Mercurial > dropbear
view libtomcrypt/src/pk/ecc/ecc_sign_hash.c @ 1930:299f4f19ba19
Add /usr/sbin and /sbin to default root PATH
When dropbear is used in a very restricted environment (such as in a
initrd), the default user shell is often also very restricted
and doesn't take care of setting the PATH so the user ends up
with the PATH set by dropbear. Unfortunately, dropbear always
sets "/usr/bin:/bin" as default PATH even for the root user
which should have /usr/sbin and /sbin too.
For a concrete instance of this problem, see the "Remote Unlocking"
section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/
It speaks of a bug in the initramfs script because it's written "blkid"
instead of "/sbin/blkid"... this is just because the scripts from the
initramfs do not expect to have a PATH without the sbin directories and
because dropbear is not setting the PATH appropriately for the root user.
I'm thus suggesting to use the attached patch to fix this misbehaviour (I
did not test it, but it's easy enough). It might seem anecdotic but
multiple Kali users have been bitten by this.
From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author | Raphael Hertzog <hertzog@debian.org> |
---|---|
date | Mon, 09 Jul 2018 16:27:53 +0200 |
parents | e9dba7abd939 |
children |
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. */ #include "tomcrypt.h" #if defined(LTC_MECC) && defined(LTC_DER) /** @file ecc_sign_hash.c ECC Crypto, Tom St Denis */ static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen, prng_state *prng, int wprng, ecc_key *key, int sigformat) { ecc_key pubkey; void *r, *s, *e, *p, *b; int err, max_iterations = LTC_PK_MAX_RETRIES; unsigned long pbits, pbytes, i, shift_right; unsigned char ch, buf[MAXBLOCKSIZE]; LTC_ARGCHK(in != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); LTC_ARGCHK(key != NULL); /* is this a private key? */ if (key->type != PK_PRIVATE) { return CRYPT_PK_NOT_PRIVATE; } /* is the IDX valid ? */ if (ltc_ecc_is_valid_idx(key->idx) != 1) { return CRYPT_PK_INVALID_TYPE; } if ((err = prng_is_valid(wprng)) != CRYPT_OK) { return err; } /* init the bignums */ if ((err = mp_init_multi(&r, &s, &p, &e, &b, NULL)) != CRYPT_OK) { return err; } if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errnokey; } /* get the hash and load it as a bignum into 'e' */ pbits = mp_count_bits(p); pbytes = (pbits+7) >> 3; if (pbits > inlen*8) { if ((err = mp_read_unsigned_bin(e, (unsigned char *)in, inlen)) != CRYPT_OK) { goto errnokey; } } else if (pbits % 8 == 0) { if ((err = mp_read_unsigned_bin(e, (unsigned char *)in, pbytes)) != CRYPT_OK) { goto errnokey; } } else { shift_right = 8 - pbits % 8; for (i=0, ch=0; i<pbytes; i++) { buf[i] = ch; ch = (in[i] << (8-shift_right)); buf[i] = buf[i] ^ (in[i] >> shift_right); } if ((err = mp_read_unsigned_bin(e, (unsigned char *)buf, pbytes)) != CRYPT_OK) { goto errnokey; } } /* make up a key and export the public copy */ do { if ((err = ecc_make_key_ex(prng, wprng, &pubkey, key->dp)) != CRYPT_OK) { goto errnokey; } /* find r = x1 mod n */ if ((err = mp_mod(pubkey.pubkey.x, p, r)) != CRYPT_OK) { goto error; } if (mp_iszero(r) == LTC_MP_YES) { ecc_free(&pubkey); } else { if ((err = rand_bn_upto(b, p, prng, wprng)) != CRYPT_OK) { goto error; } /* b = blinding value */ /* find s = (e + xr)/k */ if ((err = mp_mulmod(pubkey.k, b, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = kb */ if ((err = mp_invmod(pubkey.k, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = 1/kb */ if ((err = mp_mulmod(key->k, r, p, s)) != CRYPT_OK) { goto error; } /* s = xr */ if ((err = mp_mulmod(pubkey.k, s, p, s)) != CRYPT_OK) { goto error; } /* s = xr/kb */ if ((err = mp_mulmod(pubkey.k, e, p, e)) != CRYPT_OK) { goto error; } /* e = e/kb */ if ((err = mp_add(e, s, s)) != CRYPT_OK) { goto error; } /* s = e/kb + xr/kb */ if ((err = mp_mulmod(s, b, p, s)) != CRYPT_OK) { goto error; } /* s = b(e/kb + xr/kb) = (e + xr)/k */ ecc_free(&pubkey); if (mp_iszero(s) == LTC_MP_NO) { break; } } } while (--max_iterations > 0); if (max_iterations == 0) { goto errnokey; } if (sigformat == 1) { /* RFC7518 format */ if (*outlen < 2*pbytes) { err = CRYPT_MEM; goto errnokey; } zeromem(out, 2*pbytes); i = mp_unsigned_bin_size(r); if ((err = mp_to_unsigned_bin(r, out + (pbytes - i))) != CRYPT_OK) { goto errnokey; } i = mp_unsigned_bin_size(s); if ((err = mp_to_unsigned_bin(s, out + (2*pbytes - i))) != CRYPT_OK) { goto errnokey; } *outlen = 2*pbytes; err = CRYPT_OK; } else { /* store as ASN.1 SEQUENCE { r, s -- integer } */ err = der_encode_sequence_multi(out, outlen, LTC_ASN1_INTEGER, 1UL, r, LTC_ASN1_INTEGER, 1UL, s, LTC_ASN1_EOL, 0UL, NULL); } goto errnokey; error: ecc_free(&pubkey); errnokey: mp_clear_multi(r, s, p, e, b, NULL); return err; } /** Sign a message digest @param in The message digest to sign @param inlen The length of the digest @param out [out] The destination for the signature @param outlen [in/out] The max size and resulting size of the signature @param prng An active PRNG state @param wprng The index of the PRNG you wish to use @param key A private ECC key @return CRYPT_OK if successful */ int ecc_sign_hash(const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen, prng_state *prng, int wprng, ecc_key *key) { return _ecc_sign_hash(in, inlen, out, outlen, prng, wprng, key, 0); } /** Sign a message digest in RFC7518 format @param in The message digest to sign @param inlen The length of the digest @param out [out] The destination for the signature @param outlen [in/out] The max size and resulting size of the signature @param prng An active PRNG state @param wprng The index of the PRNG you wish to use @param key A private ECC key @return CRYPT_OK if successful */ int ecc_sign_hash_rfc7518(const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen, prng_state *prng, int wprng, ecc_key *key) { return _ecc_sign_hash(in, inlen, out, outlen, prng, wprng, key, 1); } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */