[PATCH 2/5] lib/security: add in openssl support

[Brett Grandbois]

On 14/05/18 15:35, Samuel Mendoza-Jonas wrote:
> On Fri, 2018-05-04 at 11:40 +1000, Brett Grandbois wrote:
>> Refactor to export a generic API rather than specific gpg_ prefixes by
>> changing gpg.h to security.h and renaming some of the exports.
>>
>> Break out the common and specific functionality into common.c and
>> none.c/gpg.c/openssl.c for no/gpgme/openssl modes respectively.
>>
>> gpgme should work as before
>>
>> OpenSSL support works like this:
>>
>> The pb-lockdown file is a PKCS12 file or X509 certificate or PEM-encoded
>> raw public key.  To follow the current conventions the presence of a
>> PKCS12 file as a lockdown signals decrypt mode because of the presence
>> of the private key, anything else signals signature verification mode.
>> The keyring path is currently ignored but in the future could be used to
>> point to an X509 certificate chain for validity checking. Because of
>> this self-signed certificates are currently supported and really just
>> used as a public key container.
>>
>> Signature verification mode supports:
>>
>> * Cryptographic Message Syntax (CMS) as detached S/MIME, this is really
>>    more for consistency for the encryption mode (see below). This mode
>>    requires the lockdown file to be an X509 certificate.
>>
>>    A sample creation command would be:
>>      openssl cms -sign -in (infile) -out (outfile) -binary -nocerts \
>>          -inkey (private key) -signer (recipient certificate)
>>
>> * Raw signature digest as output from openssl dgst -sign command.  This
>>    mode can have the lockdown file be an X509 certificate or a PEM raw
>>    public key but the digest algorithm must be pre-defined by the
>>    VERIFY_DIGEST configure argument. The default is SHA256.
>>
>>    A sample creation command would be:
>>      openssl dgst -sign (private key) -out (outfile) -(digest mode) \
>>           (infile)
>>
>> Decryption mode supports:
>>
>> * CMS signed-envelope as attached S/MIME.  This is for consistency with
>>    the current expectation of no external file for decryption.  Some
>>    future enhancement could be to come up with some proprietary external
>>    file format containing the cipher used, the encrypted cipher key, and
>>    the IV (if necessary).
>>
>>    A sample creation command would be:
>>      openssl cms -sign -in (infile) -signer (recipient certificate) \
>>          -binary -nocerts -nodetach -inkey (private key) | \
>>          openssl cms -encrypt -(cipher mode) -out (outfile) \
>>             (recipient certificate)
>>
>> The PKCS12 file is expecting the private key to have password of NULL or
>> "" as there is currently no mechanism to supply a custom one.
>>
>> Signed-off-by: Brett Grandbois <brett.grandbois at opengear.com>
>> ---
>>   lib/Makefile.am         |  42 +++--
>>   lib/security/common.c   | 230 ++++++++++++++++++++++++
>>   lib/security/gpg.c      | 202 +--------------------
>>   lib/security/gpg.h      |  83 ---------
>>   lib/security/none.c     |  61 +++++++
>>   lib/security/openssl.c  | 460 ++++++++++++++++++++++++++++++++++++++++++++++++
>>   lib/security/security.h |  46 +++++
>>   7 files changed, 833 insertions(+), 291 deletions(-)
>>   create mode 100644 lib/security/common.c
>>   delete mode 100644 lib/security/gpg.h
>>   create mode 100644 lib/security/none.c
>>   create mode 100644 lib/security/openssl.c
>>   create mode 100644 lib/security/security.h
> <snip>
>
>> +int verify_file_signature(const char *plaintext_filename,
>> +			  const char *signature_filename,
>> +			  FILE *authorized_signatures_handle,
>> +			  const char *keyring_path __attribute__((unused)))
>> +{
>> +	BIO *signature_bio = NULL, *plaintext_bio = NULL, *content_bio = NULL;
>> +	STACK_OF(X509) *certs = NULL;
>> +	CMS_ContentInfo *cms = NULL;
>> +	ssize_t bytes_read = -1;
>> +	EVP_PKEY *pkey = NULL;
>> +	char *sigbuf = NULL;
>> +	char rdbuf[8192];
>> +	EVP_MD_CTX ctx;
>> +	int nok = -1;
>> +	int siglen;
> My machine is running OpenSSL 1.1.0h and it complains here with:
>
> 	../lib/security/openssl.c: In function ‘verify_file_signature’:
> 	../lib/security/openssl.c:319:13: error: storage size of ‘ctx’ isn’t known
> 	  EVP_MD_CTX ctx;
> 		     ^~~
> 	../lib/security/openssl.c:425:2: warning: implicit declaration of function ‘EVP_MD_CTX_cleanup’; did you mean ‘EVP_MD_CTX_create’? [-Wimplicit-function-declaration]
> 	  EVP_MD_CTX_cleanup(&ctx);
> 	  ^~~~~~~~~~~~~~~~~~
> 	  EVP_MD_CTX_create
> 	../lib/security/openssl.c:319:13: warning: unused variable ‘ctx’ [-Wunused-variable]
> 	  EVP_MD_CTX ctx;
> 		     ^~~
>
> It looks like in 1.1 they made this struct opaque and now we need to use
> 	ctx = EVP_MD_CTX_create();
> and friends to set this up.
>
> I'm not convinced older OpenSSL recognises the new format though - we might need
> a wrapper to create the context depending on the library version :/
Hmm, I actually hadn't considered that.  Yes this was all based on 1.0.2 
not 1.1.0 but I'll take a look and see what I can do with the version 
macros.
>
> Otherwise everything else looks pretty good, fits in a lot cleaner than I expected!
>
> Cheers,
> Sam
>