Use stdio, lock less to make FILE ccache faster

Use stdio.  Don't lock to read -- we only ever rename new ccaches into
place, or overwrite endtimes to delete entries, or overwrite part of the
realm name of cc config entries.

Dropping locks around ccache iterator stepping strongly implied that we
don't expect truncation, that we only expect appends (and the
overwriting done to delete entries).

Don't unlock -- let close(2) do it, thus making fewer system calls.

lib/krb5/fcache.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
+ * Copyright (c) 1997 - 2017 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden).
  * All rights reserved.
  *
@@ -176,15 +176,11 @@ static krb5_error_code KRB5_CALLCONV
 fcc_lock(krb5_context context, krb5_ccache id,
 	 int fd, krb5_boolean exclusive)
 {
+    if (exclusive == FALSE)
+        return 0;
     return _krb5_xlock(context, fd, exclusive, fcc_get_name(context, id));
 }
 
-static krb5_error_code KRB5_CALLCONV
-fcc_unlock(krb5_context context, int fd)
-{
-    return _krb5_xunlock(context, fd);
-}
-
 static krb5_error_code KRB5_CALLCONV
 fcc_resolve(krb5_context context, krb5_ccache *id, const char *res)
 {
@@ -276,7 +272,6 @@ _krb5_erase_file(krb5_context context, const char *filename)
     }
     if (unlink(filename) < 0) {
 	ret = errno;
-	_krb5_xunlock(context, fd);
         close (fd);
 	krb5_set_error_message(context, errno,
 	    N_("krb5_cc_destroy: unlinking \"%s\": %s", ""),
@@ -286,7 +281,6 @@ _krb5_erase_file(krb5_context context, const char *filename)
     ret = fstat(fd, &sb2);
     if (ret < 0) {
 	ret = errno;
-	_krb5_xunlock(context, fd);
 	close (fd);
 	return ret;
     }
@@ -294,7 +288,6 @@ _krb5_erase_file(krb5_context context, const char *filename)
     /* check if someone was playing with symlinks */
 
     if (sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino) {
-	_krb5_xunlock(context, fd);
 	close(fd);
 	return EPERM;
     }
@@ -302,18 +295,11 @@ _krb5_erase_file(krb5_context context, const char *filename)
     /* there are still hard links to this file */
 
     if (sb2.st_nlink != 0) {
-	_krb5_xunlock(context, fd);
         close(fd);
         return 0;
     }
 
     ret = scrub_file(fd);
-    if (ret) {
-	_krb5_xunlock(context, fd);
-	close(fd);
-	return ret;
-    }
-    ret = _krb5_xunlock(context, fd);
     close(fd);
     return ret;
 }
@@ -581,7 +567,6 @@ fcc_initialize(krb5_context context,
 
 	krb5_storage_free(sp);
     }
-    fcc_unlock(context, fd);
     if (close(fd) < 0)
 	if (ret == 0) {
 	    char buf[128];
@@ -637,7 +622,6 @@ fcc_store_cred(krb5_context context,
 	    ret = write_storage(context, sp, fd);
 	krb5_storage_free(sp);
     }
-    fcc_unlock(context, fd);
     if (close(fd) < 0) {
 	if (ret == 0) {
 	    char buf[128];
@@ -672,7 +656,7 @@ init_fcc(krb5_context context,
     if(ret)
 	return ret;
 
-    sp = krb5_storage_from_fd(fd);
+    sp = krb5_storage_stdio_from_fd(fd, "r");
     if(sp == NULL) {
 	krb5_clear_error_message(context);
 	ret = ENOMEM;
@@ -798,7 +782,6 @@ init_fcc(krb5_context context,
   out:
     if(sp != NULL)
 	krb5_storage_free(sp);
-    fcc_unlock(context, fd);
     close(fd);
     return ret;
 }
@@ -819,7 +802,6 @@ fcc_get_principal(krb5_context context,
     if (ret)
 	krb5_clear_error_message(context);
     krb5_storage_free(sp);
-    fcc_unlock(context, fd);
     close(fd);
     return ret;
 }
@@ -847,7 +829,7 @@ fcc_get_first (krb5_context context,
     }
     memset(*cursor, 0, sizeof(struct fcc_cursor));
 
-    ret = init_fcc(context, id, "get-frist", &FCC_CURSOR(*cursor)->sp,
+    ret = init_fcc(context, id, "get-first", &FCC_CURSOR(*cursor)->sp,
 		   &FCC_CURSOR(*cursor)->fd, NULL);
     if (ret) {
 	free(*cursor);
@@ -861,7 +843,6 @@ fcc_get_first (krb5_context context,
 	return ret;
     }
     krb5_free_principal (context, principal);
-    fcc_unlock(context, FCC_CURSOR(*cursor)->fd);
     return 0;
 }
 
@@ -879,19 +860,16 @@ fcc_get_next (krb5_context context,
     if (FCC_CURSOR(*cursor) == NULL)
         return krb5_einval(context, 3);
 
-    if((ret = fcc_lock(context, id, FCC_CURSOR(*cursor)->fd, FALSE)) != 0)
+    FCC_CURSOR(*cursor)->cred_start =
-	return ret;
+        krb5_storage_seek(FCC_CURSOR(*cursor)->sp, 0, SEEK_CUR);
-    FCC_CURSOR(*cursor)->cred_start = lseek(FCC_CURSOR(*cursor)->fd,
-					   0, SEEK_CUR);
 
     ret = krb5_ret_creds(FCC_CURSOR(*cursor)->sp, creds);
     if (ret)
 	krb5_clear_error_message(context);
 
-    FCC_CURSOR(*cursor)->cred_end = lseek(FCC_CURSOR(*cursor)->fd,
+    FCC_CURSOR(*cursor)->cred_end =
-					 0, SEEK_CUR);
+        krb5_storage_seek(FCC_CURSOR(*cursor)->sp, 0, SEEK_CUR);
 
-    fcc_unlock(context, FCC_CURSOR(*cursor)->fd);
     return ret;
 }
 
@@ -1025,7 +1003,6 @@ cred_delete(krb5_context context,
     ret = write_storage(context, sp, fd);
 out:
     if (fd > -1) {
-	fcc_unlock(context, fd);
 	if (close(fd) < 0 && ret == 0) {
 	    krb5_set_error_message(context, errno, N_("close %s", ""),
 				   FILENAME(id));
@@ -1211,11 +1188,9 @@ fcc_move(krb5_context context, krb5_ccache from, krb5_ccache to)
 	    goto out2;
 	}
     out2:
-	fcc_unlock(context, fd2);
 	close(fd2);
 
     out1:
-	fcc_unlock(context, fd1);
 	close(fd1);
 
 	_krb5_erase_file(context, FILENAME(from));
@@ -1233,7 +1208,6 @@ fcc_move(krb5_context context, krb5_ccache from, krb5_ccache to)
 	if ((ret = init_fcc (context, to, "move", &sp, &fd, NULL)) == 0) {
 	    if (sp)
 		krb5_storage_free(sp);
-	    fcc_unlock(context, fd);
 	    close(fd);
 	}
     }
@@ -1287,7 +1261,6 @@ fcc_get_kdc_offset(krb5_context context, krb5_ccache id, krb5_deltat *kdc_offset
     ret = init_fcc(context, id, "get-kdc-offset", &sp, &fd, kdc_offset);
     if (sp)
 	krb5_storage_free(sp);
-    fcc_unlock(context, fd);
     close(fd);
 
     return ret;