From 7d27190e9948b1184286714ded580e4852fd830a Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Mon, 17 Jan 2022 16:17:17 +0000 Subject: [efi] Attempt to fetch autoexec script via TFTP Attempt to fetch the autoexec.ipxe script via TFTP using the PXE base code protocol installed on the loaded image's device handle, if present. This provides a generic alternative to the use of an embedded script for chainloaded binaries, which is particularly useful in a UEFI Secure Boot environment since it allows the script to be modified without the need to sign a new binary. As a side effect, this also provides a third method for breaking the PXE chainloading loop (as an alternative to requiring an embedded script or custom DHCP server configuration). Signed-off-by: Michael Brown --- src/interface/efi/efi_autoexec.c | 149 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) diff --git a/src/interface/efi/efi_autoexec.c b/src/interface/efi/efi_autoexec.c index 881c30c..7180fb8 100644 --- a/src/interface/efi/efi_autoexec.c +++ b/src/interface/efi/efi_autoexec.c @@ -24,11 +24,16 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); #include +#include #include #include #include +#include +#include +#include #include #include +#include #include #include @@ -170,6 +175,146 @@ static int efi_autoexec_filesystem ( EFI_HANDLE device ) { } /** + * Load autoexec script from TFTP server + * + * @v device Device handle + * @ret rc Return status code + */ +static int efi_autoexec_tftp ( EFI_HANDLE device ) { + EFI_BOOT_SERVICES *bs = efi_systab->BootServices; + union { + void *interface; + EFI_PXE_BASE_CODE_PROTOCOL *pxe; + } u; + union { + struct in_addr in; + EFI_IP_ADDRESS ip; + } server; + struct settings *settings; + size_t filename_len; + char *filename; + char *sep; + int len; + UINT64 size; + VOID *data; + EFI_STATUS efirc; + int rc; + + /* Open PXE base code protocol */ + if ( ( efirc = bs->OpenProtocol ( device, + &efi_pxe_base_code_protocol_guid, + &u.interface, efi_image_handle, + device, + EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){ + rc = -EEFI ( efirc ); + DBGC ( device, "EFI %s has no PXE base code instance: %s\n", + efi_handle_name ( device ), strerror ( rc ) ); + goto err_pxe; + } + + /* Identify settings block containing cached filename, if any */ + len = fetch_setting ( &cachedhcp_settings, &filename_setting, + &settings, NULL, NULL, 0 ); + if ( len < 0 ) { + rc = len; + DBGC ( device, "EFI %s has no PXE boot filename: %s\n", + efi_handle_name ( device ), strerror ( rc ) ); + goto err_settings; + } + + /* Allocate filename */ + filename_len = ( len + ( sizeof ( efi_autoexec_name ) - 1 /* NUL */ ) + + 1 /* NUL */ ); + filename = malloc ( filename_len ); + if ( ! filename ) { + rc = -ENOMEM; + goto err_filename; + } + + /* Fetch filename and TFTP server address */ + fetch_string_setting ( settings, &filename_setting, filename, + filename_len ); + memset ( &server, 0, sizeof ( server ) ); + fetch_ipv4_setting ( settings, &next_server_setting, &server.in ); + + /* Update filename to autoexec script name */ + sep = strrchr ( filename, '/' ); + if ( ! sep ) + sep = strrchr ( filename, '\\' ); + if ( ! sep ) + sep = ( filename - 1 ); + strcpy ( ( sep + 1 ), efi_autoexec_name ); + + /* Get file size */ + if ( ( efirc = u.pxe->Mtftp ( u.pxe, + EFI_PXE_BASE_CODE_TFTP_GET_FILE_SIZE, + NULL, FALSE, &size, NULL, &server.ip, + ( ( UINT8 * ) filename ), NULL, + FALSE ) ) != 0 ) { + rc = -EEFI ( efirc ); + DBGC ( device, "EFI %s could not get size of %s:%s: %s\n", + efi_handle_name ( device ), inet_ntoa ( server.in ), + filename, strerror ( rc ) ); + goto err_size; + } + + /* Ignore zero-length files */ + if ( ! size ) { + rc = -EINVAL; + DBGC ( device, "EFI %s has zero-length %s:%s\n", + efi_handle_name ( device ), inet_ntoa ( server.in ), + filename ); + goto err_empty; + } + + /* Allocate temporary copy */ + if ( ( efirc = bs->AllocatePool ( EfiBootServicesData, size, + &data ) ) != 0 ) { + rc = -EEFI ( efirc ); + DBGC ( device, "EFI %s could not allocate %s:%s: %s\n", + efi_handle_name ( device ), inet_ntoa ( server.in ), + filename, strerror ( rc ) ); + goto err_alloc; + } + + /* Download file */ + if ( ( efirc = u.pxe->Mtftp ( u.pxe, EFI_PXE_BASE_CODE_TFTP_READ_FILE, + data, FALSE, &size, NULL, &server.ip, + ( ( UINT8 * ) filename ), NULL, + FALSE ) ) != 0 ) { + rc = -EEFI ( efirc ); + DBGC ( device, "EFI %s could not download %s:%s: %s\n", + efi_handle_name ( device ), inet_ntoa ( server.in ), + filename, strerror ( rc ) ); + goto err_download; + } + + /* Record autoexec script */ + efi_autoexec = data; + efi_autoexec_len = size; + data = NULL; + DBGC ( device, "EFI %s found %s:%s\n", efi_handle_name ( device ), + inet_ntoa ( server.in ), filename ); + + /* Success */ + rc = 0; + + err_download: + if ( data ) + bs->FreePool ( data ); + err_alloc: + err_empty: + err_size: + free ( filename ); + err_filename: + err_settings: + bs->CloseProtocol ( device, &efi_pxe_base_code_protocol_guid, + efi_image_handle, device ); + err_pxe: + return rc; +} + +/** * Load autoexec script * * @v device Device handle @@ -186,6 +331,10 @@ int efi_autoexec_load ( EFI_HANDLE device ) { if ( ( rc = efi_autoexec_filesystem ( device ) ) == 0 ) return 0; + /* Try loading via TFTP, if supported */ + if ( ( rc = efi_autoexec_tftp ( device ) ) == 0 ) + return 0; + return -ENOENT; } -- cgit v1.1