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brew.sh: Don't allow system tmp dirs as prefixes #4397

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merged 14 commits into from
Jul 3, 2018
Merged

brew.sh: Don't allow system tmp dirs as prefixes #4397

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35138dd
brew.sh: Don't allow system tmp dirs as prefixes
woodruffw Jun 30, 2018
949c0cc
brew.sh: Use realpath to calculate tmpdir
woodruffw Jun 30, 2018
42bd544
brew.sh: Typo
woodruffw Jun 30, 2018
b6a0b04
brew.sh: Tweak language
woodruffw Jun 30, 2018
c552e65
brew.sh: Remove trailing / from prefix in message
woodruffw Jun 30, 2018
696a1d1
bin/brew: Set HOMEBREW_TEMP, allow export
woodruffw Jun 30, 2018
d7cdc9b
config: Ensure HOMEBREW_TEMP is absolute
woodruffw Jun 30, 2018
8e4aab9
brew.sh: Test HOMEBREW_TEMP, not hardcoded tmpdir
woodruffw Jun 30, 2018
72bc6b1
config: Remove /tmp fallback
woodruffw Jul 1, 2018
a8bcb5d
bin/brew: Revert allowing export of TEMP
woodruffw Jul 1, 2018
039a4ee
brew.sh: Move HOMEBREW_TEMP declaration
woodruffw Jul 1, 2018
bde7c6b
brew.sh: Use bashisms for default values
woodruffw Jul 1, 2018
68d3dc1
brew.sh: Only do tmpdir check on macOS
woodruffw Jul 1, 2018
fd01415
brew.sh: Upcase var, tweak error language
woodruffw Jul 2, 2018
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18 changes: 18 additions & 0 deletions Library/Homebrew/brew.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,8 @@ then
then
HOMEBREW_CACHE="$HOME/Library/Caches/Homebrew"
fi

HOMEBREW_TEMP="${HOMEBREW_TEMP:-/private/tmp}"
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👍 to defining here. I wonder if it's worth doing just the same -z as above for consistency? Alternatively; replace the -zs that have no complex logic with this form?

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I'm in favor of replacing with the :- form, since it's the standard bashism for a default value and we use similar bashisms elsewhere in the code.

else
HOMEBREW_PROCESSOR="$(uname -m)"
HOMEBREW_PRODUCT="${HOMEBREW_SYSTEM}brew"
Expand All @@ -124,6 +126,8 @@ else
HOMEBREW_CACHE="$HOME/.cache/Homebrew"
fi
fi

HOMEBREW_TEMP="${HOMEBREW_TEMP:-/tmp}"
fi

if [[ -n "$HOMEBREW_FORCE_BREWED_CURL" &&
Expand All @@ -144,6 +148,7 @@ export HOMEBREW_BREW_FILE
export HOMEBREW_PREFIX
export HOMEBREW_REPOSITORY
export HOMEBREW_LIBRARY
export HOMEBREW_TEMP

# Declared in brew.sh
export HOMEBREW_VERSION
Expand Down Expand Up @@ -294,6 +299,19 @@ EOS
}
check-run-command-as-root

check-prefix-is-not-tmpdir() {
if [[ "${HOMEBREW_PREFIX}" = "${HOMEBREW_TEMP}"* ]]
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This wants guarded to macOS only, check against the system temp rather than just HOMEBREW_TEMP (maybe a HOMEBREW_SYSTEM_TEMP var?) and use that directory in the output, too.

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HOMEBREW_SYSTEM_TEMP could be potentially used wherever private/tmp is hardcoded, too.

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check against the system temp rather than just HOMEBREW_TEMP

I might be misunderstanding, but: won't this leave open the case where they set both their prefix and their temp to something weird, e.g., $HOME? We want to stop all situations where Homebrew is both installing to and using the same prefix as a temporary directory, not just /private/tmp.

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@woodruffw Ok so is it fine to e.g. have the prefix in /tmp if HOMEBREW_TEMP is set elsewhere?

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Yep, exactly.

then
odie <<EOS
Your HOMEBREW_PREFIX is in the system temporary directory, which Homebrew
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Maybe worth just saying e.g. /private/tmp? Also, should we do this on Linux or with a different directory?

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I thought that the connection between /tmp and /private/tmp might confuse some users (Apple links /tmp to /private/tmp for FHS compliance), so I just went with "system temporary directory." I can change it/add those directories to the message if you think it'll improve the error, though.

The relocation code at fault isn't used on Linux, so Linuxbrew users might not encounter this problem at all. I'll confirm that in a bit with some local testing.

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HOMEBREW_TEMP isn't necessary the system temporary directory. To expand on my previous comment (and avoid the autohiding): is the issue if:

  • the prefix is in the system temporary directory
  • the prefix is the in the HOMEBREW_TEMP temporary directory
  • either

We should ensure that the wording makes that clear and the logic is as minimal as possible to the actual problems we've seen people experience.

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The issue is when the prefix is in the HOMEBREW_TEMP temporary directory. I'll correct the language here 🙂

uses to store downloads and builds. You can resolve this by installing Homebrew to
either the standard prefix (/usr/local) or to a non-standard prefix that is not
in the system temporary directory.
EOS
fi
}
check-prefix-is-not-tmpdir

if [[ "$HOMEBREW_PREFIX" = "/usr/local" &&
"$HOMEBREW_PREFIX" != "$HOMEBREW_REPOSITORY" &&
"$HOMEBREW_CELLAR" = "$HOMEBREW_REPOSITORY/Cellar" ]]
Expand Down
2 changes: 1 addition & 1 deletion Library/Homebrew/config.rb
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Expand Up @@ -39,7 +39,7 @@
HOMEBREW_LOGS = Pathname.new(ENV["HOMEBREW_LOGS"] || "~/Library/Logs/Homebrew/").expand_path

# Must use /tmp instead of $TMPDIR because long paths break Unix domain sockets
HOMEBREW_TEMP = Pathname.new(ENV.fetch("HOMEBREW_TEMP", "/tmp"))
HOMEBREW_TEMP = Pathname.new(ENV["HOMEBREW_TEMP"]).realpath
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I think this will crash when the dir doesn't exist.

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Yup. Fixing 😭

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#4415

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Thanks!


unless defined? HOMEBREW_LIBRARY_PATH
# Root of the Homebrew code base
Expand Down