Wireshark mailing list archives
Re: dissect_per_constrained_integer() with
From: "Pavel Strnad" <strnadp () tiscali cz>
Date: Thu, 22 Dec 2016 17:20:01 +0100
Hi Pascal, Thank You for fast response and clear comments. Would it make sense to implement extra dissect_per_semi_constrained_integer? I can try to implement dissect_per_semi_constrained_integer (tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 min, guint32 max, guint32 *value, gboolean has_extension, gboolean lb_infinite). Extra parameter will allow us to distinguish both cases where either min(lb_infinite=TRUE) or max(lb_infinite=FALSE) is set to NO_BOUND? I can do the same for 64b version. Afterwards I will need to update asn2wrs accordingly to have this issue fixed. This will not sort out the case of direct callers to dissect_per_constrained_integer. What do You think? Best Regards, Pavel ----------------------------------------------------------------------- Date: Wed, 21 Dec 2016 16:07:02 +0100 From: Pascal Quantin <pascal.quantin () gmail com> To: Developer support list for Wireshark <wireshark-dev () wireshark org> Subject: Re: [Wireshark-dev] dissect_per_constrained_integer() with no_bound (MAX in ASN.1) Message-ID: <CAGka-82MWxYv2aj0WJRL_p9ooEmBRpo7_sAH7KTpHc6C0vCFYA () mail gmail com> Content-Type: text/plain; charset="utf-8" Hi Pavel, 2016-12-21 15:37 GMT+01:00 Pavel Strnad <strnadp () tiscali cz>:
Hello, I am trying to understand the difference in usage of NO_BOUND or UINT_MAX in the place of max parameter in dissect_per_constrained_integer() function. In my case aligned PER
variant.
From packet-per.h: #define NO_BOUND -1 guint32 dissect_per_constrained_integer(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 min, guint32 max, guint32 *value, gboolean has_extension); Based on that it looks like that there is no different dissection of following two asn.1 definitions?
Correct, semi-constrained integer does not seem to be managed properly. This matches the comment found in line 1283.
1) seconds INTEGER (0..4294967295) 2) seconds INTEGER (0..MAX) where MAX translates to NO_BOUND=4294967295 using asn2wrs Reading X.691 (aligned PER) wireshark seems to dissect well the 1st case that is using size constraint but not the 2nd case where semi-constraint size is used and the length determinant should include padding bits in the case of aligned PER. I would like to try to fix it myself but will need some hint how to differentiate these two cases and keep API unchanged?
IMHO you can't without changing the API. Maybe we would need to extra booleans indicating whether the min and / or max values are bounded or not, and adapt asn2wrs generator accordingly. This way we could drop the NO_BOUND define Note that this sounds like a non trivial project because: - as indicated in the comments, dissect_per_constrained_integer only handle 32 bits integers and dissect_per_constrained_integer_64b only handles 64 bits integers, so both needs to be adapted - MIN or MAX parameters do not seem properly handled in other types also, and any change done in dissect_per_constrained_integer(_64b) needs to be reflected in the caller functions and any other making use of NO_BOUND Regards, Pascal. ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev () wireshark org> Archives: https://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-request () wireshark org?subject=unsubscribe
Current thread:
- Re: dissect_per_constrained_integer() with Pavel Strnad (Dec 22)
- Re: dissect_per_constrained_integer() with Pascal Quantin (Dec 22)