Scott Baker | 8487c5d | 2019-10-18 12:49:46 -0700 | [diff] [blame^] | 1 | package pac |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "errors" |
| 6 | "fmt" |
| 7 | "log" |
| 8 | |
| 9 | "gopkg.in/jcmturner/gokrb5.v7/crypto" |
| 10 | "gopkg.in/jcmturner/gokrb5.v7/iana/keyusage" |
| 11 | "gopkg.in/jcmturner/gokrb5.v7/types" |
| 12 | "gopkg.in/jcmturner/rpc.v1/mstypes" |
| 13 | ) |
| 14 | |
| 15 | const ( |
| 16 | infoTypeKerbValidationInfo uint32 = 1 |
| 17 | infoTypeCredentials uint32 = 2 |
| 18 | infoTypePACServerSignatureData uint32 = 6 |
| 19 | infoTypePACKDCSignatureData uint32 = 7 |
| 20 | infoTypePACClientInfo uint32 = 10 |
| 21 | infoTypeS4UDelegationInfo uint32 = 11 |
| 22 | infoTypeUPNDNSInfo uint32 = 12 |
| 23 | infoTypePACClientClaimsInfo uint32 = 13 |
| 24 | infoTypePACDeviceInfo uint32 = 14 |
| 25 | infoTypePACDeviceClaimsInfo uint32 = 15 |
| 26 | ) |
| 27 | |
| 28 | // PACType implements: https://msdn.microsoft.com/en-us/library/cc237950.aspx |
| 29 | type PACType struct { |
| 30 | CBuffers uint32 |
| 31 | Version uint32 |
| 32 | Buffers []InfoBuffer |
| 33 | Data []byte |
| 34 | KerbValidationInfo *KerbValidationInfo |
| 35 | CredentialsInfo *CredentialsInfo |
| 36 | ServerChecksum *SignatureData |
| 37 | KDCChecksum *SignatureData |
| 38 | ClientInfo *ClientInfo |
| 39 | S4UDelegationInfo *S4UDelegationInfo |
| 40 | UPNDNSInfo *UPNDNSInfo |
| 41 | ClientClaimsInfo *ClientClaimsInfo |
| 42 | DeviceInfo *DeviceInfo |
| 43 | DeviceClaimsInfo *DeviceClaimsInfo |
| 44 | ZeroSigData []byte |
| 45 | } |
| 46 | |
| 47 | // InfoBuffer implements the PAC Info Buffer: https://msdn.microsoft.com/en-us/library/cc237954.aspx |
| 48 | type InfoBuffer struct { |
| 49 | ULType uint32 // A 32-bit unsigned integer in little-endian format that describes the type of data present in the buffer contained at Offset. |
| 50 | CBBufferSize uint32 // A 32-bit unsigned integer in little-endian format that contains the size, in bytes, of the buffer in the PAC located at Offset. |
| 51 | Offset uint64 // A 64-bit unsigned integer in little-endian format that contains the offset to the beginning of the buffer, in bytes, from the beginning of the PACTYPE structure. The data offset MUST be a multiple of eight. The following sections specify the format of each type of element. |
| 52 | } |
| 53 | |
| 54 | // Unmarshal bytes into the PACType struct |
| 55 | func (pac *PACType) Unmarshal(b []byte) (err error) { |
| 56 | pac.Data = b |
| 57 | zb := make([]byte, len(b), len(b)) |
| 58 | copy(zb, b) |
| 59 | pac.ZeroSigData = zb |
| 60 | r := mstypes.NewReader(bytes.NewReader(b)) |
| 61 | pac.CBuffers, err = r.Uint32() |
| 62 | if err != nil { |
| 63 | return |
| 64 | } |
| 65 | pac.Version, err = r.Uint32() |
| 66 | if err != nil { |
| 67 | return |
| 68 | } |
| 69 | buf := make([]InfoBuffer, pac.CBuffers, pac.CBuffers) |
| 70 | for i := range buf { |
| 71 | buf[i].ULType, err = r.Uint32() |
| 72 | if err != nil { |
| 73 | return |
| 74 | } |
| 75 | buf[i].CBBufferSize, err = r.Uint32() |
| 76 | if err != nil { |
| 77 | return |
| 78 | } |
| 79 | buf[i].Offset, err = r.Uint64() |
| 80 | if err != nil { |
| 81 | return |
| 82 | } |
| 83 | } |
| 84 | pac.Buffers = buf |
| 85 | return nil |
| 86 | } |
| 87 | |
| 88 | // ProcessPACInfoBuffers processes the PAC Info Buffers. |
| 89 | // https://msdn.microsoft.com/en-us/library/cc237954.aspx |
| 90 | func (pac *PACType) ProcessPACInfoBuffers(key types.EncryptionKey, l *log.Logger) error { |
| 91 | for _, buf := range pac.Buffers { |
| 92 | p := make([]byte, buf.CBBufferSize, buf.CBBufferSize) |
| 93 | copy(p, pac.Data[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)]) |
| 94 | switch buf.ULType { |
| 95 | case infoTypeKerbValidationInfo: |
| 96 | if pac.KerbValidationInfo != nil { |
| 97 | //Must ignore subsequent buffers of this type |
| 98 | continue |
| 99 | } |
| 100 | var k KerbValidationInfo |
| 101 | err := k.Unmarshal(p) |
| 102 | if err != nil { |
| 103 | return fmt.Errorf("error processing KerbValidationInfo: %v", err) |
| 104 | } |
| 105 | pac.KerbValidationInfo = &k |
| 106 | case infoTypeCredentials: |
| 107 | // Currently PAC parsing is only useful on the service side in gokrb5 |
| 108 | // The CredentialsInfo are only useful when gokrb5 has implemented RFC4556 and only applied on the client side. |
| 109 | // Skipping CredentialsInfo - will be revisited under RFC4556 implementation. |
| 110 | continue |
| 111 | //if pac.CredentialsInfo != nil { |
| 112 | // //Must ignore subsequent buffers of this type |
| 113 | // continue |
| 114 | //} |
| 115 | //var k CredentialsInfo |
| 116 | //err := k.Unmarshal(p, key) // The encryption key used is the AS reply key only available to the client. |
| 117 | //if err != nil { |
| 118 | // return fmt.Errorf("error processing CredentialsInfo: %v", err) |
| 119 | //} |
| 120 | //pac.CredentialsInfo = &k |
| 121 | case infoTypePACServerSignatureData: |
| 122 | if pac.ServerChecksum != nil { |
| 123 | //Must ignore subsequent buffers of this type |
| 124 | continue |
| 125 | } |
| 126 | var k SignatureData |
| 127 | zb, err := k.Unmarshal(p) |
| 128 | copy(pac.ZeroSigData[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)], zb) |
| 129 | if err != nil { |
| 130 | return fmt.Errorf("error processing ServerChecksum: %v", err) |
| 131 | } |
| 132 | pac.ServerChecksum = &k |
| 133 | case infoTypePACKDCSignatureData: |
| 134 | if pac.KDCChecksum != nil { |
| 135 | //Must ignore subsequent buffers of this type |
| 136 | continue |
| 137 | } |
| 138 | var k SignatureData |
| 139 | zb, err := k.Unmarshal(p) |
| 140 | copy(pac.ZeroSigData[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)], zb) |
| 141 | if err != nil { |
| 142 | return fmt.Errorf("error processing KDCChecksum: %v", err) |
| 143 | } |
| 144 | pac.KDCChecksum = &k |
| 145 | case infoTypePACClientInfo: |
| 146 | if pac.ClientInfo != nil { |
| 147 | //Must ignore subsequent buffers of this type |
| 148 | continue |
| 149 | } |
| 150 | var k ClientInfo |
| 151 | err := k.Unmarshal(p) |
| 152 | if err != nil { |
| 153 | return fmt.Errorf("error processing ClientInfo: %v", err) |
| 154 | } |
| 155 | pac.ClientInfo = &k |
| 156 | case infoTypeS4UDelegationInfo: |
| 157 | if pac.S4UDelegationInfo != nil { |
| 158 | //Must ignore subsequent buffers of this type |
| 159 | continue |
| 160 | } |
| 161 | var k S4UDelegationInfo |
| 162 | err := k.Unmarshal(p) |
| 163 | if err != nil { |
| 164 | l.Printf("could not process S4U_DelegationInfo: %v", err) |
| 165 | continue |
| 166 | } |
| 167 | pac.S4UDelegationInfo = &k |
| 168 | case infoTypeUPNDNSInfo: |
| 169 | if pac.UPNDNSInfo != nil { |
| 170 | //Must ignore subsequent buffers of this type |
| 171 | continue |
| 172 | } |
| 173 | var k UPNDNSInfo |
| 174 | err := k.Unmarshal(p) |
| 175 | if err != nil { |
| 176 | l.Printf("could not process UPN_DNSInfo: %v", err) |
| 177 | continue |
| 178 | } |
| 179 | pac.UPNDNSInfo = &k |
| 180 | case infoTypePACClientClaimsInfo: |
| 181 | if pac.ClientClaimsInfo != nil || len(p) < 1 { |
| 182 | //Must ignore subsequent buffers of this type |
| 183 | continue |
| 184 | } |
| 185 | var k ClientClaimsInfo |
| 186 | err := k.Unmarshal(p) |
| 187 | if err != nil { |
| 188 | l.Printf("could not process ClientClaimsInfo: %v", err) |
| 189 | continue |
| 190 | } |
| 191 | pac.ClientClaimsInfo = &k |
| 192 | case infoTypePACDeviceInfo: |
| 193 | if pac.DeviceInfo != nil { |
| 194 | //Must ignore subsequent buffers of this type |
| 195 | continue |
| 196 | } |
| 197 | var k DeviceInfo |
| 198 | err := k.Unmarshal(p) |
| 199 | if err != nil { |
| 200 | l.Printf("could not process DeviceInfo: %v", err) |
| 201 | continue |
| 202 | } |
| 203 | pac.DeviceInfo = &k |
| 204 | case infoTypePACDeviceClaimsInfo: |
| 205 | if pac.DeviceClaimsInfo != nil { |
| 206 | //Must ignore subsequent buffers of this type |
| 207 | continue |
| 208 | } |
| 209 | var k DeviceClaimsInfo |
| 210 | err := k.Unmarshal(p) |
| 211 | if err != nil { |
| 212 | l.Printf("could not process DeviceClaimsInfo: %v", err) |
| 213 | continue |
| 214 | } |
| 215 | pac.DeviceClaimsInfo = &k |
| 216 | } |
| 217 | } |
| 218 | |
| 219 | if ok, err := pac.verify(key); !ok { |
| 220 | return err |
| 221 | } |
| 222 | |
| 223 | return nil |
| 224 | } |
| 225 | |
| 226 | func (pac *PACType) verify(key types.EncryptionKey) (bool, error) { |
| 227 | if pac.KerbValidationInfo == nil { |
| 228 | return false, errors.New("PAC Info Buffers does not contain a KerbValidationInfo") |
| 229 | } |
| 230 | if pac.ServerChecksum == nil { |
| 231 | return false, errors.New("PAC Info Buffers does not contain a ServerChecksum") |
| 232 | } |
| 233 | if pac.KDCChecksum == nil { |
| 234 | return false, errors.New("PAC Info Buffers does not contain a KDCChecksum") |
| 235 | } |
| 236 | if pac.ClientInfo == nil { |
| 237 | return false, errors.New("PAC Info Buffers does not contain a ClientInfo") |
| 238 | } |
| 239 | etype, err := crypto.GetChksumEtype(int32(pac.ServerChecksum.SignatureType)) |
| 240 | if err != nil { |
| 241 | return false, err |
| 242 | } |
| 243 | if ok := etype.VerifyChecksum(key.KeyValue, |
| 244 | pac.ZeroSigData, |
| 245 | pac.ServerChecksum.Signature, |
| 246 | keyusage.KERB_NON_KERB_CKSUM_SALT); !ok { |
| 247 | return false, errors.New("PAC service checksum verification failed") |
| 248 | } |
| 249 | |
| 250 | return true, nil |
| 251 | } |