Re: [gentoo-dev] [PATCH 1/1] ebuild-writing/users-and-groups: GLEP 81 user data guidelines.
On 9/2/19 12:32 PM, Mike Gilbert wrote: > > I can't really agree with the advice given in this section. > > If I'm maintaining a package and an associated acct-user package, I'm > going to keep the two in sync. I don't see why I should have to create > a directory via pkg_postinst when I could allow the acct-user package > to do it for me. > > That the data is "non-local" is irrelevant if I'm maintaining both ebuilds. > We already have similar policies for other sorts of dependencies. If your package links to libfoo, then libfoo goes in RDEPEND even if it would be pulled in by some other dependency that you maintain. Developers retire and packages change hands all the time -- having an implicit dependency is asking for trouble, especially considering that the explicit approach isn't much more onerous: it's one extra line. To the next guy, the dependency won't be implicit, it will be nonexistent. Whether you find this reasoning persuasive or not, there is at least some precedent for it. In the acct-user case, both methods will result in the directory being keepdir'd. But ultimately, the point I'm trying to make in the patch is that one method will always work while the other might not if something outside of your control changes. Neither is more difficult, so why not choose the way that always works, and set up the directory in the ebuild that uses it? User packages can be shared and home directories can change by the design of GLEP81. You can't guarantee that no one else is going to depend on your acct-user package, or that its home directory will never have to change, or that you will maintain both of them forever. In any of those situations, having the directory creation be a side effect of enewuser is a bad idea. Why should my package create your package's localstatedir just because I want to share a username? And why should I have to violate the principle of least privilege, giving my user a home directory it doesn't need? Yeah, we could address those problems when they arise; but if they can be avoided entirely by an extra call or two to fowners/fperms, I think it's worth doing so. Or at least worth *suggesting* that we do so. If any of this is more persuasive than the original, I can update the patch. If not, I can, uh, try harder.
Re: [gentoo-dev] [PATCH 1/1] ebuild-writing/users-and-groups: GLEP 81 user data guidelines.
On Sun, Sep 1, 2019 at 1:48 PM Michael Orlitzky wrote: > + > + Choosing a home directory > + > + > + In most cases, the default home directory (that is, no home > + directory) should be used. GLEP81 changed two aspects of user > + management with respect to home directories: > + > + > + > + > + Creating a user can now modify the permissions on an existing > + directory. Should the need arise, this is necessary for a new > + version of an acct-user package to be able to fix the > + ownership and permissions of its home directory. > + > + > + All user data aside from the username became non-local to > + ebuilds that depend on that user. This is merely a side-effect > + of moving the user creation out of the client package, and > + into a separate acct-user package. > + > + > + > + > + The first item means that you should be conservative when > + choosing a home directory. If at all possible, avoid choosing a > + home directory that is used by another package. In particular, > + no two acct-user packages should use the same home > + directory. At best, the ownership and permissions on a shared > + home directory would need to be kept synchronized between all > + packages that share it. At worst, one package goes out-of-sync > + and introduces a security hole for the others who no longer have > + the expected permissions. > + > + > + > + The second item means that if your package requires a user, you > + can no longer be sure of that user's home directory or its > + ownership and permissions. If your package requires a directory > + to be owned and writable by some user, then your package's > + ebuild should create that directory and ensure that it is > + writable by the user. In other words, you should not rely on the > + directory being created "transitively" by a dependency, even if > + that dependency is an acct-user package. > + I can't really agree with the advice given in this section. If I'm maintaining a package and an associated acct-user package, I'm going to keep the two in sync. I don't see why I should have to create a directory via pkg_postinst when I could allow the acct-user package to do it for me. That the data is "non-local" is irrelevant if I'm maintaining both ebuilds.
[gentoo-dev] [PATCH 1/1] ebuild-writing/users-and-groups: GLEP 81 user data guidelines.
GLEP 81 significantly changes the way that user management is handled, and reveals some subtle issues in existing packages that have remained hidden until now. Many of these issues can be avoided (in GLEP 81, but also in general) by exercising some discipline when choosing the data for new users and groups: * User and group names * Default shell * Home directory * Home directory ownership and permissions This commit adds a few new sections to the "Users and Groups" chapter that explain the current best practices, and give suggestions for choosing the user and group data listed above. The rationale for these choices is explained, and some notable exceptions are mentioned. --- ebuild-writing/users-and-groups/text.xml | 178 +++ 1 file changed, 178 insertions(+) diff --git a/ebuild-writing/users-and-groups/text.xml b/ebuild-writing/users-and-groups/text.xml index 190a099..fca3959 100644 --- a/ebuild-writing/users-and-groups/text.xml +++ b/ebuild-writing/users-and-groups/text.xml @@ -103,6 +103,184 @@ The defaults are the user and primary group for the owner, and 0755 for the permissions. + + Whenever possible, the default shell and home directory should be + used. The rationale for this is explained below. + + + + You should embark upon a GLEP81 migration like an EAPI + update. Rather than simply copy your user's settings into an + acct-user package, you should take the opportunity to + re-evaluate your user's name, shell, home directory, and its + permissions. Our GLEP 81 implementation will reveal many user + management issues that were allowed to fester in the past. + + + + Choosing a shell + + + In most cases, the default shell (that is, no shell) should be + used. Services can still be started as a user who has no shell, + and daemons are able to drop privileges to a user who has no + shell. If necessary, the administrator can override a user's + default shell with su -s+ . This is sufficient for testing, management + of SSH credentials, and for initial configuration in an ebuild's + pkg_config phase. + + + An obvious exception to this rule is if a human being will need + to log into the account interactively, as is the case with the + root user. Other exceptions certainly exist, but should + be evaluated case-by-case. In other words, if you haven't + checked, don't set your user's shell to /bin/bash because + you think he might need it. + + + The goal here is twofold. First, the principle of least + privilege says that if a user doesn't need a real shell, he + shouldn't have one. And along those same lines, not having a + shell gives the system administrator some peace of mind: he + doesn't have to be as concerned with whether or not that user + has a password (and how strong it is), or whether or not its + filesystem permissions are all set correctly, or whether or not + it can log in via SSH, et cetera. + + + + + Choosing a home directory + + + In most cases, the default home directory (that is, no home + directory) should be used. GLEP81 changed two aspects of user + management with respect to home directories: + + + + + Creating a user can now modify the permissions on an existing + directory. Should the need arise, this is necessary for a new + version of an acct-user package to be able to fix the + ownership and permissions of its home directory. + + + All user data aside from the username became non-local to + ebuilds that depend on that user. This is merely a side-effect + of moving the user creation out of the client package, and + into a separate acct-user package. + + + + + The first item means that you should be conservative when + choosing a home directory. If at all possible, avoid choosing a + home directory that is used by another package. In particular, + no two acct-user packages should use the same home + directory. At best, the ownership and permissions on a shared + home directory would need to be kept synchronized between all + packages that share it. At worst, one package goes out-of-sync + and introduces a security hole for the others who no longer have + the expected permissions. + + + + The second item means that if your package requires a user, you + can no longer be sure of that user's home directory or its + ownership and permissions. If your package requires a directory + to be owned and writable by some user, then your package's + ebuild should create that directory and ensure that it is + writable by the user. In other words, you should not rely on the + directory being created "transitively" by a dependency, even if + that dependency is an acct-user package. + + +
