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Thank you for your response Thulasi, this helped. I'm posting this back to the OpenSSL users list in case it helps anyone else, and in case anyone can help with my additional questions. While waiting for responses, I've been able to find out how my certificate
and keys were generated. I'd like to walk through that to hopefully verify I'm handling things correctly.
First, here is how my EC parameters file was generated:
openssl ecparam -name prime256v1 -genkey -out myecparamsfile.pem
And the resulting file:
M640A-SAIL:/etc/ssl # openssl ecparam -in myecparamsfile.pem -text ASN1 OID: prime256v1 NIST CURVE: P-256 -----BEGIN EC PARAMETERS----- BggqhkjOPQMBBw== -----END EC PARAMETERS----- # openssl ecparam -in myecparamsfile.pem -text ASN1 OID: prime256v1 NIST CURVE: P-256 -----BEGIN EC PARAMETERS----- BggqhkjOPQMBBw== -----END EC PARAMETERS-----
Is this good so far? Do I need the -genkey?
Then I take this file and use it when I generate my certificate and private key pair, here is the openssl command I used:
openssl req -nodes -sha256 -newkey ec:/etc/ssl/private/myecparamsfile.pem -keyout mykeyout.pem -new -out mycertfileout.pem -config /etc/ssl/openssl.cnf -x509 -days 365 -outform pem
Generating a EC private key
writing new private key to 'mykeyout.pem'
<parameter input snipped>
And the resulting key:
# cat mykeyout.pem
-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgbfUwVhomun9Q5IAY
xTOAn+sDoXZ+k4UWkvUyfshPBJ6hRANCAAQsakFVUTV4JmfVJH31XOvHVhhBodnV
8evYCJSd2Jgo4uOomCSh3oekKL+Tia+LOmynygfvmneOX2YadoNr9uzH
-----END PRIVATE KEY-----
# openssl ec -noout -text -in mykeyout.pem
read EC key
Private-Key: (256 bit)
priv:
6d:f5:30:56:1a:26:ba:7f:50:e4:80:18:c5:33:80:
9f:eb:03:a1:76:7e:93:85:16:92:f5:32:7e:c8:4f:
04:9e
pub:
04:2c:6a:41:55:51:35:78:26:67:d5:24:7d:f5:5c:
eb:c7:56:18:41:a1:d9:d5:f1:eb:d8:08:94:9d:d8:
98:28:e2:e3:a8:98:24:a1:de:87:a4:28:bf:93:89:
af:8b:3a:6c:a7:ca:07:ef:9a:77:8e:5f:66:1a:76:
83:6b:f6:ec:c7
ASN1 OID: prime256v1
NIST CURVE: P-256
And certificate:
M740A-PMM1:/etc/ssl # openssl x509 -text -in mycertfileout.pem
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
e2:2f:c6:e4:bf:f1:de:20
Signature Algorithm: ecdsa-with-SHA256
Issuer: C=US, ST=NY, L=Loc,
O=Org, OU=test,
CN=My Name/emailAddress=test@example.com
Validity
Not Before: Feb 13 16:11:39 2020 GMT
Not After : Feb 12 16:11:39 2021 GMT
Subject: C=US, ST=NY, L=Loc, O=Org, OU=test, CN=My Name/emailAddress=test@example.com
Subject Public Key Info:
Public Key Algorithm: id-ecPublicKey
Public-Key: (256 bit)
pub:
04:2c:6a:41:55:51:35:78:26:67:d5:24:7d:f5:5c:
eb:c7:56:18:41:a1:d9:d5:f1:eb:d8:08:94:9d:d8:
98:28:e2:e3:a8:98:24:a1:de:87:a4:28:bf:93:89:
af:8b:3a:6c:a7:ca:07:ef:9a:77:8e:5f:66:1a:76:
83:6b:f6:ec:c7
ASN1 OID: prime256v1
NIST CURVE: P-256
X509v3 extensions:
X509v3 Subject Key Identifier:
D6:8A:F3:3B:4E:A1:F8:F8:34:C1:1B:7A:EC:BF:9B:58:7F:68:4A:D9
X509v3 Authority Key Identifier:
keyid:D6:8A:F3:3B:4E:A1:F8:F8:34:C1:1B:7A:EC:BF:9B:58:7F:68:4A:D9
X509v3 Basic Constraints:
CA:TRUE
Signature Algorithm: ecdsa-with-SHA256
30:44:02:20:37:f0:f7:f7:4a:b4:8e:8f:64:72:e4:d1:31:9f:
a1:36:c5:5d:f3:42:4c:24:37:75:cf:b6:55:b0:66:1b:6e:63:
02:20:39:18:81:f8:6c:86:3a:57:74:05:cc:99:6c:d9:dc:6a:
a2:20:98:4c:66:a1:97:d1:c7:ea:42:b4:01:1a:f7:b2Then I call the APIs as described in my first email to use them:
ctx = SSL_CTX_new(TLS_method()); status = SSL_CTX_use_PrivateKey_file(ctx,<keyfile>,SSL_FILETYPE_PEM); status = SSL_CTX_use_certificate_file(ctx, ,<certfile>,SSL_FILETYPE_PEM); // Verify the cert and key are a pair status = SSL_CTX_check_private_key(ctx); Then call the APIs to set the curves and allow the server to pick the appropriate curve for the client:
status = SSL_CTX_set1_curves_list(ctx, "P-521:P-384:P-256"); status = SSL_CTX_set_ecdh_auto(ctx, 1); That should be it, right? The EC parameters file has been used to generate the private key, it does not need to be read in by an API call.
With the steps above, I get a successful TLS connection from a client using ECDHE-ECDSA-AES256-GCM-SHA384.
And yes, I think my main confusion was on what to do with the DH parameters file. I thought using ECDHE key exchange was similar to DSA with DH. With ECDHE, I don't need to read in a parameters file at all.
If there's anything wrong above, please let me know, otherwise, thanks for all the help!
From: Thulasi Goriparthi <thulasi.goriparthi@xxxxxxxxx>
Sent: Wednesday, February 12, 2020 8:29 AM To: jetson23@xxxxxxxxxxx <jetson23@xxxxxxxxxxx> Cc: rsalz@xxxxxxxxxx <rsalz@xxxxxxxxxx> Subject: Re: Questions about using Elliptic Curve ciphers in OpenSSL To clarify further, EC keys can be generated from either explicit (group) parameters or named curves which are standardized numbers to specific group parameters.
Explicit/Custom EC parameters are not recommended/convenient/usual. Your key contains parameters in the form of a named curve (p-256).
You are probably getting confused between dhparam used to generate ephemeral keys for DHE based key exchange and EC curve selection for ECDHE based key exchange.
Curve selection for ECDHE will be done from the list of curves offered by the client and can be different from the curve used in the server's certificate(ECDSA).
Thanks,
Thulasi.
On Tue, 11 Feb, 2020, 23:24 Salz, Rich via openssl-users, <openssl-users@xxxxxxxxxxx> wrote:
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