cryptsetup: avoid a segfault when a keyfile is passed along with a TPM device

When a keyfile is passed with tpm2-device=, e.g.,

 systemd-cryptsetup attach test_data /vol /my-pass tpm2-device=auto

the logic in attach_luks_or_plain_or_bitlk_by_tpm2() tries to process it as a
TPM blob first. This did not work properly because it passes n_blobs=1 to
acquire_tpm2_key(), and the key_file is only read when n_blobs == 0. As a
result, the code ends up calling tpm2_unseal(..., blobs=NULL, n_blobs=1, ...).

Before commit 5c6aad9 ("cryptsetup-tokens: Print tpm2-primary-alg: only when it
is known"), the segfault was not observed because tpm2_unseal() was bailing out
early when primary_alg == 0. However, after that change, it attempts to process
the blob (which is NULL) and crashes.

Fix this logic by passing n_blobs=0 to acquire_tpm2_key() so that it actually
reads the key_file. Additionally, assert 'blobs' in tpm2_unseal() as a
safeguard.

Fixes #41867

diff --git a/src/cryptsetup/cryptsetup.c b/src/cryptsetup/cryptsetup.c
index 2130c54047c04d95cf6f998c760cea5d45a6514e..bf313340bf6c20725d705146af526928935997f4 100644 (file)
--- a/src/cryptsetup/cryptsetup.c
+++ b/src/cryptsetup/cryptsetup.c
@@ -2060,7 +2060,7 @@ static int attach_luks_or_plain_or_bitlk_by_tpm2(
                                         /* pcrlock_path= */ NULL,
                                         /* primary_alg= */ 0,
                                         key_file, arg_keyfile_size, arg_keyfile_offset,
-                                        key_data, /* n_blobs= */ 1,
+                                        key_data, /* n_blobs= */ iovec_is_set(key_data) ? 1 : 0,
                                         /* policy_hash= */ NULL, /* we don't know the policy hash */
                                         /* n_policy_hash= */ 0,
                                         /* salt= */ NULL,

diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index 9fe3e018693fc174df0dc4beee1ee8994570dcad..091a4dba89ac3eda57f242c6ef157e611ff99920 100644 (file)
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -5804,6 +5804,7 @@ int tpm2_unseal(Tpm2Context *c,
         int r;
 
         assert(n_blobs > 0);
+        assert(blobs);
         assert(iovec_is_valid(pubkey));
         assert(ret_secret);