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mbedtls_ecp_write_key: document and test larger output buffer

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Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2024-02-19 13:30:31 +01:00
parent 5bb04e03ac
commit a395bdd066
3 changed files with 130 additions and 2 deletions
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21
include/mbedtls/ecp.h
View file

@ -1330,11 +1330,28 @@ int mbedtls_ecp_read_key(mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key,
/**
* \brief This function exports an elliptic curve private key.
*
* \note Note that although this function accepts an output
* buffer that is larger than the key, most key import
* interfaces require the output to be trimmed to the
* key's nominal length. It is generally simplest to
* pass the key's nominal length as \c buflen, after
* checking that the output buffer is large enough.
* See the description of the \p buflen parameter for
* how to calculate the nominal length.
*
* \param key The private key.
* \param buf The output buffer for containing the binary representation
* of the key. (Big endian integer for Weierstrass curves, byte
* string for Montgomery curves.)
* of the key.
* For Weierstrass curves, this is the big-endian
* representation, padded with null bytes at the beginning
* to reach \p buflen bytes.
* For Montgomery curves, this is the standard byte string
* representation (which is little-endian), padded with
* null bytes at the end to reach \p buflen bytes.
* \param buflen The total length of the buffer in bytes.
* The length of the output is always
* (`grp->nbits` + 7) / 8 bytes
* where `grp->nbits` is the private key size in bits.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL if the \p key

64
tests/suites/test_suite_ecp.data
View file

@ -736,6 +736,70 @@ ECP read key #24 (Curve25519 RFC, OK)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"70076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c6a":0:1
ECP write key: secp256r1, nominal
depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP256R1:"f12a1320760270a83cbffd53f6031ef76a5d86c8a204f2c30ca9ebf51f0f0ea7":32:0
ECP write key: secp256r1, output longer by 1
depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP256R1:"f12a1320760270a83cbffd53f6031ef76a5d86c8a204f2c30ca9ebf51f0f0ea7":33:0
ECP write key: secp256r1, output longer by 32
depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP256R1:"f12a1320760270a83cbffd53f6031ef76a5d86c8a204f2c30ca9ebf51f0f0ea7":64:0
ECP write key: secp256r1, output longer by 33
depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP256R1:"f12a1320760270a83cbffd53f6031ef76a5d86c8a204f2c30ca9ebf51f0f0ea7":65:0
ECP write key: secp384r1, nominal
depends_on:MBEDTLS_ECP_DP_SECP384R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP384R1:"d27335ea71664af244dd14e9fd1260715dfd8a7965571c48d709ee7a7962a156d706a90cbcb5df2986f05feadb9376f1":48:0
ECP write key: secp384r1, output longer by 1
depends_on:MBEDTLS_ECP_DP_SECP384R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP384R1:"d27335ea71664af244dd14e9fd1260715dfd8a7965571c48d709ee7a7962a156d706a90cbcb5df2986f05feadb9376f1":49:0
ECP write key: secp384r1, output longer by 48
depends_on:MBEDTLS_ECP_DP_SECP384R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP384R1:"d27335ea71664af244dd14e9fd1260715dfd8a7965571c48d709ee7a7962a156d706a90cbcb5df2986f05feadb9376f1":96:0
ECP write key: secp384r1, output longer by 49
depends_on:MBEDTLS_ECP_DP_SECP384R1_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_SECP384R1:"d27335ea71664af244dd14e9fd1260715dfd8a7965571c48d709ee7a7962a156d706a90cbcb5df2986f05feadb9376f1":97:0
ECP write key: Curve25519, nominal
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE25519:"a046e36bf0527c9d3b16154b82465edd62144c0ac1fc5a18506a2244ba449a44":32:0
ECP write key: Curve25519, output longer by 1
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE25519:"a046e36bf0527c9d3b16154b82465edd62144c0ac1fc5a18506a2244ba449a44":33:0
ECP write key: Curve25519, output longer by 32
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE25519:"a046e36bf0527c9d3b16154b82465edd62144c0ac1fc5a18506a2244ba449a44":64:0
ECP write key: Curve25519, output longer by 33
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE25519:"a046e36bf0527c9d3b16154b82465edd62144c0ac1fc5a18506a2244ba449a44":65:0
ECP write key: Curve448, nominal
depends_on:MBEDTLS_ECP_DP_CURVE448_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE448:"3c262fddf9ec8e88495266fea19a34d28882acef045104d0d1aae121700a779c984c24f8cdd78fbff44943eba368f54b29259a4f1c600ad3":56:0
ECP write key: Curve448, output longer by 1
depends_on:MBEDTLS_ECP_DP_CURVE448_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE448:"3c262fddf9ec8e88495266fea19a34d28882acef045104d0d1aae121700a779c984c24f8cdd78fbff44943eba368f54b29259a4f1c600ad3":57:0
ECP write key: Curve448, output longer by 32
depends_on:MBEDTLS_ECP_DP_CURVE448_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE448:"3c262fddf9ec8e88495266fea19a34d28882acef045104d0d1aae121700a779c984c24f8cdd78fbff44943eba368f54b29259a4f1c600ad3":112:0
ECP write key: Curve448, output longer by 33
depends_on:MBEDTLS_ECP_DP_CURVE448_ENABLED
ecp_write_key:MBEDTLS_ECP_DP_CURVE448:"3c262fddf9ec8e88495266fea19a34d28882acef045104d0d1aae121700a779c984c24f8cdd78fbff44943eba368f54b29259a4f1c600ad3":113:0
ECP mod p192 small (more than 192 bits, less limbs than 2 * 192 bits)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED:MBEDTLS_ECP_NIST_OPTIM
ecp_fast_mod:MBEDTLS_ECP_DP_SECP192R1:"0100000000000103010000000000010201000000000001010100000000000100"

47
tests/suites/test_suite_ecp.function
View file

@ -1236,6 +1236,53 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE */
void ecp_write_key(int grp_id, data_t *in_key,
int exported_size, int expected_ret)
{
mbedtls_ecp_keypair key;
mbedtls_ecp_keypair_init(&key);
unsigned char *exported = NULL;
TEST_EQUAL(mbedtls_ecp_read_key(grp_id, &key, in_key->x, in_key->len), 0);
TEST_CALLOC(exported, exported_size);
TEST_EQUAL(mbedtls_ecp_write_key(&key, exported, exported_size),
expected_ret);
if (expected_ret == 0) {
size_t length = (key.grp.nbits + 7) / 8;
TEST_LE_U(length, exported_size);
const unsigned char *key_start = NULL;
const unsigned char *zeros_start = NULL;
switch (mbedtls_ecp_get_type(&key.grp)) {
case MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS:
key_start = exported + exported_size - length;
zeros_start = exported;
break;
case MBEDTLS_ECP_TYPE_MONTGOMERY:
key_start = exported;
zeros_start = exported + length;
break;
default:
TEST_FAIL("Unknown ECP curve type");
break;
}
TEST_MEMORY_COMPARE(in_key->x, in_key->len,
key_start, length);
for (size_t i = 0; i < exported_size - length; i++) {
mbedtls_test_set_step(i);
TEST_EQUAL(zeros_start[i], 0);
}
}
exit:
mbedtls_ecp_keypair_free(&key);
mbedtls_free(exported);
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_TEST_HOOKS:MBEDTLS_ECP_MONTGOMERY_ENABLED:MBEDTLS_ECP_LIGHT */
void genkey_mx_known_answer(int bits, data_t *seed, data_t *expected)
{