/
dynamo.go
126 lines (113 loc) · 3.78 KB
/
dynamo.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
package watermark
import (
"fmt"
"log"
"math/big"
"os"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
)
// DynamoWatermark stores the last-signed level in memory
type DynamoWatermark struct {
table string
dynamodb *dynamodb.DynamoDB
}
// GetDynamoWatermark returns a new dynamo watermark manager
func GetDynamoWatermark(table string) Watermark {
sess, err := session.NewSession(&aws.Config{
Region: aws.String(os.Getenv("AWS_DEFAULT_REGION")),
})
if err != nil {
log.Fatal("Unable to initialize dynamo watermark")
}
return &DynamoWatermark{
table: table,
dynamodb: dynamodb.New(sess),
}
}
// getDynamoKey used as the hash identifier of each entry
func getDynamoKey(keyHash string, chainID string, opMagicByte uint8) string {
return fmt.Sprintf("%v-%v-%v", keyHash, chainID, opMagicByte)
}
// getCurrentLevel watermarked in Dynamo
func (mw *DynamoWatermark) getCurrentLevel(keyHash string, chainID string, opMagicByte uint8) (*big.Int, error) {
// Get Item
result, err := mw.dynamodb.GetItem(&dynamodb.GetItemInput{
TableName: aws.String(mw.table),
Key: map[string]*dynamodb.AttributeValue{
"KeyChainOp": {S: aws.String(getDynamoKey(keyHash, chainID, opMagicByte))},
},
ConsistentRead: aws.Bool(true),
})
if err != nil {
// There was an error retrieving the dynamo item
return nil, err
}
if result.Item["Level"] == nil {
// The key does not exist in dynamo
return nil, nil
}
newInt, _ := new(big.Int).SetString(*result.Item["Level"].S, 10)
return newInt, nil
}
// putItem for the first time into Dynamo
func (mw *DynamoWatermark) putItem(keyHash string, chainID string, opMagicByte uint8, level *big.Int) error {
_, err := mw.dynamodb.PutItem(&dynamodb.PutItemInput{
TableName: aws.String(mw.table),
Item: map[string]*dynamodb.AttributeValue{
"KeyChainOp": {S: aws.String(getDynamoKey(keyHash, chainID, opMagicByte))},
"Level": {S: aws.String(level.String())},
},
ConditionExpression: aws.String("attribute_not_exists(KeyChainOp)"),
})
return err
}
// updateItem with a new level in dynamo
func (mw *DynamoWatermark) updateItem(keyHash string, chainID string, opMagicByte uint8, currentLevel *big.Int, newLevel *big.Int) error {
// Update Item
_, err := mw.dynamodb.UpdateItem(&dynamodb.UpdateItemInput{
TableName: aws.String(mw.table),
Key: map[string]*dynamodb.AttributeValue{
"KeyChainOp": {S: aws.String(getDynamoKey(keyHash, chainID, opMagicByte))},
},
ExpressionAttributeNames: map[string]*string{
"#Level": aws.String("Level"),
},
ExpressionAttributeValues: map[string]*dynamodb.AttributeValue{
":newval": &dynamodb.AttributeValue{S: aws.String(newLevel.String())},
":currval": &dynamodb.AttributeValue{S: aws.String(currentLevel.String())},
},
UpdateExpression: aws.String("SET #Level = :newval"),
ConditionExpression: aws.String("#Level = :currval"),
})
return err
}
// IsSafeToSign returns true if the provided (key, chainID, opMagicByte) tuple has
// not yet been signed at this or greater levels
func (mw *DynamoWatermark) IsSafeToSign(keyHash string, chainID string, opMagicByte uint8, level *big.Int) bool {
currentLevel, err := mw.getCurrentLevel(keyHash, chainID, opMagicByte)
if err != nil {
log.Println("Error: Unable to get current level", err)
return false
}
// Create a new item if none currently exists
if currentLevel == nil {
err := mw.putItem(keyHash, chainID, opMagicByte, level)
if err != nil {
return false
}
return true
}
// Update existing items
if level.Cmp(currentLevel) != 1 {
log.Println("Warning: Attempted to sign at an unsafe level. Will not allow.")
return false
} else {
err := mw.updateItem(keyHash, chainID, opMagicByte, currentLevel, level)
if err != nil {
return false
}
return true
}
}