1 files changed, 142 insertions, 0 deletions
diff --git a/lib/libavb/avb_descriptor.c b/lib/libavb/avb_descriptor.c
new file mode 100644
index 0000000000..6422293293
--- /dev/null
+++ b/lib/libavb/avb_descriptor.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * SPDX-License-Identifier:	MIT
+ */
+
+#include "avb_descriptor.h"
+#include "avb_util.h"
+#include "avb_vbmeta_image.h"
+
+bool avb_descriptor_validate_and_byteswap(const AvbDescriptor* src,
+                                          AvbDescriptor* dest) {
+  dest->tag = avb_be64toh(src->tag);
+  dest->num_bytes_following = avb_be64toh(src->num_bytes_following);
+
+  if ((dest->num_bytes_following & 0x07) != 0) {
+    avb_error("Descriptor size is not divisible by 8.\n");
+    return false;
+  }
+  return true;
+}
+
+bool avb_descriptor_foreach(const uint8_t* image_data,
+                            size_t image_size,
+                            AvbDescriptorForeachFunc foreach_func,
+                            void* user_data) {
+  const AvbVBMetaImageHeader* header = NULL;
+  bool ret = false;
+  const uint8_t* image_end;
+  const uint8_t* desc_start;
+  const uint8_t* desc_end;
+  const uint8_t* p;
+
+  if (image_data == NULL) {
+    avb_error("image_data is NULL\n.");
+    goto out;
+  }
+
+  if (foreach_func == NULL) {
+    avb_error("foreach_func is NULL\n.");
+    goto out;
+  }
+
+  if (image_size < sizeof(AvbVBMetaImageHeader)) {
+    avb_error("Length is smaller than header.\n");
+    goto out;
+  }
+
+  /* Ensure magic is correct. */
+  if (avb_memcmp(image_data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
+    avb_error("Magic is incorrect.\n");
+    goto out;
+  }
+
+  /* Careful, not byteswapped - also ensure it's aligned properly. */
+  avb_assert_aligned(image_data);
+  header = (const AvbVBMetaImageHeader*)image_data;
+  image_end = image_data + image_size;
+
+  desc_start = image_data + sizeof(AvbVBMetaImageHeader) +
+               avb_be64toh(header->authentication_data_block_size) +
+               avb_be64toh(header->descriptors_offset);
+
+  desc_end = desc_start + avb_be64toh(header->descriptors_size);
+
+  if (desc_start < image_data || desc_start > image_end ||
+      desc_end < image_data || desc_end > image_end || desc_end < desc_start) {
+    avb_error("Descriptors not inside passed-in data.\n");
+    goto out;
+  }
+
+  for (p = desc_start; p < desc_end;) {
+    const AvbDescriptor* dh = (const AvbDescriptor*)p;
+    avb_assert_aligned(dh);
+    uint64_t nb_following = avb_be64toh(dh->num_bytes_following);
+    uint64_t nb_total = sizeof(AvbDescriptor) + nb_following;
+
+    if ((nb_total & 7) != 0) {
+      avb_error("Invalid descriptor length.\n");
+      goto out;
+    }
+
+    if (nb_total + p < desc_start || nb_total + p > desc_end) {
+      avb_error("Invalid data in descriptors array.\n");
+      goto out;
+    }
+
+    if (foreach_func(dh, user_data) == 0) {
+      goto out;
+    }
+
+    p += nb_total;
+  }
+
+  ret = true;
+
+out:
+  return ret;
+}
+
+static bool count_descriptors(const AvbDescriptor* descriptor,
+                              void* user_data) {
+  size_t* num_descriptors = user_data;
+  *num_descriptors += 1;
+  return true;
+}
+
+typedef struct {
+  size_t descriptor_number;
+  const AvbDescriptor** descriptors;
+} SetDescriptorData;
+
+static bool set_descriptors(const AvbDescriptor* descriptor, void* user_data) {
+  SetDescriptorData* data = user_data;
+  data->descriptors[data->descriptor_number++] = descriptor;
+  return true;
+}
+
+const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
+                                             size_t image_size,
+                                             size_t* out_num_descriptors) {
+  size_t num_descriptors = 0;
+  SetDescriptorData data;
+
+  avb_descriptor_foreach(
+      image_data, image_size, count_descriptors, &num_descriptors);
+
+  data.descriptor_number = 0;
+  data.descriptors =
+      avb_calloc(sizeof(const AvbDescriptor*) * (num_descriptors + 1));
+  if (data.descriptors == NULL) {
+    return NULL;
+  }
+  avb_descriptor_foreach(image_data, image_size, set_descriptors, &data);
+  avb_assert(data.descriptor_number == num_descriptors);
+
+  if (out_num_descriptors != NULL) {
+    *out_num_descriptors = num_descriptors;
+  }
+
+  return data.descriptors;
+}