git/shell.c, branch v2.16.2

shell: drop git-cvsserver support by default

2017-09-12T02:05:58Z

The git-cvsserver script is old and largely unmaintained these days. But git-shell allows untrusted users to run it out of the box, significantly increasing its attack surface. Let's drop it from git-shell's list of internal handlers so that it cannot be run by default. This is not backwards compatible. But given the age and development activity on CVS-related parts of Git, this is likely to impact very few users, while helping many more (i.e., anybody who runs git-shell and had no intention of supporting CVS). There's no configuration mechanism in git-shell for us to add a boolean and flip it to "off". But there is a mechanism for adding custom commands, and adding CVS support here is fairly trivial. Let's document it to give guidance to anybody who really is still running cvsserver. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'maint-2.8' into maint-2.9

2017-05-05T04:13:48Z

Merge branch 'maint-2.7' into maint-2.8

2017-05-05T04:05:03Z

shell: disallow repo names beginning with dash

2017-05-05T03:07:27Z

When a remote server uses git-shell, the client side will connect to it like: ssh server "git-upload-pack 'foo.git'" and we literally exec ("git-upload-pack", "foo.git"). In early versions of upload-pack and receive-pack, we took a repository argument and nothing else. But over time they learned to accept dashed options. If the user passes a repository name that starts with a dash, the results are confusing at best (we complain of a bogus option instead of a non-existent repository) and malicious at worst (the user can start an interactive pager via "--help"). We could pass "--" to the sub-process to make sure the user's argument is interpreted as a branch name. I.e.: git-upload-pack -- -foo.git But adding "--" automatically would make us inconsistent with a normal shell (i.e., when git-shell is not in use), where "-foo.git" would still be an error. For that case, the client would have to specify the "--", but they can't do so reliably, as existing versions of git-shell do not allow more than a single argument. The simplest thing is to simply disallow "-" at the start of the repo name argument. This hasn't worked either with or without git-shell since version 1.0.0, and nobody has complained. Note that this patch just applies to do_generic_cmd(), which runs upload-pack, receive-pack, and upload-archive. There are two other types of commands that git-shell runs: - do_cvs_cmd(), but this already restricts the argument to be the literal string "server" - admin-provided commands in the git-shell-commands directory. We'll pass along arbitrary arguments there, so these commands could have similar problems. But these commands might actually understand dashed arguments, so we cannot just block them here. It's up to the writer of the commands to make sure they are safe. With great power comes great responsibility. Reported-by: Timo Schmid Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

common-main: call git_setup_gettext()

2016-07-01T22:09:10Z

This should be part of every program, as otherwise users do not get translated error messages. However, some external commands forgot to do so (e.g., git-credential-store). This fixes them, and eliminates the repeated code in programs that did remember to use it. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

common-main: call sanitize_stdfds()

2016-07-01T22:09:10Z

This is setup that should be done in every program for safety, but we never got around to adding it everywhere (so builtins benefited from the call in git.c, but any external commands did not). Putting it in the common main() gives us this safety everywhere. Note that the case in daemon.c is a little funny. We wait until we know whether we want to daemonize, and then either: - call daemonize(), which will close stdio and reopen it to /dev/null under the hood - sanitize_stdfds(), to fix up any odd cases But that is way too late; the point of sanitizing is to give us reliable descriptors on 0/1/2, and we will already have executed code, possibly called die(), etc. The sanitizing should be the very first thing that happens. With this patch, git-daemon will sanitize first, and can remove the call in the non-daemonize case. It does mean that daemonize() may just end up closing the descriptors we opened, but that's not a big deal (it's not wrong to do so, nor is it really less optimal than the case where our parent process redirected us from /dev/null ahead of time). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

common-main: call git_extract_argv0_path()

2016-07-01T22:09:10Z

Every program which links against libgit.a must call this function, or risk hitting an assert() in system_path() that checks whether we have configured argv0_path (though only when RUNTIME_PREFIX is defined, so essentially only on Windows). Looking at the diff, you can see that putting it into the common main() saves us having to do it individually in each of the external commands. But what you can't see are the cases where we _should_ have been doing so, but weren't (e.g., git-credential-store, and all of the t/helper test programs). This has been an accident-waiting-to-happen for a long time, but wasn't triggered until recently because it involves one of those programs actually calling system_path(). That happened with git-credential-store in v2.8.0 with ae5f677 (lazily load core.sharedrepository, 2016-03-11). The program: - takes a lock file, which... - opens a tempfile, which... - calls adjust_shared_perm to fix permissions, which... - lazy-loads the config (as of ae5f677), which... - calls system_path() to find the location of /etc/gitconfig On systems with RUNTIME_PREFIX, this means credential-store reliably hits that assert() and cannot be used. We never noticed in the test suite, because we set GIT_CONFIG_NOSYSTEM there, which skips the system_path() lookup entirely. But if we were to tweak git_config() to find /etc/gitconfig even when we aren't going to open it, then the test suite shows multiple failures (for credential-store, and for some other test helpers). I didn't include that tweak here because it's way too specific to this particular call to be worth carrying around what is essentially dead code. The implementation is fairly straightforward, with one exception: there is exactly one caller (git.c) that actually cares about the result of the function, and not the side-effect of setting up argv0_path. We can accommodate that by simply replacing the value of argv[0] in the array we hand down to cmd_main(). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

add an extra level of indirection to main()

2016-07-01T22:09:10Z

There are certain startup tasks that we expect every git process to do. In some cases this is just to improve the quality of the program (e.g., setting up gettext()). In others it is a requirement for using certain functions in libgit.a (e.g., system_path() expects that you have called git_extract_argv0_path()). Most commands are builtins and are covered by the git.c version of main(). However, there are still a few external commands that use their own main(). Each of these has to remember to include the correct startup sequence, and we are not always consistent. Rather than just fix the inconsistencies, let's make this harder to get wrong by providing a common main() that can run this standard startup. We basically have two options to do this: - the compat/mingw.h file already does something like this by adding a #define that replaces the definition of main with a wrapper that calls mingw_startup(). The upside is that the code in each program doesn't need to be changed at all; it's rewritten on the fly by the preprocessor. The downside is that it may make debugging of the startup sequence a bit more confusing, as the preprocessor is quietly inserting new code. - the builtin functions are all of the form cmd_foo(), and git.c's main() calls them. This is much more explicit, which may make things more obvious to somebody reading the code. It's also more flexible (because of course we have to figure out _which_ cmd_foo() to call). The downside is that each of the builtins must define cmd_foo(), instead of just main(). This patch chooses the latter option, preferring the more explicit approach, even though it is more invasive. We introduce a new file common-main.c, with the "real" main. It expects to call cmd_main() from whatever other objects it is linked against. We link common-main.o against anything that links against libgit.a, since we know that such programs will need to do this setup. Note that common-main.o can't actually go inside libgit.a, as the linker would not pick up its main() function automatically (it has no callers). The rest of the patch is just adjusting all of the various external programs (mostly in t/helper) to use cmd_main(). I've provided a global declaration for cmd_main(), which means that all of the programs also need to match its signature. In particular, many functions need to switch to "const char **" instead of "char **" for argv. This effect ripples out to a few other variables and functions, as well. This makes the patch even more invasive, but the end result is much better. We should be treating argv strings as const anyway, and now all programs conform to the same signature (which also matches the way builtins are defined). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

strbuf: introduce strbuf_getline_{lf,nul}()

2016-01-15T18:12:51Z

The strbuf_getline() interface allows a byte other than LF or NUL as the line terminator, but this is only because I wrote these codepaths anticipating that there might be a value other than NUL and LF that could be useful when I introduced line_termination long time ago. No useful caller that uses other value has emerged. By now, it is clear that the interface is overly broad without a good reason. Many codepaths have hardcoded preference to read either LF terminated or NUL terminated records from their input, and then call strbuf_getline() with LF or NUL as the third parameter. This step introduces two thin wrappers around strbuf_getline(), namely, strbuf_getline_lf() and strbuf_getline_nul(), and mechanically rewrites these call sites to call either one of them. The changes contained in this patch are: * introduction of these two functions in strbuf.[ch] * mechanical conversion of all callers to strbuf_getline() with either '\n' or '\0' as the third parameter to instead call the respective thin wrapper. After this step, output from "git grep 'strbuf_getline('" would become a lot smaller. An interim goal of this series is to make this an empty set, so that we can have strbuf_getline_crlf() take over the shorter name strbuf_getline(). Signed-off-by: Junio C Hamano

use xstrfmt to replace xmalloc + strcpy/strcat

2014-06-19T22:20:54Z

It's easy to get manual allocation calculations wrong, and the use of strcpy/strcat raise red flags for people looking for buffer overflows (though in this case each site was fine). It's also shorter to use xstrfmt, and the printf-format tends to be easier for a reader to see what the final string will look like. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano