Mercurial > dropbear
view libtomcrypt/src/encauth/ocb/ocb_init.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. */ /** @file ocb_init.c OCB implementation, initialize state, by Tom St Denis */ #include "tomcrypt.h" #ifdef LTC_OCB_MODE static const struct { int len; unsigned char poly_div[MAXBLOCKSIZE], poly_mul[MAXBLOCKSIZE]; } polys[] = { { 8, { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D }, { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B } }, { 16, { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43 }, { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 } } }; /** Initialize an OCB context. @param ocb [out] The destination of the OCB state @param cipher The index of the desired cipher @param key The secret key @param keylen The length of the secret key (octets) @param nonce The session nonce (length of the block size of the cipher) @return CRYPT_OK if successful */ int ocb_init(ocb_state *ocb, int cipher, const unsigned char *key, unsigned long keylen, const unsigned char *nonce) { int poly, x, y, m, err; LTC_ARGCHK(ocb != NULL); LTC_ARGCHK(key != NULL); LTC_ARGCHK(nonce != NULL); /* valid cipher? */ if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { return err; } /* determine which polys to use */ ocb->block_len = cipher_descriptor[cipher].block_length; x = (int)(sizeof(polys)/sizeof(polys[0])); for (poly = 0; poly < x; poly++) { if (polys[poly].len == ocb->block_len) { break; } } if (poly == x) { return CRYPT_INVALID_ARG; /* block_len not found in polys */ } if (polys[poly].len != ocb->block_len) { return CRYPT_INVALID_ARG; } /* schedule the key */ if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) { return err; } /* find L = E[0] */ zeromem(ocb->L, ocb->block_len); if ((err = cipher_descriptor[cipher].ecb_encrypt(ocb->L, ocb->L, &ocb->key)) != CRYPT_OK) { return err; } /* find R = E[N xor L] */ for (x = 0; x < ocb->block_len; x++) { ocb->R[x] = ocb->L[x] ^ nonce[x]; } if ((err = cipher_descriptor[cipher].ecb_encrypt(ocb->R, ocb->R, &ocb->key)) != CRYPT_OK) { return err; } /* find Ls[i] = L << i for i == 0..31 */ XMEMCPY(ocb->Ls[0], ocb->L, ocb->block_len); for (x = 1; x < 32; x++) { m = ocb->Ls[x-1][0] >> 7; for (y = 0; y < ocb->block_len-1; y++) { ocb->Ls[x][y] = ((ocb->Ls[x-1][y] << 1) | (ocb->Ls[x-1][y+1] >> 7)) & 255; } ocb->Ls[x][ocb->block_len-1] = (ocb->Ls[x-1][ocb->block_len-1] << 1) & 255; if (m == 1) { for (y = 0; y < ocb->block_len; y++) { ocb->Ls[x][y] ^= polys[poly].poly_mul[y]; } } } /* find Lr = L / x */ m = ocb->L[ocb->block_len-1] & 1; /* shift right */ for (x = ocb->block_len - 1; x > 0; x--) { ocb->Lr[x] = ((ocb->L[x] >> 1) | (ocb->L[x-1] << 7)) & 255; } ocb->Lr[0] = ocb->L[0] >> 1; if (m == 1) { for (x = 0; x < ocb->block_len; x++) { ocb->Lr[x] ^= polys[poly].poly_div[x]; } } /* set Li, checksum */ zeromem(ocb->Li, ocb->block_len); zeromem(ocb->checksum, ocb->block_len); /* set other params */ ocb->block_index = 1; ocb->cipher = cipher; return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */