Mercurial > dropbear
view libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.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 |
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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" /** @file pkcs_1_pss_decode.c PKCS #1 PSS Signature Padding, Tom St Denis */ #ifdef LTC_PKCS_1 /** PKCS #1 v2.00 PSS decode @param msghash The hash to verify @param msghashlen The length of the hash (octets) @param sig The signature data (encoded data) @param siglen The length of the signature data (octets) @param saltlen The length of the salt used (octets) @param hash_idx The index of the hash desired @param modulus_bitlen The bit length of the RSA modulus @param res [out] The result of the comparison, 1==valid, 0==invalid @return CRYPT_OK if successful (even if the comparison failed) */ int pkcs_1_pss_decode(const unsigned char *msghash, unsigned long msghashlen, const unsigned char *sig, unsigned long siglen, unsigned long saltlen, int hash_idx, unsigned long modulus_bitlen, int *res) { unsigned char *DB, *mask, *salt, *hash; unsigned long x, y, hLen, modulus_len; int err; hash_state md; LTC_ARGCHK(msghash != NULL); LTC_ARGCHK(res != NULL); /* default to invalid */ *res = 0; /* ensure hash is valid */ if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { return err; } hLen = hash_descriptor[hash_idx].hashsize; modulus_bitlen--; modulus_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0); /* check sizes */ if ((saltlen > modulus_len) || (modulus_len < hLen + saltlen + 2)) { return CRYPT_PK_INVALID_SIZE; } /* allocate ram for DB/mask/salt/hash of size modulus_len */ DB = XMALLOC(modulus_len); mask = XMALLOC(modulus_len); salt = XMALLOC(modulus_len); hash = XMALLOC(modulus_len); if (DB == NULL || mask == NULL || salt == NULL || hash == NULL) { if (DB != NULL) { XFREE(DB); } if (mask != NULL) { XFREE(mask); } if (salt != NULL) { XFREE(salt); } if (hash != NULL) { XFREE(hash); } return CRYPT_MEM; } /* ensure the 0xBC byte */ if (sig[siglen-1] != 0xBC) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* copy out the DB */ x = 0; XMEMCPY(DB, sig + x, modulus_len - hLen - 1); x += modulus_len - hLen - 1; /* copy out the hash */ XMEMCPY(hash, sig + x, hLen); /* x += hLen; */ /* check the MSB */ if ((sig[0] & ~(0xFF >> ((modulus_len<<3) - (modulus_bitlen)))) != 0) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* generate mask of length modulus_len - hLen - 1 from hash */ if ((err = pkcs_1_mgf1(hash_idx, hash, hLen, mask, modulus_len - hLen - 1)) != CRYPT_OK) { goto LBL_ERR; } /* xor against DB */ for (y = 0; y < (modulus_len - hLen - 1); y++) { DB[y] ^= mask[y]; } /* now clear the first byte [make sure smaller than modulus] */ DB[0] &= 0xFF >> ((modulus_len<<3) - (modulus_bitlen)); /* DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */ /* check for zeroes and 0x01 */ for (x = 0; x < modulus_len - saltlen - hLen - 2; x++) { if (DB[x] != 0x00) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } } /* check for the 0x01 */ if (DB[x++] != 0x01) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* M = (eight) 0x00 || msghash || salt, mask = H(M) */ if ((err = hash_descriptor[hash_idx].init(&md)) != CRYPT_OK) { goto LBL_ERR; } zeromem(mask, 8); if ((err = hash_descriptor[hash_idx].process(&md, mask, 8)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].process(&md, DB+x, saltlen)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].done(&md, mask)) != CRYPT_OK) { goto LBL_ERR; } /* mask == hash means valid signature */ if (XMEM_NEQ(mask, hash, hLen) == 0) { *res = 1; } err = CRYPT_OK; LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(DB, modulus_len); zeromem(mask, modulus_len); zeromem(salt, modulus_len); zeromem(hash, modulus_len); #endif XFREE(hash); XFREE(salt); XFREE(mask); XFREE(DB); return err; } #endif /* LTC_PKCS_1 */ /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */