Mercurial > dropbear
annotate fuzz/fuzzer-verify.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 | d5680e12ac33 |
| children |
| rev | line source |
|---|---|
| 1380 | 1 #include "fuzz.h" |
| 2 #include "session.h" | |
| 3 #include "fuzz-wrapfd.h" | |
| 4 #include "debug.h" | |
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5 #include "dss.h" |
| 1380 | 6 |
| 7 static void setup_fuzzer(void) { | |
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8 fuzz_common_setup(); |
| 1380 | 9 } |
| 10 | |
| 11 static buffer *verifydata; | |
| 12 | |
| 13 /* Tests reading a public key and verifying a signature */ | |
| 14 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { | |
| 15 static int once = 0; | |
| 16 if (!once) { | |
| 17 setup_fuzzer(); | |
| 18 verifydata = buf_new(30); | |
| 19 buf_putstring(verifydata, "x", 1); | |
| 20 once = 1; | |
| 21 } | |
| 22 | |
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23 if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) { |
| 1380 | 24 return 0; |
| 25 } | |
| 26 | |
| 27 m_malloc_set_epoch(1); | |
| 28 | |
| 29 if (setjmp(fuzz.jmp) == 0) { | |
| 30 sign_key *key = new_sign_key(); | |
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31 enum signkey_type keytype = DROPBEAR_SIGNKEY_ANY; |
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32 if (buf_get_pub_key(fuzz.input, key, &keytype) == DROPBEAR_SUCCESS) { |
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33 enum signature_type sigtype; |
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34 if (keytype == DROPBEAR_SIGNKEY_RSA) { |
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35 /* Flip a coin to decide rsa signature type */ |
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36 int flag = buf_getbyte(fuzz.input); |
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37 if (flag & 0x01) { |
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38 sigtype = DROPBEAR_SIGNATURE_RSA_SHA256; |
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39 } else { |
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40 sigtype = DROPBEAR_SIGNATURE_RSA_SHA1; |
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41 } |
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42 } else { |
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43 sigtype = signature_type_from_signkey(keytype); |
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44 } |
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45 if (buf_verify(fuzz.input, key, sigtype, verifydata) == DROPBEAR_SUCCESS) { |
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46 /* The fuzzer is capable of generating keys with a signature to match. |
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47 We don't want false positives if the key is bogus, since a client/server |
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48 wouldn't be trusting a bogus key anyway */ |
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49 int boguskey = 0; |
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50 |
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51 if (keytype == DROPBEAR_SIGNKEY_DSS) { |
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52 /* So far have seen dss keys with bad p/q/g domain parameters */ |
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53 int pprime, qprime, trials; |
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54 trials = mp_prime_rabin_miller_trials(mp_count_bits(key->dsskey->p)); |
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55 assert(mp_prime_is_prime(key->dsskey->p, trials, &pprime) == MP_OKAY); |
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56 trials = mp_prime_rabin_miller_trials(mp_count_bits(key->dsskey->q)); |
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57 assert(mp_prime_is_prime(key->dsskey->q, trials, &qprime) == MP_OKAY); |
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58 boguskey = !(pprime && qprime); |
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59 /* Could also check g**q mod p == 1 */ |
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60 } |
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61 |
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62 if (!boguskey) { |
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63 printf("Random key/signature managed to verify!\n"); |
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64 abort(); |
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65 } |
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66 |
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67 |
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68 } |
| 1380 | 69 } |
| 70 sign_key_free(key); | |
| 71 m_malloc_free_epoch(1, 0); | |
| 72 } else { | |
| 73 m_malloc_free_epoch(1, 1); | |
| 74 TRACE(("dropbear_exit longjmped")) | |
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75 /* dropbear_exit jumped here */ |
| 1380 | 76 } |
| 77 | |
| 78 return 0; | |
| 79 } |