X-Git-Url: https://git.netwichtig.de/gitweb/?a=blobdiff_plain;f=src%2Fsrc%2Flog.c;h=dff7d321190d03ce8430a063a9fa153f8ce6e4af;hb=0103b34645278151851c31cf1c1976150d907bb4;hp=88cc12cd4dfe877355908059b7e818faf5ab1dc2;hpb=0bfae1bfbd555b87f1a032ee3d78c19caccdbe42;p=user%2Fhenk%2Fcode%2Fexim.git

diff --git a/src/src/log.c b/src/src/log.c
index 88cc12cd4..dff7d3211 100644
--- a/src/src/log.c
+++ b/src/src/log.c
@@ -265,14 +265,19 @@ overwrite it temporarily if it is necessary to create the directory.
 Returns:       a file descriptor, or < 0 on failure (errno set)
 */
 
-int
-log_create(uschar *name)
+static int
+log_open_already_exim(uschar * const name)
 {
-int fd = Uopen(name,
-#ifdef O_CLOEXEC
-	O_CLOEXEC |
-#endif
-	O_CREAT|O_APPEND|O_WRONLY, LOG_MODE);
+int fd = -1;
+const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NONBLOCK;
+
+if (geteuid() != exim_uid)
+  {
+  errno = EACCES;
+  return -1;
+  }
+
+fd = Uopen(name, flags, LOG_MODE);
 
 /* If creation failed, attempt to build a log directory in case that is the
 problem. */
@@ -286,11 +291,7 @@ if (fd < 0 && errno == ENOENT)
   DEBUG(D_any) debug_printf("%s log directory %s\n",
     created ? "created" : "failed to create", name);
   *lastslash = '/';
-  if (created) fd = Uopen(name,
-#ifdef O_CLOEXEC
-			O_CLOEXEC |
-#endif
-		       	O_CREAT|O_APPEND|O_WRONLY, LOG_MODE);
+  if (created) fd = Uopen(name, flags, LOG_MODE);
   }
 
 return fd;
@@ -298,6 +299,79 @@ return fd;
 
 
 
+/* Inspired by OpenSSH's mm_send_fd(). Thanks!
+Send fd over socketpair.
+Return: true iff good.
+*/
+
+static BOOL
+log_send_fd(const int sock, const int fd)
+{
+struct msghdr msg;
+union {
+  struct cmsghdr hdr;
+  char buf[CMSG_SPACE(sizeof(int))];
+} cmsgbuf;
+struct cmsghdr *cmsg;
+char ch = 'A';
+struct iovec vec = {.iov_base = &ch, .iov_len = 1};
+ssize_t n;
+
+memset(&msg, 0, sizeof(msg));
+memset(&cmsgbuf, 0, sizeof(cmsgbuf));
+msg.msg_control = &cmsgbuf.buf;
+msg.msg_controllen = sizeof(cmsgbuf.buf);
+
+cmsg = CMSG_FIRSTHDR(&msg);
+cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+cmsg->cmsg_level = SOL_SOCKET;
+cmsg->cmsg_type = SCM_RIGHTS;
+*(int *)CMSG_DATA(cmsg) = fd;
+
+msg.msg_iov = &vec;
+msg.msg_iovlen = 1;
+
+while ((n = sendmsg(sock, &msg, 0)) == -1 && errno == EINTR);
+return n == 1;
+}
+
+/* Inspired by OpenSSH's mm_receive_fd(). Thanks!
+Return fd passed over socketpair, or -1 on error.
+*/
+
+static int
+log_recv_fd(const int sock)
+{
+struct msghdr msg;
+union {
+  struct cmsghdr hdr;
+  char buf[CMSG_SPACE(sizeof(int))];
+} cmsgbuf;
+struct cmsghdr *cmsg;
+char ch = '\0';
+struct iovec vec = {.iov_base = &ch, .iov_len = 1};
+ssize_t n;
+int fd;
+
+memset(&msg, 0, sizeof(msg));
+msg.msg_iov = &vec;
+msg.msg_iovlen = 1;
+
+memset(&cmsgbuf, 0, sizeof(cmsgbuf));
+msg.msg_control = &cmsgbuf.buf;
+msg.msg_controllen = sizeof(cmsgbuf.buf);
+
+while ((n = recvmsg(sock, &msg, 0)) == -1 && errno == EINTR) ;
+if (n != 1 || ch != 'A') return -1;
+
+if (!(cmsg = CMSG_FIRSTHDR(&msg))) return -1;
+if (cmsg->cmsg_type != SCM_RIGHTS) return -1;
+if ((fd = *(const int *)CMSG_DATA(cmsg)) < 0) return -1;
+return fd;
+}
+
+
+
 /*************************************************
 *     Create a log file as the exim user         *
 *************************************************/
@@ -313,41 +387,56 @@ Returns:       a file descriptor, or < 0 on failure (errno set)
 */
 
 int
-log_create_as_exim(uschar *name)
+log_open_as_exim(uschar * const name)
 {
-pid_t pid = exim_fork(US"logfile-create");
-int status = 1;
 int fd = -1;
+const uid_t euid = geteuid();
 
-/* In the subprocess, change uid/gid and do the creation. Return 0 from the
-subprocess on success. If we don't check for setuid failures, then the file
-can be created as root, so vulnerabilities which cause setuid to fail mean
-that the Exim user can use symlinks to cause a file to be opened/created as
-root. We always open for append, so can't nuke existing content but it would
-still be Rather Bad. */
-
-if (pid == 0)
+if (euid == exim_uid)
+  fd = log_open_already_exim(name);
+else if (euid == root_uid)
   {
-  if (setgid(exim_gid) < 0)
-    die(US"exim: setgid for log-file creation failed, aborting",
-      US"Unexpected log failure, please try later");
-  if (setuid(exim_uid) < 0)
-    die(US"exim: setuid for log-file creation failed, aborting",
-      US"Unexpected log failure, please try later");
-  _exit((log_create(name) < 0)? 1 : 0);
-  }
-
-/* If we created a subprocess, wait for it. If it succeeded, try the open. */
+  int sock[2];
+  if (socketpair(AF_UNIX, SOCK_STREAM, 0, sock) == 0)
+    {
+    const pid_t pid = fork();
+    if (pid == 0)
+      {
+      (void)close(sock[0]);
+      if (  setgroups(1, &exim_gid) != 0
+         || setgid(exim_gid) != 0
+         || setuid(exim_uid) != 0
+
+         || getuid() != exim_uid || geteuid() != exim_uid
+         || getgid() != exim_gid || getegid() != exim_gid
+
+         || (fd = log_open_already_exim(name)) < 0
+         || !log_send_fd(sock[1], fd)
+	 ) _exit(EXIT_FAILURE);
+      (void)close(sock[1]);
+      _exit(EXIT_SUCCESS);
+      }
 
-while (pid > 0 && waitpid(pid, &status, 0) != pid);
-if (status == 0) fd = Uopen(name,
-#ifdef O_CLOEXEC
-			O_CLOEXEC |
-#endif
-		       	O_APPEND|O_WRONLY, LOG_MODE);
+    (void)close(sock[1]);
+    if (pid > 0)
+      {
+      fd = log_recv_fd(sock[0]);
+      while (waitpid(pid, NULL, 0) == -1 && errno == EINTR);
+      }
+    (void)close(sock[0]);
+    }
+  }
 
-/* If we failed to create a subprocess, we are in a bad way. We return
-with fd still < 0, and errno set, letting the caller handle the error. */
+if (fd >= 0)
+  {
+  int flags;
+  flags = fcntl(fd, F_GETFD);
+  if (flags != -1) (void)fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
+  flags = fcntl(fd, F_GETFL);
+  if (flags != -1) (void)fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
+  }
+else
+  errno = EACCES;
 
 return fd;
 }
@@ -398,60 +487,53 @@ people want, I hope. */
 
 ok = string_format(buffer, sizeof(buffer), CS file_path, log_names[type]);
 
-/* Save the name of the mainlog for rollover processing. Without a datestamp,
-it gets statted to see if it has been cycled. With a datestamp, the datestamp
-will be compared. The static slot for saving it is the same size as buffer,
-and the text has been checked above to fit, so this use of strcpy() is OK. */
-
-if (type == lt_main && string_datestamp_offset >= 0)
+switch (type)
   {
-  Ustrcpy(mainlog_name, buffer);
-  mainlog_datestamp = mainlog_name + string_datestamp_offset;
-  }
-
-/* Ditto for the reject log */
-
-else if (type == lt_reject && string_datestamp_offset >= 0)
-  {
-  Ustrcpy(rejectlog_name, buffer);
-  rejectlog_datestamp = rejectlog_name + string_datestamp_offset;
-  }
-
-/* and deal with the debug log (which keeps the datestamp, but does not
-update it) */
-
-else if (type == lt_debug)
-  {
-  Ustrcpy(debuglog_name, buffer);
-  if (tag)
-    {
-    /* this won't change the offset of the datestamp */
-    ok2 = string_format(buffer, sizeof(buffer), "%s%s",
-      debuglog_name, tag);
-    if (ok2)
-      Ustrcpy(debuglog_name, buffer);
-    }
-  }
-
-/* Remove any datestamp if this is the panic log. This is rare, so there's no
-need to optimize getting the datestamp length. We remove one non-alphanumeric
-char afterwards if at the start, otherwise one before. */
-
-else if (string_datestamp_offset >= 0)
-  {
-  uschar * from = buffer + string_datestamp_offset;
-  uschar * to = from + string_datestamp_length;
+  case lt_main:
+    /* Save the name of the mainlog for rollover processing. Without a datestamp,
+    it gets statted to see if it has been cycled. With a datestamp, the datestamp
+    will be compared. The static slot for saving it is the same size as buffer,
+    and the text has been checked above to fit, so this use of strcpy() is OK. */
+    Ustrcpy(mainlog_name, buffer);
+    if (string_datestamp_offset > 0)
+      mainlog_datestamp = mainlog_name + string_datestamp_offset;
+  case lt_reject:
+    /* Ditto for the reject log */
+    Ustrcpy(rejectlog_name, buffer);
+    if (string_datestamp_offset > 0)
+      rejectlog_datestamp = rejectlog_name + string_datestamp_offset;
+  case lt_debug:
+    /* and deal with the debug log (which keeps the datestamp, but does not
+    update it) */
+    Ustrcpy(debuglog_name, buffer);
+    if (tag)
+      {
+      /* this won't change the offset of the datestamp */
+      ok2 = string_format(buffer, sizeof(buffer), "%s%s",
+        debuglog_name, tag);
+      if (ok2)
+        Ustrcpy(debuglog_name, buffer);
+      }
+  default:
+    /* Remove any datestamp if this is the panic log. This is rare, so there's no
+  need to optimize getting the datestamp length. We remove one non-alphanumeric
+  char afterwards if at the start, otherwise one before. */
+    if (string_datestamp_offset >= 0)
+      {
+      uschar * from = buffer + string_datestamp_offset;
+      uschar * to = from + string_datestamp_length;
 
-  if (from == buffer || from[-1] == '/')
-    {
-    if (!isalnum(*to)) to++;
-    }
-  else
-    if (!isalnum(from[-1])) from--;
+      if (from == buffer || from[-1] == '/')
+        {
+        if (!isalnum(*to)) to++;
+        }
+      else
+        if (!isalnum(from[-1])) from--;
 
-  /* This copy is ok, because we know that to is a substring of from. But
-  due to overlap we must use memmove() not Ustrcpy(). */
-  memmove(from, to, Ustrlen(to)+1);
+      /* This copy is ok, because we know that to is a substring of from. But
+      due to overlap we must use memmove() not Ustrcpy(). */
+      memmove(from, to, Ustrlen(to)+1);
+      }
   }
 
 /* If the file name is too long, it is an unrecoverable disaster */
@@ -460,52 +542,17 @@ if (!ok)
   die(US"exim: log file path too long: aborting",
       US"Logging failure; please try later");
 
-/* We now have the file name. Try to open an existing file. After a successful
-open, arrange for automatic closure on exec(), and then return. */
+/* We now have the file name. After a successful open, return. */
 
-*fd = Uopen(buffer,
-#ifdef O_CLOEXEC
-		O_CLOEXEC |
-#endif
-	       	O_APPEND|O_WRONLY, LOG_MODE);
+*fd = log_open_as_exim(buffer);
 
 if (*fd >= 0)
   {
-#ifndef O_CLOEXEC
-  (void)fcntl(*fd, F_SETFD, fcntl(*fd, F_GETFD) | FD_CLOEXEC);
-#endif
   return;
   }
 
-/* Open was not successful: try creating the file. If this is a root process,
-we must do the creating in a subprocess set to exim:exim in order to ensure
-that the file is created with the right ownership. Otherwise, there can be a
-race if another Exim process is trying to write to the log at the same time.
-The use of SIGUSR1 by the exiwhat utility can provoke a lot of simultaneous
-writing. */
-
 euid = geteuid();
 
-/* If we are already running as the Exim user (even if that user is root),
-we can go ahead and create in the current process. */
-
-if (euid == exim_uid) *fd = log_create(buffer);
-
-/* Otherwise, if we are root, do the creation in an exim:exim subprocess. If we
-are neither exim nor root, creation is not attempted. */
-
-else if (euid == root_uid) *fd = log_create_as_exim(buffer);
-
-/* If we now have an open file, set the close-on-exec flag and return. */
-
-if (*fd >= 0)
-  {
-#ifndef O_CLOEXEC
-  (void)fcntl(*fd, F_SETFD, fcntl(*fd, F_GETFD) | FD_CLOEXEC);
-#endif
-  return;
-  }
-
 /* Creation failed. There are some circumstances in which we get here when
 the effective uid is not root or exim, which is the problem. (For example, a
 non-setuid binary with log_arguments set, called in certain ways.) Rather than
@@ -654,18 +701,36 @@ return total_written;
 }
 
 
-
-static void
-set_file_path(void)
+void
+set_file_path(BOOL *multiple)
 {
+uschar *s;
 int sep = ':';              /* Fixed separator - outside use */
-uschar *t;
-const uschar *tt = US LOG_FILE_PATH;
-while ((t = string_nextinlist(&tt, &sep, log_buffer, LOG_BUFFER_SIZE)))
+const uschar *ss = *log_file_path ? log_file_path : US LOG_FILE_PATH;
+
+logging_mode = 0;
+while ((s = string_nextinlist(&ss, &sep, log_buffer, LOG_BUFFER_SIZE)))
   {
-  if (Ustrcmp(t, "syslog") == 0 || t[0] == 0) continue;
-  file_path = string_copy(t);
-  break;
+  if (Ustrcmp(s, "syslog") == 0)
+    logging_mode |= LOG_MODE_SYSLOG;
+  else if (logging_mode & LOG_MODE_FILE)  /* we know a file already */
+    {
+    if (multiple) *multiple = TRUE;
+    }
+  else
+    {
+    logging_mode |= LOG_MODE_FILE;
+
+    /* If a non-empty path is given, use it */
+
+    if (*s)
+      file_path = string_copy(s);
+
+    /* If the path is empty, we want to use the first non-empty, non-
+    syslog item in LOG_FILE_PATH, if there is one, since the value of
+    log_file_path may have been set at runtime. If there is no such item,
+    use the ultimate default in the spool directory. */
+    }
   }
 }
 
@@ -673,7 +738,11 @@ while ((t = string_nextinlist(&tt, &sep, log_buffer, LOG_BUFFER_SIZE)))
 void
 mainlog_close(void)
 {
-if (mainlogfd < 0) return;
+/* avoid closing it if it is closed already or if we do not see a chance
+to open the file mainlog later again */
+if (mainlogfd < 0 /* already closed */
+   || !(geteuid() == 0 || geteuid() == exim_uid))
+  return;
 (void)close(mainlogfd);
 mainlogfd = -1;
 mainlog_inode = 0;
@@ -788,38 +857,7 @@ if (!path_inspected)
   /* If nothing has been set, don't waste effort... the default values for the
   statics are file_path="" and logging_mode = LOG_MODE_FILE. */
 
-  if (*log_file_path)
-    {
-    int sep = ':';              /* Fixed separator - outside use */
-    uschar *s;
-    const uschar *ss = log_file_path;
-
-    logging_mode = 0;
-    while ((s = string_nextinlist(&ss, &sep, log_buffer, LOG_BUFFER_SIZE)))
-      {
-      if (Ustrcmp(s, "syslog") == 0)
-        logging_mode |= LOG_MODE_SYSLOG;
-      else if (logging_mode & LOG_MODE_FILE)
-	multiple = TRUE;
-      else
-        {
-        logging_mode |= LOG_MODE_FILE;
-
-        /* If a non-empty path is given, use it */
-
-        if (*s)
-          file_path = string_copy(s);
-
-        /* If the path is empty, we want to use the first non-empty, non-
-        syslog item in LOG_FILE_PATH, if there is one, since the value of
-        log_file_path may have been set at runtime. If there is no such item,
-        use the ultimate default in the spool directory. */
-
-        else
-	  set_file_path();  /* Empty item in log_file_path */
-        }    /* First non-syslog item in log_file_path */
-      }      /* Scan of log_file_path */
-    }
+  if (*log_file_path) set_file_path(&multiple);
 
   /* If no modes have been selected, it is a major disaster */
 
@@ -901,6 +939,7 @@ if (!(flags & (LOG_MAIN|LOG_PANIC|LOG_REJECT)))
 if (f.disable_logging)
   {
   DEBUG(D_any) debug_printf("log writing disabled\n");
+  if ((flags & LOG_PANIC_DIE) == LOG_PANIC_DIE) exim_exit(EXIT_FAILURE);
   return;
   }
 
@@ -1436,7 +1475,7 @@ if (opts)
 resulting in certain setup not having been done.  Hack this for now so we
 do not segfault; note that nondefault log locations will not work */
 
-if (!*file_path) set_file_path();
+if (!*file_path) set_file_path(NULL);
 
 open_log(&fd, lt_debug, tag_name);
 
@@ -1458,5 +1497,12 @@ debug_file = NULL;
 unlink_log(lt_debug);
 }
 
+void
+open_logs(void)
+{
+set_file_path(NULL);
+open_log(&mainlogfd, lt_main, 0);
+open_log(&rejectlogfd, lt_reject, 0);
+}
 
 /* End of log.c */