Commit Graph

274 Commits

Author SHA1 Message Date
Jaeden Amero
25384a236e psa: Simplify RSA public key format
Remove pkcs-1 and rsaEncryption front matter from RSA public keys. Move
code that was shared between RSA and other key types (like EC keys) to
be used only with non-RSA keys.
2019-01-23 17:31:50 +00:00
Jaeden Amero
494624d299
Merge pull request #18 from gilles-peskine-arm/psa-hash_clone
New function psa_hash_clone
2019-01-22 17:35:25 +00:00
Gilles Peskine
b865df005c Merge branch 'psa-no_type_on_allocate_key' into psa-api-1.0-beta
Remove the type and bits arguments from psa_allocate_key() and
psa_create_key().
2019-01-19 12:24:18 +01:00
Gilles Peskine
d40c1fbd50 Don't require a type and size when creating a key slot
Remove the type and bits arguments to psa_allocate_key() and
psa_create_key(). They can be useful if the implementation wants to
know exactly how much space to allocate for the slot, but many
implementations (including ours) don't care, and it's possible to work
around their lack by deferring size-dependent actions to the time when
the key material is created. They are a burden to applications and
make the API more complex, and the benefits aren't worth it.

Change the API and adapt the implementation, the units test and the
sample code accordingly.
2019-01-19 12:20:52 +01:00
Gilles Peskine
b37af92eb9 Merge branch 'psa-hash_clone' into psa-api-1.0-beta
Add psa_hash_clone.
2019-01-19 12:07:27 +01:00
Gilles Peskine
ebb2c3e419 New function psa_hash_clone
Clone a hash operation.

Test good cases as part as multipart tests. Add new test functions for
the state machine.
2019-01-19 12:03:41 +01:00
Gilles Peskine
9dcc80e628 Merge branch 'psa-derive_input_steps-agreement_as_one_step' into psa-api-1.0-beta
Change the key derivation API to take inputs in multiple steps,
instead of a single one-site-fits-poorly function.

Conflicts:
* include/psa/crypto.h: merge independent changes in the documentation
  of psa_key_agreement (public_key from the work on public key formats
  vs general description and other parameters in the work on key derivation).
* tests/suites/test_suite_psa_crypto.data: update the key agreement
  tests from the work on key derivation to the format from the work on
  public key formats.
* tests/suites/test_suite_psa_crypto_metadata.function: reconcile the
  addition of unrelated ALG_IS_xxx macros
2019-01-18 18:54:15 +01:00
Gilles Peskine
969c5d61f7 Make key agreement the secret input for key derivation
* Documentation
* Proof-of-concept implementation
* Updates to the tests (work in progress)
2019-01-18 18:34:28 +01:00
Gilles Peskine
b70a0fd1a5 Key derivation by small input steps: proof-of-concept
Document the new API. Keep the old one.

Implement for HKDF. Use it in a few test cases.

Key agreement is still unchanged.
2019-01-18 18:33:12 +01:00
Gilles Peskine
1f9e58a1bb Merge branch 'psa-signature_policy_wildcard' into psa-api-1.0-beta
For hash-and-sign algorithms, allow a policy to specify a wildcard
instead of a specific hash algorithm.
2019-01-18 17:52:17 +01:00
Jaeden Amero
0ae445f8fd psa: Simplify EC public key format
Remove front matter from our EC key format, to make it just the contents
of an ECPoint as defined by SEC1 section 2.3.3.

As a consequence of the simplification, remove the restriction on not
being able to use an ECDH key with ECDSA. There is no longer any OID
specified when importing a key, so we can't reject importing of an ECDH
key for the purpose of ECDSA based on the OID.
2019-01-15 11:29:18 +00:00
Gilles Peskine
30f77cdfc1 Add a hash wildcard value for hash-and-sign algorithm
You can use PSA_ALG_ANY_HASH to build the algorithm value for a
hash-and-sign algorithm in a policy. Then the policy allows usage with
this hash-and-sign family with any hash.

Test that PSA_ALG_ANY_HASH-based policies allow a specific hash, but
not a different hash-and-sign family. Test that PSA_ALG_ANY_HASH is
not valid for operations, only in policies.
2019-01-14 19:38:56 +01:00
Jaeden Amero
6b19600fba psa: Simplify RSA public key format
Remove pkcs-1 and rsaEncryption front matter from RSA public keys. Move
code that was shared between RSA and other key types (like EC keys) to
be used only with non-RSA keys.
2019-01-11 18:08:53 +00:00
Jaeden Amero
d94d671f14 psa: Test that generator initializers work 2019-01-08 14:28:04 +00:00
Jaeden Amero
5bae227da0 psa: Add initializers for cipher operation objects
Add new initializers for cipher operation objects and use them in our
tests and library code. Prefer using the macro initializers due to their
straightforwardness.
2019-01-08 14:28:04 +00:00
Jaeden Amero
769ce27f12 psa: Add initializers for MAC operation objects
Add new initializers for MAC operation objects and use them in our tests
and library code. Prefer using the macro initializers due to their
straightforwardness.
2019-01-08 14:28:04 +00:00
Jaeden Amero
6a25b41ac3 psa: Add initializers for hash operation objects
Add new initializers for hash operation objects and use them in our
tests and library code. Prefer using the macro initializers due to their
straightforwardness.
2019-01-08 14:28:04 +00:00
Jaeden Amero
70261c513a psa: Add initializers for key policies
Add new initializers for key policies and use them in our docs, example
programs, tests, and library code. Prefer using the macro initializers
due to their straightforwardness.
2019-01-08 14:28:04 +00:00
Gilles Peskine
c08fc1d7e9 Move MIN and MAX macros from PSA tests to helpers.function 2018-12-20 18:47:53 +01:00
Gilles Peskine
d76f181617 Prefer ASSERT_ALLOC to calloc+TEST_ASSERT in PSA tests
To allocate memory dynamically in a test, call ASSERT_ALLOC which
takes care of calling calloc and of checking for NULL.
2018-12-20 18:47:53 +01:00
Gilles Peskine
1f2aa0e3b0 Remove useless null checks of data_t* parameters
The test framework never passes NULL for a data_t* parameter, so
testing them against NULL is clutter.
2018-12-20 18:47:53 +01:00
Gilles Peskine
40ab95bdbc Remove checks of test parameters against SIZE_MAX
Our code base doesn't even support 16-bit platforms, so those checks
are always trivially true.
2018-12-20 18:47:53 +01:00
Gilles Peskine
0dfba2ddf0 Use ASSERT_COMPARE in preference to memcmp in PSA tests 2018-12-20 18:47:52 +01:00
Gilles Peskine
f812dcf4ae Rewrap some lines after the macro changes
Change the way some lines are wrapped to cut at a more logical place.
This commit mainly rewrites multi-line calls to TEST_EQUAL, and also a
few calls to PSA_ASSERT.
2018-12-20 18:47:52 +01:00
Gilles Peskine
fe11b72b93 Use TEST_EQUAL(a,b) in preference to TEST_ASSERT(a==b)
This commit is the result of the following command, followed by
reindenting (but not wrapping lines):

perl -00 -i -pe 's/^( *)TEST_ASSERT\(([^;=]*)(?: |\n *)==([^;=]*)\);$/${1}TEST_EQUAL($2,$3);/gm' tests/suites/test_suite_psa_*.function
2018-12-20 18:47:52 +01:00
Gilles Peskine
8817f61007 Use PSA_ASSERT(a) in preference to TEST_ASSERT(a==PSA_SUCCESS)
This commit is the result of the following command, followed by
reindenting (but not wrapping lines):

perl -00 -i -pe 's/^( *)TEST_ASSERT\(([^;=]*)(?: |\n *)==\s*PSA_SUCCESS\s*\);$/${1}PSA_ASSERT($2 );/gm' tests/suites/test_suite_psa_*.function
2018-12-20 18:47:52 +01:00
Gilles Peskine
0f915f1d2a Indent PSA tests according to K&R rules with Mbed TLS tweaks
Only whitespace changes in this commit.
2018-12-20 18:47:52 +01:00
Gilles Peskine
9d8eea7e19 Wrap some multiline expressions in parentheses
This guarantees that they'll be indented as desired under most
indentation rules.
2018-12-20 18:47:52 +01:00
Gilles Peskine
3d2f949c86 Move the ARRAY_LENGTH macro to the common helpers file 2018-12-17 23:17:17 +01:00
Gilles Peskine
bdf309ccdb Convert the PSA crypto cryptography tests to the new handle API
Switch from the direct use of slot numbers to handles allocated by
psa_allocate_key.

This commit does not affect persistent key tests except for the one
test function in test_suite_psa_crypto that uses persistent keys
(persistent_key_load_key_from_storage).

The general principle for each function is:
* Change `psa_key_slot_t slot` to `psa_key_handle_t handle`.
* Call psa_allocate_key() before setting the policy of the slot,
  or before creating key material in functions that don't set a policy.
* Some PSA_ERROR_EMPTY_SLOT errors become PSA_ERROR_INVALID_HANDLE
  because there is now a distinction between not having a valid
  handle, and having a valid handle to a slot that doesn't contain key
  material.
* In tests that use symmetric keys, calculate the max_bits parameters
  of psa_allocate_key() from the key data size. In tests where the key
  may be asymmetric, call an auxiliary macro KEY_BITS_FROM_DATA which
  returns an overapproximation. There's no good way to find a good
  value for max_bits with the API, I think the API should be tweaked.
2018-12-11 16:48:13 +01:00
Gilles Peskine
a8860b2990 Remove lifetime test functions
With the handle-based slot management interface, psa_set_key_lifetime
will no longer exist, so remove the corresponding unit tests.
2018-12-11 16:48:13 +01:00
Gilles Peskine
dc911fd594 Remove redundant slot-based test
fill_slots is superseded by many_transient_handles.
2018-12-11 16:48:13 +01:00
Gilles Peskine
a426168cbf Test that failure of import_key preserves metadata 2018-12-11 16:48:13 +01:00
Gilles Peskine
b309eec4a5 Move library initialization tests to a new test suite 2018-11-22 13:41:38 +01:00
Darryl Green
0c6575a84d psa: Extend psa_generate_key to support persistent lifetimes 2018-11-20 15:40:32 +00:00
Darryl Green
d49a499d03 psa: Implement persistent keys
Allow use of persistent keys, including configuring them, importing and
exporting them, and destroying them.

When getting a slot using psa_get_key_slot, there are 3 scenarios that
can occur if the keys lifetime is persistent:

1. Key type is PSA_KEY_TYPE_NONE, no persistent storage entry:
   -  The key slot is treated as a standard empty key slot
2. Key type is PSA_KEY_TYPE_NONE, persistent storage entry exists:
   -  Attempt to load the key from persistent storage
3. Key type is not PSA_KEY_TYPE_NONE:
   -  As checking persistent storage on every use of the key could
      be expensive, the persistent key is assumed to be saved in
      persistent storage, the in-memory key is continued to be used.
2018-11-20 15:40:25 +00:00
Gilles Peskine
c7998b78b8 Factor common code into key_agreement_with_self 2018-11-14 21:17:16 +01:00
Gilles Peskine
3ec8ed8b51 Add multipart key agreement tests
Add test cases that do key agreement with raw selection in pieces, to
validate that selection works even when the application doesn't read
everything in one chunk.
2018-11-14 21:15:37 +01:00
Gilles Peskine
bf49197c9b key_agreement_capacity: test the actual capacity as well
After testing that the advertized capacity is what the test data says,
read that many bytes to test that this is also actual capacity.
2018-11-14 21:15:37 +01:00
Gilles Peskine
10df341436 Factor usage_to_exercise into its own function 2018-11-14 21:15:37 +01:00
Gilles Peskine
fc411f1ac1 Use ASSERT_ALLOC in key agreement tests 2018-11-14 21:15:37 +01:00
Gilles Peskine
1d7c082124 Fix a memory leak in a test 2018-11-14 21:15:37 +01:00
Gilles Peskine
5968559a9c Key agreement test functions 2018-11-14 21:15:37 +01:00
Gilles Peskine
01d718cee8 New API function: psa_key_agreement
Set up a generator from a key agreement.
2018-11-14 21:15:37 +01:00
Jaeden Amero
594a330eb7 psa: test: Fix truncation of message by snprintf
We had only allocated 40 bytes for printing into, but we wanted to print 46
bytes. Update the buffer to be 47 bytes, which is large enough to hold what
we want to print plus a terminating null byte.
2018-11-08 17:32:45 +00:00
Moran Peker
ce50007f90 Add tests of using cipher in bad state cases
- cipher setup after import key failure.
- cipher setup after set key policy but no key material
creation.
2018-11-07 16:20:07 +02:00
Moran Peker
3455009116 Add tests that check export failures after illegal behavior
- export a key after import key failure.
- export a key after the key was destroyed.
- export a key after set key policy but no key material
creation.
2018-11-07 16:19:34 +02:00
Moran Peker
28a38e6e38 Add tests that checks key management corner cases
- import a key into a non empty key slot.
- export a key from invalid slot number.
2018-11-07 16:18:24 +02:00
Jaeden Amero
fe9f771e88
Merge pull request #170 from ARMmbed/increase_psa_key_derivation_code_coverage
add tests that increase key derivation code coverage slightly
2018-11-06 09:17:19 +00:00
Jaeden Amero
40f1cb104f
Merge pull request #182 from ARMmbed/psa-asymmetric-format-raw_private_key
Asymmetric import/export format: raw private EC keys
2018-11-06 09:02:25 +00:00
itayzafrir
27e6945f43 Refactor and rename test hash_verify_bad_paths to hash_verify_bad_args
1. Updated test scenarios.
2. Renamed test and updated test description.
3. Some documentation updates.
4. Test dependency moved to .function file.
2018-11-05 18:36:05 +02:00
itayzafrir
b2dd5ed1e6 Rename test hash_finish_bad_paths to hash_finish_bad_args
Test dependency moved to .function file.
2018-11-05 18:36:05 +02:00
itayzafrir
f86548d674 Add test hash_bad_order
1. New test for testing bad order of hash function calls.
2. Removed test hash_update_bad_paths since it's test scenario
   was moved to the new test.
3. Moved some scenarios from test hash_verify_bad_paths to
   the new test.
2018-11-05 18:36:05 +02:00
itayzafrir
58028321b9 Split test hash_bad_paths into 3 different tests
1. Rename hash_bad_paths to hash_verify_bad_paths
2. Add test hash_update_bad_paths
3. Add test hash_finish_bad_paths

The different scenarios tested as part of hash_bad_paths are
moved to the relevant test.
2018-11-05 18:36:05 +02:00
itayzafrir
4271df932c Add scenario to test case hash_bad_paths
Tests where the verification hash digest is prefixed with
the expected digest but also has extra bytes appended at the end of it.
2018-11-05 18:36:05 +02:00
itayzafrir
69290f0e71 Update hash tests documentation 2018-11-05 18:36:05 +02:00
itayzafrir
02d6295e53 Move positive hash tests into a new test suite
Move hash_finish, hash_verify and hash_multi_part to a
new test suite test_suite_psa_crypto_hash.
2018-11-05 18:36:05 +02:00
itayzafrir
931fa6d663 Remove input parameter validations from hash test functions
Remove from hash_finish, hash_verify and hash_multi_part
2018-11-05 18:34:16 +02:00
itayzafrir
f5b3eb85b5 Add hash test for multipart operation
Test vectors migrated from mbedTLS
2018-11-05 18:34:16 +02:00
itayzafrir
ec93d30b45 Add hash bad paths test
Increase code coverage
2018-11-05 18:34:16 +02:00
Nir Sonnenschein
1caf6d24f2 Fix code style and clarify issue comment
* remove unneeded constants
* clarify comment reference to issue 183
* add additional reference comment
* fix brace spacing issues
2018-11-01 12:27:20 +02:00
Nir Sonnenschein
dd69d8b7ff Streamline test function API by removing parameter
streamline the API for the test test_derive_invalid_generator_state: by removing
the key_data parameter.
This parameter is not important for test flow and can be hard-coded.
2018-11-01 12:24:23 +02:00
Nir Sonnenschein
f8964b9580 updated test to work around https://github.com/ARMmbed/mbedtls-psa/issues/183
test should check the correct error values once this issue is fixed
2018-10-31 18:06:14 +02:00
Nir Sonnenschein
5078930459 fix whitespace issues 2018-10-31 12:16:38 +02:00
Nir Sonnenschein
4eda37bb9e streamline test function API by removing parameter
streamline the API for the test test_derive_invalid_generator_state by removing
the key type paramter (it is assumed to always be PSA_KEY_TYPE_DERIVE)
2018-10-31 12:15:58 +02:00
Gilles Peskine
5b802a366a Private EC key format: remove ASN.1-based sanity checks
In preparation for the import/export format change for private
elliptic curve keys from RFC 5915 to the raw secret value,
remove ASN.1-based sanity checks. For the raw secret value, most byte
strings of the correct length are valid (the details depend on the
curve), so as a sanity check, just check the length.
2018-10-29 19:21:41 +01:00
Gilles Peskine
d8b7d4f87e In export tests, also test PSA_KEY_EXPORT_MAX_SIZE
When testing psa_export_key or psa_export_public_key, test that the
expected result fits in the size given by PSA_KEY_EXPORT_MAX_SIZE.
2018-10-29 15:18:41 +01:00
Gilles Peskine
49c2591916 Improve export_public_key test function
In the test function for export_public_key, don't just check the
length of the result. Compare the actual result to the expected
result.

Take an extra argument that allows using an export buffer that's
larger or smaller than needed. Zero is the size given by
PSA_KEY_EXPORT_MAX_SIZE.

Don't check the output of psa_get_key_information. That's useful in
import_export because it tests both import and export, but not in
import_export_public_key whose goal is only to test public key export.

This commit adjusts the existing test data but does not add new test
cases.
2018-10-29 15:15:31 +01:00
Nir Sonnenschein
b46e7ca16b add additional generator tests and generalize key derivation test
Key derivation test now uses an indirect way to test generator validity
as the direct way previously used isn't compatible with the PSA IPC
implementation. Additional bad path test for the generator added
to check basic bad-path scenarios.
2018-10-25 14:46:09 +03:00
Nir Sonnenschein
e5204c94a1 add tests that increase key derivation code coverage slightly
added tests that increase code coverage for the key derivation functions slightly
by reaching error cases not covered before.
2018-10-22 17:24:55 +03:00
Gilles Peskine
e1f2d7d1ac Document and check the consistency of truncated MAC encodings
Add comments noting that the maximum length of a MAC must fit in
PSA_ALG_MAC_TRUNCATION_MASK. Add a unit test that verifies that the
maximum MAC size fits.
2018-10-17 13:54:47 +02:00
Gilles Peskine
7da96b0d91 Reorder parameters of AEAD unit tests to be more logical
Pass the nonce first, then the AD, then the input. This is the order
in which the data is processed and it's the order of the parameters to
the API functions.
2018-10-08 14:42:11 +02:00
Gilles Peskine
a7aa442c7c Add tests for mac_sign 2018-10-08 14:42:11 +02:00
Gilles Peskine
f7ab5ad13a Skip calling memset when the size is 0
memset(NULL, c, 0) has undefined behavior, so don't do it. clang-asan
complains.
2018-09-27 13:57:45 +02:00
Gilles Peskine
bd7dea9e64 Use ASSERT_COMPARE instead of memcmp in PSA tests
This commit fixes some missing size comparison. In
aead_encrypt_decrypt, aead_encrypt and aead_decrypt, the test code
would not have noticed if the library function had reported an output
length that was not the expected length.
2018-09-27 13:57:19 +02:00
Gilles Peskine
8cebbba7e6 Use ASSERT_ALLOC instead of mbedtls_calloc in PSA tests
This commit resolves a bug whereby some test cases failed on systems
where mbedtls_calloc returns NULL when the size of 0, because the test
case asserted `pointer != NULL` regardless of the size.
2018-09-27 13:54:18 +02:00
Gilles Peskine
acec7b6fa1 exercise_export_key: fix public key case
Public keys are always exportable, even if their usage doesn't include
the EXPORT flag.
2018-09-17 14:33:43 +02:00
itayzafrir
90d8c7a728 Ensure the module is initialized in key based functions 2018-09-16 12:15:47 +03:00
itayzafrir
0adf0fc31c Ensure the module is initialized in psa_generate_random 2018-09-16 12:15:46 +03:00
Jaeden Amero
c0454a7369 Merge pull request #135 from ARMmbed/export_sanity_tests
Document asymmetric key export formats
2018-09-14 10:02:30 +01:00
Gilles Peskine
dea46cf8f1 Clarify comment in test
In RSAPrivateKey, Version is an INTEGER. The version must be 0.
2018-09-14 10:02:29 +01:00
Gilles Peskine
c6290c043e Minor documentation improvements 2018-09-14 10:02:29 +01:00
Gilles Peskine
b67f308c4f Fix re-import size in import_export test with non-canonical input 2018-09-14 10:02:29 +01:00
Gilles Peskine
ae3d2a2c26 Avoid non-standard C constructs
Don't rely on static initialization of a flexible array member, that's
a GNU extension. The previous code also triggered a Clang warning
"suggest braces around initialization of subobject" (-Wmissing-braces)
for `struct {char a[]} = {"foo"}`.
2018-09-14 10:02:29 +01:00
Gilles Peskine
8f609239d5 Do export sanity checks in import_export as well
This is not useful to validate the implementation when importing
canonical input, which is the case for most import/export test cases,
but it helps validate the sanity checks themselves.
2018-09-14 10:02:29 +01:00
Gilles Peskine
dd2f95b855 Improve and augment export sanity checks
Implement sanity checks of exported public keys, using ASN.1 parsing.
Rewrite the sanity checks of key pairs using ASN.1 parsing, so as to
check more things with simpler code.
2018-09-14 10:02:29 +01:00
Jaeden Amero
df3b74f168 Merge pull request #125 from ARMmbed/key_slot_index-fix
Fix off-by-one errors in key slot index limits
2018-09-14 10:02:29 +01:00
Gilles Peskine
d14664a79b Move export key sanity check from generate to exercise
Move the code to perform sanity checks on the exported key from
generate_key to exercise_key. This way the sanity checks can be
performed after importing or deriving a key as well.

In addition to checking the exported key if its usage allows it, check
the exported public key if the key is asymmetric.
2018-09-14 10:02:29 +01:00
Gilles Peskine
9a05634558 psa_crypto_free: destroy the last slot
The last slot in the array was not freed due to an off-by-one error.

Amend the fill_slots test to serve as a non-regression test for this
issue: without this bug fix, it would cause a memory leak.
2018-09-14 10:02:29 +01:00
Gilles Peskine
996deb18cc Fix buffer overflow in the slot array
Slots are numbered from 1, but the slot array is a C array so it's
numbered from 0.

Add a non-regression test.
2018-09-14 10:02:29 +01:00
Gilles Peskine
c32f0304db Fix bad key type constant that worked by accident 2018-09-14 10:02:29 +01:00
Darryl Green
9c862253cc Add handling for zero-length buffers in tests
The buffer can be NULL if the length is zero, so we only check it's not NULL if the length is nonzero
2018-09-14 10:02:28 +01:00
Jaeden Amero
22e232ec04 Merge pull request #109 from ARMmbed/IAR-feature-psa
Ensure release testing job passes IAR tests
2018-09-12 16:50:07 +03:00
Gilles Peskine
9f900a8b25 Merge pull request #105 from ARMmbed/psa-derive_hkdf
PSA key derivation: simple-ish interface, HKDF
2018-09-12 16:50:07 +03:00
Gilles Peskine
d54931c7c4 HKDF: be more robust if we reach the maximum ouptut length
In psa_generator_hkdf_read, return BAD_STATE if we're trying to
construct more output than the algorithm allows. This can't happen
through the API due to the capacity limit, but it could potentially
happen in an internal call.

Also add a test case that verifies that we can set up HKDF with its
maximum capacity and read up to the maximum capacity.
2018-09-12 16:50:05 +03:00
Gilles Peskine
0386fbaa70 Key derivation: test deriving a key from the KDF output 2018-09-12 16:48:24 +03:00
Gilles Peskine
96ee5c70b9 HKDF: positive tests 2018-09-12 16:45:45 +03:00
Gilles Peskine
ea0fb4975c Add framework for simple key derivation
New key type PSA_KEY_TYPE_DERIVE. New usage flag PSA_KEY_USAGE_DERIVE.
New function psa_key_derivation.

No key derivation algorithm is implemented yet. The code may not
compile with -Wunused.

Write some unit test code for psa_key_derivation. Most of it cannot be
used yet due to the lack of a key derivation algorithm.
2018-09-12 16:44:04 +03:00
Moran Peker
cb088e7059 Replace ssize_t by ptrdiff_t
ssize_t is a POSIX thing, not standard C
2018-09-12 16:41:12 +03:00
Gilles Peskine
55c94dd500 Asymmetric encrypt/decrypt tests: check output length
In asymmetric_encrypt_decrypt, use the buffer size advertized by the
library for the ciphertext, and the length of the plaintext for the
re-decrypted output.

Test the output length if known. Require it to be 0 on error for
encrypt/decrypt functions. If the output length is unknown, test at
least that it's within the buffer limits.
2018-09-12 16:41:12 +03:00