Mercurial > dropbear
annotate fuzzer-kexdh.c @ 1715:3974f087d9c0
Disallow leading lines before the ident for server (#102)
Per RFC4253 4.2 clients must be able to process other lines of data
before the version string, server behavior is not defined neither
with MUST/SHOULD nor with MAY.
If server process up to 50 lines too - it may cause too long hanging
session with invalid/evil client that consume host resources and
potentially may lead to DDoS on poor embedded boxes.
Let's require first line from client to be version string and fail
early if it's not - matches both RFC and real OpenSSH behavior.
| author | Vladislav Grishenko <themiron@users.noreply.github.com> |
|---|---|
| date | Mon, 15 Jun 2020 18:22:18 +0500 |
| parents | a57822db3eac |
| 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 | |
| 9 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { | |
| 10 static int once = 0; | |
| 11 static struct key_context* keep_newkeys = NULL; | |
|
1601
b711a8256919
reduce fuzzer-kexdh params count again, still hitting timeout
Matt Johnston <matt@ucc.asn.au>
parents:
1595
diff
changeset
|
12 /* number of generated parameters is limited by the timeout for the first run. |
|
b711a8256919
reduce fuzzer-kexdh params count again, still hitting timeout
Matt Johnston <matt@ucc.asn.au>
parents:
1595
diff
changeset
|
13 TODO move this to the libfuzzer initialiser function instead if the timeout |
|
b711a8256919
reduce fuzzer-kexdh params count again, still hitting timeout
Matt Johnston <matt@ucc.asn.au>
parents:
1595
diff
changeset
|
14 doesn't apply there */ |
|
b711a8256919
reduce fuzzer-kexdh params count again, still hitting timeout
Matt Johnston <matt@ucc.asn.au>
parents:
1595
diff
changeset
|
15 #define NUM_PARAMS 20 |
| 1589 | 16 static struct kex_dh_param *dh_params[NUM_PARAMS]; |
| 17 | |
| 18 if (!once) { | |
| 19 fuzz_common_setup(); | |
| 20 fuzz_svr_setup(); | |
| 21 | |
| 22 keep_newkeys = (struct key_context*)m_malloc(sizeof(struct key_context)); | |
| 23 keep_newkeys->algo_kex = fuzz_get_algo(sshkex, "diffie-hellman-group14-sha256"); | |
| 24 keep_newkeys->algo_hostkey = DROPBEAR_SIGNKEY_ECDSA_NISTP256; | |
| 25 ses.newkeys = keep_newkeys; | |
| 26 | |
| 27 /* Pre-generate parameters */ | |
| 28 int i; | |
| 29 for (i = 0; i < NUM_PARAMS; i++) { | |
| 30 dh_params[i] = gen_kexdh_param(); | |
| 31 } | |
| 32 | |
| 33 once = 1; | |
| 34 } | |
| 35 | |
| 36 if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) { | |
| 37 return 0; | |
| 38 } | |
| 39 | |
| 40 m_malloc_set_epoch(1); | |
| 41 | |
| 42 if (setjmp(fuzz.jmp) == 0) { | |
| 43 /* Based on recv_msg_kexdh_init()/send_msg_kexdh_reply() | |
| 44 with DROPBEAR_KEX_NORMAL_DH */ | |
| 45 ses.newkeys = keep_newkeys; | |
| 46 | |
| 47 /* Choose from the collection of ecdh params */ | |
| 48 unsigned int e = buf_getint(fuzz.input); | |
| 49 struct kex_dh_param * dh_param = dh_params[e % NUM_PARAMS]; | |
| 50 | |
| 51 DEF_MP_INT(dh_e); | |
| 52 m_mp_init(&dh_e); | |
| 53 if (buf_getmpint(fuzz.input, &dh_e) != DROPBEAR_SUCCESS) { | |
| 54 dropbear_exit("Bad kex value"); | |
| 55 } | |
| 56 | |
|
1606
98d2b125eb89
kexhashbuf was much to small in kex fuzzers
Matt Johnston <matt@ucc.asn.au>
parents:
1601
diff
changeset
|
57 ses.kexhashbuf = buf_new(KEXHASHBUF_MAX_INTS); |
| 1589 | 58 kexdh_comb_key(dh_param, &dh_e, svr_opts.hostkey); |
| 59 | |
| 1609 | 60 mp_clear(ses.dh_K); |
| 1589 | 61 m_free(ses.dh_K); |
| 62 mp_clear(&dh_e); | |
| 63 | |
| 1609 | 64 buf_free(ses.hash); |
| 65 buf_free(ses.session_id); | |
| 66 /* kexhashbuf is freed in kexdh_comb_key */ | |
| 67 | |
| 1589 | 68 m_malloc_free_epoch(1, 0); |
| 69 } else { | |
| 70 m_malloc_free_epoch(1, 1); | |
| 71 TRACE(("dropbear_exit longjmped")) | |
| 72 /* dropbear_exit jumped here */ | |
| 73 } | |
| 74 | |
| 75 return 0; | |
| 76 } |