Mercurial > dropbear
annotate libtomcrypt/notes/tech0005.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> |
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date | Mon, 09 Jul 2018 16:27:53 +0200 |
parents | f849a5ca2efc |
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1 Tech Note 0005 |
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2 Minimizing Code Space |
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3 Tom St Denis |
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4 |
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5 Introduction |
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6 ------------ |
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8 Tweaking... |
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9 |
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10 You can disable whole classes of algorithms on the command line with the LTC_NO_* defines. From there you can manually turn on what you want to enable. |
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11 |
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12 The following build with GCC 3.4.4 on an AMD64 box gets you AES, CTR mode, SHA-256, HMAC, Yarrow, full RSA PKCS #1, PKCS #5 and ASN.1 DER in |
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13 roughly 40KB of code (49KB on the ARMv4) (both excluding the math library). |
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14 |
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15 CFLAGS="-DLTC_NO_CIPHERS -DLTC_NO_HASHES -DLTC_NO_PRNGS -DLTC_NO_MACS -DLTC_NO_MODES -DLTC_NO_PK -DLTC_RIJNDAEL -DLTC_CTR_MODE -DSHA256 \ |
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16 -DLTC_HMAC -DYARROW -DMRSA -DMPI -DTFM_DESC -DARGTYPE=3 -Os -DLTC_SMALL_CODE -fomit-frame-pointer" make IGNORE_SPEED=1 |
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18 Obviously this won't get you performance but if you need to pack a crypto lib in a device with limited means it's more than enough... |
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19 |
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20 Neato eh? |