Closed Bug 379753 Opened 14 years ago Closed 14 years ago
S/MIME should support AES
User-Agent: Mozilla/5.0 (compatible; Konqueror/3.5; Linux) KHTML/3.5.4 (like Gecko) Build Identifier: S/MIME should support AES. AES has been around for a while and is supported by other S/MIME implementations like KDE KMail/gpgsm. Most recently, AES (RFC 3565) has been added as a SHOULD implement to S/MIME 3.1 (RFC 3851). It's time for NSS AES support to move from planning to the implementation stage. ;) http://www.apps.ietf.org/rfc/rfc3851.html#sec-2.7 http://www.apps.ietf.org/rfc/rfc3565.html 2.7 ContentEncryptionAlgorithmIdentifier Sending and receiving agents MUST support encryption and decryption with DES EDE3 CBC, hereinafter called "tripleDES" [CMSALG]. Receiving agents SHOULD support encryption and decryption using the RC2 [CMSALG] or a compatible algorithm at a key size of 40 bits, hereinafter called "RC2/40". Sending and receiving agents SHOULD support encryption and decryption with AES [CMSAES] at a key size of 128, 192, and 256 bits. ... [CMSAES] Schaad, J., "Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)", RFC 3565, July 2003. Reproducible: Always
This patch causes a) the CMIME capabilities record in outgoing signed emails to say that I can receive (and prefer) AES_128_CBC, b) when looking for the cipher to use for sending encrypted messages, it recognizes AES_128_CBC in other people's SMIME capabilities (stored in their SMIME profiles), But it DOES NOT enable me to send a message encrypted with AES_128_CBC. And I think the reason is due to another latent bug, undiscovered since libSMIME was written, until now. The problem occurs in function smime_choose_cipher() in file lib/smime/smimeutil.c. That function has a loop (see the comment " /* walk all the recipient's certs */" ) that tries to get the stored SMIME profile for every recipient. If it fails to find a profile for ANY recipient, then it ends up using a "default" cipher, which is either RC2-40 or 3DES. The problem is that it ALWAYS fails to find the stored SMIME profile for the sending user, that is, for any recipient with a "user" cert. The function CERT_FindSMimeProfile() always returns NULL for the user's own cert. This causes libSMIME to always send an encrypted message using the "default" cipher, which is never AES, always RC2-40 or 3DES. It seems that the cert DB has an SMIME profile record, but it contains a zero length SMIME capabilities, and a zero-length capabilities timestamp. Now, I'm not sure how this is SUPPOSED to work. When we're looking for our own profile, the profile of a cert for which we are the user, should we look for it in the cert DB? Is the SMIME profile record for a user cert supposed to contain a valid set of SMIME capabilities? Or should we say "hey, this is MY cert, I'm going to generate an SMIME capabilities with my current capabilities and substitute that"? It seems to me that we do NOT want to store oru own capabilities in the cert DB, because our capabilities can change. So, I think we want to generate our own capabilities and use them, rather than using old stores ones, for our own cert. If that analysis is correct, then a bunch of code needs to be written, because neither smime_choose_cipher() nor CERT_FindSMimeProfile() has any logic that does anything like that. Suggestions?
Maybe Sean will have some ideas.
I was mistaken. CERT_FindSMimeProfile() does not return NULL. It returns a pointer to a SECItem with a zero len value. Same effect as if it returned a NULL. When I try to send an encrypted message, pipnss calls CERT_SaveSMimeProfile() with NULL pointers for emailProfile and profileTime. THAT appears to be the reason why my cert DB doesn't have a valid set of SMIME capabilities in the SMIME profile record for my user certs. For some reason, while trying to send an encrypted message, pipnss calls NSS_SMIMEUtil_FindBulkAlgForRecipients more than once. Seems wasteful to recompute all that over and over for a single sent message. I *suspect* it is regenerating the message a second time to store it in the SENT folder. That's evil, if true, because it means the message saved in the SENT folder is NOT a true copy of the message actually sent!
I have successfully read and decrypted an AES_128_CBC message with the first patch above. So, the only remaining issue is why pipnss clobbers the SMIME capabilities in the SMIME profile for my user cert when I send a signed or encrypted email message (as described in the previous comment). :-/ There probably should be a separate bug filed on that.
Assignee: nobody → nelson
Comment on attachment 264085 [details] [diff] [review] patch v1 (checked in on trunk) I believe this patch actually is complete. There is another separate bug that must also be fixed before AES encryption can be done, but that is the subject of bug 380091. There is a workaround patch for that bug, which I shall attach to this bug shortly.
This patch, copied from bug 380091, works around a PSM problem that clobbers the SMIME capabilities for local user certs. This patch is NOT for checkin, but is useful for testing the other patch attached to this bug, which IS for checkin.
Status: NEW → RESOLVED
Closed: 14 years ago
Resolution: --- → FIXED
Status: RESOLVED → REOPENED
Resolution: FIXED → ---
Comment on attachment 264085 [details] [diff] [review] patch v1 (checked in on trunk) r+=rrelyea
Attachment #264085 - Flags: review?(rrelyea) → review+
Priority: -- → P2
Target Milestone: --- → 3.12
Comment on attachment 264085 [details] [diff] [review] patch v1 (checked in on trunk) First patch checked in on trunk Checking in util/ciferfam.h; new revision: 1.3; previous revision: 1.2 Checking in smime/smimeutil.c; new revision: 1.20; previous revision: 1.19
Attachment #264085 - Attachment description: patch v1 → patch v1 (checked in on trunk)
Comment on attachment 264204 [details] [diff] [review] NSS workaround for bug 380091 (checked in) I've changed my mind about this patch. I still regard it as something of a hack, but it has been working for me ever since I wrote it, without ill effects that I can see. I had originally thought that this patch might stop the code from saving an SMIME profile record for some user cert in some circumstance where it would be desirable to do save the profile anyway. But I can no longer think of any case where that would occur. So, now I'm requesting two reviews.
(I marked 3 prior comments in this bug as private, because they were comments made in the wrong bug. Marking them private reduces confusion in this bug.)
Comment on attachment 264204 [details] [diff] [review] NSS workaround for bug 380091 (checked in) r+=relyea Julian, if you get here before kai, you can take his review slot. While this patch works around an existing bug, it is also not an unreasonable sanity check. my only concern is the 'bootstrap' case. What happens when you first get your cert (can you encrypt to yourself?). bob
Attachment #264204 - Flags: superreview?(julien.pierre.boogz) → superreview+
Comment on attachment 264204 [details] [diff] [review] NSS workaround for bug 380091 (checked in) Checking in certdb/stanpcertdb.c; new revision: 1.75; previous revision: 1.74
Status: ASSIGNED → RESOLVED
Closed: 14 years ago → 14 years ago
Resolution: --- → FIXED
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