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0002-Requiring-authentication-after-tpm-unlock-...
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File 0002-Requiring-authentication-after-tpm-unlock-for-CLI-ac.patch of Package grub2
From af8b106667aa2ca7a7613e10d8746959e182f8f1 Mon Sep 17 00:00:00 2001 From: Michael Chang <mchang@suse.com> Date: Thu, 29 Aug 2024 13:27:30 +0800 Subject: [PATCH 2/2] Requiring authentication after tpm unlock for CLI access GRUB may use TPM to verify the integrity of boot components, and the result can determine whether a previously sealed key can be released. If everything checks out, showing nothing has been tampered with, the key is released, and grub unlocks the encrypted root partition for the next stage of booting. However, the liberal command line interface (CLI) can be misused by anyone in this case to access files in the encrypted partition one way or another. Despite efforts to keep the CLI secure by preventing utility command output from leaking file content, many techniques in the wild could still be used to exploit the CLI, enabling attacks or learning methods to attack. It's nearly impossible to account for all scenarios where a hack could be applied. Therefore, to mitigate potential misuse of the CLI after the root device has been successfully unlocked via TPM, the user should be required to authenticate using the LUKS password. This added layer of security ensures that only authorized users can access the CLI, reducing the risk of exploitation or unauthorized access to the encrypted partition. Fixes: CVE-2024-49504 Signed-off-by: Michael Chang <mchang@suse.com> --- grub-core/disk/cryptodisk.c | 80 +++++++++++++++++++++++++++++++++++ grub-core/kern/main.c | 12 ++++++ grub-core/normal/auth.c | 30 +++++++++++++ grub-core/normal/main.c | 4 ++ grub-core/normal/menu_entry.c | 4 ++ include/grub/auth.h | 1 + include/grub/cryptodisk.h | 3 ++ include/grub/misc.h | 2 + 8 files changed, 136 insertions(+) diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c index babc94868..77bc782fd 100644 --- a/grub-core/disk/cryptodisk.c +++ b/grub-core/disk/cryptodisk.c @@ -1188,6 +1188,7 @@ grub_cryptodisk_scan_device_real (const char *name, goto error; #ifndef GRUB_UTIL is_tpmkey = 1; + grub_cli_set_auth_needed (); #endif goto cleanup; } @@ -1706,6 +1707,85 @@ luks_script_get (grub_size_t *sz) return ret; } +#ifdef GRUB_MACHINE_EFI +grub_err_t +grub_cryptodisk_challenge_password (void) +{ + grub_cryptodisk_t cr_dev; + + for (cr_dev = cryptodisk_list; cr_dev != NULL; cr_dev = cr_dev->next) + { + grub_cryptodisk_dev_t cr; + grub_disk_t source = NULL; + grub_err_t ret = GRUB_ERR_NONE; + grub_cryptodisk_t dev = NULL; + char *part = NULL; + struct grub_cryptomount_args cargs = {0}; + + cargs.check_boot = 0; + cargs.search_uuid = cr_dev->uuid; + + source = grub_disk_open (cr_dev->source); + + if (source == NULL) + goto error_out; + + FOR_CRYPTODISK_DEVS (cr) + { + dev = cr->scan (source, &cargs); + if (grub_errno) + goto error_out; + if (!dev) + continue; + break; + } + + if (dev == NULL) + { + grub_error (GRUB_ERR_BAD_MODULE, + "no cryptodisk module can handle this device"); + goto error_out; + } + + part = grub_partition_get_name (source->partition); + grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name, + source->partition != NULL ? "," : "", + part != NULL ? part : N_("UNKNOWN"), cr_dev->uuid); + grub_free (part); + + cargs.key_data = grub_malloc (GRUB_CRYPTODISK_MAX_PASSPHRASE); + if (cargs.key_data == NULL) + goto error_out; + + if (!grub_password_get ((char *) cargs.key_data, GRUB_CRYPTODISK_MAX_PASSPHRASE)) + { + grub_error (GRUB_ERR_BAD_ARGUMENT, "passphrase not supplied"); + goto error_out; + } + cargs.key_len = grub_strlen ((char *) cargs.key_data); + ret = cr->recover_key (source, dev, &cargs); + if (ret != GRUB_ERR_NONE) + goto error_out; + + error_out: + if (source) + grub_disk_close (source); + if (dev) + cryptodisk_close (dev); + if (cargs.key_data) + { + grub_memset (cargs.key_data, 0, cargs.key_len); + grub_free (cargs.key_data); + } + + if (grub_errno != GRUB_ERR_NONE) + return grub_errno; + } + + return GRUB_ERR_NONE; +} +#endif /* GRUB_MACHINE_EFI */ + struct grub_procfs_entry luks_script = { .name = "luks_script", diff --git a/grub-core/kern/main.c b/grub-core/kern/main.c index 07b6940d2..ef3b3756d 100644 --- a/grub-core/kern/main.c +++ b/grub-core/kern/main.c @@ -37,6 +37,7 @@ #endif static bool cli_disabled = false; +static bool cli_need_auth = false; grub_addr_t grub_modules_get_end (void) @@ -246,6 +247,17 @@ grub_is_cli_disabled (void) return cli_disabled; } +bool +grub_is_cli_need_auth (void) +{ + return cli_need_auth; +} + +void grub_cli_set_auth_needed (void) +{ + cli_need_auth = true; +} + static void check_is_cli_disabled (void) { diff --git a/grub-core/normal/auth.c b/grub-core/normal/auth.c index d94020186..2931ba604 100644 --- a/grub-core/normal/auth.c +++ b/grub-core/normal/auth.c @@ -25,6 +25,10 @@ #include <grub/time.h> #include <grub/i18n.h> +#ifdef GRUB_MACHINE_EFI +#include <grub/cryptodisk.h> +#endif + struct grub_auth_user { struct grub_auth_user *next; @@ -200,6 +204,32 @@ grub_username_get (char buf[], unsigned buf_size) return (key != GRUB_TERM_ESC); } +grub_err_t +grub_auth_check_cli_access (void) +{ + if (grub_is_cli_need_auth () == true) + { +#ifdef GRUB_MACHINE_EFI + static bool authenticated = false; + + if (authenticated == false) + { + grub_err_t ret; + + ret = grub_cryptodisk_challenge_password (); + if (ret == GRUB_ERR_NONE) + authenticated = true; + return ret; + } + return GRUB_ERR_NONE; +#else + return GRUB_ACCESS_DENIED; +#endif + } + + return GRUB_ERR_NONE; +} + grub_err_t grub_auth_check_authentication (const char *userlist) { diff --git a/grub-core/normal/main.c b/grub-core/normal/main.c index 8e58ced67..b08fd6977 100644 --- a/grub-core/normal/main.c +++ b/grub-core/normal/main.c @@ -560,9 +560,13 @@ grub_cmdline_run (int nested, int force_auth) } while (err && force_auth); + if (err == GRUB_ERR_NONE) + err = grub_auth_check_cli_access (); + if (err) { grub_print_error (); + grub_wait_after_message (); grub_errno = GRUB_ERR_NONE; return; } diff --git a/grub-core/normal/menu_entry.c b/grub-core/normal/menu_entry.c index e5ba91ea4..06682a396 100644 --- a/grub-core/normal/menu_entry.c +++ b/grub-core/normal/menu_entry.c @@ -1256,9 +1256,13 @@ grub_menu_entry_run (grub_menu_entry_t entry) err = grub_auth_check_authentication (NULL); + if (err == GRUB_ERR_NONE) + err = grub_auth_check_cli_access (); + if (err) { grub_print_error (); + grub_wait_after_message (); grub_errno = GRUB_ERR_NONE; return; } diff --git a/include/grub/auth.h b/include/grub/auth.h index 747334451..21d5190f0 100644 --- a/include/grub/auth.h +++ b/include/grub/auth.h @@ -33,5 +33,6 @@ grub_err_t grub_auth_unregister_authentication (const char *user); grub_err_t grub_auth_authenticate (const char *user); grub_err_t grub_auth_deauthenticate (const char *user); grub_err_t grub_auth_check_authentication (const char *userlist); +grub_err_t grub_auth_check_cli_access (void); #endif /* ! GRUB_AUTH_HEADER */ diff --git a/include/grub/cryptodisk.h b/include/grub/cryptodisk.h index 0b41e249e..b3291519b 100644 --- a/include/grub/cryptodisk.h +++ b/include/grub/cryptodisk.h @@ -203,4 +203,7 @@ grub_util_get_geli_uuid (const char *dev); grub_cryptodisk_t grub_cryptodisk_get_by_uuid (const char *uuid); grub_cryptodisk_t grub_cryptodisk_get_by_source_disk (grub_disk_t disk); +#ifdef GRUB_MACHINE_EFI +grub_err_t grub_cryptodisk_challenge_password (void); +#endif #endif diff --git a/include/grub/misc.h b/include/grub/misc.h index 1578f36c3..6e94d18f5 100644 --- a/include/grub/misc.h +++ b/include/grub/misc.h @@ -392,6 +392,8 @@ grub_uint64_t EXPORT_FUNC(grub_divmod64) (grub_uint64_t n, grub_uint64_t *r); extern bool EXPORT_FUNC(grub_is_cli_disabled) (void); +extern bool EXPORT_FUNC(grub_is_cli_need_auth) (void); +extern void EXPORT_FUNC(grub_cli_set_auth_needed) (void); /* Must match softdiv group in gentpl.py. */ #if !defined(GRUB_MACHINE_EMU) && (defined(__arm__) || defined(__ia64__) || \ -- 2.47.0
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