From 4e8599886ba4802fef1683811a725e7c4bc4fe72 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Tue, 12 Jul 2022 18:00:38 +0100
Subject: [PATCH] luks: Check return values from malloc more carefully

Found by Coverity:

  Error: GCC_ANALYZER_WARNING (CWE-688): [#def53]
  nbdkit-1.30.7/filters/luks/luks-encryption.c: scope_hint: In function 'calculate_iv'
  nbdkit-1.30.7/filters/luks/luks-encryption.c:175:5: warning[-Wanalyzer-possible-null-argument]: use of possibly-NULL 'iv' where non-null expected
  nbdkit-1.30.7/filters/luks/luks-encryption.c:39: included_from: Included from here.
  /usr/include/string.h:43:14: note: argument 1 of 'memcpy' must be non-null
  #  173|       sector32 = (uint32_t) sector; /* truncate to only lower bits */
  #  174|       sector32 = htole32 (sector32);
  #  175|->     memcpy (iv, &sector32, prefixlen);
  #  176|       memset (iv + prefixlen, 0, ivlen - prefixlen);
  #  177|       break;

  Error: GCC_ANALYZER_WARNING (CWE-688): [#def54]
  nbdkit-1.30.7/filters/luks/luks-encryption.c:184:5: warning[-Wanalyzer-possible-null-argument]: use of possibly-NULL 'iv' where non-null expected
  nbdkit-1.30.7/filters/luks/luks-encryption.c:39: included_from: Included from here.
  /usr/include/string.h:43:14: note: argument 1 of 'memcpy' must be non-null
  #  182|         prefixlen = ivlen;
  #  183|       sector = htole64 (sector);
  #  184|->     memcpy (iv, &sector, prefixlen);
  #  185|       memset (iv + prefixlen, 0, ivlen - prefixlen);
  #  186|       break;

  Error: NULL_RETURNS (CWE-476): [#def55]
  nbdkit-1.30.7/filters/luks/luks-encryption.c:498: returned_null: "malloc" returns "NULL" (checked 86 out of 94 times).
  nbdkit-1.30.7/filters/luks/luks-encryption.c:498: var_assigned: Assigning: "temp" = "NULL" return value from "malloc".
  nbdkit-1.30.7/filters/luks/luks-encryption.c:523: dereference: Dereferencing a pointer that might be "NULL" "temp" when calling "memcpy". [Note: The source code implementation of the function has been overridden by a builtin model.]
  #  521|       gnutls_hash_deinit (hash, temp);
  #  522|
  #  523|->     memcpy (&block[i*digest_bytes], temp, blen);
  #  524|     }
  #  525|

Fixes: commit 468919dce6c5eb57503eacac0f67e5dd87c58e6c
(cherry picked from commit 00c8bbd9e321681843140f697985505de7177f34)
---
 filters/luks/luks-encryption.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/filters/luks/luks-encryption.c b/filters/luks/luks-encryption.c
index 8ee0eb35..19aaf06a 100644
--- a/filters/luks/luks-encryption.c
+++ b/filters/luks/luks-encryption.c
@@ -495,9 +495,15 @@ af_hash (gnutls_digest_algorithm_t hash_alg, uint8_t *block, size_t len)
   size_t digest_bytes = gnutls_hash_get_len (hash_alg);
   size_t nr_blocks, last_block_len;
   size_t i;
-  CLEANUP_FREE uint8_t *temp = malloc (digest_bytes);
   int r;
   gnutls_hash_hd_t hash;
+  CLEANUP_FREE uint8_t *temp;
+
+  temp = malloc (digest_bytes);
+  if (!temp) {
+    nbdkit_error ("malloc: %m");
+    return -1;
+  }
 
   nr_blocks = len / digest_bytes;
   last_block_len = len % digest_bytes;
@@ -874,9 +880,15 @@ int
 do_decrypt (struct luks_data *h, gnutls_cipher_hd_t cipher,
             uint64_t sector, uint8_t *buf, size_t nr_sectors)
 {
-  const size_t ivlen = cipher_alg_iv_len (h->cipher_alg, h->cipher_mode);
-  CLEANUP_FREE uint8_t *iv = malloc (ivlen);
   int r;
+  const size_t ivlen = cipher_alg_iv_len (h->cipher_alg, h->cipher_mode);
+  CLEANUP_FREE uint8_t *iv;
+
+  iv = malloc (ivlen);
+  if (!iv) {
+    nbdkit_error ("malloc: %m");
+    return -1;
+  }
 
   while (nr_sectors) {
     calculate_iv (h->ivgen_alg, iv, ivlen, sector);
@@ -902,9 +914,15 @@ int
 do_encrypt (struct luks_data *h, gnutls_cipher_hd_t cipher,
             uint64_t sector, uint8_t *buf, size_t nr_sectors)
 {
-  const size_t ivlen = cipher_alg_iv_len (h->cipher_alg, h->cipher_mode);
-  CLEANUP_FREE uint8_t *iv = malloc (ivlen);
   int r;
+  const size_t ivlen = cipher_alg_iv_len (h->cipher_alg, h->cipher_mode);
+  CLEANUP_FREE uint8_t *iv;
+
+  iv = malloc (ivlen);
+  if (!iv) {
+    nbdkit_error ("malloc: %m");
+    return -1;
+  }
 
   while (nr_sectors) {
     calculate_iv (h->ivgen_alg, iv, ivlen, sector);
-- 
2.31.1