Dinesh Belwalkar | e63f7f9 | 2019-11-22 23:11:16 +0000 | [diff] [blame^] | 1 | // Copyright 2009 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package asn1 |
| 6 | |
| 7 | import ( |
| 8 | "reflect" |
| 9 | "strconv" |
| 10 | "strings" |
| 11 | ) |
| 12 | |
| 13 | // ASN.1 objects have metadata preceding them: |
| 14 | // the tag: the type of the object |
| 15 | // a flag denoting if this object is compound or not |
| 16 | // the class type: the namespace of the tag |
| 17 | // the length of the object, in bytes |
| 18 | |
| 19 | // Here are some standard tags and classes |
| 20 | |
| 21 | // ASN.1 tags represent the type of the following object. |
| 22 | const ( |
| 23 | TagBoolean = 1 |
| 24 | TagInteger = 2 |
| 25 | TagBitString = 3 |
| 26 | TagOctetString = 4 |
| 27 | TagOID = 6 |
| 28 | TagEnum = 10 |
| 29 | TagUTF8String = 12 |
| 30 | TagSequence = 16 |
| 31 | TagSet = 17 |
| 32 | TagPrintableString = 19 |
| 33 | TagT61String = 20 |
| 34 | TagIA5String = 22 |
| 35 | TagUTCTime = 23 |
| 36 | TagGeneralizedTime = 24 |
| 37 | TagGeneralString = 27 |
| 38 | ) |
| 39 | |
| 40 | // ASN.1 class types represent the namespace of the tag. |
| 41 | const ( |
| 42 | ClassUniversal = 0 |
| 43 | ClassApplication = 1 |
| 44 | ClassContextSpecific = 2 |
| 45 | ClassPrivate = 3 |
| 46 | ) |
| 47 | |
| 48 | type tagAndLength struct { |
| 49 | class, tag, length int |
| 50 | isCompound bool |
| 51 | } |
| 52 | |
| 53 | // ASN.1 has IMPLICIT and EXPLICIT tags, which can be translated as "instead |
| 54 | // of" and "in addition to". When not specified, every primitive type has a |
| 55 | // default tag in the UNIVERSAL class. |
| 56 | // |
| 57 | // For example: a BIT STRING is tagged [UNIVERSAL 3] by default (although ASN.1 |
| 58 | // doesn't actually have a UNIVERSAL keyword). However, by saying [IMPLICIT |
| 59 | // CONTEXT-SPECIFIC 42], that means that the tag is replaced by another. |
| 60 | // |
| 61 | // On the other hand, if it said [EXPLICIT CONTEXT-SPECIFIC 10], then an |
| 62 | // /additional/ tag would wrap the default tag. This explicit tag will have the |
| 63 | // compound flag set. |
| 64 | // |
| 65 | // (This is used in order to remove ambiguity with optional elements.) |
| 66 | // |
| 67 | // You can layer EXPLICIT and IMPLICIT tags to an arbitrary depth, however we |
| 68 | // don't support that here. We support a single layer of EXPLICIT or IMPLICIT |
| 69 | // tagging with tag strings on the fields of a structure. |
| 70 | |
| 71 | // fieldParameters is the parsed representation of tag string from a structure field. |
| 72 | type fieldParameters struct { |
| 73 | optional bool // true iff the field is OPTIONAL |
| 74 | explicit bool // true iff an EXPLICIT tag is in use. |
| 75 | application bool // true iff an APPLICATION tag is in use. |
| 76 | defaultValue *int64 // a default value for INTEGER typed fields (maybe nil). |
| 77 | tag *int // the EXPLICIT or IMPLICIT tag (maybe nil). |
| 78 | stringType int // the string tag to use when marshaling. |
| 79 | timeType int // the time tag to use when marshaling. |
| 80 | set bool // true iff this should be encoded as a SET |
| 81 | omitEmpty bool // true iff this should be omitted if empty when marshaling. |
| 82 | |
| 83 | // Invariants: |
| 84 | // if explicit is set, tag is non-nil. |
| 85 | } |
| 86 | |
| 87 | // Given a tag string with the format specified in the package comment, |
| 88 | // parseFieldParameters will parse it into a fieldParameters structure, |
| 89 | // ignoring unknown parts of the string. |
| 90 | func parseFieldParameters(str string) (ret fieldParameters) { |
| 91 | for _, part := range strings.Split(str, ",") { |
| 92 | switch { |
| 93 | case part == "optional": |
| 94 | ret.optional = true |
| 95 | case part == "explicit": |
| 96 | ret.explicit = true |
| 97 | if ret.tag == nil { |
| 98 | ret.tag = new(int) |
| 99 | } |
| 100 | case part == "generalized": |
| 101 | ret.timeType = TagGeneralizedTime |
| 102 | case part == "utc": |
| 103 | ret.timeType = TagUTCTime |
| 104 | case part == "ia5": |
| 105 | ret.stringType = TagIA5String |
| 106 | // jtasn1 case below added |
| 107 | case part == "generalstring": |
| 108 | ret.stringType = TagGeneralString |
| 109 | case part == "printable": |
| 110 | ret.stringType = TagPrintableString |
| 111 | case part == "utf8": |
| 112 | ret.stringType = TagUTF8String |
| 113 | case strings.HasPrefix(part, "default:"): |
| 114 | i, err := strconv.ParseInt(part[8:], 10, 64) |
| 115 | if err == nil { |
| 116 | ret.defaultValue = new(int64) |
| 117 | *ret.defaultValue = i |
| 118 | } |
| 119 | case strings.HasPrefix(part, "tag:"): |
| 120 | i, err := strconv.Atoi(part[4:]) |
| 121 | if err == nil { |
| 122 | ret.tag = new(int) |
| 123 | *ret.tag = i |
| 124 | } |
| 125 | case part == "set": |
| 126 | ret.set = true |
| 127 | case part == "application": |
| 128 | ret.application = true |
| 129 | if ret.tag == nil { |
| 130 | ret.tag = new(int) |
| 131 | } |
| 132 | case part == "omitempty": |
| 133 | ret.omitEmpty = true |
| 134 | } |
| 135 | } |
| 136 | return |
| 137 | } |
| 138 | |
| 139 | // Given a reflected Go type, getUniversalType returns the default tag number |
| 140 | // and expected compound flag. |
| 141 | func getUniversalType(t reflect.Type) (tagNumber int, isCompound, ok bool) { |
| 142 | switch t { |
| 143 | case objectIdentifierType: |
| 144 | return TagOID, false, true |
| 145 | case bitStringType: |
| 146 | return TagBitString, false, true |
| 147 | case timeType: |
| 148 | return TagUTCTime, false, true |
| 149 | case enumeratedType: |
| 150 | return TagEnum, false, true |
| 151 | case bigIntType: |
| 152 | return TagInteger, false, true |
| 153 | } |
| 154 | switch t.Kind() { |
| 155 | case reflect.Bool: |
| 156 | return TagBoolean, false, true |
| 157 | case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: |
| 158 | return TagInteger, false, true |
| 159 | case reflect.Struct: |
| 160 | return TagSequence, true, true |
| 161 | case reflect.Slice: |
| 162 | if t.Elem().Kind() == reflect.Uint8 { |
| 163 | return TagOctetString, false, true |
| 164 | } |
| 165 | if strings.HasSuffix(t.Name(), "SET") { |
| 166 | return TagSet, true, true |
| 167 | } |
| 168 | return TagSequence, true, true |
| 169 | case reflect.String: |
| 170 | return TagPrintableString, false, true |
| 171 | } |
| 172 | return 0, false, false |
| 173 | } |