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Re: Android 6

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From Daniel James <daniel@me.invalid>
Newsgroups comp.mobile.android
Subject Re: Android 6
Date Sun, 15 Jan 2017 18:23:23 -0000
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In article <a2e50d8a-4983-8f71-e13b-526cef47b069@arnowelzel.de>, Arno 
Welzel wrote:
>> Yes, of course ... but we're talking about a removable SD card, here. 
>> There is NO POINT in trying to implement security within Android when 
>> the user can take the card out and mount it in a PC and read/write 
>> everything anyway.
> 
> It's not about the *user* - the security protects the data agains
> *apps* on the device.

It *is* about the user, to the extent that it is the user who should get 
to choose whether or not to trust the other apps with his data.

>> If you care about security in that case you simply encrypt the data.
> 
> Which does not protect data from being read by other apps on the
> device itself since the devices will have access to *all* data on
> the card.

It doesn't protect the encrypted data written to the card from being 
read in its encrypted form by other apps, but those apps can't decrypt 
the data (they could corrupt it, though, if they can write to the card).

If other apps can read the cleartext data in memory then we have more to 
worry about than permissions to access the card.

Note that I'm not talking about card-wide encryption that can be 
performed by Android, here, but application-specific encryption carried 
out by individual apps using encryption keys that are not available to 
other apps.

Essentially, though, you should not install any apps that you don't 
trust, and have good reason to trust. Running dodgy software and hoping 
that Android will somehow save you from its actions is bound to end in 
tears.

>> Android apps can access the images in the DCIM directory in internal 
>> storage without any special permission, but can only access images in 
>> the DCIM directory on an SD card if they have permission to read 
>> external storage.
> 
> No, they need storage access even for the "internal" storage. It's
> only called "internal" because it uses another mount point in the
> file system. But nevertheless it is treated as "storage".

Yes, sorry ... that little word "internal" confused me. Android uses the 
term "external" to refer to both emulated and physical storage areas and 
we've been using "internal" to refer to an emulated external storage 
area ... what with the tortuous naming in Android and the fact that the 
rules change between SDK versions it's amazing anyone gets this stuff 
right! The docs (sometimes) talk about "primary" (aka emulated) and 
"secondary" (aka physical) external storage, but don't often enough 
(IMHO) distinguish between them.

However, we were talking about photos, and they're stored in a "public" 
area (the DCIM directory) of "external" storage (that may be emulated in 
internal memory). 

Being a public area, of course, the DCIM directory is readable by all 
apps so your point about protecting data from other apps doesn't apply.

Note: I have read (but I have not tested or verified this) that the 
READ_EXTERNAL_STORAGE permission is required to read a public directory 
in external storage if it is held on a physical SD card (or USB stick) 
but not if it's on an emulated SD card ... maybe that's not correct?

-- 
Cheers,
 Daniel.

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Android 6 Bill <Billaboard@gmail.com> - 2016-12-22 17:21 +0000
  Re: Android 6 The Real Bev <bashley101@gmail.com> - 2016-12-22 10:00 -0800
    Re: Android 6 Bill <Billaboard@gmail.com> - 2016-12-23 00:23 +0000
      Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-22 19:30 -0500
        Re: Android 6 Bill <Billaboard@gmail.com> - 2016-12-23 12:42 +0000
          Re: Android 6 tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2016-12-23 11:58 -0500
            Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-29 13:43 +0100
              Re: Android 6 Daniel James <daniel@me.invalid> - 2016-12-30 15:34 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-30 22:33 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2016-12-31 13:27 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-04 08:59 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-04 13:40 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-11 09:00 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-15 18:23 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-15 21:20 +0100
                Re: Android 6 AL <45364747@invalid.com> - 2017-01-04 10:06 -0700
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-11 09:00 +0100
                Re: Android 6 tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2017-01-05 01:34 -0500
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-07 14:14 +0000
                Re: Android 6 tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2017-01-07 13:09 -0500
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-08 18:18 +0000
                Re: Android 6 tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2017-01-08 15:42 -0500
                Re: Android 6 The Real Bev <bashley101@gmail.com> - 2017-01-08 17:11 -0800
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-08 20:19 -0500
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-09 23:55 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-11 18:07 +0100
                Re: Android 6 Frank Slootweg <this@ddress.is.invalid> - 2017-01-08 21:34 +0000
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-09 23:55 +0000
          Re: Android 6 Joerg Lorenz <hugybear@gmx.ch> - 2016-12-24 10:49 +0100
  Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-22 23:55 +0100
    Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-22 19:15 -0500
      Re: Android 6 Joerg Lorenz <hugybear@gmx.ch> - 2016-12-23 05:46 +0100
        Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-23 00:15 -0500
      Re: Android 6 Dave Higton <dave@davehigton.me.uk> - 2016-12-23 17:11 +0000
        Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-23 12:43 -0500
          Re: Android 6 Dave Higton <dave@davehigton.me.uk> - 2016-12-23 21:22 +0000
            Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-24 14:29 -0500
              Re: Android 6 Dave Higton <dave@davehigton.me.uk> - 2016-12-25 11:10 +0000
                Re: Android 6 Piet <www.godfatherof.nl/@opt-in.invalid> - 2016-12-25 12:37 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-25 11:18 -0500
                Re: Android 6 Dave Higton <dave@davehigton.me.uk> - 2016-12-25 20:28 +0000
          Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-29 12:02 -0500
            Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-29 23:45 +0100
              Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-29 18:02 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-30 22:24 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-31 11:55 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-04 09:04 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-04 10:14 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-11 18:11 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-11 13:05 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-13 17:23 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-16 15:35 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-17 05:39 +0100
              Re: Android 6 Daniel James <daniel@me.invalid> - 2016-12-30 15:34 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-30 22:26 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2016-12-31 13:27 +0000
                Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-31 11:55 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-04 09:11 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-04 13:40 +0000
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-04 10:14 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-11 18:12 +0100
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-11 13:05 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-13 17:24 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-15 18:23 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-15 21:30 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-16 15:42 +0000
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-16 15:35 -0500
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-17 05:44 +0100
                Re: Android 6 Daniel James <daniel@me.invalid> - 2017-01-17 17:47 +0000
                Re: Android 6 Bill <Billaboard@gmail.com> - 2017-01-01 01:05 +0000
                Re: Android 6 tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2017-01-02 02:08 -0500
                Re: Android 6 David Taylor <david-taylor@blueyonder.co.uk.invalid> - 2017-01-02 08:01 +0000
                Re: Android 6 nospam <nospam@nospam.invalid> - 2017-01-02 08:51 -0500
                Re: Android 6 Bill <Billaboard@gmail.com> - 2017-01-02 20:41 +0000
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-04 09:18 +0100
                Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2017-01-04 09:14 +0100
          Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-29 14:05 +0100
      Re: Android 6 nospam <nospam@nospam.invalid> - 2016-12-29 12:02 -0500
        Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-29 23:46 +0100
          Re: Android 6 Dave Higton <dave@davehigton.me.uk> - 2016-12-31 20:18 +0000
      Re: Android 6 Arno Welzel <usenet@arnowelzel.de> - 2016-12-29 13:47 +0100

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