Change in pysim[master]: Fixed reading of MSISDN parameter

[herlesupreeth]

herlesupreeth has posted comments on this change. ( https://gerrit.osmocom.org/c/pysim/+/16947 )

Change subject: Fixed reading of MSISDN parameter
......................................................................


Patch Set 6:

> Patch Set 6:
> 
> > Patch Set 6:
> > 
> > > P.S: I have verified the MSISDN programmed on the SIM represented in the same way as it was programmed
> > 
> > Sorry, i swallowed some of my words :P. I meant, I verified the MSISDN number programmed on the SIM by putting it in a UE and it represented in the same way as it was programmed
> 
> Ok, thanks for explanation. I also checked the specs, and here is what I propose:
> 
>   # Make sure mandatory fields are present
>   if len(res) < 14:
>     raise ValueError("EF-MSISDN length is too short")
> 
>   # Skip optional Alpha Identifier
>   xlen = len(res) - 14
>   msisdn_lhv = res[xlen:][:12]
> 
>   # Parse the length (in bytes) of BCD encoded number
>   # FIXME: it seems the length of ToN/NPI is also included
>   bcd_len = int(msisdn_lhv[0])
>   if bcd_len > 11: # "This means that the maximum value is 11"
>     raise ValueError("EF-MSISDN contains odd BCD length")
> 
>   # Parse ToN / NPI
>   ton = (int(msisdn_lhv[1]) >> 4) & 0x07
>   npi = int(msisdn_lhv[1]) & 0x0f
>   bcd_len -= 1
> 
>   # Parse MSISDN
>   msisdn = swap_nibbles(msisdn_lhv[2:][:bcd_len]).rstrip('f')
> 
> I did not test this code though...

len(res) gives (number of bytes * 2) and the value 14 is in bytes hence,

xlen = len(res) - 14 must be as follows

xlen = len(res)/2 - 14


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Gerrit-Project: pysim
Gerrit-Branch: master
Gerrit-Change-Id: Ie914ae83d787e3f1a90f9f305bffd45053b8c863
Gerrit-Change-Number: 16947
Gerrit-PatchSet: 6
Gerrit-Owner: herlesupreeth <herlesupreeth at gmail.com>
Gerrit-Assignee: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: herlesupreeth <herlesupreeth at gmail.com>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-CC: dexter <pmaier at sysmocom.de>
Gerrit-Comment-Date: Wed, 22 Jan 2020 15:58:36 +0000
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