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
|
#
msgid ""
msgstr ""
msgid ""
"title: Verifying \"npm ci\" reproducibility\n"
"date: 2018-08-01\n"
"layout: post\n"
"lang: en\n"
"ref: verifying-npm-ci-reproducibility\n"
"updated_at: 2019-05-22"
msgstr ""
msgid ""
"When [npm@5](https://blog.npmjs.org/post/161081169345/v500) came bringing "
"[package-locks](https://docs.npmjs.com/files/package-locks) with it, I was "
"confused about the benefits it provided, since running `npm install` more "
"than once could resolve all the dependencies again and yield yet another "
"fresh `package-lock.json` file. The message saying \"you should add this "
"file to version control\" left me hesitant on what to do[^package-lock-"
"message](The)."
msgstr ""
msgid ""
"However the [addition of `npm "
"ci`](https://blog.npmjs.org/post/171556855892/introducing-npm-ci-for-faster-"
"more-reliable) filled this gap: it's a stricter variation of `npm install` "
"which guarantees that \"[subsequent installs are able to generate identical "
"trees](https://docs.npmjs.com/files/package-lock.json)\". But are they "
"really identical? I could see that I didn't have the same problems of "
"different installation outputs, but I didn't know for **sure** if it was "
"really identical."
msgstr ""
msgid "Computing the hash of a directory's content"
msgstr ""
msgid ""
"I quickly searched for a way to check for the hash signature of an entire "
"directory tree, but I couldn't find one. I've made a poor man's [Merkle "
"tree](https://en.wikipedia.org/wiki/Merkle_tree) implementation using "
"`sha256sum` and a few piped commands at the terminal:"
msgstr ""
msgid "Going through it line by line:"
msgstr ""
msgid "#1 we define a Bash function called `merkle-tree`;"
msgstr ""
msgid ""
"#2 it accepts a single argument: the directory to compute the merkle tree "
"from. If nothing is given, it runs on the current directory (`.`);"
msgstr ""
msgid ""
"#3 we go to the directory, so we don't get different prefixes in `find`'s "
"output (like `../a/b`);"
msgstr ""
msgid ""
"#4 we get all files from the directory tree. Since we're using `sha256sum` "
"to compute the hash of the file contents, we need to filter out folders from"
" it;"
msgstr ""
msgid ""
"#5 we need to sort the output, since different file systems and `find` "
"implementations may return files in different orders;"
msgstr ""
msgid ""
"#6 we use `xargs` to compute the hash of each file individually through "
"`sha256sum`. Since a file may contain spaces we need to escape it with "
"quotes;"
msgstr ""
msgid ""
"#7 we compute the hash of the combined hashes. Since `sha256sum` output is "
"formatted like `<hash> <filename>`, it produces a different final hash if a "
"file ever changes name without changing it's content;"
msgstr ""
msgid ""
"#8 we get the final hash output, excluding the `<filename>` (which is `-` in"
" this case, aka `stdin`)."
msgstr ""
msgid "Positive points:"
msgstr ""
msgid ""
"ignore timestamp: running more than once on different installation yields "
"the same hash;"
msgstr ""
msgid "the name of the file is included in the final hash computation."
msgstr ""
msgid "Limitations:"
msgstr ""
msgid "it ignores empty folders from the hash computation;"
msgstr ""
msgid ""
"the implementation's only goal is to represent using a digest whether the "
"content of a given directory is the same or not. Leaf presence checking is "
"obviously missing from it."
msgstr ""
msgid "Testing locally with sample data"
msgstr ""
msgid "It seems to work for this simple test case."
msgstr ""
msgid "You can try copying and pasting it to verify the hash signatures."
msgstr ""
msgid "Using `merkle-tree` to check the output of `npm ci`"
msgstr ""
msgid "*I've done all of the following using Node.js v8.11.3 and npm@6.1.0.*"
msgstr ""
msgid ""
"In this test case I'll take the main repo of "
"[Lerna](https://lernajs.io/)[^lerna-package-lock]:"
msgstr ""
msgid "Good job `npm ci` :)"
msgstr ""
msgid ""
"#6 and #9 take some time to run (21 seconds in my machine), but this "
"specific use case isn't performance sensitive. The slowest step is computing"
" the hash of each individual file."
msgstr ""
msgid "Conclusion"
msgstr ""
msgid "`npm ci` really \"generates identical trees\"."
msgstr ""
msgid ""
"I'm not aware of any other existing solution for verifying the hash "
"signature of a directory. If you know any I'd [like to know](mailto:{{ "
"site.author.email }})."
msgstr ""
msgid "*Edit*"
msgstr ""
msgid "2019/05/22: Fix spelling."
msgstr ""
msgid ""
"[documentation](https://docs.npmjs.com/cli/install#description) claims `npm "
"install` is driven by the existing `package-lock.json`, but that's actually "
"[a little bit "
"tricky](https://github.com/npm/npm/issues/17979#issuecomment-332701215)."
msgstr ""
msgid ""
"[^lerna-package-lock]: Finding a big known repo that actually committed the "
"`package-lock.json` file was harder than I expected."
msgstr ""
|
