Mercurial > dropbear
view libtomcrypt/notes/tech0006.txt @ 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 | 1b9e69c058d2 |
children |
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Tech Note 0006 PK Standards Compliance Tom St Denis RSA ---- PKCS #1 compliance. Key Format: RSAPublicKey and RSAPrivateKey as per PKCS #1 v2.1 Encryption: OAEP as per PKCS #1 Signature : PSS as per PKCS #1 DSA ---- The NIST DSA algorithm Key Format: HomeBrew [see below] Signature : ANSI X9.62 format [see below]. Keys are stored as DSAPublicKey ::= SEQUENCE { publicFlags BIT STRING(1), -- must be 0 g INTEGER , -- base generator, check that g^q mod p == 1 -- and that 1 < g < p - 1 p INTEGER , -- prime modulus q INTEGER , -- order of sub-group (must be prime) y INTEGER , -- public key, specifically, g^x mod p, -- check that y^q mod p == 1 -- and that 1 < y < p - 1 } DSAPrivateKey ::= SEQUENCE { publicFlags BIT STRING(1), -- must be 1 g INTEGER , -- base generator, check that g^q mod p == 1 -- and that 1 < g < p - 1 p INTEGER , -- prime modulus q INTEGER , -- order of sub-group (must be prime) y INTEGER , -- public key, specifically, g^x mod p, -- check that y^q mod p == 1 -- and that 1 < y < p - 1 x INTEGER -- private key } Signatures are stored as DSASignature ::= SEQUENCE { r, s INTEGER -- signature parameters } ECC ---- The ANSI X9.62 and X9.63 algorithms [partial]. Supports all NIST GF(p) curves. Key Format : Homebrew [see below, only GF(p) NIST curves supported] Signature : X9.62 compliant Encryption : Homebrew [based on X9.63, differs in that the public point is stored as an ECCPublicKey] Shared Secret: X9.63 compliant ECCPublicKey ::= SEQUENCE { flags BIT STRING(1), -- public/private flag (always zero), keySize INTEGER, -- Curve size (in bits) divided by eight -- and rounded down, e.g. 521 => 65 pubkey.x INTEGER, -- The X co-ordinate of the public key point pubkey.y INTEGER, -- The Y co-ordinate of the public key point } ECCPrivateKey ::= SEQUENCE { flags BIT STRING(1), -- public/private flag (always one), keySize INTEGER, -- Curve size (in bits) divided by eight -- and rounded down, e.g. 521 => 65 pubkey.x INTEGER, -- The X co-ordinate of the public key point pubkey.y INTEGER, -- The Y co-ordinate of the public key point secret.k INTEGER, -- The secret key scalar } The encryption works by finding the X9.63 shared secret and hashing it. The hash is then simply XOR'ed against the message [which must be at most the size of the hash digest]. The format of the encrypted text is as follows ECCEncrypted ::= SEQUENCE { hashOID OBJECT IDENTIFIER, -- The OID of the hash used pubkey OCTET STRING , -- Encapsulation of a random ECCPublicKey skey OCTET STRING -- The encrypted text (which the hash was XOR'ed against) } % $Source: /cvs/libtom/libtomcrypt/notes/tech0006.txt,v $ % $Revision: 1.2 $ % $Date: 2005/06/18 02:26:27 $