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EKCD: Preload error strings, PRNG seed; use OAEP padding

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Preload OpenSSL ERR string data so that the formatted error messages are
vaguely meaningful. Add OpenSSL error information to the RSA_public_encrypt()
operation failure case in one-time key generation.

For obsolescent OpenSSL versions (*cough* FIPS *cough*), pre-seed the PRNG
before entering Cap mode, as old versions of OpenSSL are unaware of kernel
RNG interfaces aside from /dev/random (such as the long-supported kern.arnd, or
the slightly more recent getentropy(3) or getrandom(2)). (RSA_public_encrypt()
wants a seeded PRNG to randomize the "PS" portion of PKCS 1.5 padding or the
"MGF" pseudo-random function in OAEP padding.)

Switch dumpon to encrypt the one-time key with OAEP padding (recommended since
1998; RFC2437) rather than the obsolescent PKCS 1.5 padding (1993; RFC2313).

Switch decryptcore to attempt OAEP decryption first, and try PKCS 1.5
decryption on failure. This is intended only for transition convenience, and
we should obsolete support for non-OAEP padding in a release or two.

Reviewed by:	markj
MFC After:	2 weeks
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D24534
This commit is contained in:
cem 2020-04-23 17:56:48 +00:00
parent ad71d1415e
commit 62aab8f9b8
2 changed files with 24 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
sbin/decryptcore/decryptcore.c
View File

@ -218,6 +218,10 @@ decrypt(int ofd, const char *privkeyfile, const char *keyfile,
}
if (RSA_private_decrypt(kdk->kdk_encryptedkeysize,
kdk->kdk_encryptedkey, key, privkey,
RSA_PKCS1_OAEP_PADDING) != sizeof(key) &&
/* Fallback to deprecated, formerly-used PKCS 1.5 padding. */
RSA_private_decrypt(kdk->kdk_encryptedkeysize,
kdk->kdk_encryptedkey, key, privkey,
RSA_PKCS1_PADDING) != sizeof(key)) {
pjdlog_error("Unable to decrypt key: %s",

23
sbin/dumpon/dumpon.c
View File

@ -77,6 +77,7 @@ __FBSDID("$FreeBSD$");
#ifdef HAVE_CRYPTO
#include <openssl/err.h>
#include <openssl/pem.h>
#include <openssl/rand.h>
#include <openssl/rsa.h>
#endif
@ -224,6 +225,18 @@ genkey(const char *pubkeyfile, struct diocskerneldump_arg *kdap)
if (fp == NULL)
err(1, "Unable to open %s", pubkeyfile);
/*
* Obsolescent OpenSSL only knows about /dev/random, and needs to
* pre-seed before entering cap mode. For whatever reason,
* RSA_pub_encrypt uses the internal PRNG.
*/
#if OPENSSL_VERSION_NUMBER < 0x10100000L
{
unsigned char c[1];
RAND_bytes(c, 1);
}
#endif
if (caph_enter() < 0)
err(1, "Unable to enter capability mode");
@ -286,8 +299,9 @@ genkey(const char *pubkeyfile, struct diocskerneldump_arg *kdap)
arc4random_buf(kdap->kda_key, sizeof(kdap->kda_key));
if (RSA_public_encrypt(sizeof(kdap->kda_key), kdap->kda_key,
kdap->kda_encryptedkey, pubkey,
RSA_PKCS1_PADDING) != (int)kdap->kda_encryptedkeysize) {
errx(1, "Unable to encrypt the one-time key.");
RSA_PKCS1_OAEP_PADDING) != (int)kdap->kda_encryptedkeysize) {
errx(1, "Unable to encrypt the one-time key: %s",
ERR_error_string(ERR_get_error(), NULL));
}
RSA_free(pubkey);
}
@ -470,8 +484,11 @@ main(int argc, char *argv[])
usage();
#ifdef HAVE_CRYPTO
if (cipher != KERNELDUMP_ENC_NONE && pubkeyfile == NULL)
if (cipher != KERNELDUMP_ENC_NONE && pubkeyfile == NULL) {
errx(EX_USAGE, "-C option requires a public key file.");
} else if (pubkeyfile != NULL) {
ERR_load_crypto_strings();
}
#else
if (pubkeyfile != NULL)
errx(EX_UNAVAILABLE,"Unable to use the public key."