dovecot 2.4 issue with openssl >= 3.0.8

Michal Hlavinka Tue, 15 Aug 2023 15:16:33 -0700

Hi,

I've started testing main git branch and found an issue with openssl 3.


Test suite fails:
test_load_v1_key ........................................... : ok
test-crypto.c:445: Assert failed: ret == TRUE
test-crypto.c:446: Assert failed: error == NULL

Panic: file dcrypt-openssl3.c: line 2917(dcrypt_openssl_public_key_type): assertion failed: (key != NULL &&key->key != NULL)Error: Raw backtrace: test-crypto(+0x5af01) [0x55951b667f01] ->test-crypto(backtrace_get+0x2f) [0x55951b66877f] ->test-crypto(+0x31291) [0x55951b63e291] -> test-crypto(+0x312d5)[0x55951b63e2d5] -> test-crypto(+0x16025) [0x55951b623025] ->libdcrypt_openssl.so(+0x70ff) [0x7f5a995b60ff] -> test-crypto(+0x2a17b)[0x55951b63717b] -> test-crypto(+0x3055d) [0x55951b63d55d] ->test-crypto(test_run+0x6c) [0x55951b63d61c] -> test-crypto(main+0x4e)[0x55951b62b66e] -> libc.so.6(+0x27b4a) [0x7f5a995eeb4a] ->libc.so.6(__libc_start_main+0x8b) [0x7f5a995eec0b] ->test-crypto(_start+0x25) [0x55951b62b7e5]


The issue is caused by change in openssl >= 3.0.8

in lib-dcryt/dcrypt-openssl3.c method ec_key_get_pub_point_hex(...)

in old version (for openssl 1.x) it uses compressed format:

EC_POINT_point2hex(g, p, POINT_CONVERSION_COMPRESSED, NULL);

in openssl3 version it uses

EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY, buf,sizeof(buf), &len);


but key is created in dcrypt_evp_pkey_from_point(...)
with OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT, "uncompressed"

this was working in openssl pre 3.0.8 as compression format was ignoredwhen dumping data and used always compressed format.


From https://www.openssl.org/docs/man3.0/man7/EVP_KEYMGMT-EC.html

""" Before OpenSSL 3.0.8, the implementation of providers included withOpenSSL always opted for an encoding in compressed format,unconditionally. Since OpenSSL 3.0.8, the implementation has beenchanged to honor the OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMATparameter, if set, or to default to uncompressed format."""

I don't see simple way how to force compressed format just for dumpingdata without effecting the key itself. Method that can be used withcompression format argument is EC_POINT_point2hex but it requires quitelengthy extraction of EC_POINT first. I've tried this for testing with:


static const char *ec_key_get_pub_point_hex(const EVP_PKEY *pkey)
{
        if (!EVP_PKEY_is_a(pkey, "EC"))
                return NULL;
        size_t len;

EVP_PKEY_get_utf8_string_param(pkey, OSSL_PKEY_PARAM_GROUP_NAME, NULL,0, &len);

        buffer_t *parambuf = t_buffer_create(len+1);

EVP_PKEY_get_utf8_string_param(pkey, OSSL_PKEY_PARAM_GROUP_NAME, (char*)parambuf->data, len+1, &len);

        int nid = OBJ_txt2nid(parambuf->data);

EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY, NULL, 0,&len);

        parambuf = t_buffer_create(len+1);

EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY,(unsigned char *)parambuf->data, len+1, &len);


        EC_GROUP *ec_grp = EC_GROUP_new_by_curve_name(nid);
        if (ec_grp == NULL)
                return NULL;
        EC_POINT *point = EC_POINT_new(ec_grp);
        if (point == NULL) {
                EC_GROUP_free(ec_grp);
                return NULL;
        }

        if (!EC_POINT_oct2point(ec_grp, point, parambuf->data, len, NULL))
                return NULL;

char *ret = EC_POINT_point2hex(ec_grp, point,POINT_CONVERSION_COMPRESSED, NULL);

        EC_GROUP_free(ec_grp);
        EC_POINT_free(point);
        return ret;
}

and it fixed the issue, but there may be an easier way how to achieve that.

Cheers
Michal Hlavinka


_______________________________________________
dovecot mailing list -- dovecot@dovecot.org
To unsubscribe send an email to dovecot-le...@dovecot.org

dovecot 2.4 issue with openssl >= 3.0.8

Reply via email to