add read_file_to_str_from_fifo which is used by read_file_to_str

if the file happens to be one.

change file_status() to return FN_FILE if st_mode matches S_IFIFO
so that init_key_from_file() will read from a FIFO.

src/common/util.c

@@ -1805,7 +1805,7 @@ file_status(const char *fname)
   }
   if (st.st_mode & S_IFDIR)
     return FN_DIR;
-  else if (st.st_mode & S_IFREG)
+  else if (st.st_mode & (S_IFREG | S_IFIFO))
     return FN_FILE;
   else
     return FN_ERROR;
@@ -2237,6 +2237,42 @@ write_bytes_to_new_file(const char *fname, const char *str, size_t len,
                                   (bin?O_BINARY:O_TEXT));
 }
 
+/**
+ * Read the contents of the open file <b>fd</b> presuming it is a FIFO
+ * (or similar) file descriptor for which the size of the file isn't
+ * known ahead of time. NULL is returned if this fails for some reason.
+ */
+
+char *
+read_file_to_str_from_fifo(int fd)
+{
+  ssize_t r;
+  size_t pos = 0;
+  char *string = 0;
+  char buf[256];
+  string = NULL;
+
+  do {
+    r = read(fd, buf, 256);
+    if (r < 0) {
+      if (string)
+        tor_free(string);
+      return NULL;
+    }
+
+    if (r == 0)
+      break;
+
+    string = tor_realloc(string, pos + (size_t)r + 1);
+
+    memcpy(string+pos, buf, r);
+    pos += r;
+  } while (r > 0);
+
+  string[pos] = '\0';
+  return string;
+}
+
 /** Read the contents of <b>filename</b> into a newly allocated
  * string; return the string on success or NULL on failure.
  *
@@ -2285,6 +2321,14 @@ read_file_to_str(const char *filename, int flags, struct stat *stat_out)
     return NULL;
   }
 
+  if (S_ISFIFO(statbuf.st_mode)) {
+      string = read_file_to_str_from_fifo(fd);
+      if (string && stat_out) {
+        memcpy(stat_out, &statbuf, sizeof(struct stat));
+      }
+      return string;
+  }
+
   if ((uint64_t)(statbuf.st_size)+1 >= SIZE_T_CEILING)
     return NULL;
 

src/common/util.h

@@ -360,6 +360,8 @@ struct stat;
 #endif
 char *read_file_to_str(const char *filename, int flags, struct stat *stat_out)
   ATTR_MALLOC;
+char *read_file_to_str_from_fifo(int fd)
+  ATTR_MALLOC;
 const char *parse_config_line_from_str(const char *line,
                                        char **key_out, char **value_out);
 char *expand_filename(const char *filename);

src/test/test_util.c

@@ -18,6 +18,28 @@
 #include <tchar.h>
 #endif
 
+static void
+test_util_read_file_fifo(void)
+{
+#ifndef _WIN32
+  char fifo_name[64];
+  strcpy(fifo_name, "/tmp/tor_test_fifo.XXXXXX");
+  int fd = mkstemp(fifo_name);
+  test_neq(fd, -1);
+  test_eq(write(fd, "somethingsomething", 19), 19);
+  close(fd);
+
+  int read_fd = open(fifo_name, O_RDONLY);
+  char *str = read_file_to_str_from_fifo(read_fd);
+  close(read_fd);
+
+  test_eq(strcmp(str, "somethingsomething"), 0);
+
+ done:
+  unlink(fifo_name);
+#endif
+}
+
 static void
 test_util_time(void)
 {
@@ -3191,6 +3213,7 @@ struct testcase_t util_tests[] = {
   UTIL_TEST(envnames, 0),
   UTIL_TEST(make_environment, 0),
   UTIL_TEST(set_env_var_in_sl, 0),
+  UTIL_TEST(read_file_fifo, 0),
   END_OF_TESTCASES
 };