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| Date: Mon, 30 Sep 1996 12:43:15 +1000 (EST) |
| From: Eric Young <eay@mincom.com> |
| X-Sender: eay@orb |
| To: Sampo Kellomaki <sampo@neuronio.pt> |
| Cc: ssl-users@mincom.com, sampo@brutus.neuronio.pt |
| Subject: Re: Signing with envelope routines |
| In-Reply-To: <199609300037.BAA08729@brutus.neuronio.pt> |
| Message-Id: <Pine.SOL.3.91.960930121504.11800Y-100000@orb> |
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| |
| On Mon, 30 Sep 1996, Sampo Kellomaki wrote: |
| > I have been trying to figure out how to produce signatures with EVP_ |
| > routines. I seem to be able to read in private key and sign some |
| > data ok, but I can't figure out how I am supposed to read in |
| > public key so that I could verify my signature. I use self signed |
| > certificate. |
| |
| hmm... a rather poorly documented are of the library at this point in time. |
| |
| > I figured I should use |
| > EVP_PKEY* pkey = PEM_ASN1_read(d2i_PrivateKey, PEM_STRING_EVP_PKEY, |
| > fp, NULL, NULL); |
| > to read in private key and this seems to work Ok. |
| > |
| > However when I try analogous |
| > EVP_PKEY* pkey = PEM_ASN1_read(d2i_PublicKey, PEM_STRING_X509, |
| > fp, NULL, NULL); |
| |
| What you should do is |
| X509 *x509=PEM_read_X509(fp,NULL,NULL); |
| /* which is the same as PEM_ASN1_read(d2i_X509,PEM_STRING_X509,fp, |
| * NULL,NULL); */ |
| Then |
| EVP_PKEY *pkey=X509_extract_key(x509); |
| |
| There is also a X509_REQ_extract_key(req); |
| which gets the public key from a certificate request. |
| |
| I re-worked quite a bit of this when I cleaned up the dependancy on |
| RSA as the private key. |
| |
| > I figured that the second argument to PEM_ASN1_read should match the |
| > name in my PEM encoded object, hence PEM_STRING_X509. |
| > PEM_STRING_EVP_PKEY seems to be somehow magical |
| > because it matches whatever private key there happens to be. I could |
| > not find a similar constant to use with getting the certificate, however. |
| |
| :-), PEM_STRING_EVP_PKEY is 'magical' :-). In theory I should be using a |
| standard such as PKCS#8 to store the private key so that the type is |
| encoded in the asn.1 encoding of the object. |
| |
| > Is my approach of using PEM_ASN1_read correct? What should I pass in |
| > as name? Can I use normal (or even self signed) X509 certificate for |
| > verifying the signature? |
| |
| The actual public key is kept in the certificate, so basically you have |
| to load the certificate and then 'unpack' the public key from the |
| certificate. |
| |
| > When will SSLeay documentation be written ;-)? If I would contribute |
| > comments to the code, would Eric take time to review them and include |
| > them in distribution? |
| |
| :-) After SSLv3 and PKCS#7 :-). I actually started doing a function list |
| but what I really need to do is do quite a few 'this is how you do xyz' |
| type documents. I suppose the current method is to post to ssl-users and |
| I'll respond :-). |
| |
| I'll add a 'demo' directory for the next release, I've appended a |
| modified version of your program that works, you were very close :-). |
| |
| eric |
| |
| /* sign-it.cpp - Simple test app using SSLeay envelopes to sign data |
| 29.9.1996, Sampo Kellomaki <sampo@iki.fi> */ |
| |
| /* converted to C - eay :-) */ |
| |
| #include <stdio.h> |
| #include "rsa.h" |
| #include "evp.h" |
| #include "objects.h" |
| #include "x509.h" |
| #include "err.h" |
| #include "pem.h" |
| #include "ssl.h" |
| |
| void main () |
| { |
| int err; |
| int sig_len; |
| unsigned char sig_buf [4096]; |
| static char certfile[] = "plain-cert.pem"; |
| static char keyfile[] = "plain-key.pem"; |
| static char data[] = "I owe you..."; |
| EVP_MD_CTX md_ctx; |
| EVP_PKEY * pkey; |
| FILE * fp; |
| X509 * x509; |
| |
| /* Just load the crypto library error strings, |
| * SSL_load_error_strings() loads the crypto AND the SSL ones */ |
| /* SSL_load_error_strings();*/ |
| ERR_load_crypto_strings(); |
| |
| /* Read private key */ |
| |
| fp = fopen (keyfile, "r"); if (fp == NULL) exit (1); |
| pkey = (EVP_PKEY*)PEM_ASN1_read ((char *(*)())d2i_PrivateKey, |
| PEM_STRING_EVP_PKEY, |
| fp, |
| NULL, NULL); |
| if (pkey == NULL) { ERR_print_errors_fp (stderr); exit (1); } |
| fclose (fp); |
| |
| /* Do the signature */ |
| |
| EVP_SignInit (&md_ctx, EVP_md5()); |
| EVP_SignUpdate (&md_ctx, data, strlen(data)); |
| sig_len = sizeof(sig_buf); |
| err = EVP_SignFinal (&md_ctx, |
| sig_buf, |
| &sig_len, |
| pkey); |
| if (err != 1) { ERR_print_errors_fp (stderr); exit (1); } |
| EVP_PKEY_free (pkey); |
| |
| /* Read public key */ |
| |
| fp = fopen (certfile, "r"); if (fp == NULL) exit (1); |
| x509 = (X509 *)PEM_ASN1_read ((char *(*)())d2i_X509, |
| PEM_STRING_X509, |
| fp, NULL, NULL); |
| if (x509 == NULL) { ERR_print_errors_fp (stderr); exit (1); } |
| fclose (fp); |
| |
| /* Get public key - eay */ |
| pkey=X509_extract_key(x509); |
| if (pkey == NULL) { ERR_print_errors_fp (stderr); exit (1); } |
| |
| /* Verify the signature */ |
| |
| EVP_VerifyInit (&md_ctx, EVP_md5()); |
| EVP_VerifyUpdate (&md_ctx, data, strlen((char*)data)); |
| err = EVP_VerifyFinal (&md_ctx, |
| sig_buf, |
| sig_len, |
| pkey); |
| if (err != 1) { ERR_print_errors_fp (stderr); exit (1); } |
| EVP_PKEY_free (pkey); |
| printf ("Signature Verified Ok.\n"); |
| } |
| |
| |
| |
| |
| |