First working version

[nsscash/nsscash.git] / nss / file.c

diff --git a/nss/file.c b/nss/file.c
new file mode 100644 (file)
index 0000000..30ea4f9
--- /dev/null
+++ b/nss/file.c
@@ -0,0 +1,88 @@
+/*
+ * Load and unload nsscash files
+ *
+ * Copyright (C) 2019  Simon Ruderich
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "file.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+
+bool map_file(const char *path, struct file *f) {
+    // Fully initialize the struct for unmap_file() and other users
+    f->fd = -1;
+    f->size = 0;
+    f->next_index = 0;
+    f->header = NULL;
+
+    f->fd = open(path, O_RDONLY | O_CLOEXEC);
+    if (f->fd < 0) {
+        goto fail;
+    }
+    struct stat s;
+    if (fstat(f->fd, &s)) {
+        goto fail;
+    }
+    f->size = (size_t)s.st_size;
+
+    void *x = mmap(NULL, f->size, PROT_READ, MAP_PRIVATE, f->fd, 0);
+    if (x == MAP_FAILED) {
+        goto fail;
+    }
+
+    const struct header *h = x;
+    f->header = h;
+
+    // Check MAGIC
+    if (memcmp(h->magic, MAGIC, sizeof(h->magic))) {
+        errno = EINVAL;
+        goto fail;
+    }
+    // Only version 1 is supported at the moment; this will also prevent
+    // running on big-endian systems which is currently not possible
+    if (h->version != 1) {
+        errno = EINVAL;
+        goto fail;
+    }
+
+    return true;
+
+fail: {
+        int save_errno = errno;
+        unmap_file(f);
+        errno = save_errno;
+        return false;
+    }
+}
+
+void unmap_file(struct file *f) {
+    if (f->header != NULL) {
+        munmap((void *)f->header, f->size);
+        f->header = NULL;
+    }
+    if (f->fd != -1) {
+        close(f->fd);
+        f->fd = -1;
+    }
+}