txscript

package
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 Go to latest Published: May 25, 2016 License: ISC Imports: 18 Imported by: 8

README

txscript

[Build Status] (https://travis-ci.org/decred/dcrd) ![ISC License] (http://img.shields.io/badge/license-ISC-blue.svg) [GoDoc] (http://godoc.org/github.com/decred/dcrd/txscript)

Package txscript implements the decred transaction script language. There is a comprehensive test suite.

This package has intentionally been designed so it can be used as a standalone package for any projects needing to use or validate decred transaction scripts.

Decred Scripts

Decred provides a stack-based, FORTH-like langauge for the scripts in the decred transactions. This language is not turing complete although it is still fairly powerful.

Installation and Updating

$ go get -u github.com/decred/dcrd/txscript

Examples

License

Package txscript is licensed under the copyfree ISC License.

Documentation

Overview

Package txscript implements the decred transaction script language.

This package provides data structures and functions to parse and execute decred transaction scripts.

Script Overview

Decred transaction scripts are written in a stack-base, FORTH-like language.

The decred script language consists of a number of opcodes which fall into several categories such pushing and popping data to and from the stack, performing basic and bitwise arithmetic, conditional branching, comparing hashes, and checking cryptographic signatures. Scripts are processed from left to right and intentionally do not provide loops.

The vast majority of Decred scripts at the time of this writing are of several standard forms which consist of a spender providing a public key and a signature which proves the spender owns the associated private key. This information is used to prove the the spender is authorized to perform the transaction.

One benefit of using a scripting language is added flexibility in specifying what conditions must be met in order to spend decreds.

Errors

Errors returned by this package are of the form txscript.ErrStackX where X indicates the specific error. See Variables in the package documentation for a full list.

Index

Examples

Constants

View Source 
const (
	OP_0                   = 0x00 // 0
	OP_FALSE               = 0x00 // 0 - AKA OP_0
	OP_DATA_1              = 0x01 // 1
	OP_DATA_2              = 0x02 // 2
	OP_DATA_3              = 0x03 // 3
	OP_DATA_4              = 0x04 // 4
	OP_DATA_5              = 0x05 // 5
	OP_DATA_6              = 0x06 // 6
	OP_DATA_7              = 0x07 // 7
	OP_DATA_8              = 0x08 // 8
	OP_DATA_9              = 0x09 // 9
	OP_DATA_10             = 0x0a // 10
	OP_DATA_11             = 0x0b // 11
	OP_DATA_12             = 0x0c // 12
	OP_DATA_13             = 0x0d // 13
	OP_DATA_14             = 0x0e // 14
	OP_DATA_15             = 0x0f // 15
	OP_DATA_16             = 0x10 // 16
	OP_DATA_17             = 0x11 // 17
	OP_DATA_18             = 0x12 // 18
	OP_DATA_19             = 0x13 // 19
	OP_DATA_20             = 0x14 // 20
	OP_DATA_21             = 0x15 // 21
	OP_DATA_22             = 0x16 // 22
	OP_DATA_23             = 0x17 // 23
	OP_DATA_24             = 0x18 // 24
	OP_DATA_25             = 0x19 // 25
	OP_DATA_26             = 0x1a // 26
	OP_DATA_27             = 0x1b // 27
	OP_DATA_28             = 0x1c // 28
	OP_DATA_29             = 0x1d // 29
	OP_DATA_30             = 0x1e // 30
	OP_DATA_31             = 0x1f // 31
	OP_DATA_32             = 0x20 // 32
	OP_DATA_33             = 0x21 // 33
	OP_DATA_34             = 0x22 // 34
	OP_DATA_35             = 0x23 // 35
	OP_DATA_36             = 0x24 // 36
	OP_DATA_37             = 0x25 // 37
	OP_DATA_38             = 0x26 // 38
	OP_DATA_39             = 0x27 // 39
	OP_DATA_40             = 0x28 // 40
	OP_DATA_41             = 0x29 // 41
	OP_DATA_42             = 0x2a // 42
	OP_DATA_43             = 0x2b // 43
	OP_DATA_44             = 0x2c // 44
	OP_DATA_45             = 0x2d // 45
	OP_DATA_46             = 0x2e // 46
	OP_DATA_47             = 0x2f // 47
	OP_DATA_48             = 0x30 // 48
	OP_DATA_49             = 0x31 // 49
	OP_DATA_50             = 0x32 // 50
	OP_DATA_51             = 0x33 // 51
	OP_DATA_52             = 0x34 // 52
	OP_DATA_53             = 0x35 // 53
	OP_DATA_54             = 0x36 // 54
	OP_DATA_55             = 0x37 // 55
	OP_DATA_56             = 0x38 // 56
	OP_DATA_57             = 0x39 // 57
	OP_DATA_58             = 0x3a // 58
	OP_DATA_59             = 0x3b // 59
	OP_DATA_60             = 0x3c // 60
	OP_DATA_61             = 0x3d // 61
	OP_DATA_62             = 0x3e // 62
	OP_DATA_63             = 0x3f // 63
	OP_DATA_64             = 0x40 // 64
	OP_DATA_65             = 0x41 // 65
	OP_DATA_66             = 0x42 // 66
	OP_DATA_67             = 0x43 // 67
	OP_DATA_68             = 0x44 // 68
	OP_DATA_69             = 0x45 // 69
	OP_DATA_70             = 0x46 // 70
	OP_DATA_71             = 0x47 // 71
	OP_DATA_72             = 0x48 // 72
	OP_DATA_73             = 0x49 // 73
	OP_DATA_74             = 0x4a // 74
	OP_DATA_75             = 0x4b // 75
	OP_PUSHDATA1           = 0x4c // 76
	OP_PUSHDATA2           = 0x4d // 77
	OP_PUSHDATA4           = 0x4e // 78
	OP_1NEGATE             = 0x4f // 79
	OP_RESERVED            = 0x50 // 80
	OP_1                   = 0x51 // 81 - AKA OP_TRUE
	OP_TRUE                = 0x51 // 81
	OP_2                   = 0x52 // 82
	OP_3                   = 0x53 // 83
	OP_4                   = 0x54 // 84
	OP_5                   = 0x55 // 85
	OP_6                   = 0x56 // 86
	OP_7                   = 0x57 // 87
	OP_8                   = 0x58 // 88
	OP_9                   = 0x59 // 89
	OP_10                  = 0x5a // 90
	OP_11                  = 0x5b // 91
	OP_12                  = 0x5c // 92
	OP_13                  = 0x5d // 93
	OP_14                  = 0x5e // 94
	OP_15                  = 0x5f // 95
	OP_16                  = 0x60 // 96
	OP_NOP                 = 0x61 // 97
	OP_VER                 = 0x62 // 98
	OP_IF                  = 0x63 // 99
	OP_NOTIF               = 0x64 // 100
	OP_VERIF               = 0x65 // 101
	OP_VERNOTIF            = 0x66 // 102
	OP_ELSE                = 0x67 // 103
	OP_ENDIF               = 0x68 // 104
	OP_VERIFY              = 0x69 // 105
	OP_RETURN              = 0x6a // 106
	OP_TOALTSTACK          = 0x6b // 107
	OP_FROMALTSTACK        = 0x6c // 108
	OP_2DROP               = 0x6d // 109
	OP_2DUP                = 0x6e // 110
	OP_3DUP                = 0x6f // 111
	OP_2OVER               = 0x70 // 112
	OP_2ROT                = 0x71 // 113
	OP_2SWAP               = 0x72 // 114
	OP_IFDUP               = 0x73 // 115
	OP_DEPTH               = 0x74 // 116
	OP_DROP                = 0x75 // 117
	OP_DUP                 = 0x76 // 118
	OP_NIP                 = 0x77 // 119
	OP_OVER                = 0x78 // 120
	OP_PICK                = 0x79 // 121
	OP_ROLL                = 0x7a // 122
	OP_ROT                 = 0x7b // 123
	OP_SWAP                = 0x7c // 124
	OP_TUCK                = 0x7d // 125
	OP_CAT                 = 0x7e // 126
	OP_SUBSTR              = 0x7f // 127
	OP_LEFT                = 0x80 // 128
	OP_RIGHT               = 0x81 // 129
	OP_SIZE                = 0x82 // 130
	OP_INVERT              = 0x83 // 131
	OP_AND                 = 0x84 // 132
	OP_OR                  = 0x85 // 133
	OP_XOR                 = 0x86 // 134
	OP_EQUAL               = 0x87 // 135
	OP_EQUALVERIFY         = 0x88 // 136
	OP_ROTR                = 0x89 // 137
	OP_ROTL                = 0x8a // 138
	OP_1ADD                = 0x8b // 139
	OP_1SUB                = 0x8c // 140
	OP_2MUL                = 0x8d // 141
	OP_2DIV                = 0x8e // 142
	OP_NEGATE              = 0x8f // 143
	OP_ABS                 = 0x90 // 144
	OP_NOT                 = 0x91 // 145
	OP_0NOTEQUAL           = 0x92 // 146
	OP_ADD                 = 0x93 // 147
	OP_SUB                 = 0x94 // 148
	OP_MUL                 = 0x95 // 149
	OP_DIV                 = 0x96 // 150
	OP_MOD                 = 0x97 // 151
	OP_LSHIFT              = 0x98 // 152
	OP_RSHIFT              = 0x99 // 153
	OP_BOOLAND             = 0x9a // 154
	OP_BOOLOR              = 0x9b // 155
	OP_NUMEQUAL            = 0x9c // 156
	OP_NUMEQUALVERIFY      = 0x9d // 157
	OP_NUMNOTEQUAL         = 0x9e // 158
	OP_LESSTHAN            = 0x9f // 159
	OP_GREATERTHAN         = 0xa0 // 160
	OP_LESSTHANOREQUAL     = 0xa1 // 161
	OP_GREATERTHANOREQUAL  = 0xa2 // 162
	OP_MIN                 = 0xa3 // 163
	OP_MAX                 = 0xa4 // 164
	OP_WITHIN              = 0xa5 // 165
	OP_RIPEMD160           = 0xa6 // 166
	OP_SHA1                = 0xa7 // 167
	OP_SHA256              = 0xa8 // 168
	OP_HASH160             = 0xa9 // 169
	OP_HASH256             = 0xaa // 170
	OP_CODESEPARATOR       = 0xab // 171
	OP_CHECKSIG            = 0xac // 172
	OP_CHECKSIGVERIFY      = 0xad // 173
	OP_CHECKMULTISIG       = 0xae // 174
	OP_CHECKMULTISIGVERIFY = 0xaf // 175
	OP_NOP1                = 0xb0 // 176
	OP_NOP2                = 0xb1 // 177
	OP_CHECKLOCKTIMEVERIFY = 0xb1 // 177 - AKA OP_NOP2
	OP_NOP3                = 0xb2 // 178
	OP_NOP4                = 0xb3 // 179
	OP_NOP5                = 0xb4 // 180
	OP_NOP6                = 0xb5 // 181
	OP_NOP7                = 0xb6 // 182
	OP_NOP8                = 0xb7 // 183
	OP_NOP9                = 0xb8 // 184
	OP_NOP10               = 0xb9 // 185
	OP_SSTX                = 0xba // 186 DECRED
	OP_SSGEN               = 0xbb // 187 DECRED
	OP_SSRTX               = 0xbc // 188 DECRED
	OP_SSTXCHANGE          = 0xbd // 189 DECRED
	OP_CHECKSIGALT         = 0xbe // 190 DECRED
	OP_CHECKSIGALTVERIFY   = 0xbf // 191 DECRED
	OP_UNKNOWN192          = 0xc0 // 192
	OP_UNKNOWN193          = 0xc1 // 193
	OP_UNKNOWN194          = 0xc2 // 194
	OP_UNKNOWN195          = 0xc3 // 195
	OP_UNKNOWN196          = 0xc4 // 196
	OP_UNKNOWN197          = 0xc5 // 197
	OP_UNKNOWN198          = 0xc6 // 198
	OP_UNKNOWN199          = 0xc7 // 199
	OP_UNKNOWN200          = 0xc8 // 200
	OP_UNKNOWN201          = 0xc9 // 201
	OP_UNKNOWN202          = 0xca // 202
	OP_UNKNOWN203          = 0xcb // 203
	OP_UNKNOWN204          = 0xcc // 204
	OP_UNKNOWN205          = 0xcd // 205
	OP_UNKNOWN206          = 0xce // 206
	OP_UNKNOWN207          = 0xcf // 207
	OP_UNKNOWN208          = 0xd0 // 208
	OP_UNKNOWN209          = 0xd1 // 209
	OP_UNKNOWN210          = 0xd2 // 210
	OP_UNKNOWN211          = 0xd3 // 211
	OP_UNKNOWN212          = 0xd4 // 212
	OP_UNKNOWN213          = 0xd5 // 213
	OP_UNKNOWN214          = 0xd6 // 214
	OP_UNKNOWN215          = 0xd7 // 215
	OP_UNKNOWN216          = 0xd8 // 216
	OP_UNKNOWN217          = 0xd9 // 217
	OP_UNKNOWN218          = 0xda // 218
	OP_UNKNOWN219          = 0xdb // 219
	OP_UNKNOWN220          = 0xdc // 220
	OP_UNKNOWN221          = 0xdd // 221
	OP_UNKNOWN222          = 0xde // 222
	OP_UNKNOWN223          = 0xdf // 223
	OP_UNKNOWN224          = 0xe0 // 224
	OP_UNKNOWN225          = 0xe1 // 225
	OP_UNKNOWN226          = 0xe2 // 226
	OP_UNKNOWN227          = 0xe3 // 227
	OP_UNKNOWN228          = 0xe4 // 228
	OP_UNKNOWN229          = 0xe5 // 229
	OP_UNKNOWN230          = 0xe6 // 230
	OP_UNKNOWN231          = 0xe7 // 231
	OP_UNKNOWN232          = 0xe8 // 232
	OP_UNKNOWN233          = 0xe9 // 233
	OP_UNKNOWN234          = 0xea // 234
	OP_UNKNOWN235          = 0xeb // 235
	OP_UNKNOWN236          = 0xec // 236
	OP_UNKNOWN237          = 0xed // 237
	OP_UNKNOWN238          = 0xee // 238
	OP_UNKNOWN239          = 0xef // 239
	OP_UNKNOWN240          = 0xf0 // 240
	OP_UNKNOWN241          = 0xf1 // 241
	OP_UNKNOWN242          = 0xf2 // 242
	OP_UNKNOWN243          = 0xf3 // 243
	OP_UNKNOWN244          = 0xf4 // 244
	OP_UNKNOWN245          = 0xf5 // 245
	OP_UNKNOWN246          = 0xf6 // 246
	OP_UNKNOWN247          = 0xf7 // 247
	OP_UNKNOWN248          = 0xf8 // 248
	OP_SMALLDATA           = 0xf9 // 249 - bitcoin core internal
	OP_SMALLINTEGER        = 0xfa // 250 - bitcoin core internal
	OP_PUBKEYS             = 0xfb // 251 - bitcoin core internal
	OP_UNKNOWN252          = 0xfc // 252
	OP_PUBKEYHASH          = 0xfd // 253 - bitcoin core internal
	OP_PUBKEY              = 0xfe // 254 - bitcoin core internal
	OP_INVALIDOPCODE       = 0xff // 255 - bitcoin core internal
)

These constants are the values of the official opcodes used on the btc wiki, in bitcoin core and in most if not all other references and software related to handling DCR scripts.

View Source 
const (
	OpCondFalse = 0
	OpCondTrue  = 1
	OpCondSkip  = 2
)

Conditional execution constants.

View Source 
const (
	MaxOpsPerScript       = 255  // Max number of non-push operations.
	MaxPubKeysPerMultiSig = 20   // Multisig can't have more sigs than this.
	MaxScriptElementSize  = 2048 // Max bytes pushable to the stack.
)

These are the constants specified for maximums in individual scripts.

View Source 
const (
	// MaxDataCarrierSize is the maximum number of bytes allowed in pushed
	// data to be considered a nulldata transaction.
	MaxDataCarrierSize = 256

	// StandardVerifyFlags are the script flags which are used when
	// executing transaction scripts to enforce additional checks which
	// are required for the script to be considered standard.  These checks
	// help reduce issues related to transaction malleability as well as
	// allow pay-to-script hash transactions.  Note these flags are
	// different than what is required for the consensus rules in that they
	// are more strict.
	//
	// TODO: This definition does not belong here.  It belongs in a policy
	// package.
	StandardVerifyFlags = ScriptBip16 |
		ScriptVerifyDERSignatures |
		ScriptVerifyStrictEncoding |
		ScriptVerifyMinimalData |
		ScriptDiscourageUpgradableNops |
		ScriptVerifyCleanStack |
		ScriptVerifyCheckLockTimeVerify |
		ScriptVerifyLowS
)
View Source 
const (

	// DefaultScriptVersion is the default scripting language version
	// representing extended Decred script.
	DefaultScriptVersion = uint16(0)
)
View Source 
const (
	// LockTimeThreshold is the number below which a lock time is
	// interpreted to be a block number.  Since an average of one block
	// is generated per 10 minutes, this allows blocks for about 9,512
	// years.  However, if the field is interpreted as a timestamp, given
	// the lock time is a uint32, the max is sometime around 2106.
	LockTimeThreshold uint32 = 5e8 // Tue Nov 5 00:53:20 1985 UTC
)

Variables

View Source 
var (
	// ErrStackShortScript is returned if the script has an opcode that is
	// too long for the length of the script.
	ErrStackShortScript = errors.New("execute past end of script")

	// ErrStackLongScript is returned if the script has an opcode that is
	// too long for the length of the script.
	ErrStackLongScript = errors.New("script is longer than maximum allowed")

	// ErrStackUnderflow is returned if an opcode requires more items on the
	// stack than is present.f
	ErrStackUnderflow = errors.New("stack underflow")

	// ErrStackInvalidArgs is returned if the argument for an opcode is out
	// of acceptable range.
	ErrStackInvalidArgs = errors.New("invalid argument")

	// ErrStackOpDisabled is returned when a disabled opcode is encountered
	// in the script.
	ErrStackOpDisabled = errors.New("disabled opcode")

	// ErrStackVerifyFailed is returned when one of the OP_VERIFY or
	// OP_*VERIFY instructions is executed and the conditions fails.
	ErrStackVerifyFailed = errors.New("verify failed")

	// ErrStackNumberTooBig is returned when the argument for an opcode that
	// should be an offset is obviously far too large.
	ErrStackNumberTooBig = errors.New("number too big")

	// ErrStackInvalidOpcode is returned when an opcode marked as invalid or
	// a completely undefined opcode is encountered.
	ErrStackInvalidOpcode = errors.New("invalid opcode")

	// ErrStackReservedOpcode is returned when an opcode marked as reserved
	// is encountered.
	ErrStackReservedOpcode = errors.New("reserved opcode")

	// ErrStackEarlyReturn is returned when OP_RETURN is executed in the
	// script.
	ErrStackEarlyReturn = errors.New("script returned early")

	// ErrStackNoIf is returned if an OP_ELSE or OP_ENDIF is encountered
	// without first having an OP_IF or OP_NOTIF in the script.
	ErrStackNoIf = errors.New("OP_ELSE or OP_ENDIF with no matching OP_IF")

	// ErrStackMissingEndif is returned if the end of a script is reached
	// without and OP_ENDIF to correspond to a conditional expression.
	ErrStackMissingEndif = fmt.Errorf("execute fail, in conditional execution")

	// ErrStackTooManyPubKeys is returned if an OP_CHECKMULTISIG is
	// encountered with more than MaxPubKeysPerMultiSig pubkeys present.
	ErrStackTooManyPubKeys = errors.New("invalid pubkey count in OP_CHECKMULTISIG")

	// ErrStackTooManyOperations is returned if a script has more than
	// MaxOpsPerScript opcodes that do not push data.
	ErrStackTooManyOperations = errors.New("too many operations in script")

	// ErrStackElementTooBig is returned if the size of an element to be
	// pushed to the stack is over MaxScriptElementSize.
	ErrStackElementTooBig = errors.New("element in script too large")

	// ErrStackUnknownAddress is returned when ScriptToAddrHash does not
	// recognise the pattern of the script and thus can not find the address
	// for payment.
	ErrStackUnknownAddress = errors.New("non-recognised address")

	// ErrStackScriptFailed is returned when at the end of a script the
	// boolean on top of the stack is false signifying that the script has
	// failed.
	ErrStackScriptFailed = errors.New("execute fail, fail on stack")

	// ErrStackScriptUnfinished is returned when CheckErrorCondition is
	// called on a script that has not finished executing.
	ErrStackScriptUnfinished = errors.New("error check when script unfinished")

	// ErrStackEmptyStack is returned when the stack is empty at the end of
	// execution. Normal operation requires that a boolean is on top of the
	// stack when the scripts have finished executing.
	ErrStackEmptyStack = errors.New("stack empty at end of execution")

	// ErrStackP2SHNonPushOnly is returned when a Pay-to-Script-Hash
	// transaction is encountered and the ScriptSig does operations other
	// than push data (in violation of bip16).
	ErrStackP2SHNonPushOnly = errors.New("pay to script hash with non " +
		"pushonly input")

	// ErrStackInvalidParseType is an internal error returned from
	// ScriptToAddrHash ony if the internal data tables are wrong.
	ErrStackInvalidParseType = errors.New("internal error: invalid parsetype found")

	// ErrStackInvalidAddrOffset is an internal error returned from
	// ScriptToAddrHash ony if the internal data tables are wrong.
	ErrStackInvalidAddrOffset = errors.New("internal error: invalid offset found")

	// ErrStackInvalidIndex is returned when an out-of-bounds index was
	// passed to a function.
	ErrStackInvalidIndex = errors.New("invalid script index")

	// ErrStackNonPushOnly is returned when ScriptInfo is called with a
	// pkScript that peforms operations other that pushing data to the stack.
	ErrStackNonPushOnly = errors.New("SigScript is non pushonly")

	// ErrStackOverflow is returned when stack and altstack combined depth
	// is over the limit.
	ErrStackOverflow = errors.New("stack overflow")

	// ErrStackInvalidLowSSignature is returned when the ScriptVerifyLowS
	// flag is set and the script contains any signatures whose S values
	// are higher than the half order.
	ErrStackInvalidLowSSignature = errors.New("invalid low s signature")

	// ErrStackInvalidPubKey is returned when the ScriptVerifyScriptEncoding
	// flag is set and the script contains invalid pubkeys.
	ErrStackInvalidPubKey = errors.New("invalid strict pubkey")

	// ErrStackCleanStack is returned when the ScriptVerifyCleanStack flag
	// is set and after evalution the stack does not contain only one element,
	// which also must be true if interpreted as a boolean.
	ErrStackCleanStack = errors.New("stack is not clean")

	// ErrStackMinimalData is returned when the ScriptVerifyMinimalData flag
	// is set and the script contains push operations that do not use
	// the minimal opcode required.
	ErrStackMinimalData = errors.New("non-minimally encoded script number")
)

Engine execution errors.

View Source 
var (
	// ErrInvalidFlags is returned when the passed flags to NewScript
	// contain an invalid combination.
	ErrInvalidFlags = errors.New("invalid flags combination")

	// ErrInvalidIndex is returned when the passed input index for the
	// provided transaction is out of range.
	ErrInvalidIndex = errors.New("invalid input index")

	// ErrUnsupportedAddress is returned when a concrete type that
	// implements a dcrutil.Address is not a supported type.
	ErrUnsupportedAddress = errors.New("unsupported address type")

	// ErrBadNumRequired is returned from MultiSigScript when nrequired is
	// larger than the number of provided public keys.
	ErrBadNumRequired = errors.New("more signatures required than keys present")

	// ErrSighashSingleIdx
	ErrSighashSingleIdx = errors.New("invalid SIGHASH_SINGLE script index")

	// ErrSubstrIndexNegative indicates that the substring index was negative
	// and thus invalid.
	ErrSubstrIdxNegative = errors.New("negative number given for substring " +
		"index")

	// ErrSubstrIdxOutOfBounds indicates that the substring index was too large
	// and thus invalid.
	ErrSubstrIdxOutOfBounds = errors.New("out of bounds number given for " +
		"substring index")

	// ErrNegativeRotation indicates that too low of a rotation depth was given
	// for a uint32 bit rotation.
	ErrNegativeRotation = errors.New("rotation depth negative")

	// ErrRotationOverflow indicates that too high of a rotation depth was given
	// for a uint32 bit rotation.
	ErrRotationOverflow = errors.New("rotation depth out of bounds")

	// ErrNegativeRotation indicates that too low of a shift depth was given
	// for a uint32 bit shift.
	ErrNegativeShift = errors.New("shift depth negative")

	// ErrShiftOverflow indicates that too high of a shift depth was given
	// for a uint32 bit shift.
	ErrShiftOverflow = errors.New("shift depth out of bounds")

	// ErrDivideByZero indicates that a user attempted to divide by zero.
	ErrDivideByZero = errors.New("division by zero")

	// ErrP2SHStakeOpCodes indicates a P2SH script contained stake op codes.
	ErrP2SHStakeOpCodes = errors.New("stake opcodes were found in a p2sh script")
)

Engine script errors.

View Source 
var OpcodeByName = make(map[string]byte)

OpcodeByName is a map that can be used to lookup an opcode by its human-readable name (OP_CHECKMULTISIG, OP_CHECKSIG, etc).

Functions

func CalcMultiSigStats 

func CalcMultiSigStats(script []byte) (int, int, error)

CalcMultiSigStats returns the number of public keys and signatures from a multi-signature transaction script. The passed script MUST already be known to be a multi-signature script.

func CalcSignatureHash 

func CalcSignatureHash(script []parsedOpcode, hashType SigHashType,
	tx *wire.MsgTx, idx int, cachedPrefix *chainhash.Hash) ([]byte, error)

CalcSignatureHash is an exported version for testing.

func ContainsStakeOpCodes 

func ContainsStakeOpCodes(pkScript []byte) (bool, error)

ContainsStakeOpCodes returns whether or not a pkScript contains stake tagging OP codes.

func DisableLog 

func DisableLog()

DisableLog disables all library log output. Logging output is disabled by default until either UseLogger or SetLogWriter are called.

func DisasmString 

func DisasmString(buf []byte) (string, error)

DisasmString formats a disassembled script for one line printing. When the script fails to parse, the returned string will contain the disassembled script up to the point the failure occurred along with the string '[error]' appended. In addition, the reason the script failed to parse is returned if the caller wants more information about the failure.

func ExtractPkScriptAltSigType 

func ExtractPkScriptAltSigType(pkScript []byte) (int, error)

ExtractPkScriptAltSigType returns the signature scheme to use for an alternative check signature script.

func GenerateProvablyPruneableOut 

func GenerateProvablyPruneableOut(data []byte) ([]byte, error)

GenerateProvablyPruneableOut creates an OP_RETURN push of arbitrary data.

func GenerateSSGenBlockRef 

func GenerateSSGenBlockRef(blockHash chainhash.Hash, height uint32) ([]byte,
	error)

GenerateSSGenBlockRef generates an OP_RETURN push for the block header hash and height which the block votes on.

func GenerateSSGenVotes 

func GenerateSSGenVotes(votebits uint16) ([]byte, error)

GenerateSSGenVotes generates an OP_RETURN push for the vote bits in an SSGen tx.

func GenerateSStxAddrPush 

func GenerateSStxAddrPush(addr dcrutil.Address, amount dcrutil.Amount,
	limits uint16) ([]byte, error)

GenerateSStxAddrPush generates an OP_RETURN push for SSGen payment addresses in an SStx.

func GetMultisigMandN 

func GetMultisigMandN(script []byte) (uint8, uint8, error)

GetMultisigMandN returns the number of public keys and the number of signatures required to redeem the multisignature script.

func GetNullDataContent 

func GetNullDataContent(version uint16, pkScript []byte) ([]byte, error)

GetNullDataContent returns the content of a NullData (OP_RETURN) data push and an error if the script is not a NullData script.

func GetPkScriptFromP2SHSigScript 

func GetPkScriptFromP2SHSigScript(sigScript []byte) ([]byte, error)

GetPkScriptFromP2SHSigScript returns the embedded pkScript from the signature script of a transaction spending a P2SH output.

func GetPreciseSigOpCount 

func GetPreciseSigOpCount(scriptSig, scriptPubKey []byte, bip16 bool) int

GetPreciseSigOpCount returns the number of signature operations in scriptPubKey. If bip16 is true then scriptSig may be searched for the Pay-To-Script-Hash script in order to find the precise number of signature operations in the transaction. If the script fails to parse, then the count up to the point of failure is returned.

func GetScriptHashFromP2SHScript 

func GetScriptHashFromP2SHScript(pkScript []byte) ([]byte, error)

GetScriptHashFromP2SHScript extracts the script hash from a valid P2SH pkScript.

func GetSigOpCount 

func GetSigOpCount(script []byte) int

GetSigOpCount provides a quick count of the number of signature operations in a script. a CHECKSIG operations counts for 1, and a CHECK_MULTISIG for 20. If the script fails to parse, then the count up to the point of failure is returned.

func HasP2SHScriptSigStakeOpCodes 

func HasP2SHScriptSigStakeOpCodes(version uint16, scriptSig,
	scriptPubKey []byte) error

HasP2SHScriptSigStakeOpCodes returns an error is the p2sh script has either stake opcodes or if the pkscript cannot be retrieved.

func IsMultisigScript 

func IsMultisigScript(script []byte) (bool, error)

IsMultisigScript takes a script, parses it, then returns whether or not it is a multisignature script.

func IsMultisigSigScript 

func IsMultisigSigScript(script []byte) bool

IsMultisigSigScript takes a script, parses it, then returns whether or not it is a multisignature script.

func IsPayToScriptHash 

func IsPayToScriptHash(script []byte) bool

IsPayToScriptHash returns true if the script is in the standard pay-to-script-hash (P2SH) format, false otherwise.

func IsPushOnlyScript 

func IsPushOnlyScript(script []byte) bool

IsPushOnlyScript returns whether or not the passed script only pushes data.

False will be returned when the script does not parse.

func IsStakeOutput 

func IsStakeOutput(pkScript []byte) bool

IsStakeOutput returns true is a script output is a stake type.

func IsUnspendable added in v0.0.9 

func IsUnspendable(pkScript []byte) bool

IsUnspendable returns whether the passed public key script is unspendable, or guaranteed to fail at execution. This allows inputs to be pruned instantly when entering the UTXO set.

func MultiSigScript 

func MultiSigScript(pubkeys []*dcrutil.AddressSecpPubKey, nrequired int) ([]byte,
	error)

MultiSigScript returns a valid script for a multisignature redemption where nrequired of the keys in pubkeys are required to have signed the transaction for success. An ErrBadNumRequired will be returned if nrequired is larger than the number of keys provided.

func MultisigRedeemScriptFromScriptSig 

func MultisigRedeemScriptFromScriptSig(script []byte) ([]byte, error)

MultisigRedeemScriptFromScriptSig attempts to extract a multi- signature redeem script from a P2SH-redeeming input. It returns nil if the signature script is not a multisignature script.

func PayToAddrScript 

func PayToAddrScript(addr dcrutil.Address) ([]byte, error)

PayToAddrScript creates a new script to pay a transaction output to a the specified address.

Example

This example demonstrates creating a script which pays to a decred address. It also prints the created script hex and uses the DisasmString function to display the disassembled script. 

package main

import (
	"fmt"

	"github.com/decred/dcrd/chaincfg"
	"github.com/decred/dcrd/txscript"
	"github.com/decred/dcrutil"
)

func main() {
	// Parse the address to send the coins to into a dcrutil.Address
	// which is useful to ensure the accuracy of the address and determine
	// the address type.  It is also required for the upcoming call to
	// PayToAddrScript.
	addressStr := "DsSej1qR3Fyc8kV176DCh9n9cY9nqf9Quxk"
	address, err := dcrutil.DecodeAddress(addressStr, &chaincfg.MainNetParams)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Create a public key script that pays to the address.
	script, err := txscript.PayToAddrScript(address)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Printf("Script Hex: %x\n", script)

	disasm, err := txscript.DisasmString(script)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Script Disassembly:", disasm)

}

Output:

Script Hex: 76a914128004ff2fcaf13b2b91eb654b1dc2b674f7ec6188ac
Script Disassembly: OP_DUP OP_HASH160 128004ff2fcaf13b2b91eb654b1dc2b674f7ec61 OP_EQUALVERIFY OP_CHECKSIG

func PayToSSGen 

func PayToSSGen(addr dcrutil.Address) ([]byte, error)

PayToSSGen creates a new script to pay a transaction output to a public key hash or script hash, but tags the output with OP_SSGEN. For use in constructing valid SSGen txs.

func PayToSSGenPKHDirect 

func PayToSSGenPKHDirect(pkh []byte) ([]byte, error)

PayToSSGenPKHDirect creates a new script to pay a transaction output to a public key hash, but tags the output with OP_SSGEN. For use in constructing valid SSGen txs. Unlike PayToSSGen, this function directly uses the HASH160 pubkeyhash (instead of an address).

func PayToSSGenSHDirect 

func PayToSSGenSHDirect(sh []byte) ([]byte, error)

PayToSSGenSHDirect creates a new script to pay a transaction output to a script hash, but tags the output with OP_SSGEN. For use in constructing valid SSGen txs. Unlike PayToSSGen, this function directly uses the HASH160 script hash (instead of an address).

func PayToSSRtx 

func PayToSSRtx(addr dcrutil.Address) ([]byte, error)

PayToSSRtx creates a new script to pay a transaction output to a public key hash, but tags the output with OP_SSRTX. For use in constructing valid SSRtx.

func PayToSSRtxPKHDirect 

func PayToSSRtxPKHDirect(pkh []byte) ([]byte, error)

PayToSSRtxPKHDirect creates a new script to pay a transaction output to a public key hash, but tags the output with OP_SSRTX. For use in constructing valid SSRtx. Unlike PayToSSRtx, this function directly uses the HASH160 pubkeyhash (instead of an address).

func PayToSSRtxSHDirect 

func PayToSSRtxSHDirect(sh []byte) ([]byte, error)

PayToSSRtxSHDirect creates a new script to pay a transaction output to a script hash, but tags the output with OP_SSRTX. For use in constructing valid SSRtx. Unlike PayToSSRtx, this function directly uses the HASH160 script hash (instead of an address).

func PayToSStx 

func PayToSStx(addr dcrutil.Address) ([]byte, error)

PayToSStx creates a new script to pay a transaction output to a script hash or public key hash, but tags the output with OP_SSTX. For use in constructing valid SStxs.

func PayToSStxChange 

func PayToSStxChange(addr dcrutil.Address) ([]byte, error)

PayToSStxChange creates a new script to pay a transaction output to a public key hash, but tags the output with OP_SSTXCHANGE. For use in constructing valid SStxs.

func PayToScriptHashScript 

func PayToScriptHashScript(scriptHash []byte) ([]byte, error)

PayToScriptHashScript is the exported version of payToScriptHashScript.

func PushedData 

func PushedData(script []byte) ([][]byte, error)

PushedData returns an array of byte slices containing any pushed data found in the passed script. This includes OP_0, but not OP_1 - OP_16.

func RawTxInSignature 

func RawTxInSignature(tx *wire.MsgTx, idx int, subScript []byte,
	hashType SigHashType, key chainec.PrivateKey) ([]byte, error)

RawTxInSignature returns the serialized ECDSA signature for the input idx of the given transaction, with hashType appended to it.

func RawTxInSignatureAlt 

func RawTxInSignatureAlt(tx *wire.MsgTx, idx int, subScript []byte,
	hashType SigHashType, key chainec.PrivateKey, sigType sigTypes) ([]byte,
	error)

RawTxInSignatureAlt returns the serialized ECDSA signature for the input idx of the given transaction, with hashType appended to it.

func SetLogWriter 

func SetLogWriter(w io.Writer, level string) error

SetLogWriter uses a specified io.Writer to output package logging info. This allows a caller to direct package logging output without needing a dependency on seelog. If the caller is also using btclog, UseLogger should be used instead.

func SignTxOutput 

func SignTxOutput(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
	pkScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
	previousScript []byte, sigType int) ([]byte, error)

SignTxOutput signs output idx of the given tx to resolve the script given in pkScript with a signature type of hashType. Any keys required will be looked up by calling getKey() with the string of the given address. Any pay-to-script-hash signatures will be similarly looked up by calling getScript. If previousScript is provided then the results in previousScript will be merged in a type-dependant manner with the newly generated. signature script.

Example

This example demonstrates manually creating and signing a redeem transaction. 

package main

import (
	"encoding/hex"
	"fmt"

	"github.com/decred/dcrd/chaincfg"
	"github.com/decred/dcrd/chaincfg/chainec"
	"github.com/decred/dcrd/chaincfg/chainhash"
	"github.com/decred/dcrd/txscript"
	"github.com/decred/dcrd/wire"
	"github.com/decred/dcrutil"
)

var secp = 0

func main() {
	// Ordinarily the private key would come from whatever storage mechanism
	// is being used, but for this example just hard code it.
	privKeyBytes, err := hex.DecodeString("22a47fa09a223f2aa079edf85a7c2" +
		"d4f8720ee63e502ee2869afab7de234b80c")
	if err != nil {
		fmt.Println(err)
		return
	}
	privKey, pubKey := chainec.Secp256k1.PrivKeyFromBytes(privKeyBytes)
	pubKeyHash := dcrutil.Hash160(pubKey.SerializeCompressed())
	addr, err := dcrutil.NewAddressPubKeyHash(pubKeyHash,
		&chaincfg.MainNetParams, chainec.ECTypeSecp256k1)
	if err != nil {
		fmt.Println(err)
		return
	}

	// For this example, create a fake transaction that represents what
	// would ordinarily be the real transaction that is being spent.  It
	// contains a single output that pays to address in the amount of 1 DCR.
	originTx := wire.NewMsgTx()
	prevOut := wire.NewOutPoint(&chainhash.Hash{}, ^uint32(0), dcrutil.TxTreeRegular)
	txIn := wire.NewTxIn(prevOut, []byte{txscript.OP_0, txscript.OP_0})
	originTx.AddTxIn(txIn)
	pkScript, err := txscript.PayToAddrScript(addr)
	if err != nil {
		fmt.Println(err)
		return
	}
	txOut := wire.NewTxOut(100000000, pkScript)
	originTx.AddTxOut(txOut)
	originTxHash := originTx.TxSha()

	// Create the transaction to redeem the fake transaction.
	redeemTx := wire.NewMsgTx()

	// Add the input(s) the redeeming transaction will spend.  There is no
	// signature script at this point since it hasn't been created or signed
	// yet, hence nil is provided for it.
	prevOut = wire.NewOutPoint(&originTxHash, 0, dcrutil.TxTreeRegular)
	txIn = wire.NewTxIn(prevOut, nil)
	redeemTx.AddTxIn(txIn)

	// Ordinarily this would contain that actual destination of the funds,
	// but for this example don't bother.
	txOut = wire.NewTxOut(0, nil)
	redeemTx.AddTxOut(txOut)

	// Sign the redeeming transaction.
	lookupKey := func(a dcrutil.Address) (chainec.PrivateKey, bool, error) {
		// Ordinarily this function would involve looking up the private
		// key for the provided address, but since the only thing being
		// signed in this example uses the address associated with the
		// private key from above, simply return it with the compressed
		// flag set since the address is using the associated compressed
		// public key.
		//
		// NOTE: If you want to prove the code is actually signing the
		// transaction properly, uncomment the following line which
		// intentionally returns an invalid key to sign with, which in
		// turn will result in a failure during the script execution
		// when verifying the signature.
		//
		// privKey.D.SetInt64(12345)
		//
		return privKey, true, nil
	}
	// Notice that the script database parameter is nil here since it isn't
	// used.  It must be specified when pay-to-script-hash transactions are
	// being signed.
	sigScript, err := txscript.SignTxOutput(&chaincfg.MainNetParams,
		redeemTx, 0, originTx.TxOut[0].PkScript, txscript.SigHashAll,
		txscript.KeyClosure(lookupKey), nil, nil, secp)
	if err != nil {
		fmt.Println(err)
		return
	}
	redeemTx.TxIn[0].SignatureScript = sigScript

	// Prove that the transaction has been validly signed by executing the
	// script pair.
	flags := txscript.ScriptBip16 | txscript.ScriptVerifyDERSignatures |
		txscript.ScriptDiscourageUpgradableNops
	vm, err := txscript.NewEngine(originTx.TxOut[0].PkScript, redeemTx, 0,
		flags, 0, nil)
	if err != nil {
		fmt.Println(err)
		return
	}
	if err := vm.Execute(); err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Transaction successfully signed")

}

Output:

Transaction successfully signed

func SignatureScript 

func SignatureScript(tx *wire.MsgTx, idx int, subscript []byte,
	hashType SigHashType, privKey chainec.PrivateKey, compress bool) ([]byte,
	error)

SignatureScript creates an input signature script for tx to spend coins sent from a previous output to the owner of privKey. tx must include all transaction inputs and outputs, however txin scripts are allowed to be filled or empty. The returned script is calculated to be used as the idx'th txin sigscript for tx. subscript is the PkScript of the previous output being used as the idx'th input. privKey is serialized in either a compressed or uncompressed format based on compress. This format must match the same format used to generate the payment address, or the script validation will fail.

func SignatureScriptAlt 

func SignatureScriptAlt(tx *wire.MsgTx, idx int, subscript []byte,
	hashType SigHashType, privKey chainec.PrivateKey, compress bool,
	sigType int) ([]byte,
	error)

SignatureScriptAlt creates an input signature script for tx to spend coins sent from a previous output to the owner of privKey. tx must include all transaction inputs and outputs, however txin scripts are allowed to be filled or empty. The returned script is calculated to be used as the idx'th txin sigscript for tx. subscript is the PkScript of the previous output being used as the idx'th input. privKey is serialized in the respective format for the ECDSA type. This format must match the same format used to generate the payment address, or the script validation will fail.

func UseLogger 

func UseLogger(logger btclog.Logger)

UseLogger uses a specified Logger to output package logging info. This should be used in preference to SetLogWriter if the caller is also using btclog.

Types

type Engine 

type Engine struct {
	// contains filtered or unexported fields
}

Engine is the virtual machine that executes scripts.

func NewEngine 

func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int,
	flags ScriptFlags, scriptVersion uint16, sigCache *SigCache) (*Engine, error)

NewEngine returns a new script engine for the provided public key script, transaction, and input index. The flags modify the behavior of the script engine according to the description provided by each flag.

func (*Engine) CheckErrorCondition 

func (vm *Engine) CheckErrorCondition(finalScript bool) error

CheckErrorCondition returns nil if the running script has ended and was successful, leaving a a true boolean on the stack. An error otherwise, including if the script has not finished.

func (*Engine) DisasmPC 

func (vm *Engine) DisasmPC() (string, error)

DisasmPC returns the string for the disassembly of the opcode that will be next to execute when Step() is called.

func (*Engine) DisasmScript 

func (vm *Engine) DisasmScript(idx int) (string, error)

DisasmScript returns the disassembly string for the script at the requested offset index. Index 0 is the signature script and 1 is the public key script.

func (*Engine) Execute 

func (vm *Engine) Execute() (err error)

Execute will execute all scripts in the script engine and return either nil for successful validation or an error if one occurred.

func (*Engine) GetAltStack 

func (vm *Engine) GetAltStack() [][]byte

GetAltStack returns the contents of the primary stack as an array. where the last item in the array is the top of the stack.

func (*Engine) GetStack 

func (vm *Engine) GetStack() [][]byte

GetStack returns the contents of the primary stack as an array. where the last item in the array is the top of the stack.

func (*Engine) SetAltStack 

func (vm *Engine) SetAltStack(data [][]byte)

SetAltStack sets the contents of the primary stack to the contents of the provided array where the last item in the array will be the top of the stack.

func (*Engine) SetStack 

func (vm *Engine) SetStack(data [][]byte)

SetStack sets the contents of the primary stack to the contents of the provided array where the last item in the array will be the top of the stack.

func (*Engine) Step 

func (vm *Engine) Step() (done bool, err error)

Step will execute the next instruction and move the program counter to the next opcode in the script, or the next script if the current has ended. Step will return true in the case that the last opcode was successfully executed.

The result of calling Step or any other method is undefined if an error is returned.

type ErrScriptNotCanonical 

type ErrScriptNotCanonical string

ErrScriptNotCanonical identifies a non-canonical script. The caller can use a type assertion to detect this error type.

func (ErrScriptNotCanonical) Error 

func (e ErrScriptNotCanonical) Error() string

Error implements the error interface.

type KeyClosure 

type KeyClosure func(dcrutil.Address) (chainec.PrivateKey, bool, error)

KeyClosure implements KeyDB with a closure.

func (KeyClosure) GetKey 

func (kc KeyClosure) GetKey(address dcrutil.Address) (chainec.PrivateKey,
	bool, error)

GetKey implements KeyDB by returning the result of calling the closure.

type KeyDB 

type KeyDB interface {
	GetKey(dcrutil.Address) (chainec.PrivateKey, bool, error)
}

KeyDB is an interface type provided to SignTxOutput, it encapsulates any user state required to get the private keys for an address.

type ScriptBuilder 

type ScriptBuilder struct {
	// contains filtered or unexported fields
}

ScriptBuilder provides a facility for building custom scripts. It allows you to push opcodes, ints, and data while respecting canonical encoding. In general it does not ensure the script will execute correctly, however any data pushes which would exceed the maximum allowed script engine limits and are therefore guaranteed not to execute will not be pushed and will result in the Script function returning an error.

For example, the following would build a 2-of-3 multisig script for usage in a pay-to-script-hash (although in this situation MultiSigScript() would be a better choice to generate the script): 

builder := txscript.NewScriptBuilder()
builder.AddOp(txscript.OP_2).AddData(pubKey1).AddData(pubKey2)
builder.AddData(pubKey3).AddOp(txscript.OP_3)
builder.AddOp(txscript.OP_CHECKMULTISIG)
script, err := builder.Script()
if err != nil {
	// Handle the error.
	return
}
fmt.Printf("Final multi-sig script: %x\n", script)

func NewScriptBuilder 

func NewScriptBuilder() *ScriptBuilder

NewScriptBuilder returns a new instance of a script builder. See ScriptBuilder for details.

func (*ScriptBuilder) AddData 

func (b *ScriptBuilder) AddData(data []byte) *ScriptBuilder

AddData pushes the passed data to the end of the script. It automatically chooses canonical opcodes depending on the length of the data. A zero length buffer will lead to a push of empty data onto the stack (OP_0) and any push of data greater than MaxScriptElementSize will not modify the script since that is not allowed by the script engine. Also, the script will not be modified if pushing the data would cause the script to exceed the maximum allowed script engine size.

func (*ScriptBuilder) AddFullData 

func (b *ScriptBuilder) AddFullData(data []byte) *ScriptBuilder

AddFullData should not typically be used by ordinary users as it does not include the checks which prevent data pushes larger than the maximum allowed sizes which leads to scripts that can't be executed. This is provided for testing purposes such as regression tests where sizes are intentionally made larger than allowed.

Use AddData instead.

func (*ScriptBuilder) AddInt64 

func (b *ScriptBuilder) AddInt64(val int64) *ScriptBuilder

AddInt64 pushes the passed integer to the end of the script. The script will not be modified if pushing the data would cause the script to exceed the maximum allowed script engine size.

func (*ScriptBuilder) AddOp 

func (b *ScriptBuilder) AddOp(opcode byte) *ScriptBuilder

AddOp pushes the passed opcode to the end of the script. The script will not be modified if pushing the opcode would cause the script to exceed the maximum allowed script engine size.

func (*ScriptBuilder) Reset 

func (b *ScriptBuilder) Reset() *ScriptBuilder

Reset resets the script so it has no content.

func (*ScriptBuilder) Script 

func (b *ScriptBuilder) Script() ([]byte, error)

Script returns the currently built script. When any errors occured while building the script, the script will be returned up the point of the first error along with the error.

type ScriptClass 

type ScriptClass byte

ScriptClass is an enumeration for the list of standard types of script. 

const (
	NonStandardTy     ScriptClass = iota // None of the recognized forms.
	PubKeyTy                             // Pay pubkey.
	PubKeyHashTy                         // Pay pubkey hash.
	ScriptHashTy                         // Pay to script hash.
	MultiSigTy                           // Multi signature.
	NullDataTy                           // Empty data-only (provably prunable).
	StakeSubmissionTy                    // Stake submission.
	StakeGenTy                           // Stake generation
	StakeRevocationTy                    // Stake revocation.
	StakeSubChangeTy                     // Change for stake submission tx.
	PubkeyAltTy                          // Alternative signature pubkey.
	PubkeyHashAltTy                      // Alternative signature pubkey hash.
)

Classes of script payment known about in the blockchain.

func ExtractPkScriptAddrs 

func ExtractPkScriptAddrs(version uint16, pkScript []byte,
	chainParams *chaincfg.Params) (ScriptClass, []dcrutil.Address, int, error)

ExtractPkScriptAddrs returns the type of script, addresses and required signatures associated with the passed PkScript. Note that it only works for 'standard' transaction script types. Any data such as public keys which are invalid are omitted from the results.

Example

This example demonstrates extracting information from a standard public key script. 

package main

import (
	"encoding/hex"
	"fmt"

	"github.com/decred/dcrd/chaincfg"
	"github.com/decred/dcrd/txscript"
)

func main() {
	// Start with a standard pay-to-pubkey-hash script.
	scriptHex := "76a914128004ff2fcaf13b2b91eb654b1dc2b674f7ec6188ac"
	script, err := hex.DecodeString(scriptHex)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Extract and print details from the script.
	scriptClass, addresses, reqSigs, err := txscript.ExtractPkScriptAddrs(
		txscript.DefaultScriptVersion, script, &chaincfg.MainNetParams)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Script Class:", scriptClass)
	fmt.Println("Addresses:", addresses)
	fmt.Println("Required Signatures:", reqSigs)

}

Output:

Script Class: pubkeyhash
Addresses: [DsSej1qR3Fyc8kV176DCh9n9cY9nqf9Quxk]
Required Signatures: 1

func GetScriptClass 

func GetScriptClass(version uint16, script []byte) ScriptClass

GetScriptClass returns the class of the script passed.

NonStandardTy will be returned when the script does not parse.

func GetStakeOutSubclass 

func GetStakeOutSubclass(pkScript []byte) (ScriptClass, error)

GetStakeOutSubclass extracts the subclass (P2PKH or P2SH) from a stake output.

func (ScriptClass) String 

func (t ScriptClass) String() string

String implements the Stringer interface by returning the name of the enum script class. If the enum is invalid then "Invalid" will be returned.

type ScriptClosure 

type ScriptClosure func(dcrutil.Address) ([]byte, error)

ScriptClosure implements ScriptDB with a closure.

func (ScriptClosure) GetScript 

func (sc ScriptClosure) GetScript(address dcrutil.Address) ([]byte, error)

GetScript implements ScriptDB by returning the result of calling the closure.

type ScriptDB 

type ScriptDB interface {
	GetScript(dcrutil.Address) ([]byte, error)
}

ScriptDB is an interface type provided to SignTxOutput, it encapsulates any user state required to get the scripts for an pay-to-script-hash address.

type ScriptFlags 

type ScriptFlags uint32

ScriptFlags is a bitmask defining additional operations or tests that will be done when executing a script pair. 

const (
	// ScriptBip16 defines whether the bip16 threshhold has passed and thus
	// pay-to-script hash transactions will be fully validated.
	ScriptBip16 ScriptFlags = 1 << iota

	// ScriptStrictMultiSig defines whether to verify the stack item
	// used by CHECKMULTISIG is zero length.
	ScriptStrictMultiSig

	// ScriptDiscourageUpgradableNops defines whether to verify that
	// NOP1 through NOP10 are reserved for future soft-fork upgrades.  This
	// flag must not be used for consensus critical code nor applied to
	// blocks as this flag is only for stricter standard transaction
	// checks.  This flag is only applied when the above opcodes are
	// executed.
	ScriptDiscourageUpgradableNops

	// ScriptVerifyCheckLockTimeVerify defines whether to verify that
	// a transaction output is spendable based on the locktime.
	// This is BIP0065.
	ScriptVerifyCheckLockTimeVerify

	// ScriptVerifyCleanStack defines that the stack must contain only
	// one stack element after evaluation and that the element must be
	// true if interpreted as a boolean.  This is rule 6 of BIP0062.
	// This flag should never be used without the ScriptBip16 flag.
	ScriptVerifyCleanStack

	// ScriptVerifyDERSignatures defines that signatures are required
	// to compily with the DER format.
	ScriptVerifyDERSignatures

	// ScriptVerifyLowS defines that signtures are required to comply with
	// the DER format and whose S value is <= order / 2.  This is rule 5
	// of BIP0062.
	ScriptVerifyLowS

	// ScriptVerifyMinimalData defines that signatures must use the smallest
	// push operator. This is both rules 3 and 4 of BIP0062.
	ScriptVerifyMinimalData

	// ScriptVerifySigPushOnly defines that signature scripts must contain
	// only pushed data.  This is rule 2 of BIP0062.
	ScriptVerifySigPushOnly

	// ScriptVerifyStrictEncoding defines that signature scripts and
	// public keys must follow the strict encoding requirements.
	ScriptVerifyStrictEncoding
)

type ScriptInfo 

type ScriptInfo struct {
	// PkScriptClass is the class of the public key script and is equivalent
	// to calling GetScriptClass on it.
	PkScriptClass ScriptClass

	// NumInputs is the number of inputs provided by the public key script.
	NumInputs int

	// ExpectedInputs is the number of outputs required by the signature
	// script and any pay-to-script-hash scripts. The number will be -1 if
	// unknown.
	ExpectedInputs int

	// SigOps is the number of signature operations in the script pair.
	SigOps int
}

ScriptInfo houses information about a script pair that is determined by CalcScriptInfo.

func CalcScriptInfo 

func CalcScriptInfo(sigScript, pkScript []byte, bip16 bool) (*ScriptInfo, error)

CalcScriptInfo returns a structure providing data about the provided script pair. It will error if the pair is in someway invalid such that they can not be analysed, i.e. if they do not parse or the pkScript is not a push-only script

type SigCache added in v0.1.4 

type SigCache struct {
	sync.RWMutex
	// contains filtered or unexported fields
}

SigCache implements an ECDSA signature verification cache with a randomized entry eviction policy. Only valid signatures will be added to the cache. The benefits of SigCache are two fold. Firstly, usage of SigCache mitigates a DoS attack wherein an attack causes a victim's client to hang due to worst-case behavior triggered while processing attacker crafted invalid transactions. A detailed description of the mitigated DoS attack can be found here: https://bitslog.wordpress.com/2013/01/23/fixed-bitcoin-vulnerability-explanation-why-the-signature-cache-is-a-dos-protection/. Secondly, usage of the SigCache introduces a signature verification optimization which speeds up the validation of transactions within a block, if they've already been seen and verified within the mempool.

func NewSigCache added in v0.1.4 

func NewSigCache(maxEntries uint) *SigCache

NewSigCache creates and initializes a new instance of SigCache. Its sole parameter 'maxEntries' represents the maximum number of entries allowed to exist in the SigCache and any particular moment. Random entries are evicted to make room for new entries that would cause the number of entries in the cache to exceed the max.

func (*SigCache) Add added in v0.1.4 

func (s *SigCache) Add(sigHash chainhash.Hash, sig chainec.Signature, pubKey chainec.PublicKey)

Add adds an entry for a signature over 'sigHash' under public key 'pubKey' to the signature cache. In the event that the SigCache is 'full', an existing entry it randomly chosen to be evicted in order to make space for the new entry.

NOTE: This function is safe for concurrent access. Writers will block simultaneous readers until function execution has concluded.

func (*SigCache) Exists added in v0.1.4 

func (s *SigCache) Exists(sigHash chainhash.Hash, sig chainec.Signature, pubKey chainec.PublicKey) bool

Exists returns true if an existing entry of 'sig' over 'sigHash' for public key 'pubKey' is found within the SigCache. Otherwise, false is returned.

NOTE: This function is safe for concurrent access. Readers won't be blocked unless there exists a writer, adding an entry to the SigCache.

type SigHashType 

type SigHashType byte

SigHashType represents hash type bits at the end of a signature. 

const (
	SigHashOld          SigHashType = 0x0
	SigHashAll          SigHashType = 0x1
	SigHashNone         SigHashType = 0x2
	SigHashSingle       SigHashType = 0x3
	SigHashAllValue     SigHashType = 0x4
	SigHashAnyOneCanPay SigHashType = 0x80
)

Hash type bits from the end of a signature.

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