Re: [openssl-users] beginner needs advice on data signature/verification
(continuing top posting to keep thread consistent) Note that the point of using an X.509 signature at file creation time and/or client approval time was to reuse the internal file structure that is already designed to hold that particular signature format (specifically, the internal file structure that would eventually hold the final signature, which was already specified to be in that format). Thus the idea was to simplify and reuse code, given the existence of code, tools and data formats to sign those particular files with X.509 signatures. This was also (presumably) the reason Microsoft did it this way. But yes, of cause if the file generation is already secure, then the secure file generation machine should apply an initial signature and the client just add some kind of counter-signature authorizing this particular one of the securely generated files. On 24/06/2015 15:24, Michael Wojcik wrote: In Marco's original description, the file is created by a trusted system and then transmitted to the client. Then, later, the client transmits it to the server, which verifies the contents. If the file is signed by the creating system, it doesn't matter if the client is compromised. A compromised client can refuse to send the file, or it can send a forged or corrupted file, but the server can dectect all of those cases. It's not clear from Marco's description whether the system that creates the file can perform the signing process, but I don't see any reason (in the description) why not. It would help if this point were clarified. The Windows driver-signing process and similar look wildly overengineered for Marco's purposes, if my understanding of his requirements is correct. They have a very different threat model - and that's why this isn't a common requirement. Windows drivers are created by thousands of organizations and consumed by thousands of end users. Marco has files created on a trusted system (or handful of trusted systems) he controls, and verified by trusted systems he controls. His followup message below says data has to be signed with an X.509 certificates public key that already exists. I'm guessing this actually means data has to be signed with the private key corresponding to a public key that happens to be in an X.509 certificate that already exists. That doesn't mean X.509 PKI must be used; X.509 isn't some sort of virus that infects everything it touches (appearances to the contrary). There's an asymmetric key pair of some sort - RSA probably - and we need to use it for signing. Fine. Here's what I'd do: the originating trusted system creates the data and runs openssl rsautl -sign with appropriate parameters to create a signature. (Just script the openssl command-line utility; this is a trusted system, so why reimplement the code?) Add the signature to the proprietary file format. Send the whole thing to the client. Client subsequently sends the signed data and signature to the server, as part of a file in the proprietary format, along with whatever unsigned data is included. Server extracts the signed data and signature, and uses openssl rsautl -verify to verify it. Michael Wojcik Technology Specialist, Micro Focus (original text snipped) Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded ___ openssl-users mailing list To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users
Re: [openssl-users] beginner needs advice on data signature/verification
In Marco's original description, the file is created by a trusted system and then transmitted to the client. Then, later, the client transmits it to the server, which verifies the contents. If the file is signed by the creating system, it doesn't matter if the client is compromised. A compromised client can refuse to send the file, or it can send a forged or corrupted file, but the server can dectect all of those cases. It's not clear from Marco's description whether the system that creates the file can perform the signing process, but I don't see any reason (in the description) why not. It would help if this point were clarified. The Windows driver-signing process and similar look wildly overengineered for Marco's purposes, if my understanding of his requirements is correct. They have a very different threat model - and that's why this isn't a common requirement. Windows drivers are created by thousands of organizations and consumed by thousands of end users. Marco has files created on a trusted system (or handful of trusted systems) he controls, and verified by trusted systems he controls. His followup message below says data has to be signed with an X.509 certificates public key that already exists. I'm guessing this actually means data has to be signed with the private key corresponding to a public key that happens to be in an X.509 certificate that already exists. That doesn't mean X.509 PKI must be used; X.509 isn't some sort of virus that infects everything it touches (appearances to the contrary). There's an asymmetric key pair of some sort - RSA probably - and we need to use it for signing. Fine. Here's what I'd do: the originating trusted system creates the data and runs openssl rsautl -sign with appropriate parameters to create a signature. (Just script the openssl command-line utility; this is a trusted system, so why reimplement the code?) Add the signature to the proprietary file format. Send the whole thing to the client. Client subsequently sends the signed data and signature to the server, as part of a file in the proprietary format, along with whatever unsigned data is included. Server extracts the signed data and signature, and uses openssl rsautl -verify to verify it. Michael Wojcik Technology Specialist, Micro Focus From: openssl-users [mailto:openssl-users-boun...@openssl.org] On Behalf Of Jakob Bohm Sent: Wednesday, June 24, 2015 01:53 To: openssl-users@openssl.org Subject: Re: [openssl-users] beginner needs advice on data signature/verification (Continuing top posting to keep thread consistent). First of all, if the client itself is compromised, the file content can be compromised just before you do whatever you do to assure the server that this was what the user of the client wanted. No way to fix that other than to keep the client free of compromise. Now the common solution used by driver and program signing programs such as Symbian signed (discontinued), Windows driver package signing for compatibility, Windows driver binary signing for Windows 10, and older versions of Windows Mobile 5.x/6.x signing is this: 1. Client has a unique X509 certificate with a private key known only to that client. Doesn't matter who issued the certificate, but the server needs to have its own known genuine copy of that certificate. That certificate should be such that no one except that client and that server trusts things for being signed by it. 2. Client signs the file/message with its private certificate exactly as if that would be the final signature (even though almost no one will trust it). 3. Client sends signed file/message to server. 4. Server verifies the signed file/message using its private list of trusted client certificates. 5. Server maps the verified signature to the identity to be used for the final signature. 6. Server talks to its closely related CA to get a brand new single-use-only certificate for the identity (with a serial number added as an extra subject name element). 7. Server removes the client signature and signs the file/message with the brand new certificate for the final identity. 8. Server throws away the private key, so that no more files can be signed with that certificate, ever. 9. If the server ever signs anything by mistake, it (or an admin if the server was permanently compromised) asks its closely related CA to revoke the affected single-use certificate. 10. If the client certificate needs to be revoked due to the certificate or its user being compromised on some current or past time/date, the related CA revokes all the single-use certificates for that identity since that date/time. Other/replacement client certificates for the same (visible) identity remain valid because single-use certificates for those requests were never revoked. 11. Note that in this setup, there is no need for a time stamping service, simply give the single-use certificate the long
Re: [openssl-users] beginner needs advice on data signature/verification
Many thanks for the answer. I should have been more specific on the requirements right away. The file was really just an example to keep it simple. Reading my own writing, I would probably have suggested what you did :-) So here are the facts: - client/server are not connected to the internet - the network protocol is existing and proprietary - the file structure is existing and proprietary, but can be extended to allow for additional signature information to be embedded that will be sent to the server - the data actually transferred (and to be signed) is part of that file - the data has to be signed with an X.509 certificates public key that already exists S/MIME does pretty much do what I want to do. However the network protocol or the data to be signed cannot be changed for compatibility reasons. Under these circumstances, I don't really see how I could achieve my goal easier than by openssl directly. Considering the very common requirement: I was thinking of i.e. windows driver signatures, android/ios app signatures and similar mechanisms to ensure that files are from a trusted source. Am 22.06.2015 um 14:44 schrieb Michael Wojcik: Response inline below, prefixed with MW. (Unfortunately Outlook is incapable of replying to HTML messages properly, so you'll have to excuse the formatting.) Michael Wojcik Technology Specialist, Micro Focus *From:*openssl-users [mailto:openssl-users-boun...@openssl.org] *On Behalf Of *Marco Warga *Sent:* Saturday, June 20, 2015 04:48 *To:* openssl-users@openssl.org *Subject:* [openssl-users] beginner needs advice on data signature/verification Hi, I hope some of you could give me advice on my project using openssl. MW: Why are you using OpenSSL for this application? You want to create a file on a trusted system, pass it through an untrusted intermediary, and process it on another trusted system. Why not simply use an existing mechanism like secure email? (GPG is the obvious choice, unless there are licensing issues.) If you are determined to create your own protocol from primitives, then really all you appear to need here is an HMAC. Don't involve the horrific mess that is X.509 PKI unless it actually provides some benefit. Lets say I have a server/service on a machine processing a file a corresponding client sends. That file is usually created by me on a clean third machine. The server side is assumed to be uncompromised (no hacker). The client side may be compromised. Now I need to make sure that the service only accepts those files that are created by me. I believe that is a very common requirement and has been done alot of times - I just can't find tutorials on how to implement it. Know any ? MW: No, but that's probably because what you've described isn't a very common requirement. It's too vague. We don't know what problem you're actually trying to solve. It may be that you just need to send a file with a verifier, which - as I noted above - /is/ commonly done, generally using something like GPG or (for roll-your-own protocols where both ends are controlled by the same party) an HMAC. Lets assume I have an x509 cert together with its private key signed by a ca owned by me. The trusted ca cert will be present on the server side. This is what I plan to do: 1.) Create the data files/blobs and sign them using the priv key of the cert. Distribute the cert and the signature along with (or inside) the data file. 2.) Have the client send that data file to the server (cert/sig first) 3.) Service receives the cert, builds a cert store with the local ca cert in it and verifies the client's cert with X509_verify_cert() 4.) if cert verifies ok, service compares the signature against the one calculated from the incoming data using the public key that came inside the cert just verified Would this be the right approach considering that anything the client sends may be forged (cert, sig, data...) ? MW: It's safe from malicious behavior by the client, under a threat model where an attacker is not able to forge client certificates or client signatures. In other words, it's safe as long as the private keys are neither leaked nor forced. Or would it be safer to have the cert used for signing stored on the server side and not send with the data (instead just its subject protected by the signature) ? MW: Irrelevant to the security of the scheme. Simpler from a development and operations standpoint. But using something like PGP/GPG or S/MIME would be simpler yet. There are any number of examples online for signing a file and verifying its signature. Thanks alot, Marco X509_verify_cert X509_verify_cert Click here https://www.mailcontrol.com/sr/SMsSvn1riRfGX2PQPOmvUsrLibhXE7+S86glxWVUEjKk%21XLlG9uNumpG1wkqEL+kqdX9II%21hjWj1JTd%211uc+%21w== to report this email as spam. ___ openssl-users mailing list To unsubscribe: https://mta.openssl.org/mailman
Re: [openssl-users] beginner needs advice on data signature/verification
for the e-mail signing or document-signing extended usage attribute, not the object-signing one. On 23/06/2015 19:55, Marco Warga wrote: Many thanks for the answer. I should have been more specific on the requirements right away. The file was really just an example to keep it simple. Reading my own writing, I would probably have suggested what you did :-) So here are the facts: - client/server are not connected to the internet - the network protocol is existing and proprietary - the file structure is existing and proprietary, but can be extended to allow for additional signature information to be embedded that will be sent to the server - the data actually transferred (and to be signed) is part of that file - the data has to be signed with an X.509 certificates public key that already exists S/MIME does pretty much do what I want to do. However the network protocol or the data to be signed cannot be changed for compatibility reasons. Under these circumstances, I don't really see how I could achieve my goal easier than by openssl directly. Considering the very common requirement: I was thinking of i.e. windows driver signatures, android/ios app signatures and similar mechanisms to ensure that files are from a trusted source. Am 22.06.2015 um 14:44 schrieb Michael Wojcik: Response inline below, prefixed with MW. (Unfortunately Outlook is incapable of replying to HTML messages properly, so you'll have to excuse the formatting.) *From:*openssl-users [mailto:openssl-users-boun...@openssl.org] *On Behalf Of *Marco Warga *Sent:* Saturday, June 20, 2015 04:48 *To:* openssl-users@openssl.org *Subject:* [openssl-users] beginner needs advice on data signature/verification Hi, I hope some of you could give me advice on my project using openssl. MW: Why are you using OpenSSL for this application? You want to create a file on a trusted system, pass it through an untrusted intermediary, and process it on another trusted system. Why not simply use an existing mechanism like secure email? (GPG is the obvious choice, unless there are licensing issues.) If you are determined to create your own protocol from primitives, then really all you appear to need here is an HMAC. Don't involve the horrific mess that is X.509 PKI unless it actually provides some benefit. Lets say I have a server/service on a machine processing a file a corresponding client sends. That file is usually created by me on a clean third machine. The server side is assumed to be uncompromised (no hacker). The client side may be compromised. Now I need to make sure that the service only accepts those files that are created by me. I believe that is a very common requirement and has been done alot of times - I just can't find tutorials on how to implement it. Know any ? MW: No, but that's probably because what you've described isn't a very common requirement. It's too vague. We don't know what problem you're actually trying to solve. It may be that you just need to send a file with a verifier, which - as I noted above - /is/ commonly done, generally using something like GPG or (for roll-your-own protocols where both ends are controlled by the same party) an HMAC. Lets assume I have an x509 cert together with its private key signed by a ca owned by me. The trusted ca cert will be present on the server side. This is what I plan to do: 1.) Create the data files/blobs and sign them using the priv key of the cert. Distribute the cert and the signature along with (or inside) the data file. 2.) Have the client send that data file to the server (cert/sig first) 3.) Service receives the cert, builds a cert store with the local ca cert in it and verifies the client's cert with X509_verify_cert() 4.) if cert verifies ok, service compares the signature against the one calculated from the incoming data using the public key that came inside the cert just verified Would this be the right approach considering that anything the client sends may be forged (cert, sig, data...) ? MW: It's safe from malicious behavior by the client, under a threat model where an attacker is not able to forge client certificates or client signatures. In other words, it's safe as long as the private keys are neither leaked nor forced. Or would it be safer to have the cert used for signing stored on the server side and not send with the data (instead just its subject protected by the signature) ? MW: Irrelevant to the security of the scheme. Simpler from a development and operations standpoint. But using something like PGP/GPG or S/MIME would be simpler yet. There are any number of examples online for signing a file and verifying its signature. Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones
Re: [openssl-users] beginner needs advice on data signature/verification
Response inline below, prefixed with MW. (Unfortunately Outlook is incapable of replying to HTML messages properly, so you'll have to excuse the formatting.) Michael Wojcik Technology Specialist, Micro Focus From: openssl-users [mailto:openssl-users-boun...@openssl.org] On Behalf Of Marco Warga Sent: Saturday, June 20, 2015 04:48 To: openssl-users@openssl.org Subject: [openssl-users] beginner needs advice on data signature/verification Hi, I hope some of you could give me advice on my project using openssl. MW: Why are you using OpenSSL for this application? You want to create a file on a trusted system, pass it through an untrusted intermediary, and process it on another trusted system. Why not simply use an existing mechanism like secure email? (GPG is the obvious choice, unless there are licensing issues.) If you are determined to create your own protocol from primitives, then really all you appear to need here is an HMAC. Don't involve the horrific mess that is X.509 PKI unless it actually provides some benefit. Lets say I have a server/service on a machine processing a file a corresponding client sends. That file is usually created by me on a clean third machine. The server side is assumed to be uncompromised (no hacker). The client side may be compromised. Now I need to make sure that the service only accepts those files that are created by me. I believe that is a very common requirement and has been done alot of times - I just can't find tutorials on how to implement it. Know any ? MW: No, but that's probably because what you've described isn't a very common requirement. It's too vague. We don't know what problem you're actually trying to solve. It may be that you just need to send a file with a verifier, which - as I noted above - is commonly done, generally using something like GPG or (for roll-your-own protocols where both ends are controlled by the same party) an HMAC. Lets assume I have an x509 cert together with its private key signed by a ca owned by me. The trusted ca cert will be present on the server side. This is what I plan to do: 1.) Create the data files/blobs and sign them using the priv key of the cert. Distribute the cert and the signature along with (or inside) the data file. 2.) Have the client send that data file to the server (cert/sig first) 3.) Service receives the cert, builds a cert store with the local ca cert in it and verifies the client's cert with X509_verify_cert() 4.) if cert verifies ok, service compares the signature against the one calculated from the incoming data using the public key that came inside the cert just verified Would this be the right approach considering that anything the client sends may be forged (cert, sig, data...) ? MW: It's safe from malicious behavior by the client, under a threat model where an attacker is not able to forge client certificates or client signatures. In other words, it's safe as long as the private keys are neither leaked nor forced. Or would it be safer to have the cert used for signing stored on the server side and not send with the data (instead just its subject protected by the signature) ? MW: Irrelevant to the security of the scheme. Simpler from a development and operations standpoint. But using something like PGP/GPG or S/MIME would be simpler yet. There are any number of examples online for signing a file and verifying its signature. Thanks alot, Marco X509_verify_cert X509_verify_cert Click herehttps://www.mailcontrol.com/sr/SMsSvn1riRfGX2PQPOmvUsrLibhXE7+S86glxWVUEjKk!XLlG9uNumpG1wkqEL+kqdX9II!hjWj1JTd!1uc+!w== to report this email as spam. ___ openssl-users mailing list To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users
[openssl-users] beginner needs advice on data signature/verification
Hi, I hope some of you could give me advice on my project using openssl. Lets say I have a server/service on a machine processing a file a corresponding client sends. That file is usually created by me on a clean third machine. The server side is assumed to be uncompromised (no hacker). The client side may be compromised. Now I need to make sure that the service only accepts those files that are created by me. I believe that is a very common requirement and has been done alot of times - I just can't find tutorials on how to implement it. Know any ? Lets assume I have an x509 cert together with its private key signed by a ca owned by me. The trusted ca cert will be present on the server side. This is what I plan to do: 1.) Create the data files/blobs and sign them using the priv key of the cert. Distribute the cert and the signature along with (or inside) the data file. 2.) Have the client send that data file to the server (cert/sig first) 3.) Service receives the cert, builds a cert store with the local ca cert in it and verifies the client's cert with X509_verify_cert() 4.) if cert verifies ok, service compares the signature against the one calculated from the incoming data using the public key that came inside the cert just verified Would this be the right approach considering that anything the client sends may be forged (cert, sig, data...) ? Or would it be safer to have the cert used for signing stored on the server side and not send with the data (instead just its subject protected by the signature) ? Thanks alot, Marco X509_verify_cert X509_verify_cert ___ openssl-users mailing list To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users
