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sbin/decryptcore/decryptcore.c

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/*-
* Copyright (c) 2015 Konrad Witaszczyk <def@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
oshogboUnsubmitted
Done
Inline Actions

Missing cdefs and __FBSDID.

oshogbo: Missing cdefs and __FBSDID.
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/capsicum.h>
#include <sys/endian.h>
#include <sys/kerneldump.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/wait.h>
#include <ctype.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>
#include <openssl/engine.h>
#include "pjdlog.h"
cemUnsubmitted
Done
Inline Actions

I believe openssl headers and pjdlog should be in block(s) following standard C headers.

cem: I believe openssl headers and pjdlog should be in block(s) following standard C headers.
#define DECRYPTCORE_CRASHDIR "/var/crash"
static void
usage(void)
{
pjdlog_exitx(1,
"usage: decryptcore [-Lv] -p privatekey -k key -e encryptedcore -c core\n"
" decryptcore [-Lv] [-d crashdir] -p privatekey -n dumpnr");
}
static int
wait_for_process(pid_t pid)
{
int status;
if (waitpid(pid, &status, WUNTRACED | WEXITED) == -1) {
pjdlog_errno(LOG_ERR, "Unable to wait for a child process");
return (1);
}
if (WIFEXITED(status))
return (WEXITSTATUS(status));
return (1);
}
static struct kerneldumpkey *
read_key(int kfd)
{
uint8_t *buf, *p;
struct kerneldumpkey *kdk;
uint32_t encryptedkeysize;
ssize_t size;
size_t kdksize, bytes;
PJDLOG_ASSERT(kfd >= 0);
buf = NULL;
kdk = NULL;
kdksize = sizeof(*kdk);
kdk = calloc(1, kdksize);
if (kdk == NULL) {
pjdlog_errno(LOG_ERR, "Unable to allocate kernel dump key");
goto failed;
}
bytes = sizeof(kdk->kdk_encryption) + sizeof(kdk->kdk_iv) +
sizeof(kdk->kdk_encryptedkeysize);
buf = calloc(1, bytes);
if (buf == NULL) {
pjdlog_errno(LOG_ERR, "Unable to allocate buffer");
goto failed;
}
size = read(kfd, buf, bytes);
if (size == (ssize_t)bytes) {
p = buf;
kdk->kdk_encryption = *p;
p += sizeof(kdk->kdk_encryption);
bcopy(p, kdk->kdk_iv, sizeof(kdk->kdk_iv));
p += sizeof(kdk->kdk_iv);
bcopy(p, &encryptedkeysize, sizeof(encryptedkeysize));
kdk->kdk_encryptedkeysize = dtoh32(encryptedkeysize);
p += sizeof(encryptedkeysize);
kdksize += (size_t)kdk->kdk_encryptedkeysize;
kdk = realloc(kdk, kdksize);
if (kdk == NULL) {
pjdlog_errno(LOG_ERR, "Unable to reallocate kernel dump key");
goto failed;
}
bytes += (size_t)kdk->kdk_encryptedkeysize;
size += read(kfd, &kdk->kdk_encryptedkey,
kdk->kdk_encryptedkeysize);
}
if (size != (ssize_t)bytes) {
pjdlog_errno(LOG_ERR, "Unable to read key");
goto failed;
}
free(buf);
return (kdk);
failed:
free(buf);
free(kdk);
return (NULL);
}
static bool
decrypt(const char *privkeyfile, const char *keyfile, const char *input,
const char *output)
{
uint8_t buf[KERNELDUMP_BUFFER_SIZE], key[KERNELDUMP_KEY_MAX_SIZE];
EVP_CIPHER_CTX ctx;
const EVP_CIPHER *cipher;
FILE *fp;
struct kerneldumpkey *kdk;
RSA *privkey;
int ifd, kfd, ofd, olen, privkeysize;
ssize_t bytes;
pid_t pid;
PJDLOG_ASSERT(privkeyfile != NULL);
PJDLOG_ASSERT(keyfile != NULL);
PJDLOG_ASSERT(input != NULL);
PJDLOG_ASSERT(output != NULL);
privkey = NULL;
/*
* Decrypt a core dump in a child process so we can unlink a partially
* decrypted core if the child process fails.
*/
pid = fork();
if (pid == -1) {
pjdlog_errno(LOG_ERR, "Unable to create child process");
return (false);
}
if (pid > 0)
return (wait_for_process(pid) == 0);
kfd = open(keyfile, O_RDONLY);
if (kfd == -1) {
pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile);
goto failed;
}
ifd = open(input, O_RDONLY);
if (ifd == -1) {
pjdlog_errno(LOG_ERR, "Unable to open %s", input);
goto failed;
}
ofd = open(output, O_WRONLY | O_CREAT | O_TRUNC, 0600);
if (ofd == -1) {
pjdlog_errno(LOG_ERR, "Unable to open %s", output);
goto failed;
delphijUnsubmitted
Done
Inline Actions

Should we disable coredump at this point if not debugging? Otherwise it may defeat the purpose if the process crashes.

delphij: Should we disable coredump at this point if not debugging? Otherwise it may defeat the purpose…
oshogboUnsubmitted
Done
Inline Actions

Every where where you using cap_enter it should be checked like that:
cap_enter() < 0 && errno != ENOSYS
As far as I know dumps can work without CAPSICUM.

oshogbo: Every where where you using cap_enter it should be checked like that: cap_enter() < 0 && errno !
defAuthorUnsubmitted
Done
Inline Actions

It's assumed that disabling Capsicum doesn't disable a functionality which uses Capsicum.

def: It's assumed that disabling Capsicum doesn't disable a functionality which uses Capsicum.
}
fp = fopen(privkeyfile, "r");
if (fp == NULL) {
pjdlog_errno(LOG_ERR, "Unable to open %s", privkeyfile);
goto failed;
delphijUnsubmitted
Done
Inline Actions

Is there some reason that this section (193-199) is done after entering capability mode? (Or other words, can they be moved to before opening the files?)

delphij: Is there some reason that this section (193-199) is done after entering capability mode? (Or…
pjdUnsubmitted
Done
Inline Actions

Why do you want to increase TCB? Even if the code doesn't introduce any risk now, it may be modified in the future. I'd need to hear a convincing argument to agree on this one:)

pjd: Why do you want to increase TCB? Even if the code doesn't introduce any risk now, it may be…
defAuthorUnsubmitted
Done
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As Paweł said we don't want to perform any unnecessary operation before entering capability mode.

def: As Paweł said we don't want to perform any unnecessary operation before entering capability…
}
if (cap_enter() < 0 && errno != ENOSYS) {
pjdlog_errno(LOG_ERR, "Unable to enter capability mode");
goto failed;
}
privkey = RSA_new();
if (privkey == NULL) {
pjdlog_error("Unable to allocate an RSA structure: %s",
ERR_error_string(ERR_get_error(), NULL));
goto failed;
}
EVP_CIPHER_CTX_init(&ctx);
kdk = read_key(kfd);
close(kfd);
if (kdk == NULL)
goto failed;
privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL);
fclose(fp);
if (privkey == NULL) {
pjdlog_error("Unable to read data from %s.", privkeyfile);
goto failed;
}
privkeysize = RSA_size(privkey);
if (privkeysize != (int)kdk->kdk_encryptedkeysize) {
pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.",
8 * privkeysize, 8 * kdk->kdk_encryptedkeysize);
goto failed;
}
switch (kdk->kdk_encryption) {
case KERNELDUMP_ENC_AES_256_CBC:
cipher = EVP_aes_256_cbc();
break;
default:
pjdlog_error("Invalid encryption algorithm.");
goto failed;
}
if (RSA_private_decrypt(kdk->kdk_encryptedkeysize,
kdk->kdk_encryptedkey, key, privkey,
RSA_PKCS1_PADDING) != sizeof(key)) {
pjdlog_error("Unable to decrypt key: %s",
ERR_error_string(ERR_get_error(), NULL));
goto failed;
delphijUnsubmitted
Done
Inline Actions

Perhaps explicit_bzero(3)?

delphij: Perhaps explicit_bzero(3)?
}
RSA_free(privkey);
privkey = NULL;
EVP_DecryptInit_ex(&ctx, cipher, NULL, key, kdk->kdk_iv);
EVP_CIPHER_CTX_set_padding(&ctx, 0);
explicit_bzero(key, sizeof(key));
do {
bytes = read(ifd, buf, sizeof(buf));
if (bytes < 0) {
pjdlog_errno(LOG_ERR, "Unable to read data from %s",
input);
goto failed;
} else if (bytes == 0) {
break;
}
if (bytes > 0) {
if (EVP_DecryptUpdate(&ctx, buf, &olen, buf,
bytes) == 0) {
pjdlog_error("Unable to decrypt core.");
goto failed;
}
} else {
if (EVP_DecryptFinal_ex(&ctx, buf, &olen) == 0) {
pjdlog_error("Unable to decrypt core.");
goto failed;
}
}
if (olen == 0)
continue;
if (write(ofd, buf, olen) != olen) {
pjdlog_errno(LOG_ERR, "Unable to write data to %s",
output);
goto failed;
}
} while (bytes > 0);
explicit_bzero(buf, sizeof(buf));
EVP_CIPHER_CTX_cleanup(&ctx);
exit(0);
failed:
explicit_bzero(key, sizeof(key));
explicit_bzero(buf, sizeof(buf));
RSA_free(privkey);
EVP_CIPHER_CTX_cleanup(&ctx);
exit(1);
}
int
main(int argc, char **argv)
{
char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX];
struct stat sb;
const char *crashdir, *dumpnr, *privatekey;
int ch, debug;
size_t ii;
bool usesyslog;
pjdlog_init(PJDLOG_MODE_STD);
pjdlog_prefix_set("(decryptcore) ");
debug = 0;
*core = '\0';
crashdir = NULL;
dumpnr = NULL;
*encryptedcore = '\0';
*keyfile = '\0';
privatekey = NULL;
usesyslog = false;
while ((ch = getopt(argc, argv, "Lc:d:e:k:n:p:v")) != -1) {
delphijUnsubmitted
Done
Inline Actions

This construction is Okay, but if I was you, I would probably go with standard getopt_long which would avoid the hardcoding of parameters and allow more flexible command line options ordering. Just a suggestion.

delphij: This construction is Okay, but if I was you, I would probably go with standard getopt_long…
pjdUnsubmitted
Done
Inline Actions

I'm fine with this suggestion, but I'd stick to regular getopt(3), which should be more than enough here.

pjd: I'm fine with this suggestion, but I'd stick to regular getopt(3), which should be more than…
switch (ch) {
case 'L':
usesyslog = true;
break;
case 'c':
strncpy(core, optarg, sizeof(core));
break;
case 'd':
crashdir = optarg;
break;
case 'e':
strncpy(encryptedcore, optarg, sizeof(encryptedcore));
break;
case 'k':
strncpy(keyfile, optarg, sizeof(keyfile));
break;
case 'n':
dumpnr = optarg;
break;
oshogboUnsubmitted
Done
Inline Actions

Why just don't use
output = argv[3] ?
and so any.
Code would be a little bit smaller.

oshogbo: Why just don't use output = argv[3] ? and so any. Code would be a little bit smaller.
case 'p':
privatekey = optarg;
break;
case 'v':
debug++;
break;
default:
usage();
}
}
argc -= optind;
argv += optind;
if (argc != 0)
usage();
/* Verify mutually exclusive options. */
if ((crashdir != NULL || dumpnr != NULL) &&
(*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) {
usage();
}
/*
* Set key, encryptedcore and core file names using crashdir and dumpnr.
*/
if (dumpnr != NULL) {
for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) {
if (isdigit((int)dumpnr[ii]) == 0)
usage();
}
if (crashdir == NULL)
crashdir = DECRYPTCORE_CRASHDIR;
PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile),
"%s/key.%s", crashdir, dumpnr) > 0);
PJDLOG_VERIFY(snprintf(core, sizeof(core),
"%s/vmcore.%s", crashdir, dumpnr) > 0);
PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore),
"%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0);
}
if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' ||
*core == '\0') {
usage();
}
if (usesyslog)
pjdlog_mode_set(PJDLOG_MODE_SYSLOG);
pjdlog_debug_set(debug);
if (!decrypt(privatekey, keyfile, encryptedcore, core)) {
if (stat(core, &sb) == 0 && unlink(core) != 0)
pjdlog_exit(1, "Unable to remove core");
exit(1);
}
pjdlog_fini();
exit(0);
}