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Hugo Vasconcelos Saldanha
c580b62cb2
Refer to: http://www.libssh2.org/adv_20150311.html Signed-off-by: Hugo Vasconcelos Saldanha <hugo.saldanha@aker.com.br> Signed-off-by: Armin Kuster <akuster808@gmail.com>
116 lines
3.9 KiB
Diff
116 lines
3.9 KiB
Diff
From c7f66cca285033da9b8c9de8eceff52d7b3c3ef3 Mon Sep 17 00:00:00 2001
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From: Mariusz Ziulek <mzet@owasp.org>
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Date: Sat, 21 Feb 2015 23:31:36 +0100
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Subject: [PATCH] kex: bail out on rubbish in the incoming packet
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Upstream-Status: Backport
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Signed-off-by: Hugo Vasconcelos Saldanha <hugo.saldanha@aker.com.br>
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---
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src/kex.c | 73 +++++++++++++++++++++++++++++++++++----------------------------
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1 file changed, 41 insertions(+), 32 deletions(-)
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diff --git a/src/kex.c b/src/kex.c
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index fa4c4e1..ad7498a 100644
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--- a/src/kex.c
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+++ b/src/kex.c
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@@ -1547,10 +1547,34 @@ static int kex_agree_comp(LIBSSH2_SESSION *session,
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/* TODO: When in server mode we need to turn this logic on its head
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* The Client gets to make the final call on "agreed methods"
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*/
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+/*
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+ * kex_string_pair() extracts a string from the packet and makes sure it fits
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+ * within the given packet.
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+ */
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+static int kex_string_pair(unsigned char **sp, /* parsing position */
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+ unsigned char *data, /* start pointer to packet */
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+ size_t data_len, /* size of total packet */
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+ size_t *lenp, /* length of the string */
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+ unsigned char **strp) /* pointer to string start */
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+{
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+ unsigned char *s = *sp;
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+ *lenp = _libssh2_ntohu32(s);
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+
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+ /* the length of the string must fit within the current pointer and the
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+ end of the packet */
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+ if (*lenp > (data_len - (s - data) -4))
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+ return 1;
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+ *strp = s + 4;
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+ s += 4 + *lenp;
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+
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+ *sp = s;
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+ return 0;
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+}
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+
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/* kex_agree_methods
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* Decide which specific method to use of the methods offered by each party
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*/
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static int kex_agree_methods(LIBSSH2_SESSION * session, unsigned char *data,
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unsigned data_len)
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@@ -1566,42 +1590,27 @@ static int kex_agree_methods(LIBSSH2_SESSION * session, unsigned char *data,
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/* Skip cookie, don't worry, it's preserved in the kexinit field */
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s += 16;
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/* Locate each string */
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- kex_len = _libssh2_ntohu32(s);
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- kex = s + 4;
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- s += 4 + kex_len;
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- hostkey_len = _libssh2_ntohu32(s);
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- hostkey = s + 4;
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- s += 4 + hostkey_len;
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- crypt_cs_len = _libssh2_ntohu32(s);
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- crypt_cs = s + 4;
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- s += 4 + crypt_cs_len;
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- crypt_sc_len = _libssh2_ntohu32(s);
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- crypt_sc = s + 4;
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- s += 4 + crypt_sc_len;
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- mac_cs_len = _libssh2_ntohu32(s);
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- mac_cs = s + 4;
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- s += 4 + mac_cs_len;
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- mac_sc_len = _libssh2_ntohu32(s);
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- mac_sc = s + 4;
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- s += 4 + mac_sc_len;
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- comp_cs_len = _libssh2_ntohu32(s);
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- comp_cs = s + 4;
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- s += 4 + comp_cs_len;
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- comp_sc_len = _libssh2_ntohu32(s);
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- comp_sc = s + 4;
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-#if 0
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- s += 4 + comp_sc_len;
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- lang_cs_len = _libssh2_ntohu32(s);
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- lang_cs = s + 4;
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- s += 4 + lang_cs_len;
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- lang_sc_len = _libssh2_ntohu32(s);
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- lang_sc = s + 4;
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- s += 4 + lang_sc_len;
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-#endif
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+ if(kex_string_pair(&s, data, data_len, &kex_len, &kex))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &hostkey_len, &hostkey))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &crypt_cs_len, &crypt_cs))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &crypt_sc_len, &crypt_sc))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &mac_cs_len, &mac_cs))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &mac_sc_len, &mac_sc))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &comp_cs_len, &comp_cs))
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+ return -1;
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+ if(kex_string_pair(&s, data, data_len, &comp_sc_len, &comp_sc))
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+ return -1;
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+
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/* If the server sent an optimistic packet, assume that it guessed wrong.
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* If the guess is determined to be right (by kex_agree_kex_hostkey)
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* This flag will be reset to zero so that it's not ignored */
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session->burn_optimistic_kexinit = *(s++);
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/* Next uint32 in packet is all zeros (reserved) */
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--
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2.1.4
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