1 files changed, 516 insertions, 0 deletions

diff --git a/lib/avb/libavb_ab/avb_ab_flow.c b/lib/avb/libavb_ab/avb_ab_flow.c
new file mode 100644
index 0000000..3adb927
--- /dev/null
+++ b/lib/avb/libavb_ab/avb_ab_flow.c
@@ -0,0 +1,516 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "avb_ab_flow.h"
+
+bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest) {
+  /* Ensure magic is correct. */
+  if (avb_safe_memcmp(src->magic, AVB_AB_MAGIC, AVB_AB_MAGIC_LEN) != 0) {
+    avb_error("Magic is incorrect.\n");
+    return false;
+  }
+
+  avb_memcpy(dest, src, sizeof(AvbABData));
+  dest->crc32 = avb_be32toh(dest->crc32);
+
+  /* Ensure we don't attempt to access any fields if the major version
+   * is not supported.
+   */
+  if (dest->version_major > AVB_AB_MAJOR_VERSION) {
+    avb_error("No support for given major version.\n");
+    return false;
+  }
+
+  /* Bail if CRC32 doesn't match. */
+  if (dest->crc32 !=
+      avb_crc32((const uint8_t*)dest, sizeof(AvbABData) - sizeof(uint32_t))) {
+    avb_error("CRC32 does not match.\n");
+    return false;
+  }
+
+  return true;
+}
+
+void avb_ab_data_update_crc_and_byteswap(const AvbABData* src,
+                                         AvbABData* dest) {
+  avb_memcpy(dest, src, sizeof(AvbABData));
+  dest->crc32 = avb_htobe32(
+      avb_crc32((const uint8_t*)dest, sizeof(AvbABData) - sizeof(uint32_t)));
+}
+
+void avb_ab_data_init(AvbABData* data) {
+  avb_memset(data, '\0', sizeof(AvbABData));
+  avb_memcpy(data->magic, AVB_AB_MAGIC, AVB_AB_MAGIC_LEN);
+  data->version_major = AVB_AB_MAJOR_VERSION;
+  data->version_minor = AVB_AB_MINOR_VERSION;
+  data->slots[0].priority = AVB_AB_MAX_PRIORITY;
+  data->slots[0].tries_remaining = AVB_AB_MAX_TRIES_REMAINING;
+  data->slots[0].successful_boot = 0;
+  data->slots[1].priority = AVB_AB_MAX_PRIORITY - 1;
+  data->slots[1].tries_remaining = AVB_AB_MAX_TRIES_REMAINING;
+  data->slots[1].successful_boot = 0;
+}
+
+/* The AvbABData struct is stored 2048 bytes into the 'misc' partition
+ * following the 'struct bootloader_message' field. The struct is
+ * compatible with the guidelines in bootable/recovery/bootloader.h -
+ * e.g. it is stored in the |slot_suffix| field, starts with a
+ * NUL-byte, and is 32 bytes long.
+ */
+#define AB_METADATA_MISC_PARTITION_OFFSET 2048
+
+AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data) {
+  AvbOps* ops = ab_ops->ops;
+  AvbABData serialized;
+  AvbIOResult io_ret;
+  size_t num_bytes_read;
+
+  io_ret = ops->read_from_partition(ops,
+                                    "misc",
+                                    AB_METADATA_MISC_PARTITION_OFFSET,
+                                    sizeof(AvbABData),
+                                    &serialized,
+                                    &num_bytes_read);
+  if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+    return AVB_IO_RESULT_ERROR_OOM;
+  } else if (io_ret != AVB_IO_RESULT_OK ||
+             num_bytes_read != sizeof(AvbABData)) {
+    avb_error("Error reading A/B metadata.\n");
+    return AVB_IO_RESULT_ERROR_IO;
+  }
+
+  if (!avb_ab_data_verify_and_byteswap(&serialized, data)) {
+    avb_error(
+        "Error validating A/B metadata from disk. "
+        "Resetting and writing new A/B metadata to disk.\n");
+    avb_ab_data_init(data);
+    return avb_ab_data_write(ab_ops, data);
+  }
+
+  return AVB_IO_RESULT_OK;
+}
+
+AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data) {
+  AvbOps* ops = ab_ops->ops;
+  AvbABData serialized;
+  AvbIOResult io_ret;
+
+  avb_ab_data_update_crc_and_byteswap(data, &serialized);
+  io_ret = ops->write_to_partition(ops,
+                                   "misc",
+                                   AB_METADATA_MISC_PARTITION_OFFSET,
+                                   sizeof(AvbABData),
+                                   &serialized);
+  if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+    return AVB_IO_RESULT_ERROR_OOM;
+  } else if (io_ret != AVB_IO_RESULT_OK) {
+    avb_error("Error writing A/B metadata.\n");
+    return AVB_IO_RESULT_ERROR_IO;
+  }
+  return AVB_IO_RESULT_OK;
+}
+
+static bool slot_is_bootable(AvbABSlotData* slot) {
+  return slot->priority > 0 &&
+         (slot->successful_boot || (slot->tries_remaining > 0));
+}
+
+static void slot_set_unbootable(AvbABSlotData* slot) {
+  slot->priority = 0;
+  slot->tries_remaining = 0;
+  slot->successful_boot = 0;
+}
+
+/* Ensure all unbootable and/or illegal states are marked as the
+ * canonical 'unbootable' state, e.g. priority=0, tries_remaining=0,
+ * and successful_boot=0.
+ */
+static void slot_normalize(AvbABSlotData* slot) {
+  if (slot->priority > 0) {
+    if (slot->tries_remaining == 0 && !slot->successful_boot) {
+      /* We've exhausted all tries -> unbootable. */
+      slot_set_unbootable(slot);
+    }
+    if (slot->tries_remaining > 0 && slot->successful_boot) {
+      /* Illegal state - avb_ab_mark_slot_successful() will clear
+       * tries_remaining when setting successful_boot.
+       */
+      slot_set_unbootable(slot);
+    }
+  } else {
+    slot_set_unbootable(slot);
+  }
+}
+
+static const char* slot_suffixes[2] = {"_a", "_b"};
+
+/* Helper function to load metadata - returns AVB_IO_RESULT_OK on
+ * success, error code otherwise.
+ */
+static AvbIOResult load_metadata(AvbABOps* ab_ops,
+                                 AvbABData* ab_data,
+                                 AvbABData* ab_data_orig) {
+  AvbIOResult io_ret;
+
+  io_ret = ab_ops->read_ab_metadata(ab_ops, ab_data);
+  if (io_ret != AVB_IO_RESULT_OK) {
+    avb_error("I/O error while loading A/B metadata.\n");
+    return io_ret;
+  }
+  *ab_data_orig = *ab_data;
+
+  /* Ensure data is normalized, e.g. illegal states will be marked as
+   * unbootable and all unbootable states are represented with
+   * (priority=0, tries_remaining=0, successful_boot=0).
+   */
+  slot_normalize(&ab_data->slots[0]);
+  slot_normalize(&ab_data->slots[1]);
+  return AVB_IO_RESULT_OK;
+}
+
+/* Writes A/B metadata to disk only if it has changed - returns
+ * AVB_IO_RESULT_OK on success, error code otherwise.
+ */
+static AvbIOResult save_metadata_if_changed(AvbABOps* ab_ops,
+                                            AvbABData* ab_data,
+                                            AvbABData* ab_data_orig) {
+  if (avb_safe_memcmp(ab_data, ab_data_orig, sizeof(AvbABData)) != 0) {
+    avb_debug("Writing A/B metadata to disk.\n");
+    return ab_ops->write_ab_metadata(ab_ops, ab_data);
+  }
+  return AVB_IO_RESULT_OK;
+}
+
+AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops,
+                            const char* const* requested_partitions,
+                            bool allow_verification_error,
+                            AvbSlotVerifyData** out_data) {
+  AvbOps* ops = ab_ops->ops;
+  AvbSlotVerifyData* slot_data[2] = {NULL, NULL};
+  AvbSlotVerifyData* data = NULL;
+  AvbABFlowResult ret;
+  AvbABData ab_data, ab_data_orig;
+  size_t slot_index_to_boot, n;
+  AvbIOResult io_ret;
+  bool saw_and_allowed_verification_error = false;
+
+  io_ret = load_metadata(ab_ops, &ab_data, &ab_data_orig);
+  if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+    ret = AVB_AB_FLOW_RESULT_ERROR_OOM;
+    goto out;
+  } else if (io_ret != AVB_IO_RESULT_OK) {
+    ret = AVB_AB_FLOW_RESULT_ERROR_IO;
+    goto out;
+  }
+
+  /* Validate all bootable slots. */
+  for (n = 0; n < 2; n++) {
+    if (slot_is_bootable(&ab_data.slots[n])) {
+      AvbSlotVerifyResult verify_result;
+      bool set_slot_unbootable = false;
+
+      verify_result = avb_slot_verify(ops,
+                                      requested_partitions,
+                                      slot_suffixes[n],
+                                      allow_verification_error,
+                                      &slot_data[n]);
+      switch (verify_result) {
+        case AVB_SLOT_VERIFY_RESULT_ERROR_OOM:
+          ret = AVB_AB_FLOW_RESULT_ERROR_OOM;
+          goto out;
+
+        case AVB_SLOT_VERIFY_RESULT_ERROR_IO:
+          ret = AVB_AB_FLOW_RESULT_ERROR_IO;
+          goto out;
+
+        case AVB_SLOT_VERIFY_RESULT_OK:
+          break;
+
+        case AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_METADATA:
+        case AVB_SLOT_VERIFY_RESULT_ERROR_UNSUPPORTED_VERSION:
+          /* Even with |allow_verification_error| these mean game over. */
+          set_slot_unbootable = true;
+          break;
+
+        /* explicit fallthrough. */
+        case AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION:
+        case AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX:
+        case AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED:
+          if (allow_verification_error) {
+            /* Do nothing since we allow this. */
+            avb_debugv("Allowing slot ",
+                       slot_suffixes[n],
+                       " which verified "
+                       "with result ",
+                       avb_slot_verify_result_to_string(verify_result),
+                       " because |allow_verification_error| is true.\n",
+                       NULL);
+            saw_and_allowed_verification_error = true;
+          } else {
+            set_slot_unbootable = true;
+          }
+          break;
+      }
+
+      if (set_slot_unbootable) {
+        avb_errorv("Error verifying slot ",
+                   slot_suffixes[n],
+                   " with result ",
+                   avb_slot_verify_result_to_string(verify_result),
+                   " - setting unbootable.\n",
+                   NULL);
+        slot_set_unbootable(&ab_data.slots[n]);
+      }
+    }
+  }
+
+  if (slot_is_bootable(&ab_data.slots[0]) &&
+      slot_is_bootable(&ab_data.slots[1])) {
+    if (ab_data.slots[1].priority > ab_data.slots[0].priority) {
+      slot_index_to_boot = 1;
+    } else {
+      slot_index_to_boot = 0;
+    }
+  } else if (slot_is_bootable(&ab_data.slots[0])) {
+    slot_index_to_boot = 0;
+  } else if (slot_is_bootable(&ab_data.slots[1])) {
+    slot_index_to_boot = 1;
+  } else {
+    /* No bootable slots! */
+    avb_error("No bootable slots found.\n");
+    ret = AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS;
+    goto out;
+  }
+
+  /* Update stored rollback index such that the stored rollback index
+   * is the largest value supporting all currently bootable slots. Do
+   * this for every rollback index location.
+   */
+  for (n = 0; n < AVB_MAX_NUMBER_OF_ROLLBACK_INDEX_LOCATIONS; n++) {
+    uint64_t rollback_index_value = 0;
+
+    if (slot_data[0] != NULL && slot_data[1] != NULL) {
+      uint64_t a_rollback_index = slot_data[0]->rollback_indexes[n];
+      uint64_t b_rollback_index = slot_data[1]->rollback_indexes[n];
+      rollback_index_value =
+          (a_rollback_index < b_rollback_index ? a_rollback_index
+                                               : b_rollback_index);
+    } else if (slot_data[0] != NULL) {
+      rollback_index_value = slot_data[0]->rollback_indexes[n];
+    } else if (slot_data[1] != NULL) {
+      rollback_index_value = slot_data[1]->rollback_indexes[n];
+    }
+
+    if (rollback_index_value != 0) {
+      uint64_t current_rollback_index_value;
+      io_ret = ops->read_rollback_index(ops, n, &current_rollback_index_value);
+      if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+        ret = AVB_AB_FLOW_RESULT_ERROR_OOM;
+        goto out;
+      } else if (io_ret != AVB_IO_RESULT_OK) {
+        avb_error("Error getting rollback index for slot.\n");
+        ret = AVB_AB_FLOW_RESULT_ERROR_IO;
+        goto out;
+      }
+      if (current_rollback_index_value != rollback_index_value) {
+        io_ret = ops->write_rollback_index(ops, n, rollback_index_value);
+        if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+          ret = AVB_AB_FLOW_RESULT_ERROR_OOM;
+          goto out;
+        } else if (io_ret != AVB_IO_RESULT_OK) {
+          avb_error("Error setting stored rollback index.\n");
+          ret = AVB_AB_FLOW_RESULT_ERROR_IO;
+          goto out;
+        }
+      }
+    }
+  }
+
+  /* Finally, select this slot. */
+  avb_assert(slot_data[slot_index_to_boot] != NULL);
+  data = slot_data[slot_index_to_boot];
+  slot_data[slot_index_to_boot] = NULL;
+  if (saw_and_allowed_verification_error) {
+    avb_assert(allow_verification_error);
+    ret = AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR;
+  } else {
+    ret = AVB_AB_FLOW_RESULT_OK;
+  }
+
+  /* ... and decrement tries remaining, if applicable. */
+  if (!ab_data.slots[slot_index_to_boot].successful_boot &&
+      ab_data.slots[slot_index_to_boot].tries_remaining > 0) {
+    ab_data.slots[slot_index_to_boot].tries_remaining -= 1;
+  }
+
+out:
+  io_ret = save_metadata_if_changed(ab_ops, &ab_data, &ab_data_orig);
+  if (io_ret != AVB_IO_RESULT_OK) {
+    if (io_ret == AVB_IO_RESULT_ERROR_OOM) {
+      ret = AVB_AB_FLOW_RESULT_ERROR_OOM;
+    } else {
+      ret = AVB_AB_FLOW_RESULT_ERROR_IO;
+    }
+    if (data != NULL) {
+      avb_slot_verify_data_free(data);
+      data = NULL;
+    }
+  }
+
+  for (n = 0; n < 2; n++) {
+    if (slot_data[n] != NULL) {
+      avb_slot_verify_data_free(slot_data[n]);
+    }
+  }
+
+  if (out_data != NULL) {
+    *out_data = data;
+  } else {
+    if (data != NULL) {
+      avb_slot_verify_data_free(data);
+    }
+  }
+
+  return ret;
+}
+
+AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops,
+                                    unsigned int slot_number) {
+  AvbABData ab_data, ab_data_orig;
+  unsigned int other_slot_number;
+  AvbIOResult ret;
+
+  avb_assert(slot_number < 2);
+
+  ret = load_metadata(ab_ops, &ab_data, &ab_data_orig);
+  if (ret != AVB_IO_RESULT_OK) {
+    goto out;
+  }
+
+  /* Make requested slot top priority, unsuccessful, and with max tries. */
+  ab_data.slots[slot_number].priority = AVB_AB_MAX_PRIORITY;
+  ab_data.slots[slot_number].tries_remaining = AVB_AB_MAX_TRIES_REMAINING;
+  ab_data.slots[slot_number].successful_boot = 0;
+
+  /* Ensure other slot doesn't have as high a priority. */
+  other_slot_number = 1 - slot_number;
+  if (ab_data.slots[other_slot_number].priority == AVB_AB_MAX_PRIORITY) {
+    ab_data.slots[other_slot_number].priority = AVB_AB_MAX_PRIORITY - 1;
+  }
+
+  ret = AVB_IO_RESULT_OK;
+
+out:
+  if (ret == AVB_IO_RESULT_OK) {
+    ret = save_metadata_if_changed(ab_ops, &ab_data, &ab_data_orig);
+  }
+  return ret;
+}
+
+AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops,
+                                        unsigned int slot_number) {
+  AvbABData ab_data, ab_data_orig;
+  AvbIOResult ret;
+
+  avb_assert(slot_number < 2);
+
+  ret = load_metadata(ab_ops, &ab_data, &ab_data_orig);
+  if (ret != AVB_IO_RESULT_OK) {
+    goto out;
+  }
+
+  slot_set_unbootable(&ab_data.slots[slot_number]);
+
+  ret = AVB_IO_RESULT_OK;
+
+out:
+  if (ret == AVB_IO_RESULT_OK) {
+    ret = save_metadata_if_changed(ab_ops, &ab_data, &ab_data_orig);
+  }
+  return ret;
+}
+
+AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops,
+                                        unsigned int slot_number) {
+  AvbABData ab_data, ab_data_orig;
+  AvbIOResult ret;
+
+  avb_assert(slot_number < 2);
+
+  ret = load_metadata(ab_ops, &ab_data, &ab_data_orig);
+  if (ret != AVB_IO_RESULT_OK) {
+    goto out;
+  }
+
+  if (!slot_is_bootable(&ab_data.slots[slot_number])) {
+    avb_error("Cannot mark unbootable slot as successful.\n");
+    ret = AVB_IO_RESULT_OK;
+    goto out;
+  }
+
+  ab_data.slots[slot_number].tries_remaining = 0;
+  ab_data.slots[slot_number].successful_boot = 1;
+
+  ret = AVB_IO_RESULT_OK;
+
+out:
+  if (ret == AVB_IO_RESULT_OK) {
+    ret = save_metadata_if_changed(ab_ops, &ab_data, &ab_data_orig);
+  }
+  return ret;
+}
+
+const char* avb_ab_flow_result_to_string(AvbABFlowResult result) {
+  const char* ret = NULL;
+
+  switch (result) {
+    case AVB_AB_FLOW_RESULT_OK:
+      ret = "OK";
+      break;
+
+    case AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR:
+      ret = "OK_WITH_VERIFICATION_ERROR";
+      break;
+
+    case AVB_AB_FLOW_RESULT_ERROR_OOM:
+      ret = "ERROR_OOM";
+      break;
+
+    case AVB_AB_FLOW_RESULT_ERROR_IO:
+      ret = "ERROR_IO";
+      break;
+
+    case AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS:
+      ret = "ERROR_NO_BOOTABLE_SLOTS";
+      break;
+      /* Do not add a 'default:' case here because of -Wswitch. */
+  }
+
+  if (ret == NULL) {
+    avb_error("Unknown AvbABFlowResult value.\n");
+    ret = "(unknown)";
+  }
+
+  return ret;
+}