Sign digest only (/ds) - Githubissues

0x0ACB commented 4 months ago

The signtool from microsoft offers the options

/dg Generates the digest to be signed and the unsigned PKCS7 files
/di Creates the signature by ingesting the signed digest to the unsigned PKCS7 file and
/ds Signs the digest only

Which can be used for easier integration in CI/CD pipelines since it is not neccessary to send potantially large binaries to the signing server. From looking at the doc and code it doesn't seem like this is supported by osslsigncode. This is an option that we would be interested in since code signing certificates are required to be on a hardware token now and the cloud HSM solutions are quite expensive. As such we would like to have a small local signing server that just does the code signing step while still using the gh action runners to do the actual building.

If this option is currently not available and I am not just missing something, would you be interested in a PR to implement this? And if so would you be kind enough to point me in the right direction? From a quick inspection of the code it seems I would just need to use https://github.com/mtrojnar/osslsigncode/blob/42e97339167282cb1e9b55c4d3b4e6485fed13ea/pe.c#L446 this function here (and the matching ones for the other file formats) to generate the signature itself. Would just need to figure out how to parse the digest into the hash BIO I guess.

olszomal commented 4 months ago

osslsigncode supports equivalent but not identical functionality:

Use the "extract-data" command to extract a data content to be signed:

$ ./osslsigncode extract-data -ph -in unsigned.exe -out data.der
Calculated page hash            : 0000000043CE7BFD7EEA479340D0EA3F8B5903D3F85BB18AE184A662372C64F8 ...
Succeeded

You can parse this data content using openssl asn1parse:

$ openssl asn1parse -i -inform der -in data.der 
    0:d=0  hl=4 l=1191 cons: SEQUENCE          
    4:d=1  hl=2 l=   9 prim:  OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1176 cons:  cont [ 0 ]        
   19:d=2  hl=4 l=1172 cons:   SEQUENCE          
   23:d=3  hl=2 l=   1 prim:    INTEGER           :01
   26:d=3  hl=2 l=   0 cons:    SET               
   28:d=3  hl=4 l=1161 cons:    SEQUENCE          
   32:d=4  hl=2 l=  10 prim:     OBJECT            :1.3.6.1.4.1.311.2.1.4
   44:d=4  hl=4 l=1145 cons:     cont [ 0 ]        
   48:d=5  hl=4 l=1141 cons:      SEQUENCE          
   52:d=6  hl=4 l=1086 cons:       SEQUENCE          
   56:d=7  hl=2 l=  10 prim:        OBJECT            :1.3.6.1.4.1.311.2.1.15
   68:d=7  hl=4 l=1070 cons:        SEQUENCE          
   72:d=8  hl=2 l=   2 prim:         BIT STRING        
   76:d=8  hl=4 l=1062 cons:         cont [ 0 ]        
   80:d=9  hl=4 l=1058 cons:          cont [ 1 ]        
   84:d=10 hl=2 l=  16 prim:           OCTET STRING      [HEX DUMP]:A6B586D5B4A12466AE05A217DA8E60D6
  102:d=10 hl=4 l=1036 prim:           OCTET STRING      [HEX DUMP]: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
 1142:d=6  hl=2 l=  49 cons:       SEQUENCE          
 1144:d=7  hl=2 l=  13 cons:        SEQUENCE          
 1146:d=8  hl=2 l=   9 prim:         OBJECT            :sha256
 1157:d=8  hl=2 l=   0 prim:         NULL              
 1159:d=7  hl=2 l=  32 prim:        OCTET STRING      [HEX DUMP]:2D2C7B382C8163A419B9FF214A7B651C33F9EA43335907F11377290C5158A7A4
 1193:d=3  hl=2 l=   0 cons:    SET

Sign extracted data on the signing server (use the private key), add a timestamp (optionally), create completed PKCS#7 signature:

$ ./osslsigncode sign -certs cert.pem -key key.pem -in data.der -out signed_data.der
Succeeded

Use the "attach-signature" command to attach the PKCS#7 signature to the file:

$ ./osslsigncode attach-signature -in unsigned.exe -sigin signed_data.der -out signed.exe -CAfile CACert.pem 
PE checksum   : 0001E9CF

Signature Index: 0  (Primary Signature)

Message digest algorithm  : SHA256
Current message digest    : 2D2C7B382C8163A419B9FF214A7B651C33F9EA43335907F11377290C5158A7A4 
Calculated message digest : 2D2C7B382C8163A419B9FF214A7B651C33F9EA43335907F11377290C5158A7A4 

Page hash algorithm  : SHA256
Page hash            : 0000000043CE7BFD7EEA479340D0EA3F8B5903D3F85BB18AE184A662372C64F8 ...
Calculated page hash : 0000000043CE7BFD7EEA479340D0EA3F8B5903D3F85BB18AE184A662372C64F8 ...

Signer's certificate:
    ------------------
    Signer #0:
        Subject: /C=PL/ST=Mazovia Province/L=Warsaw/O=osslsigncode/OU=CSP/CN=Certificate/emailAddress=osslsigncode@example.com
        Issuer : /C=PL/O=osslsigncode/OU=Certification Authority/CN=Intermediate CA
        Serial : 68C6F0E7ECD2F051581799BE7C8A37158783BE20
        Certificate expiration date:
            notBefore : Jan  1 00:00:00 2018 GMT
            notAfter : Dec 31 00:00:00 2024 GMT

Message digest algorithm: SHA256
(...)

Signature verification: ok

Number of verified signatures: 1
Signature successfully attached
Succeeded

0x0ACB commented 4 months ago

Oh thank you that is perfect.

mtrojnar / osslsigncode

Sign digest only (/ds) #356