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Diffstat (limited to 'g13/sh-dmcrypt.c')
| -rw-r--r-- | g13/sh-dmcrypt.c | 406 |
1 files changed, 406 insertions, 0 deletions
diff --git a/g13/sh-dmcrypt.c b/g13/sh-dmcrypt.c new file mode 100644 index 000000000..49950fd2b --- /dev/null +++ b/g13/sh-dmcrypt.c @@ -0,0 +1,406 @@ +/* sh-dmcrypt.c - The DM-Crypt part for g13-syshelp + * Copyright (C) 2015 Werner Koch + * + * This file is part of GnuPG. + * + * GnuPG is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3 of the License, or + * (at your option) any later version. + * + * GnuPG is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <stdarg.h> +#include <errno.h> +#include <assert.h> +#include <sys/types.h> +#ifdef HAVE_STAT +# include <sys/stat.h> +#endif +#include <unistd.h> + +#include "g13-syshelp.h" +#include <assuan.h> +#include "i18n.h" +#include "utils.h" +#include "keyblob.h" + +/* The standard disk block size (logical). */ +#define SECTOR_SIZE 512 + +/* The physical block size used by modern devices. */ +#define PHY_SECTOR_SIZE (SECTOR_SIZE*8) /* 4 KiB */ + +/* The length of the crypto setup area in sectors. 16 KiB is a nice + multiple of a modern block size and should be sufficient for all + kind of extra public key encryption packet. */ +#define SETUP_AREA_SECTORS 32 /* 16 KiB */ + +/* The number of header block copies stored at the begin and end of + the device. */ +#define HEADER_SETUP_AREA_COPIES 2 +#define FOOTER_SETUP_AREA_COPIES 2 + +/* The length in blocks of the space we put at the start and at the + end of the device. This space is used to store N copies of the + setup area for the actual encrypted container inbetween. */ +#define HEADER_SECTORS (SETUP_AREA_SECTORS * HEADER_SETUP_AREA_COPIES) +#define FOOTER_SECTORS (SETUP_AREA_SECTORS * FOOTER_SETUP_AREA_COPIES) + +/* Minimim size of the encrypted space in blocks. This is more or + less an arbitrary value. */ +#define MIN_ENCRYPTED_SPACE 32 + +/* Some consistency checks for the above constants. */ +#if (PHY_SECTOR_SIZE % SECTOR_SIZE) +# error the physical secotor size should be a multiple of 512 +#endif +#if ((SETUP_AREA_SECTORS*SECTOR_SIZE) % PHY_SECTOR_SIZE) +# error The setup area size should be a multiple of the phy. sector size. +#endif + + +/* Check whether the block device DEVNAME is used by device mapper. + Returns: 0 if the device is good and not yet used by DM. */ +static gpg_error_t +check_blockdev (const char *devname) +{ + gpg_error_t err; + struct stat sb; + unsigned int devmajor, devminor; + char *result = NULL; + char **lines = NULL; + char **fields = NULL; + int lno, count; + + if (stat (devname, &sb)) + { + err = gpg_error_from_syserror (); + log_error ("error stating '%s': %s\n", devname, gpg_strerror (err)); + return err; + } + if (!S_ISBLK (sb.st_mode)) + { + err = gpg_error (GPG_ERR_ENOTBLK); + log_error ("can't use '%s': %s\n", devname, gpg_strerror (err)); + return err; + } + devmajor = major (sb.st_rdev); + devminor = minor (sb.st_rdev); + + { + const char *argv[2]; + + argv[0] = "deps"; + argv[1] = NULL; + err = sh_exec_tool ("/sbin/dmsetup", argv, NULL, &result, NULL); + } + if (err) + { + log_error ("error running '%s' to search for '%s': %s\n", + "dmsetup deps", devname, gpg_strerror (err)); + goto leave; + } + lines = strsplit (result, '\n', 0, NULL); + if (!lines) + { + err = gpg_error_from_syserror (); + goto leave; + } + if (lines[0] && !strcmp (lines[0], "No devices found")) + ; + else + { + for (lno=0; lines[lno]; lno++) + { + unsigned int xmajor, xminor; + + if (!*lines[lno]) + continue; + xfree (fields); + fields = strsplit (lines[lno], ':', 0, &count); + if (!fields) + { + err = gpg_error_from_syserror (); + goto leave; + } + if (count < 3 + || sscanf (fields[2], " (%u,%u)", &xmajor, &xminor) != 2) + { + log_error ("error running '%s' to search for '%s': %s\n", + "dmsetup deps", devname, "unexpected output"); + err = gpg_error (GPG_ERR_INV_VALUE); + goto leave; + } + + if (xmajor == devmajor && xminor == devminor) + { + log_error ("device '%s' (%u:%u) already used by device mapper\n", + devname, devmajor, devminor); + err = gpg_error (GPG_ERR_EBUSY); + goto leave; + } + } + } + + + leave: + xfree (fields); + xfree (lines); + xfree (result); + return err; +} + + +/* Return a malloced buffer with the prefix of the setup area. This + is the data written right before the encrypted keyblob. Return NULL + on error and sets ERRNO. */ +static void * +mk_setup_area_prefix (size_t *r_length) +{ + unsigned char *packet; + size_t setuparealen; + + packet = xtrymalloc (32); + if (!packet) + return NULL; + *r_length = 32; + + setuparealen = SETUP_AREA_SECTORS * SECTOR_SIZE; + + packet[0] = (0xc0|61); /* CTB for the private packet type 0x61. */ + packet[1] = 0xff; /* 5 byte length packet, value 20. */ + packet[2] = 0; + packet[3] = 0; + packet[4] = 0; + packet[5] = 26; + memcpy (packet+6, "GnuPG/G13", 10); /* Packet subtype. */ + packet[16] = 1; /* G13 packet format version. */ + packet[17] = 0; /* Reserved. */ + packet[18] = 0; /* Reserved. */ + packet[19] = 1; /* OS Flag = Linux */ + packet[20] = (setuparealen >> 24); /* Total length of header. */ + packet[21] = (setuparealen >> 16); + packet[22] = (setuparealen >> 8); + packet[23] = (setuparealen); + packet[24] = HEADER_SETUP_AREA_COPIES; + packet[25] = FOOTER_SETUP_AREA_COPIES; + packet[26] = 0; /* Reserved. */ + packet[27] = 0; /* Reserved. */ + packet[28] = 0; /* Reserved. */ + packet[29] = 0; /* Reserved. */ + packet[30] = 0; /* Reserved. */ + packet[31] = 0; /* Reserved. */ + + return packet; +} + + +gpg_error_t +sh_dmcrypt_create_container (ctrl_t ctrl, const char *devname, estream_t devfp) +{ + gpg_error_t err; + char *header_space; + char *targetname = NULL; + size_t nread; + char *p; + char hexkey[16*2+1]; + char *table = NULL; + unsigned long long nblocks; + char *result = NULL; + unsigned char twobyte[2]; + membuf_t keyblob; + void *keyblob_buf = NULL; + size_t keyblob_len; + size_t n; + const char *s; + + if (!ctrl->devti) + return gpg_error (GPG_ERR_INV_ARG); + + header_space = xtrymalloc (HEADER_SECTORS * SECTOR_SIZE); + if (!header_space) + return gpg_error_from_syserror (); + + /* Start building the keyblob. */ + init_membuf (&keyblob, 512); + append_tuple (&keyblob, KEYBLOB_TAG_BLOBVERSION, "\x01", 1); + n = CONTTYPE_DM_CRYPT; + twobyte[0] = (n >> 8); + twobyte[1] = n; + append_tuple (&keyblob, KEYBLOB_TAG_CONTTYPE, twobyte, 2); + { + gnupg_isotime_t tbuf; + + gnupg_get_isotime (tbuf); + append_tuple (&keyblob, KEYBLOB_TAG_CREATED, tbuf, strlen (tbuf)); + } + + /* Rewind out stream. */ + if (es_fseeko (devfp, 0, SEEK_SET)) + { + err = gpg_error_from_syserror (); + log_error ("error seeking to begin of '%s': %s\n", + devname, gpg_strerror (err)); + goto leave; + } + es_clearerr (devfp); + + /* Extra check that the device is empty. */ + if (es_read (devfp, header_space, HEADER_SECTORS * SECTOR_SIZE, &nread)) + err = gpg_error_from_syserror (); + else if (nread != HEADER_SECTORS * SECTOR_SIZE) + err = gpg_error (GPG_ERR_TOO_SHORT); + else + err = 0; + if (err) + { + log_error ("error reading header space of '%s': %s\n", + devname, gpg_strerror (err)); + goto leave; + } + for (p=header_space; nread && !*p; nread--, p++) + ; + if (nread) + { + log_error ("header space of '%s' already used - use %s to override\n", + devname, "--force"); + err = gpg_error (GPG_ERR_NOT_SUPPORTED); + goto leave; + } + + /* Check that the device is not used by device mapper. */ + err = check_blockdev (devname); + if (err) + goto leave; + + /* Compute the number of blocks. */ + err = sh_blockdev_getsz (devname, &nblocks); + if (err) + { + log_error ("error getting size of '%s': %s\n", + devname, gpg_strerror (err)); + goto leave; + } + if (nblocks <= HEADER_SECTORS + MIN_ENCRYPTED_SPACE + FOOTER_SECTORS) + { + log_error ("device '%s' is too small (min=%d blocks)\n", + devname, + HEADER_SECTORS + MIN_ENCRYPTED_SPACE + FOOTER_SECTORS); + err = gpg_error (GPG_ERR_TOO_SHORT); + goto leave; + } + nblocks -= HEADER_SECTORS + FOOTER_SECTORS; + + /* Device mapper needs a name for the device: Take it from the label + or use "0". */ + targetname = strconcat ("g13-", ctrl->client.uname, "-", + ctrl->devti->label? ctrl->devti->label : "0", + NULL); + if (!targetname) + { + err = gpg_error_from_syserror (); + goto leave; + } + + /* Create the key. */ + { + char key[16]; + gcry_randomize (key, sizeof key, GCRY_STRONG_RANDOM); + append_tuple (&keyblob, KEYBLOB_TAG_ENCKEY, key, sizeof key); + bin2hex (key, 16, hexkey); + wipememory (key, 16); + /* Add a 2*(4+16) byte filler to conceal the fact that we use + AES-128. If we ever want to switch to 256 bit we can resize + that filler to keep the keyblob at the same size. */ + append_tuple (&keyblob, KEYBLOB_TAG_FILLER, key, sizeof key); + append_tuple (&keyblob, KEYBLOB_TAG_FILLER, key, sizeof key); + } + + /* Build dmcrypt table. */ + s = "aes-cbc-essiv:sha256"; + append_tuple (&keyblob, KEYBLOB_TAG_ALGOSTR, s, strlen (s)); + table = es_bsprintf ("0 %llu crypt %s %s 0 %s %d", + nblocks, s, hexkey, devname, HEADER_SECTORS); + if (!table) + { + err = gpg_error_from_syserror (); + goto leave; + } + wipememory (hexkey, sizeof hexkey); + + /* Add a copy of the setup area prefix to the keyblob. */ + p = mk_setup_area_prefix (&n); + if (!p) + { + err = gpg_error_from_syserror (); + goto leave; + } + append_tuple (&keyblob, KEYBLOB_TAG_HDRCOPY, p, n); + + /* Turn the keyblob into a buffer and callback to encrypt it. */ + keyblob_buf = get_membuf (&keyblob, &keyblob_len); + if (!keyblob_buf) + { + err = gpg_error_from_syserror (); + goto leave; + } + err = sh_encrypt_keyblob (ctrl, keyblob_buf, keyblob_len, &p, &n); + if (err) + { + log_error ("encrypting the keyblob failed: %s\n", gpg_strerror (err)); + goto leave; + } + wipememory (keyblob_buf, keyblob_len); + xfree (keyblob_buf); + keyblob_buf = NULL; + + /* Create the container. */ + /* { */ + /* const char *argv[3]; */ + + /* argv[0] = "create"; */ + /* argv[1] = targetname; */ + /* argv[2] = NULL; */ + /* err = sh_exec_tool ("/sbin/dmsetup", argv, table, &result, NULL); */ + /* } */ + /* if (err) */ + /* { */ + /* log_error ("error running dmsetup for '%s': %s\n", */ + /* devname, gpg_strerror (err)); */ + /* goto leave; */ + /* } */ + /* log_debug ("dmsetup result: %s\n", result); */ + + /* Write the setup area. */ + + + leave: + wipememory (hexkey, sizeof hexkey); + if (table) + { + wipememory (table, strlen (table)); + xfree (table); + } + if (keyblob_buf) + { + wipememory (keyblob_buf, keyblob_len); + xfree (keyblob_buf); + } + xfree (get_membuf (&keyblob, NULL)); + xfree (targetname); + xfree (result); + xfree (header_space); + return err; +} |