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Add support for minimum-tag-length AEAD and MAC policies

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Includes tests.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>

# Conflicts:
#	include/psa/crypto_values.h
#	tests/suites/test_suite_psa_crypto.function
This commit is contained in:
Steven Cooreman
2021-02-18 12:03:50 +01:00
parent 34045c1d6a
commit b3ce8156ce
6 changed files with 394 additions and 55 deletions
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131
library/psa_crypto.c
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@ -663,16 +663,79 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
/* Common case: both sides actually specify the same policy. */
if( alg1 == alg2 )
return( alg1 );
/* If the policies are from the same hash-and-sign family, check
* if one is a wildcard. If so the other has the specific algorithm. */
if( PSA_ALG_IS_HASH_AND_SIGN( alg1 ) &&
PSA_ALG_IS_HASH_AND_SIGN( alg2 ) &&
( alg1 & ~PSA_ALG_HASH_MASK ) == ( alg2 & ~PSA_ALG_HASH_MASK ) )
/* Special case: one or both sides contain a wildcard. */
if( PSA_ALG_IS_WILDCARD( alg1 ) || PSA_ALG_IS_WILDCARD( alg2 ) )
{
if( PSA_ALG_SIGN_GET_HASH( alg1 ) == PSA_ALG_ANY_HASH )
return( alg2 );
if( PSA_ALG_SIGN_GET_HASH( alg2 ) == PSA_ALG_ANY_HASH )
return( alg1 );
/* If the policies are from the same hash-and-sign family, check
* if one is a wildcard. If so the other has the specific algorithm. */
if( PSA_ALG_IS_HASH_AND_SIGN( alg1 ) &&
PSA_ALG_IS_HASH_AND_SIGN( alg2 ) &&
( alg1 & ~PSA_ALG_HASH_MASK ) == ( alg2 & ~PSA_ALG_HASH_MASK ) )
{
if( PSA_ALG_SIGN_GET_HASH( alg1 ) == PSA_ALG_ANY_HASH )
return( alg2 );
if( PSA_ALG_SIGN_GET_HASH( alg2 ) == PSA_ALG_ANY_HASH )
return( alg1 );
}
/* If the policies are from the same AEAD family, then at least one
* of them is a minimum-tag-length policy. Calculate the most
* restrictive tag length. */
if( PSA_ALG_IS_AEAD( alg1 ) && PSA_ALG_IS_AEAD( alg2 ) &&
( PSA_ALG_AEAD_WITH_SHORTENED_TAG( alg1, 0 ) ==
PSA_ALG_AEAD_WITH_SHORTENED_TAG( alg2, 0 ) ) )
{
size_t alg1_len = PSA_ALG_AEAD_GET_TAG_LENGTH( alg1 );
size_t alg2_len = PSA_ALG_AEAD_GET_TAG_LENGTH( alg2 );
size_t max_len = alg1_len > alg2_len ? alg1_len : alg2_len;
/* If both are wildcards, return most restricitve wildcard */
if( PSA_ALG_IS_WILDCARD( alg1 ) && PSA_ALG_IS_WILDCARD( alg2 ) )
{
return( PSA_ALG_AEAD_WITH_MINIMUM_LENGTH_TAG( alg1, max_len ) );
}
/* If only one is a wildcard, return specific algorithm if compatible. */
if( PSA_ALG_IS_WILDCARD( alg1 ) && (alg1_len <= alg2_len) )
{
return( alg2 );
}
if( PSA_ALG_IS_WILDCARD( alg2 ) && (alg2_len <= alg1_len) )
{
return( alg1 );
}
}
/* If the policies are from the same MAC family, then at least one
* of them is a minimum-tag-length policy. Calculate the most
* restrictive tag length. */
if( PSA_ALG_IS_MAC( alg1 ) && PSA_ALG_IS_MAC( alg2 ) &&
( PSA_ALG_FULL_LENGTH_MAC( alg1 ) ==
PSA_ALG_FULL_LENGTH_MAC( alg2 ) ) )
{
size_t alg1_len = PSA_MAC_TRUNCATED_LENGTH( alg1 );
size_t alg2_len = PSA_MAC_TRUNCATED_LENGTH( alg2 );
size_t max_len = alg1_len > alg2_len ? alg1_len : alg2_len;
/* If both are wildcards, return most restricitve wildcard */
if( PSA_ALG_IS_WILDCARD( alg1 ) && PSA_ALG_IS_WILDCARD( alg2 ) )
{
return( PSA_ALG_MAC_WITH_MINIMUM_LENGTH_TAG( alg1, max_len ) );
}
/* If only one is a wildcard, return specific algorithm if compatible.
* Special case: specific MAC algorithm with '0' as length means full-
* length MAC, which is always allowed by a wildcard with the same
* base algorithm. */
if( PSA_ALG_IS_WILDCARD( alg1 ) &&
( ( alg1_len <= alg2_len) ||
( alg2 == PSA_ALG_FULL_LENGTH_MAC( alg1 ) ) ) )
{
return( alg2 );
}
if( PSA_ALG_IS_WILDCARD( alg2 ) &&
( (alg2_len <= alg1_len) ||
( alg1 == PSA_ALG_FULL_LENGTH_MAC( alg2 ) ) ) )
{
return( alg1 );
}
}
}
/* If the policies are incompatible, allow nothing. */
return( 0 );
@ -681,17 +744,51 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
static int psa_key_algorithm_permits( psa_algorithm_t policy_alg,
psa_algorithm_t requested_alg )
{
/* A requested algorithm cannot be a wildcard. */
if( PSA_ALG_IS_WILDCARD( requested_alg ) )
return( 0 );
/* Common case: the policy only allows requested_alg. */
if( requested_alg == policy_alg )
return( 1 );
/* If policy_alg is a hash-and-sign with a wildcard for the hash,
* and requested_alg is the same hash-and-sign family with any hash,
* then requested_alg is compliant with policy_alg. */
if( PSA_ALG_IS_HASH_AND_SIGN( requested_alg ) &&
PSA_ALG_SIGN_GET_HASH( policy_alg ) == PSA_ALG_ANY_HASH )
/* Special cases: the policy is an algorithm collection. */
if( PSA_ALG_IS_WILDCARD( policy_alg ) )
{
return( ( policy_alg & ~PSA_ALG_HASH_MASK ) ==
( requested_alg & ~PSA_ALG_HASH_MASK ) );
/* If policy_alg is a hash-and-sign with a wildcard for the hash,
* and requested_alg is the same hash-and-sign family with any hash,
* then requested_alg is compliant with policy_alg. */
if( PSA_ALG_IS_HASH_AND_SIGN( requested_alg ) &&
PSA_ALG_SIGN_GET_HASH( policy_alg ) == PSA_ALG_ANY_HASH )
{
return( ( policy_alg & ~PSA_ALG_HASH_MASK ) ==
( requested_alg & ~PSA_ALG_HASH_MASK ) );
}
/* If policy_alg is a wildcard AEAD algorithm of the same base as
* the requested algorithm, check the requested tag length to be
* equal-length or longer than the wildcard-specified length. */
if( PSA_ALG_IS_AEAD( policy_alg ) &&
PSA_ALG_IS_AEAD( requested_alg ) &&
( PSA_ALG_AEAD_WITH_SHORTENED_TAG( policy_alg, 0 ) ==
PSA_ALG_AEAD_WITH_SHORTENED_TAG( requested_alg, 0 ) ) )
{
return( PSA_ALG_AEAD_GET_TAG_LENGTH( policy_alg ) <=
PSA_ALG_AEAD_GET_TAG_LENGTH( requested_alg ) );
}
/* If policy_alg is a wildcard MAC algorithm of the same base as
* the requested algorithm, check the requested tag length to be
* equal-length or longer than the wildcard-specified length. */
if( PSA_ALG_IS_MAC( policy_alg ) &&
PSA_ALG_IS_MAC( requested_alg ) &&
( PSA_ALG_FULL_LENGTH_MAC( policy_alg ) ==
PSA_ALG_FULL_LENGTH_MAC( requested_alg ) ) )
{
/* Special case: full-length MAC is encoded with 0-length.
* A minimum-length policy will always allow a full-length MAC. */
if( PSA_ALG_FULL_LENGTH_MAC( requested_alg ) == requested_alg )
return( 1 );
return( PSA_MAC_TRUNCATED_LENGTH( policy_alg ) <=
PSA_MAC_TRUNCATED_LENGTH( requested_alg ) );
}
}
/* If policy_alg is a generic key agreement operation, then using it for
* a key derivation with that key agreement should also be allowed. This
@ -702,7 +799,7 @@ static int psa_key_algorithm_permits( psa_algorithm_t policy_alg,
return( PSA_ALG_KEY_AGREEMENT_GET_BASE( requested_alg ) ==
policy_alg );
}
/* If it isn't permitted, it's forbidden. */
/* If it isn't explicitly permitted, it's forbidden. */
return( 0 );
}