khenaidoo | 106c61a | 2021-08-11 18:05:46 -0400 | [diff] [blame] | 1 | package pac |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | |
| 6 | "github.com/jcmturner/gokrb5/v8/iana/chksumtype" |
| 7 | "github.com/jcmturner/rpc/v2/mstypes" |
| 8 | ) |
| 9 | |
| 10 | /* |
| 11 | https://msdn.microsoft.com/en-us/library/cc237955.aspx |
| 12 | |
| 13 | The Key Usage Value MUST be KERB_NON_KERB_CKSUM_SALT (17) [MS-KILE] (section 3.1.5.9). |
| 14 | |
| 15 | Server Signature (SignatureType = 0x00000006) |
| 16 | https://msdn.microsoft.com/en-us/library/cc237957.aspx |
| 17 | |
| 18 | KDC Signature (SignatureType = 0x00000007) |
| 19 | https://msdn.microsoft.com/en-us/library/dd357117.aspx |
| 20 | */ |
| 21 | |
| 22 | // SignatureData implements https://msdn.microsoft.com/en-us/library/cc237955.aspx |
| 23 | type SignatureData struct { |
| 24 | SignatureType uint32 // A 32-bit unsigned integer value in little-endian format that defines the cryptographic system used to calculate the checksum. This MUST be one of the following checksum types: KERB_CHECKSUM_HMAC_MD5 (signature size = 16), HMAC_SHA1_96_AES128 (signature size = 12), HMAC_SHA1_96_AES256 (signature size = 12). |
| 25 | Signature []byte // Size depends on the type. See comment above. |
| 26 | RODCIdentifier uint16 // A 16-bit unsigned integer value in little-endian format that contains the first 16 bits of the key version number ([MS-KILE] section 3.1.5.8) when the KDC is an RODC. When the KDC is not an RODC, this field does not exist. |
| 27 | } |
| 28 | |
| 29 | // Unmarshal bytes into the SignatureData struct |
| 30 | func (k *SignatureData) Unmarshal(b []byte) (rb []byte, err error) { |
| 31 | r := mstypes.NewReader(bytes.NewReader(b)) |
| 32 | |
| 33 | k.SignatureType, err = r.Uint32() |
| 34 | if err != nil { |
| 35 | return |
| 36 | } |
| 37 | |
| 38 | var c int |
| 39 | switch k.SignatureType { |
| 40 | case chksumtype.KERB_CHECKSUM_HMAC_MD5_UNSIGNED: |
| 41 | c = 16 |
| 42 | case uint32(chksumtype.HMAC_SHA1_96_AES128): |
| 43 | c = 12 |
| 44 | case uint32(chksumtype.HMAC_SHA1_96_AES256): |
| 45 | c = 12 |
| 46 | } |
| 47 | k.Signature, err = r.ReadBytes(c) |
| 48 | if err != nil { |
| 49 | return |
| 50 | } |
| 51 | |
| 52 | // When the KDC is not an Read Only Domain Controller (RODC), this field does not exist. |
| 53 | if len(b) >= 4+c+2 { |
| 54 | k.RODCIdentifier, err = r.Uint16() |
| 55 | if err != nil { |
| 56 | return |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | // Create bytes with zeroed signature needed for checksum verification |
| 61 | rb = make([]byte, len(b), len(b)) |
| 62 | copy(rb, b) |
| 63 | z := make([]byte, len(b), len(b)) |
| 64 | copy(rb[4:4+c], z) |
| 65 | |
| 66 | return |
| 67 | } |