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ssh2userauth: be more careful about s->ki_scc being NULL.

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Coverity points out that we're inconsistent about checking it for
NULL: seat_stripctrl_new() *can* return NULL, so in principle, we can
go through the initialisation code for s->ki_scc and have it still be
NULL afterwards. I check that in the code that uses it to sanitise the
prompt strings out of USERAUTH_INFO_REQUEST, but not in the code that
sanitises the name or instruction strings. Now all uses are checked in
the same way.

This is only a latent bug, because the four main Seat implementations
(GUI and console, on Windows and Unix) never return NULL. The only
implementation of seat_stripctrl_new which _can_ return NULL is the
trivial nullseat_stripctrl_new, currently only used by Uppity.

However, of course, if that changes in future, this latent bug could
turn into a real one, so better to fix it before that happens. Thanks
Coverity.
This commit is contained in:
Simon Tatham 2019-07-23 18:51:59 +01:00
parent 8872a97ebd
commit 061ca8d844
1 changed files with 16 additions and 8 deletions
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24
ssh2userauth.c
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@ -1302,10 +1302,14 @@ static void ssh2_userauth_process_queue(PacketProtocolLayer *ppl)
sb = strbuf_new();
if (name.len) {
stripctrl_retarget(s->ki_scc, BinarySink_UPCAST(sb));
put_datapl(s->ki_scc, name);
stripctrl_retarget(s->ki_scc, NULL);
if (s->ki_scc) {
stripctrl_retarget(s->ki_scc,
BinarySink_UPCAST(sb));
put_datapl(s->ki_scc, name);
stripctrl_retarget(s->ki_scc, NULL);
} else {
put_datapl(sb, name);
}
s->cur_prompt->name_reqd = true;
} else {
put_datapl(sb, PTRLEN_LITERAL(
@ -1316,10 +1320,14 @@ static void ssh2_userauth_process_queue(PacketProtocolLayer *ppl)
sb = strbuf_new();
if (inst.len) {
stripctrl_retarget(s->ki_scc, BinarySink_UPCAST(sb));
put_datapl(s->ki_scc, inst);
stripctrl_retarget(s->ki_scc, NULL);
if (s->ki_scc) {
stripctrl_retarget(s->ki_scc,
BinarySink_UPCAST(sb));
put_datapl(s->ki_scc, inst);
stripctrl_retarget(s->ki_scc, NULL);
} else {
put_datapl(sb, inst);
}
s->cur_prompt->instr_reqd = true;
} else {
s->cur_prompt->instr_reqd = false;