Am Montag, 9. Mai 2016, 11:15:04 schrieb Tadeusz Struk: Hi Tadeusz, > Hi Strphan, > > On 05/09/2016 03:24 AM, Stephan Mueller wrote: > > Hi, > > > > I am experimenting with pkcs1pad(rsa-generic) signature verify. The > > following numbers shall serve as examples -- using other valid > > signatures, similar results are visible. > > > > All signatures are correct. > > > > The result of the signature verify operation is the following byte stream: > > > > 3021300906052b0e03021a05000414ba3bc9c6fb57dfa3103e5991e8992d4387afa6f2d93e > > 4f478d3cb74138b28cc5d1601f2bc549c2297e5bf76578fbaf5defe617748ac29f825aa974 > > a56b7fdffe21f8d5c6abd7d9050525c60d94a36b3ce7a763af66b1ed501ebd0edd4b686a6b > > b8afd903c9ab97a60853fa7345fdd28fcc > > > > The hash of the message is: > > > > ba3bc9c6fb57dfa3103e5991e8992d4387afa6f2 > > > > > > The hash of the message is embedded in the data stream returned by the > > signature verify operation. > > > > Looking at the first bytes of the data stream from the signature verify, > > it > > looks like an ASN.1 sequence. > > > > Looking into the function pkcs1pad_verify_complete, that suspicion is > > confirmed: the padding is removed, but the decoding is not implemented. > > Shall a caller implement the decoding? > > > > If so, what is the purpose of the pkcs1pad implementation when only a part > > of the sig ver is implemented? > > Verify operation decrypts data provided in src, verifies, if the result has > valid padding and DER wrappings, strips the padding and wrapping and copies > the decrypted message to the dst. If padding or wrappings are not as > expected it returns -EBADMSG. > It is done in > https://git.kernel.org/cgit/linux/kernel/git/herbert/cryptodev-2.6.git/tree/ > crypto/rsa-pkcs1pad.c#n517 see up to line #550 I think I see my error: pkcs1pad(rsa,HASH) -- I missed the hash part that activates the decoding. Thank you for the pointer. Once I completed my testing, I think I need to beef up the documentation a bit. > > An example of how it is used can be found here: > https://git.kernel.org/cgit/linux/kernel/git/herbert/cryptodev-2.6.git/tree/ > crypto/asymmetric_keys/public_key.c#n71 > > Looking into pkcs1pad_sign, I also do not see the BER encoding. Again, > > shall the caller do that? > > No, the sign operation prepends the padding and hash wrappings to the > message provided in src, encrypts the whole thing and returns the cipher > text in the dst, which is the opposite to what is done in verify. > Thanks, Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
