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);
  42 void __scm_destroy(struct scm_cookie *scm);
  43 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
  44
  45 #ifdef CONFIG_SECURITY_NETWORK
  46 static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
  47 {
  48         security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
  49 }
  50 #else
  51 static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
  52 { }
  53 #endif /* CONFIG_SECURITY_NETWORK */
  54
  55 static __inline__ void scm_set_cred(struct scm_cookie *scm,
  56                                     struct pid *pid, kuid_t uid, kgid_t gid)
  57 {
  58         scm->pid  = get_pid(pid);
  59         scm->creds.pid = pid_vnr(pid);
  60         scm->creds.uid = uid;
  61         scm->creds.gid = gid;
  62 }
  63
  64 static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
  65 {
  66         put_pid(scm->pid);
  67         scm->pid  = NULL;
  68 }
  69
  70 static __inline__ void scm_destroy(struct scm_cookie *scm)
  71 {
  72         scm_destroy_cred(scm);
  73         if (scm->fp)
  74                 __scm_destroy(scm);
  75 }
  76
  77 static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
  78                                struct scm_cookie *scm, bool forcecreds)
  79 {
  80         memset(scm, 0, sizeof(*scm));
  81         scm->creds.uid = INVALID_UID;
  82         scm->creds.gid = INVALID_GID;
  83         if (forcecreds)
  84                 scm_set_cred(scm, task_tgid(current), current_uid(), current_gid());
  85         unix_get_peersec_dgram(sock, scm);
  86         if (msg->msg_controllen <= 0)
  87                 return 0;
  88         return __scm_send(sock, msg, scm);
  89 }
  90
  91 #ifdef CONFIG_SECURITY_NETWORK
  92 static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
  93 {
  94         char *secdata;
  95         u32 seclen;
  96         int err;
  97
  98         if (test_bit(SOCK_PASSSEC, &sock->flags)) {
  99                 err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
 100
 101                 if (!err) {
 102                         put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
 103                         security_release_secctx(secdata, seclen);
 104                 }
 105         }
 106 }
 107
 108 static inline bool scm_has_secdata(struct socket *sock)
 109 {
 110         return test_bit(SOCK_PASSSEC, &sock->flags);
 111 }
 112 #else
 113 static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
 114 { }
 115
 116 static inline bool scm_has_secdata(struct socket *sock)
 117 {
 118         return false;
 119 }
 120 #endif /* CONFIG_SECURITY_NETWORK */
 121
 122 static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
 123                                 struct scm_cookie *scm, int flags)
 124 {
 125         if (!msg->msg_control) {
 126                 if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp ||
 127                     scm_has_secdata(sock))
 128                         msg->msg_flags |= MSG_CTRUNC;
 129                 scm_destroy(scm);
 130                 return;
 131         }
 132
 133         if (test_bit(SOCK_PASSCRED, &sock->flags)) {
 134                 struct user_namespace *current_ns = current_user_ns();
 135                 struct ucred ucreds = {
 136                         .pid = scm->creds.pid,
 137                         .uid = from_kuid_munged(current_ns, scm->creds.uid),
 138                         .gid = from_kgid_munged(current_ns, scm->creds.gid),
 139                 };
 140                 put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds);
 141         }
 142
 143         scm_destroy_cred(scm);
 144
 145         scm_passec(sock, msg, scm);
 146
 147         if (!scm->fp)
 148                 return;
 149
 150         scm_detach_fds(msg, scm);
 151 }
 152
 153
 154 #endif /* __LINUX_NET_SCM_H */
 155