laforge has submitted this change. ( https://gerrit.osmocom.org/c/onomondo-eim/+/43177?usp=email )

Change subject: SGP32Definitions: add JSON specific variant of SGP32-CancelSessionResponse ......................................................................

SGP32Definitions: add JSON specific variant of SGP32-CancelSessionResponse

When the CancelSessionResponse is referenced in CancelSessionRequestEsipa, there is not context specific tag set. It is not entirely clear if this is a bug in the ASN.1 specification or if it is by a deliberate design choice. Nevertheless, most ASN.1 compilers (asn1c, TTCN3 asn1_compiler) will not apply the context specific tag. Which means that the CancelSessionResponse will be tagged with 0xA1 (1) instead 0xBF41 (65).

Example (asn1c/asn1_compiler): $ ./contrib/unber.py --hex BF41248003ABCDEFA11DA01B30118003ABCDEF8107678112010201018201055F37051234567890 bf41 l=36 80 l=3 abcdef a1 l=29 a0 l=27 30 l=17 80 l=3 abcdef 81 l=7 67811201020101 82 l=1 05 5f37 l=5 1234567890

However, Erlang's asn1ct compiler behaves differently. It will apply the application specific tag from the SGP32-CancelSessionResponse as context specific tag. Which means it will expect to see 0xBF41 (65) and not 0xA1 (1) when decoding the ASN.1 object.

The problem was known before and has been fixed by removing the tag from the SGP32-CancelSessionResponse definition. Unfortunately this workaround is only valid for the ASN.1 ESipa bindings because when building the JSON structs for the JSON ESipa bindings we have to access SGP32-CancelSessionResponse directly. And since the type definition has normally has the application secific tag. The decoder on the other end will expect to mee a 0xBF41 tag at the beginning of the encoded string.

This eventually means that we have to introduce a tagged variant of SGP32-CancelSessionResponse that we will use for the JSON encoding.

Change-Id: I566571778d2433bd87a46276e81d9d526ae97325 Related: SYS#8100 --- M asn1/SGP32Definitions.asn1 M src/esipa_json_handler.erl 2 files changed, 8 insertions(+), 1 deletion(-)

Approvals: Jenkins Builder: Verified jolly: Looks good to me, but someone else must approve laforge: Looks good to me, approved

diff --git a/asn1/SGP32Definitions.asn1 b/asn1/SGP32Definitions.asn1 index 5bae2c7..4fbb495 100644 --- a/asn1/SGP32Definitions.asn1 +++ b/asn1/SGP32Definitions.asn1 @@ -701,6 +701,13 @@ cancelSessionResponseError INTEGER {invalidTransactionId(5), undefinedError(127)}, compactCancelSessionResponseOk CompactCancelSessionResponseOk } +-- workaround for erlang asn1ct: add a JSON specific variant of the SGP32-CancelSessionResponse to ensure application specific tag [65] +SGP32-JSON-CancelSessionResponse ::= [65] CHOICE { -- Tag 'BF41' + cancelSessionResponseOk CancelSessionResponseOk, + cancelSessionResponseError INTEGER {invalidTransactionId(5), undefinedError(127)}, + compactCancelSessionResponseOk CompactCancelSessionResponseOk +} + CompactCancelSessionResponseOk ::= SEQUENCE { compactEuiccCancelSessionSigned CompactEuiccCancelSessionSigned, -- Compact version of euiccCancelSessionSigned euiccCancelSessionSignature [APPLICATION 55] OCTET STRING -- tag 5F37 signature on euiccCancelSessionSigned diff --git a/src/esipa_json_handler.erl b/src/esipa_json_handler.erl index a0911b5..f5fc3e3 100644 --- a/src/esipa_json_handler.erl +++ b/src/esipa_json_handler.erl @@ -390,7 +390,7 @@ {cancelSessionResponse, from_base64asn1( 'SGP32Definitions', - 'SGP32-CancelSessionResponse', + 'SGP32-JSON-CancelSessionResponse', maps:get(<<"cancelSessionResponse">>, EsipaReq) )} ]),