selftests/bpf: Test packet range of pointers sharing an idgrafted

Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.

These refused a valid program or accepted an out-of-bounds access before
the fix:

- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
  8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
  bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
  was accepted.

These pass with and without the fix and cover nearby paths:

- subtract an unknown scalar from a checked pointer and load below it
  (the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
  the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
  one byte past the checked range: the load is refused, and the copy
  has the range of the check.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/include/crypto/xts.h b/include/crypto/xts.h
new file mode 100644
index 000000000..16aef89f0
--- /dev/null
+++ b/include/crypto/xts.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _CRYPTO_XTS_H
+#define _CRYPTO_XTS_H
+
+#include <crypto/b128ops.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/fips.h>
+
+#define XTS_BLOCK_SIZE 16
+#define XTS_FORBID_WEAK_KEYS (1 << 0)
+
+static inline int __xts_verify_key(const u8 *key, size_t keylen, int flags)
+{
+	/*
+	 * key consists of keys of equal size concatenated, therefore
+	 * the length must be even.
+	 */
+	if (keylen % 2)
+		return -EINVAL;
+
+	/*
+	 * In FIPS mode only a combined key length of either 256 or
+	 * 512 bits is allowed, c.f. FIPS 140-3 IG C.I.
+	 */
+	if (fips_enabled && keylen != 32 && keylen != 64)
+		return -EINVAL;
+
+	/*
+	 * Ensure that the AES and tweak key are not identical when
+	 * in FIPS mode or the FORBID_WEAK_KEYS flag is set.
+	 */
+	if ((fips_enabled || (flags & XTS_FORBID_WEAK_KEYS)) &&
+	    !crypto_memneq(key, key + (keylen / 2), keylen / 2))
+		return -EINVAL;
+
+	return 0;
+}
+
+static inline int xts_verify_key(struct crypto_skcipher *tfm, const u8 *key,
+				 unsigned int keylen)
+{
+	int flags = (crypto_skcipher_get_flags(tfm) &
+		     CRYPTO_TFM_REQ_FORBID_WEAK_KEYS) ?
+			    XTS_FORBID_WEAK_KEYS :
+			    0;
+
+	return __xts_verify_key(key, keylen, flags);
+}
+
+#endif  /* _CRYPTO_XTS_H */