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use fixed authentication tag length of 16 octets in AES GCM decryption #126

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use fixed authentication tag length of 16 octets in AES GCM decryption #126

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6 changes: 6 additions & 0 deletions src/jwe.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1225,6 +1225,12 @@ static bool _cjose_jwe_decrypt_dat_a256gcm(cjose_jwe_t *jwe, cjose_err *err)
goto _cjose_jwe_decrypt_dat_a256gcm_fail;
}

if (jwe->enc_auth_tag.raw_len != 16)
{
CJOSE_ERROR(err, CJOSE_ERR_CRYPTO);
goto _cjose_jwe_decrypt_dat_aes_gcm_fail;
}

// set the expected GCM-mode authentication tag
if (EVP_CIPHER_CTX_ctrl(ctx, CJOSE_EVP_CTRL_GCM_SET_TAG, jwe->enc_auth_tag.raw_len, jwe->enc_auth_tag.raw) != 1)
{
Expand Down
58 changes: 58 additions & 0 deletions test/check_jwe.c
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Expand Up @@ -809,6 +809,63 @@ START_TEST(test_cjose_jwe_decrypt_aes)
}
END_TEST

START_TEST(test_cjose_jwe_decrypt_aes_gcm)
{
cjose_err err;

const char *key = JWK_OCT_32;
const char *plain1 = "Live long and prosper.";
char *compact1 = "eyJhbGciOiAiZGlyIiwgImVuYyI6ICJBMjU2R0NNIn0..Du_9fxxV-zrReaWC.aS_rpokeuxkaPc2sykcQDCQuJCYoww.GpeKGEqd8KQ0v6JNea5aSA";
char *compact2 = "eyJhbGciOiAiZGlyIiwgImVuYyI6ICJBMjU2R0NNIn0..Du_9fxxV-zrReaWC.aS_rpokeuxkaPc2sykcQDCQuJCYoww.Gp";

cjose_jwk_t *jwk = cjose_jwk_import(key, strlen(key), &err);
ck_assert_msg(NULL != jwk,
"cjose_jwk_import failed: "
"%s, file: %s, function: %s, line: %ld",
err.message, err.file, err.function, err.line);

cjose_jwe_t *jwe1 = cjose_jwe_import(compact1, strlen(compact1), &err);
ck_assert_msg(NULL != jwe1,
"cjose_jwe_import failed: "
"%s, file: %s, function: %s, line: %ld",
err.message, err.file, err.function, err.line);

uint8_t *plain2 = NULL;
size_t plain2_len = 0;
plain2 = cjose_jwe_decrypt(jwe1, jwk, &plain2_len, &err);
ck_assert_msg(NULL != plain2,
"cjose_jwe_decrypt failed: "
"%s, file: %s, function: %s, line: %ld",
err.message, err.file, err.function, err.line);

ck_assert_msg(plain2_len == strlen(plain1),
"length of decrypted plaintext does not match length of original, "
"expected: %lu, found: %lu",
strlen(plain1), plain2_len);
ck_assert_msg(strncmp(plain1, plain2, plain2_len) == 0, "decrypted plaintext does not match encrypted plaintext");

cjose_get_dealloc()(plain2);
cjose_jwe_release(jwe1);

cjose_jwe_t *jwe2 = cjose_jwe_import(compact2, strlen(compact2), &err);
ck_assert_msg(NULL != jwe2,
"cjose_jwe_import failed: "
"%s, file: %s, function: %s, line: %ld",
err.message, err.file, err.function, err.line);

uint8_t *plain3 = NULL;
size_t plain3_len = 0;
plain3 = cjose_jwe_decrypt(jwe2, jwk, &plain3_len, &err);
ck_assert_msg(NULL == plain3,
"cjose_jwe_decrypt succeeded where it should have failed: "
"%s, file: %s, function: %s, line: %ld",
err.message, err.file, err.function, err.line);

cjose_jwe_release(jwe2);
cjose_jwk_release(jwk);
}
END_TEST

START_TEST(test_cjose_jwe_decrypt_rsa)
{
struct cjose_jwe_decrypt_rsa
Expand Down Expand Up @@ -1210,6 +1267,7 @@ Suite *cjose_jwe_suite()
tcase_add_test(tc_jwe, test_cjose_jwe_self_encrypt_self_decrypt_large);
tcase_add_test(tc_jwe, test_cjose_jwe_self_encrypt_self_decrypt_many);
tcase_add_test(tc_jwe, test_cjose_jwe_decrypt_aes);
tcase_add_test(tc_jwe, test_cjose_jwe_decrypt_aes_gcm);
tcase_add_test(tc_jwe, test_cjose_jwe_decrypt_rsa);
tcase_add_test(tc_jwe, test_cjose_jwe_encrypt_with_bad_header);
tcase_add_test(tc_jwe, test_cjose_jwe_encrypt_with_bad_key);
Expand Down