We now correctly and opportunistically use the webcrypto API if
available, polyfilling if it's not detected. This change also includes a
layer of abstraction over the webcrypto interface so we no longer have
to deal with key-imports or algorithm names all over the place. Since we
no longer support AES-CTR, code outside this file can simply call
`textsecure.subtle.<encrypt|decrypt|sign>(key, data [, iv])`.
TypedArray.prototype.set doesn't handle ArrayBuffers correctly (it
writes all zeros). Instead, wrap each ArrayBuffer in a typed array
for concatenation.
DRY up protobuf declarations and move to a slightly briefer naming
convention.
Also dropped some ArrayBuffer -> string conversions as
ProtoBuf.js handles ArrayBuffers just fine, and in fact, more
efficiently than strings.
Finally, dropped the btoa() wrappers, because that incurs an extra
string -> string conversion before the protobuf's internal string ->
array buffer conversion. In lieu of btoa, we can simply pass in the
optional string encoding argument to the protobuf's decode method,
which in these cases should be 'binary'.
Related: #17
Slight revert from said commit. We really do need the
IncomingPushMessageSignal protobuf at the UI layer, mostly because
it contains the 'source' attribute, without which we don't know
who sent the message.
Also fix a crash when there are no attachments on a message.
lilia
Matt Corallo
Marco