From 2418e9c1409ba04ddff516a83d83b2daa3417832 Mon Sep 17 00:00:00 2001

From: Grigori Goronzy <greg@chown.ath.cx>

Date: Fri, 18 Feb 2022 11:56:02 +0100

Subject: [PATCH] cryptsetup: add support for TPM2 pin

Extend cryptsetup for TPM2 pin entry, similar to FIDO2.

(cherry picked from commit bea344a1a426e615ba87b66b6d3ff4b265c57a95)

Related: #2087652

---

 src/cryptsetup/cryptsetup-tpm2.c | 108 ++++++++++++++++++++++++++++++-

 src/cryptsetup/cryptsetup-tpm2.h |  16 ++++-

 src/cryptsetup/cryptsetup.c      |  16 ++++-

 3 files changed, 135 insertions(+), 5 deletions(-)

diff --git a/src/cryptsetup/cryptsetup-tpm2.c b/src/cryptsetup/cryptsetup-tpm2.c

index 05d76a684d..b84d64def8 100644

--- a/src/cryptsetup/cryptsetup-tpm2.c

+++ b/src/cryptsetup/cryptsetup-tpm2.c

@@ -1,7 +1,9 @@

 /* SPDX-License-Identifier: LGPL-2.1-or-later */

 #include "alloc-util.h"

+#include "ask-password-api.h"

 #include "cryptsetup-tpm2.h"

+#include "env-util.h"

 #include "fileio.h"

 #include "hexdecoct.h"

 #include "json.h"

@@ -9,6 +11,47 @@

 #include "random-util.h"

 #include "tpm2-util.h"

+static int get_pin(usec_t until, AskPasswordFlags ask_password_flags, bool headless, char **ret_pin_str) {

+        _cleanup_free_ char *pin_str = NULL;

+        _cleanup_strv_free_erase_ char **pin = NULL;

+        int r;

+

+        assert(ret_pin_str);

+

+        r = getenv_steal_erase("PIN", &pin_str);

+        if (r < 0)

+                return log_error_errno(r, "Failed to acquire PIN from environment: %m");

+        if (!r) {

+                if (headless)

+                        return log_error_errno(

+                                        SYNTHETIC_ERRNO(ENOPKG),

+                                        "PIN querying disabled via 'headless' option. "

+                                        "Use the '$PIN' environment variable.");

+

+                pin = strv_free_erase(pin);

+                r = ask_password_auto(

+                                "Please enter TPM2 PIN:",

+                                "drive-harddisk",

+                                NULL,

+                                "tpm2-pin",

+                                "cryptsetup.tpm2-pin",

+                                until,

+                                ask_password_flags,

+                                &pin;;

+                if (r < 0)

+                        return log_error_errno(r, "Failed to ask for user pin: %m");

+                assert(strv_length(pin) == 1);

+

+                pin_str = strdup(pin[0]);

+                if (!pin_str)

+                        return log_oom();

+        }

+

+        *ret_pin_str = TAKE_PTR(pin_str);

+

+        return r;

+}

+

 int acquire_tpm2_key(

                 const char *volume_name,

                 const char *device,

@@ -22,6 +65,10 @@ int acquire_tpm2_key(

                 size_t key_data_size,

                 const void *policy_hash,

                 size_t policy_hash_size,

+                TPM2Flags flags,

+                usec_t until,

+                bool headless,

+                AskPasswordFlags ask_password_flags,

                 void **ret_decrypted_key,

                 size_t *ret_decrypted_key_size) {

@@ -64,7 +111,51 @@ int acquire_tpm2_key(

                 blob = loaded_blob;

         }

-        return tpm2_unseal(device, pcr_mask, pcr_bank, primary_alg, blob, blob_size, policy_hash, policy_hash_size, NULL, ret_decrypted_key, ret_decrypted_key_size);

+        if (!(flags & TPM2_FLAGS_USE_PIN))

+                return tpm2_unseal(

+                                device,

+                                pcr_mask,

+                                pcr_bank,

+                                primary_alg,

+                                blob,

+                                blob_size,

+                                policy_hash,

+                                policy_hash_size,

+                                NULL,

+                                ret_decrypted_key,

+                                ret_decrypted_key_size);

+

+        for (int i = 5;; i--) {

+                _cleanup_(erase_and_freep) char *pin_str = NULL;

+

+                if (i <= 0)

+                        return -EACCES;

+

+                r = get_pin(until, ask_password_flags, headless, &pin_str);

+                if (r < 0)

+                        return r;

+

+                r = tpm2_unseal(

+                                device,

+                                pcr_mask,

+                                pcr_bank,

+                                primary_alg,

+                                blob,

+                                blob_size,

+                                policy_hash,

+                                policy_hash_size,

+                                pin_str,

+                                ret_decrypted_key,

+                                ret_decrypted_key_size);

+                /* We get this error in case there is an authentication policy mismatch. This should

+                 * not happen, but this avoids confusing behavior, just in case. */

+                if (IN_SET(r, -EPERM, -ENOLCK))

+                        return r;

+                if (r < 0)

+                        continue;

+

+                return r;

+        }

 }

 int find_tpm2_auto_data(

@@ -79,11 +170,13 @@ int find_tpm2_auto_data(

                 void **ret_policy_hash,

                 size_t *ret_policy_hash_size,

                 int *ret_keyslot,

-                int *ret_token) {

+                int *ret_token,

+                TPM2Flags *ret_flags) {

         _cleanup_free_ void *blob = NULL, *policy_hash = NULL;

         size_t blob_size = 0, policy_hash_size = 0;

         int r, keyslot = -1, token = -1;

+        TPM2Flags flags = 0;

         uint32_t pcr_mask = 0;

         uint16_t pcr_bank = UINT16_MAX; /* default: pick automatically */

         uint16_t primary_alg = TPM2_ALG_ECC; /* ECC was the only supported algorithm in systemd < 250, use that as implied default, for compatibility */

@@ -196,6 +289,16 @@ int find_tpm2_auto_data(

                         return log_error_errno(SYNTHETIC_ERRNO(EINVAL),

                                                "Invalid base64 data in 'tpm2-policy-hash' field.");

+                w = json_variant_by_key(v, "tpm2-pin");

+                if (w) {

+                        if (!json_variant_is_boolean(w))

+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),

+                                                       "TPM2 PIN policy is not a boolean.");

+

+                        if (json_variant_boolean(w))

+                                flags |= TPM2_FLAGS_USE_PIN;

+                }

+

                 break;

         }

@@ -215,6 +318,7 @@ int find_tpm2_auto_data(

         *ret_token = token;

         *ret_pcr_bank = pcr_bank;

         *ret_primary_alg = primary_alg;

+        *ret_flags = flags;

         return 0;

 }

diff --git a/src/cryptsetup/cryptsetup-tpm2.h b/src/cryptsetup/cryptsetup-tpm2.h

index bd04620462..ab16d0a18f 100644

--- a/src/cryptsetup/cryptsetup-tpm2.h

+++ b/src/cryptsetup/cryptsetup-tpm2.h

@@ -3,9 +3,11 @@

 #include <sys/types.h>

+#include "ask-password-api.h"

 #include "cryptsetup-util.h"

 #include "log.h"

 #include "time-util.h"

+#include "tpm2-util.h"

 #if HAVE_TPM2

@@ -22,6 +24,10 @@ int acquire_tpm2_key(

                 size_t key_data_size,

                 const void *policy_hash,

                 size_t policy_hash_size,

+                TPM2Flags flags,

+                usec_t until,

+                bool headless,

+                AskPasswordFlags ask_password_flags,

                 void **ret_decrypted_key,

                 size_t *ret_decrypted_key_size);

@@ -37,7 +43,8 @@ int find_tpm2_auto_data(

                 void **ret_policy_hash,

                 size_t *ret_policy_hash_size,

                 int *ret_keyslot,

-                int *ret_token);

+                int *ret_token,

+                TPM2Flags *ret_flags);

 #else

@@ -54,6 +61,10 @@ static inline int acquire_tpm2_key(

                 size_t key_data_size,

                 const void *policy_hash,

                 size_t policy_hash_size,

+                TPM2Flags flags,

+                usec_t until,

+                bool headless,

+                AskPasswordFlags ask_password_flags,

                 void **ret_decrypted_key,

                 size_t *ret_decrypted_key_size) {

@@ -73,7 +84,8 @@ static inline int find_tpm2_auto_data(

                 void **ret_policy_hash,

                 size_t *ret_policy_hash_size,

                 int *ret_keyslot,

-                int *ret_token) {

+                int *ret_token,

+                TPM2Flags *ret_flags) {

         return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),

                                "TPM2 support not available.");

diff --git a/src/cryptsetup/cryptsetup.c b/src/cryptsetup/cryptsetup.c

index dddd976dc8..ede0f7ed0b 100644

--- a/src/cryptsetup/cryptsetup.c

+++ b/src/cryptsetup/cryptsetup.c

@@ -1301,9 +1301,15 @@ static int attach_luks_or_plain_or_bitlk_by_tpm2(

                                         key_file, arg_keyfile_size, arg_keyfile_offset,

                                         key_data, key_data_size,

                                         NULL, 0, /* we don't know the policy hash */

+                                        0, /* PIN is currently unhandled in this case */

+                                        until,

+                                        arg_headless,

+                                        arg_ask_password_flags,

                                         &decrypted_key, &decrypted_key_size);

                         if (r >= 0)

                                 break;

+                        if (IN_SET(r, -EACCES, -ENOLCK))

+                                return log_error_errno(SYNTHETIC_ERRNO(EAGAIN), "TPM2 PIN unlock failed, falling back to traditional unlocking.");

                         if (ERRNO_IS_NOT_SUPPORTED(r)) /* TPM2 support not compiled in? */

                                 return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN), "TPM2 support not available, falling back to traditional unlocking.");

                         if (r != -EAGAIN) /* EAGAIN means: no tpm2 chip found */

@@ -1335,6 +1341,7 @@ static int attach_luks_or_plain_or_bitlk_by_tpm2(

                         for (;;) {

                                 uint32_t pcr_mask;

                                 uint16_t pcr_bank, primary_alg;

+                                TPM2Flags tpm2_flags;

                                 r = find_tpm2_auto_data(

                                                 cd,

@@ -1346,7 +1353,8 @@ static int attach_luks_or_plain_or_bitlk_by_tpm2(

                                                 &blob, &blob_size,

                                                 &policy_hash, &policy_hash_size,

                                                 &keyslot,

-                                                &token);

+                                                &token,

+                                                &tpm2_flags);

                                 if (r == -ENXIO)

                                         /* No further TPM2 tokens found in the LUKS2 header. */

                                         return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN),

@@ -1369,7 +1377,13 @@ static int attach_luks_or_plain_or_bitlk_by_tpm2(

                                                 NULL, 0, 0, /* no key file */

                                                 blob, blob_size,

                                                 policy_hash, policy_hash_size,

+                                                tpm2_flags,

+                                                until,

+                                                arg_headless,

+                                                arg_ask_password_flags,

                                                 &decrypted_key, &decrypted_key_size);

+                                if (IN_SET(r, -EACCES, -ENOLCK))

+                                        return log_error_errno(SYNTHETIC_ERRNO(EAGAIN), "TPM2 PIN unlock failed, falling back to traditional unlocking.");

                                 if (r != -EPERM)

                                         break;