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pkg/idtools: refactor to avoid string-splitting

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The package used a lot of string-formatting, followed by string-splitting.
This looked to originate from attempts to use templating to allow future
extensibility (9a3ab0358e).

Looking at the history of the package, only a single update was made to
these templates, 5 years go, which makes it unlikely that more templating
will be needed.

This patch simplifies the handling of arguments to use `[]string` instead
of a single `string` (and splitting to a `[]string`). This both simplifies
the code somewhat, and prevents user/group-names containing spaces to be
splitted (causing, e.g. `getent` to fail).

Note that user/group-names containing spaces are invalid (or at least
discouraged), there are situations where such names may be used, so we
should avoid breaking on such names.

Before this change, a user/group name with a space in its name would fail;

    dockerd --userns-remap="user:domain users"
    INFO[2020-08-19T10:26:59.288868661+02:00] Starting up
    Error during groupname lookup for "domain users": getent unable to find entry "domain" in group database

With this change:

    # Add some possibly problematic usernames for testing
    # need to do this manually, as `adduser` / `useradd` won't accept these names
    echo 'user name❌1002:1002::/home/one:/bin/false' >> /etc/passwd; \
    echo 'user name❌1002:' >> /etc/group; \
    echo 'user name:1266401166:65536' >> /etc/subuid; \
    echo 'user name:1266401153:65536' >> /etc/subgid; \
    echo 'user$HOME❌1003:1003::/home/one:/bin/false' >> /etc/passwd; \
    echo 'user$HOME❌1003:' >> /etc/group; \
    echo 'user$HOME:1266401166:65536' >> /etc/subuid; \
    echo 'user$HOME:1266401153:65536' >> /etc/subgid; \
    echo 'user'"'"'name❌1004:1004::/home/one:/bin/false' >> /etc/passwd; \
    echo 'user'"'"'name❌1004:' >> /etc/group; \
    echo 'user'"'"'name:1266401166:65536' >> /etc/subuid; \
    echo 'user'"'"'name:1266401153:65536' >> /etc/subgid; \
    echo 'user"name❌1005:1005::/home/one:/bin/false' >> /etc/passwd; \
    echo 'user"name❌1005:' >> /etc/group; \
    echo 'user"name:1266401166:65536' >> /etc/subuid; \
    echo 'user"name:1266401153:65536' >> /etc/subgid;

    # Start the daemon using those users
    dockerd --userns-remap="user name:user name"
    dockerd --userns-remap='user$HOME:user$HOME'
    dockerd --userns-remap="user'name":"user'name"
    dockerd --userns-remap='user"name':'user"name'

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2020-08-20 10:40:06 +02:00
parent d0eff1f86f
commit ea9886cec4
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3 changed files with 44 additions and 47 deletions
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5
pkg/idtools/utils_unix.go
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@ -6,7 +6,6 @@ import (
"fmt"
"os/exec"
"path/filepath"
"strings"
)
func resolveBinary(binname string) (string, error) {
@ -26,7 +25,7 @@ func resolveBinary(binname string) (string, error) {
return "", fmt.Errorf("Binary %q does not resolve to a binary of that name in $PATH (%q)", binname, resolvedPath)
}
func execCmd(cmd, args string) ([]byte, error) {
execCmd := exec.Command(cmd, strings.Split(args, " ")...)
func execCmd(cmd string, arg ...string) ([]byte, error) {
execCmd := exec.Command(cmd, arg...)
return execCmd.CombinedOutput()
}