Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright 2018 by David A. Golden. All rights reserved. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package scram |
| 8 | |
| 9 | import ( |
| 10 | "encoding/base64" |
| 11 | "errors" |
| 12 | "fmt" |
| 13 | "strconv" |
| 14 | "strings" |
| 15 | ) |
| 16 | |
| 17 | type c1Msg struct { |
| 18 | gs2Header string |
| 19 | authzID string |
| 20 | username string |
| 21 | nonce string |
| 22 | c1b string |
| 23 | } |
| 24 | |
| 25 | type c2Msg struct { |
| 26 | cbind []byte |
| 27 | nonce string |
| 28 | proof []byte |
| 29 | c2wop string |
| 30 | } |
| 31 | |
| 32 | type s1Msg struct { |
| 33 | nonce string |
| 34 | salt []byte |
| 35 | iters int |
| 36 | } |
| 37 | |
| 38 | type s2Msg struct { |
| 39 | verifier []byte |
| 40 | err string |
| 41 | } |
| 42 | |
| 43 | func parseField(s, k string) (string, error) { |
| 44 | t := strings.TrimPrefix(s, k+"=") |
| 45 | if t == s { |
| 46 | return "", fmt.Errorf("error parsing '%s' for field '%s'", s, k) |
| 47 | } |
| 48 | return t, nil |
| 49 | } |
| 50 | |
| 51 | func parseGS2Flag(s string) (string, error) { |
| 52 | if s[0] == 'p' { |
| 53 | return "", fmt.Errorf("channel binding requested but not supported") |
| 54 | } |
| 55 | |
| 56 | if s == "n" || s == "y" { |
| 57 | return s, nil |
| 58 | } |
| 59 | |
| 60 | return "", fmt.Errorf("error parsing '%s' for gs2 flag", s) |
| 61 | } |
| 62 | |
| 63 | func parseFieldBase64(s, k string) ([]byte, error) { |
| 64 | raw, err := parseField(s, k) |
| 65 | if err != nil { |
| 66 | return nil, err |
| 67 | } |
| 68 | |
| 69 | dec, err := base64.StdEncoding.DecodeString(raw) |
| 70 | if err != nil { |
| 71 | return nil, err |
| 72 | } |
| 73 | |
| 74 | return dec, nil |
| 75 | } |
| 76 | |
| 77 | func parseFieldInt(s, k string) (int, error) { |
| 78 | raw, err := parseField(s, k) |
| 79 | if err != nil { |
| 80 | return 0, err |
| 81 | } |
| 82 | |
| 83 | num, err := strconv.Atoi(raw) |
| 84 | if err != nil { |
| 85 | return 0, fmt.Errorf("error parsing field '%s': %v", k, err) |
| 86 | } |
| 87 | |
| 88 | return num, nil |
| 89 | } |
| 90 | |
| 91 | func parseClientFirst(c1 string) (msg c1Msg, err error) { |
| 92 | |
| 93 | fields := strings.Split(c1, ",") |
| 94 | if len(fields) < 4 { |
| 95 | err = errors.New("not enough fields in first server message") |
| 96 | return |
| 97 | } |
| 98 | |
| 99 | gs2flag, err := parseGS2Flag(fields[0]) |
| 100 | if err != nil { |
| 101 | return |
| 102 | } |
| 103 | |
| 104 | // 'a' field is optional |
| 105 | if len(fields[1]) > 0 { |
| 106 | msg.authzID, err = parseField(fields[1], "a") |
| 107 | if err != nil { |
| 108 | return |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | // Recombine and save the gs2 header |
| 113 | msg.gs2Header = gs2flag + "," + msg.authzID + "," |
| 114 | |
| 115 | // Check for unsupported extensions field "m". |
| 116 | if strings.HasPrefix(fields[2], "m=") { |
| 117 | err = errors.New("SCRAM message extensions are not supported") |
| 118 | return |
| 119 | } |
| 120 | |
| 121 | msg.username, err = parseField(fields[2], "n") |
| 122 | if err != nil { |
| 123 | return |
| 124 | } |
| 125 | |
| 126 | msg.nonce, err = parseField(fields[3], "r") |
| 127 | if err != nil { |
| 128 | return |
| 129 | } |
| 130 | |
| 131 | msg.c1b = strings.Join(fields[2:], ",") |
| 132 | |
| 133 | return |
| 134 | } |
| 135 | |
| 136 | func parseClientFinal(c2 string) (msg c2Msg, err error) { |
| 137 | fields := strings.Split(c2, ",") |
| 138 | if len(fields) < 3 { |
| 139 | err = errors.New("not enough fields in first server message") |
| 140 | return |
| 141 | } |
| 142 | |
| 143 | msg.cbind, err = parseFieldBase64(fields[0], "c") |
| 144 | if err != nil { |
| 145 | return |
| 146 | } |
| 147 | |
| 148 | msg.nonce, err = parseField(fields[1], "r") |
| 149 | if err != nil { |
| 150 | return |
| 151 | } |
| 152 | |
| 153 | // Extension fields may come between nonce and proof, so we |
| 154 | // grab the *last* fields as proof. |
| 155 | msg.proof, err = parseFieldBase64(fields[len(fields)-1], "p") |
| 156 | if err != nil { |
| 157 | return |
| 158 | } |
| 159 | |
| 160 | msg.c2wop = c2[:strings.LastIndex(c2, ",")] |
| 161 | |
| 162 | return |
| 163 | } |
| 164 | |
| 165 | func parseServerFirst(s1 string) (msg s1Msg, err error) { |
| 166 | |
| 167 | // Check for unsupported extensions field "m". |
| 168 | if strings.HasPrefix(s1, "m=") { |
| 169 | err = errors.New("SCRAM message extensions are not supported") |
| 170 | return |
| 171 | } |
| 172 | |
| 173 | fields := strings.Split(s1, ",") |
| 174 | if len(fields) < 3 { |
| 175 | err = errors.New("not enough fields in first server message") |
| 176 | return |
| 177 | } |
| 178 | |
| 179 | msg.nonce, err = parseField(fields[0], "r") |
| 180 | if err != nil { |
| 181 | return |
| 182 | } |
| 183 | |
| 184 | msg.salt, err = parseFieldBase64(fields[1], "s") |
| 185 | if err != nil { |
| 186 | return |
| 187 | } |
| 188 | |
| 189 | msg.iters, err = parseFieldInt(fields[2], "i") |
| 190 | |
| 191 | return |
| 192 | } |
| 193 | |
| 194 | func parseServerFinal(s2 string) (msg s2Msg, err error) { |
| 195 | fields := strings.Split(s2, ",") |
| 196 | |
| 197 | msg.verifier, err = parseFieldBase64(fields[0], "v") |
| 198 | if err == nil { |
| 199 | return |
| 200 | } |
| 201 | |
| 202 | msg.err, err = parseField(fields[0], "e") |
| 203 | |
| 204 | return |
| 205 | } |