From 37daeb220e461b842ad9708497699f15c5fa5df3 Mon Sep 17 00:00:00 2001 From: Isaac Boukris Date: Thu, 3 Oct 2019 13:09:29 +0300 Subject: spnego: ignore server mech_types list We should not use the mech list sent by the server in the last 'negotiate' packet in CIFS protocol, as it is not protected and may be subject to downgrade attacks. BUG: https://bugzilla.samba.org/show_bug.cgi?id=14106 Signed-off-by: Isaac Boukris Reviewed-by: Andreas Schneider Reviewed-by: Andrew Bartlett Reviewed-by: Stefan Metzmacher --- auth/gensec/spnego.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-) (limited to 'auth') diff --git a/auth/gensec/spnego.c b/auth/gensec/spnego.c index 565d5a975bf..c4b7efbed76 100644 --- a/auth/gensec/spnego.c +++ b/auth/gensec/spnego.c @@ -511,7 +511,11 @@ static NTSTATUS gensec_spnego_client_negTokenInit_start( } n->mech_idx = 0; - n->mech_types = spnego_in->negTokenInit.mechTypes; + + /* Do not use server mech list as it isn't protected. Instead, get all + * supported mechs (excluding SPNEGO). */ + n->mech_types = gensec_security_oids(gensec_security, n, + GENSEC_OID_SPNEGO); if (n->mech_types == NULL) { return NT_STATUS_INVALID_PARAMETER; } @@ -658,13 +662,30 @@ static NTSTATUS gensec_spnego_client_negTokenInit_finish( DATA_BLOB *out) { struct spnego_data spnego_out; - const char *my_mechs[] = {NULL, NULL}; + const char * const *mech_types = NULL; bool ok; - my_mechs[0] = spnego_state->neg_oid; + if (n->mech_types == NULL) { + DBG_WARNING("No mech_types list\n"); + return NT_STATUS_INVALID_PARAMETER; + } + + for (mech_types = n->mech_types; *mech_types != NULL; mech_types++) { + int cmp = strcmp(*mech_types, spnego_state->neg_oid); + + if (cmp == 0) { + break; + } + } + + if (*mech_types == NULL) { + DBG_ERR("Can't find selected sub mechanism in mech_types\n"); + return NT_STATUS_INVALID_PARAMETER; + } + /* compose reply */ spnego_out.type = SPNEGO_NEG_TOKEN_INIT; - spnego_out.negTokenInit.mechTypes = my_mechs; + spnego_out.negTokenInit.mechTypes = mech_types; spnego_out.negTokenInit.reqFlags = data_blob_null; spnego_out.negTokenInit.reqFlagsPadding = 0; spnego_out.negTokenInit.mechListMIC = data_blob_null; @@ -676,7 +697,7 @@ static NTSTATUS gensec_spnego_client_negTokenInit_finish( } ok = spnego_write_mech_types(spnego_state, - my_mechs, + mech_types, &spnego_state->mech_types); if (!ok) { DBG_ERR("failed to write mechTypes\n"); -- cgit v1.2.1