/
merge-statements.ts
176 lines (147 loc) · 4.86 KB
/
merge-statements.ts
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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
const LENGTH_CACHE_SYM = Symbol();
type IamValue = unknown | unknown[];
/**
* Only the parts of the policy schema we're interested in
*/
interface StatementSchema {
readonly Sid?: string;
readonly Effect?: string;
readonly Principal?: IamValue | Record<string, IamValue>;
readonly Resource?: IamValue;
readonly Action?: IamValue;
}
/**
* Merge as many statements as possible to shrink the total policy doc, modifying the input array in place
*/
export function mergeStatements(statements: StatementSchema[]): StatementSchema[] {
let merges = findMerges(statements);
while (merges.length > 0) {
merges.sort((a, b) => a.sizeDelta - b.sizeDelta); // Most negative number first
if (merges[0].sizeDelta >= 0) { break; } // Nothing more to be gained
// Apply all merges, order biggest to smallest gain
while (merges.length > 0 && merges[0].sizeDelta < 0) { // Only while we're not adding size
const merge = merges.shift()!;
statements[merge.i0] = merge.combined;
statements.splice(merge.i1, 1);
// This invalidates all merges involving i0 or i1, and adjusts all indices > i1
const invalidIndices = [merge.i0, merge.i1];
let j = 0;
while (j < merges.length) {
if (invalidIndices.includes(merges[j].i0) || invalidIndices.includes(merges[j].i1)) {
merges.splice(j, 1);
} else {
if (merges[j].i0 > merge.i1) { merges[j].i0 -= 1; }
if (merges[j].i1 > merge.i1) { merges[j].i1 -= 1; }
j++;
}
}
}
merges = findMerges(statements);
}
return statements;
}
function findMerges(statements: StatementSchema[]): StatementMerge[] {
const ret = new Array<StatementMerge>();
for (let i0 = 0; i0 < statements.length; i0++) {
for (let i1 = i0 + 1; i1 < statements.length; i1++) {
tryMerge(statements, i0, i1, ret);
}
}
return ret;
}
function tryMerge(statements: StatementSchema[], i0: number, i1: number, into: StatementMerge[]) {
const a = statements[i0];
const b = statements[i1];
if (a.Effect !== 'Allow' || b.Effect !== 'Allow') { return; }
if (a.Sid || b.Sid) { return; }
const beforeLen = jsonLength(a) + jsonLength(b);
tryMerging('Resource');
tryMerging('Action');
tryMerging('Principal');
function tryMerging<A extends keyof StatementSchema>(key: A) {
if (!deepEqual(a, b, [key])) { return; }
const combined = {
...a,
[key]: mergeValues(a[key], b[key]),
};
into.push({
i0,
i1,
combined,
sizeDelta: jsonLength(combined) - beforeLen,
});
}
}
/**
* Return the length of a JSON representation of the given object, cached on the object
*/
function jsonLength<A extends StatementSchema>(x: A): number {
if ((x as any)[LENGTH_CACHE_SYM]) {
return (x as any)[LENGTH_CACHE_SYM];
}
const length = JSON.stringify(x).length;
Object.defineProperty(x, LENGTH_CACHE_SYM, {
value: length,
enumerable: false,
});
return length;
}
function deepEqual(a: any, b: any, ignoreKeys: string[]): boolean {
// Short-circuit same object identity as well
if (a === b) { return true; }
if (Array.isArray(a) || Array.isArray(b)) {
if (!Array.isArray(a) || !Array.isArray(b) || a.length !== b.length) { return false; }
return a.every((x, i) => deepEqual(x, b[i], []));
}
if (typeof a === 'object' || typeof b === 'object') {
if (typeof a !== 'object' || typeof b !== 'object') { return false; }
const keysA = new Set(Object.keys(a));
const keysB = new Set(Object.keys(b));
for (const k of ignoreKeys) {
keysA.delete(k);
keysB.delete(k);
}
for (const k of keysA) {
if (!deepEqual(a[k], b[k], [])) { return false; }
keysB.delete(k);
}
return keysB.size === 0;
}
return false;
}
function mergeValues(a: IamValue, b: IamValue): any {
if (!a && !b) { return a; }
if (Array.isArray(a) && Array.isArray(b)) { return normalizedArray(...a, ...b); }
if (Array.isArray(a) && typeof b === 'string') { return normalizedArray(...a, b); }
if (Array.isArray(b) && typeof a === 'string') { return normalizedArray(a, ...b); }
if (typeof a === 'string' && typeof b === 'string') { return normalizedArray(a, b); }
if (typeof a === 'object' && typeof b === 'object' && b != null) {
const ret: any = { ...a };
for (const [k, v] of Object.entries(b)) {
ret[k] = ret[k] ? mergeValues(ret[k], v) : v;
}
return ret;
}
throw new Error(`Don't know how to merge ${JSON.stringify(a)} and ${JSON.stringify(b)}`);
}
function normalizedArray(...xs: unknown[]) {
return Array.from(new Set(xs)).sort();
}
interface StatementMerge {
/**
* Index of statement 0
*/
i0: number;
/**
* Index of statement 1
*/
i1: number;
/**
* The result of combining them
*/
readonly combined: StatementSchema;
/**
* How many bytes the new schema is bigger than the old one
*/
readonly sizeDelta: number;
}