Mercurial > dropbear
view libtomcrypt/src/pk/dsa/dsa_verify_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 | 6dba84798cd5 |
children |
line wrap: on
line source
/* 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" /** @file dsa_verify_hash.c DSA implementation, verify a signature, Tom St Denis */ #ifdef LTC_MDSA /** Verify a DSA signature @param r DSA "r" parameter @param s DSA "s" parameter @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DSA key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash_raw( void *r, void *s, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { void *w, *v, *u1, *u2; int err; LTC_ARGCHK(r != NULL); LTC_ARGCHK(s != NULL); LTC_ARGCHK(stat != NULL); LTC_ARGCHK(key != NULL); /* default to invalid signature */ *stat = 0; /* init our variables */ if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != CRYPT_OK) { return err; } /* neither r or s can be null or >q*/ if (mp_cmp_d(r, 0) != LTC_MP_GT || mp_cmp_d(s, 0) != LTC_MP_GT || mp_cmp(r, key->q) != LTC_MP_LT || mp_cmp(s, key->q) != LTC_MP_LT) { err = CRYPT_INVALID_PACKET; goto error; } /* FIPS 186-4 4.7: use leftmost min(bitlen(q), bitlen(hash)) bits of 'hash' */ hashlen = MIN(hashlen, (unsigned long)(key->qord)); /* w = 1/s mod q */ if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; } /* u1 = m * w mod q */ if ((err = mp_read_unsigned_bin(u1, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, w, key->q, u1)) != CRYPT_OK) { goto error; } /* u2 = r*w mod q */ if ((err = mp_mulmod(r, w, key->q, u2)) != CRYPT_OK) { goto error; } /* v = g^u1 * y^u2 mod p mod q */ if ((err = mp_exptmod(key->g, u1, key->p, u1)) != CRYPT_OK) { goto error; } if ((err = mp_exptmod(key->y, u2, key->p, u2)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, u2, key->p, v)) != CRYPT_OK) { goto error; } if ((err = mp_mod(v, key->q, v)) != CRYPT_OK) { goto error; } /* if r = v then we're set */ if (mp_cmp(r, v) == LTC_MP_EQ) { *stat = 1; } err = CRYPT_OK; error: mp_clear_multi(w, v, u1, u2, NULL); return err; } /** Verify a DSA signature @param sig The signature @param siglen The length of the signature (octets) @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DSA key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash(const unsigned char *sig, unsigned long siglen, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { int err; void *r, *s; ltc_asn1_list sig_seq[2]; unsigned long reallen = 0; LTC_ARGCHK(stat != NULL); *stat = 0; /* must be set before the first return */ if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) { return err; } LTC_SET_ASN1(sig_seq, 0, LTC_ASN1_INTEGER, r, 1UL); LTC_SET_ASN1(sig_seq, 1, LTC_ASN1_INTEGER, s, 1UL); err = der_decode_sequence(sig, siglen, sig_seq, 2); if (err != CRYPT_OK) { goto LBL_ERR; } err = der_length_sequence(sig_seq, 2, &reallen); if (err != CRYPT_OK || reallen != siglen) { goto LBL_ERR; } /* do the op */ err = dsa_verify_hash_raw(r, s, hash, hashlen, stat, key); LBL_ERR: mp_clear_multi(r, s, NULL); return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */