Mercurial > dropbear
annotate fuzz/fuzzer-kexdh.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 | 0cc85b4a4abb |
| children |
| rev | line source |
|---|---|
| 1589 | 1 #include "fuzz.h" |
| 2 #include "session.h" | |
| 3 #include "fuzz-wrapfd.h" | |
| 4 #include "debug.h" | |
| 5 #include "runopts.h" | |
| 6 #include "algo.h" | |
| 7 #include "bignum.h" | |
| 8 | |
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9 static struct key_context* keep_newkeys = NULL; |
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10 #define NUM_PARAMS 80 |
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11 static struct kex_dh_param *dh_params[NUM_PARAMS]; |
| 1589 | 12 |
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13 static void setup() __attribute__((constructor)); |
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14 // Perform initial setup here to avoid hitting timeouts on first run |
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15 static void setup() { |
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16 fuzz_common_setup(); |
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17 fuzz_svr_setup(); |
| 1589 | 18 |
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19 keep_newkeys = (struct key_context*)m_malloc(sizeof(struct key_context)); |
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20 keep_newkeys->algo_kex = fuzz_get_algo(sshkex, "diffie-hellman-group14-sha256"); |
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21 keep_newkeys->algo_hostkey = DROPBEAR_SIGNKEY_ECDSA_NISTP256; |
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22 ses.newkeys = keep_newkeys; |
| 1589 | 23 |
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24 /* Pre-generate parameters */ |
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25 int i; |
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26 for (i = 0; i < NUM_PARAMS; i++) { |
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27 dh_params[i] = gen_kexdh_param(); |
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28 } |
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29 } |
| 1589 | 30 |
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31 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { |
| 1589 | 32 if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) { |
| 33 return 0; | |
| 34 } | |
| 35 | |
| 36 m_malloc_set_epoch(1); | |
| 37 | |
| 38 if (setjmp(fuzz.jmp) == 0) { | |
| 39 /* Based on recv_msg_kexdh_init()/send_msg_kexdh_reply() | |
| 40 with DROPBEAR_KEX_NORMAL_DH */ | |
| 41 ses.newkeys = keep_newkeys; | |
| 42 | |
| 43 /* Choose from the collection of ecdh params */ | |
| 44 unsigned int e = buf_getint(fuzz.input); | |
| 45 struct kex_dh_param * dh_param = dh_params[e % NUM_PARAMS]; | |
| 46 | |
| 47 DEF_MP_INT(dh_e); | |
| 48 m_mp_init(&dh_e); | |
| 49 if (buf_getmpint(fuzz.input, &dh_e) != DROPBEAR_SUCCESS) { | |
| 50 dropbear_exit("Bad kex value"); | |
| 51 } | |
| 52 | |
|
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53 ses.kexhashbuf = buf_new(KEXHASHBUF_MAX_INTS); |
| 1589 | 54 kexdh_comb_key(dh_param, &dh_e, svr_opts.hostkey); |
| 55 | |
| 1609 | 56 mp_clear(ses.dh_K); |
| 1589 | 57 m_free(ses.dh_K); |
| 58 mp_clear(&dh_e); | |
| 59 | |
| 1609 | 60 buf_free(ses.hash); |
| 61 buf_free(ses.session_id); | |
| 62 /* kexhashbuf is freed in kexdh_comb_key */ | |
| 63 | |
| 1589 | 64 m_malloc_free_epoch(1, 0); |
| 65 } else { | |
| 66 m_malloc_free_epoch(1, 1); | |
| 67 TRACE(("dropbear_exit longjmped")) | |
| 68 /* dropbear_exit jumped here */ | |
| 69 } | |
| 70 | |
| 71 return 0; | |
| 72 } |