avb2.0: add Android Verified Boot 2.0 library

Add libavb lib (3rd party library from AOSP), that implements support of
AVB 2.0. This library is used for integrity checking of Android partitions
on eMMC.

libavb was added as it is and minimal changes were introduced to reduce
maintenance cost, because it will be deviated from AOSP upstream in the future.

Changes:
- license headers changed to conform SPDX-style
- avb_crc32.c dropped
- updates in avb_sysdeps_posix.c/avb_sysdeps.h

For additional details check [1] AVB 2.0 README.

[1] https://android.googlesource.com/platform/external/avb/+/master/README.md

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>

1 files changed, 276 insertions, 0 deletions

diff --git a/lib/libavb/avb_rsa.c b/lib/libavb/avb_rsa.c
new file mode 100644
index 00000000000..269f7d00b46
--- /dev/null
+++ b/lib/libavb/avb_rsa.c
@@ -0,0 +1,276 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * SPDX-License-Identifier:	(MIT or BSD-3-Clause)
+ */
+
+/* Implementation of RSA signature verification which uses a pre-processed
+ * key for computation. The code extends libmincrypt RSA verification code to
+ * support multiple RSA key lengths and hash digest algorithms.
+ */
+
+#include "avb_rsa.h"
+#include "avb_sha.h"
+#include "avb_util.h"
+#include "avb_vbmeta_image.h"
+
+typedef struct IAvbKey {
+  unsigned int len; /* Length of n[] in number of uint32_t */
+  uint32_t n0inv;   /* -1 / n[0] mod 2^32 */
+  uint32_t* n;      /* modulus as array (host-byte order) */
+  uint32_t* rr;     /* R^2 as array (host-byte order) */
+} IAvbKey;
+
+static IAvbKey* iavb_parse_key_data(const uint8_t* data, size_t length) {
+  AvbRSAPublicKeyHeader h;
+  IAvbKey* key = NULL;
+  size_t expected_length;
+  unsigned int i;
+  const uint8_t* n;
+  const uint8_t* rr;
+
+  if (!avb_rsa_public_key_header_validate_and_byteswap(
+          (const AvbRSAPublicKeyHeader*)data, &h)) {
+    avb_error("Invalid key.\n");
+    goto fail;
+  }
+
+  if (!(h.key_num_bits == 2048 || h.key_num_bits == 4096 ||
+        h.key_num_bits == 8192)) {
+    avb_error("Unexpected key length.\n");
+    goto fail;
+  }
+
+  expected_length = sizeof(AvbRSAPublicKeyHeader) + 2 * h.key_num_bits / 8;
+  if (length != expected_length) {
+    avb_error("Key does not match expected length.\n");
+    goto fail;
+  }
+
+  n = data + sizeof(AvbRSAPublicKeyHeader);
+  rr = data + sizeof(AvbRSAPublicKeyHeader) + h.key_num_bits / 8;
+
+  /* Store n and rr following the key header so we only have to do one
+   * allocation.
+   */
+  key = (IAvbKey*)(avb_malloc(sizeof(IAvbKey) + 2 * h.key_num_bits / 8));
+  if (key == NULL) {
+    goto fail;
+  }
+
+  key->len = h.key_num_bits / 32;
+  key->n0inv = h.n0inv;
+  key->n = (uint32_t*)(key + 1); /* Skip ahead sizeof(IAvbKey) bytes. */
+  key->rr = key->n + key->len;
+
+  /* Crypto-code below (modpowF4() and friends) expects the key in
+   * little-endian format (rather than the format we're storing the
+   * key in), so convert it.
+   */
+  for (i = 0; i < key->len; i++) {
+    key->n[i] = avb_be32toh(((uint32_t*)n)[key->len - i - 1]);
+    key->rr[i] = avb_be32toh(((uint32_t*)rr)[key->len - i - 1]);
+  }
+  return key;
+
+fail:
+  if (key != NULL) {
+    avb_free(key);
+  }
+  return NULL;
+}
+
+static void iavb_free_parsed_key(IAvbKey* key) {
+  avb_free(key);
+}
+
+/* a[] -= mod */
+static void subM(const IAvbKey* key, uint32_t* a) {
+  int64_t A = 0;
+  uint32_t i;
+  for (i = 0; i < key->len; ++i) {
+    A += (uint64_t)a[i] - key->n[i];
+    a[i] = (uint32_t)A;
+    A >>= 32;
+  }
+}
+
+/* return a[] >= mod */
+static int geM(const IAvbKey* key, uint32_t* a) {
+  uint32_t i;
+  for (i = key->len; i;) {
+    --i;
+    if (a[i] < key->n[i]) {
+      return 0;
+    }
+    if (a[i] > key->n[i]) {
+      return 1;
+    }
+  }
+  return 1; /* equal */
+}
+
+/* montgomery c[] += a * b[] / R % mod */
+static void montMulAdd(const IAvbKey* key,
+                       uint32_t* c,
+                       const uint32_t a,
+                       const uint32_t* b) {
+  uint64_t A = (uint64_t)a * b[0] + c[0];
+  uint32_t d0 = (uint32_t)A * key->n0inv;
+  uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A;
+  uint32_t i;
+
+  for (i = 1; i < key->len; ++i) {
+    A = (A >> 32) + (uint64_t)a * b[i] + c[i];
+    B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A;
+    c[i - 1] = (uint32_t)B;
+  }
+
+  A = (A >> 32) + (B >> 32);
+
+  c[i - 1] = (uint32_t)A;
+
+  if (A >> 32) {
+    subM(key, c);
+  }
+}
+
+/* montgomery c[] = a[] * b[] / R % mod */
+static void montMul(const IAvbKey* key, uint32_t* c, uint32_t* a, uint32_t* b) {
+  uint32_t i;
+  for (i = 0; i < key->len; ++i) {
+    c[i] = 0;
+  }
+  for (i = 0; i < key->len; ++i) {
+    montMulAdd(key, c, a[i], b);
+  }
+}
+
+/* In-place public exponentiation. (65537}
+ * Input and output big-endian byte array in inout.
+ */
+static void modpowF4(const IAvbKey* key, uint8_t* inout) {
+  uint32_t* a = (uint32_t*)avb_malloc(key->len * sizeof(uint32_t));
+  uint32_t* aR = (uint32_t*)avb_malloc(key->len * sizeof(uint32_t));
+  uint32_t* aaR = (uint32_t*)avb_malloc(key->len * sizeof(uint32_t));
+  if (a == NULL || aR == NULL || aaR == NULL) {
+    goto out;
+  }
+
+  uint32_t* aaa = aaR; /* Re-use location. */
+  int i;
+
+  /* Convert from big endian byte array to little endian word array. */
+  for (i = 0; i < (int)key->len; ++i) {
+    uint32_t tmp = (inout[((key->len - 1 - i) * 4) + 0] << 24) |
+                   (inout[((key->len - 1 - i) * 4) + 1] << 16) |
+                   (inout[((key->len - 1 - i) * 4) + 2] << 8) |
+                   (inout[((key->len - 1 - i) * 4) + 3] << 0);
+    a[i] = tmp;
+  }
+
+  montMul(key, aR, a, key->rr); /* aR = a * RR / R mod M   */
+  for (i = 0; i < 16; i += 2) {
+    montMul(key, aaR, aR, aR);  /* aaR = aR * aR / R mod M */
+    montMul(key, aR, aaR, aaR); /* aR = aaR * aaR / R mod M */
+  }
+  montMul(key, aaa, aR, a); /* aaa = aR * a / R mod M */
+
+  /* Make sure aaa < mod; aaa is at most 1x mod too large. */
+  if (geM(key, aaa)) {
+    subM(key, aaa);
+  }
+
+  /* Convert to bigendian byte array */
+  for (i = (int)key->len - 1; i >= 0; --i) {
+    uint32_t tmp = aaa[i];
+    *inout++ = (uint8_t)(tmp >> 24);
+    *inout++ = (uint8_t)(tmp >> 16);
+    *inout++ = (uint8_t)(tmp >> 8);
+    *inout++ = (uint8_t)(tmp >> 0);
+  }
+
+out:
+  if (a != NULL) {
+    avb_free(a);
+  }
+  if (aR != NULL) {
+    avb_free(aR);
+  }
+  if (aaR != NULL) {
+    avb_free(aaR);
+  }
+}
+
+/* Verify a RSA PKCS1.5 signature against an expected hash.
+ * Returns false on failure, true on success.
+ */
+bool avb_rsa_verify(const uint8_t* key,
+                    size_t key_num_bytes,
+                    const uint8_t* sig,
+                    size_t sig_num_bytes,
+                    const uint8_t* hash,
+                    size_t hash_num_bytes,
+                    const uint8_t* padding,
+                    size_t padding_num_bytes) {
+  uint8_t* buf = NULL;
+  IAvbKey* parsed_key = NULL;
+  bool success = false;
+
+  if (key == NULL || sig == NULL || hash == NULL || padding == NULL) {
+    avb_error("Invalid input.\n");
+    goto out;
+  }
+
+  parsed_key = iavb_parse_key_data(key, key_num_bytes);
+  if (parsed_key == NULL) {
+    avb_error("Error parsing key.\n");
+    goto out;
+  }
+
+  if (sig_num_bytes != (parsed_key->len * sizeof(uint32_t))) {
+    avb_error("Signature length does not match key length.\n");
+    goto out;
+  }
+
+  if (padding_num_bytes != sig_num_bytes - hash_num_bytes) {
+    avb_error("Padding length does not match hash and signature lengths.\n");
+    goto out;
+  }
+
+  buf = (uint8_t*)avb_malloc(sig_num_bytes);
+  if (buf == NULL) {
+    avb_error("Error allocating memory.\n");
+    goto out;
+  }
+  avb_memcpy(buf, sig, sig_num_bytes);
+
+  modpowF4(parsed_key, buf);
+
+  /* Check padding bytes.
+   *
+   * Even though there are probably no timing issues here, we use
+   * avb_safe_memcmp() just to be on the safe side.
+   */
+  if (avb_safe_memcmp(buf, padding, padding_num_bytes)) {
+    avb_error("Padding check failed.\n");
+    goto out;
+  }
+
+  /* Check hash. */
+  if (avb_safe_memcmp(buf + padding_num_bytes, hash, hash_num_bytes)) {
+    avb_error("Hash check failed.\n");
+    goto out;
+  }
+
+  success = true;
+
+out:
+  if (parsed_key != NULL) {
+    iavb_free_parsed_key(parsed_key);
+  }
+  if (buf != NULL) {
+    avb_free(buf);
+  }
+  return success;
+}