There was an unused file-scope static variable left in http.c when
building for versions of libCURL that is older than 7.19.4, which
has been fixed.
* rj/http-code-cleanup:
http: fix an unused variable warning for 'curl_no_proxy'
Rename C++ keyword in order to bring the codebase closer to being able
to be compiled with a C++ compiler.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The http tracing code, often used to debug connection issues,
learned to redact potentially sensitive information from its output
so that it can be more safely sharable.
* jt/http-redact-cookies:
http: support omitting data from traces
http: support cookie redaction when tracing
GIT_TRACE_CURL provides a way to debug what is being sent and received
over HTTP, with automatic redaction of sensitive information. But it
also logs data transmissions, which significantly increases the log file
size, sometimes unnecessarily. Add an option "GIT_TRACE_CURL_NO_DATA" to
allow the user to omit such data transmissions.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When using GIT_TRACE_CURL, Git already redacts the "Authorization:" and
"Proxy-Authorization:" HTTP headers. Extend this redaction to a
user-specified list of cookies, specified through the
"GIT_REDACT_COOKIES" environment variable.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Using a static buffer in sha1_file_name() is error prone
and the performance improvements it gives are not needed
in many of the callers.
So let's get rid of this static buffer and, if necessary
or helpful, let's use one in the caller.
Suggested-by: Jeff Hostetler <git@jeffhostetler.com>
Helped-by: Kevin Daudt <me@ikke.info>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Code cleanup.
* rs/use-argv-array-in-child-process:
send-pack: use internal argv_array of struct child_process
http: use internal argv_array of struct child_process
Git has been taught to support an https:// URL used for http.proxy
when using recent versions of libcurl.
* ws/curl-http-proxy-over-https:
http: support CURLPROXY_HTTPS
Avoid a strangely magic array size (it's slightly too big) and explicit
index numbers by building the command line for index-pack using the
embedded argv_array of the child_process. Add the flag -o and its
argument with argv_array_pushl() to make it obvious that they belong
together. The resulting code is shorter and easier to extend.
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
HTTP proxy over SSL is supported by curl since 7.52.0.
This is very useful for networks with protocol whitelist.
Signed-off-by: Wei Shuyu <wsy@dogben.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A new mechanism to upgrade the wire protocol in place is proposed
and demonstrated that it works with the older versions of Git
without harming them.
* bw/protocol-v1:
Documentation: document Extra Parameters
ssh: introduce a 'simple' ssh variant
i5700: add interop test for protocol transition
http: tell server that the client understands v1
connect: tell server that the client understands v1
connect: teach client to recognize v1 server response
upload-pack, receive-pack: introduce protocol version 1
daemon: recognize hidden request arguments
protocol: introduce protocol extension mechanisms
pkt-line: add packet_write function
connect: in ref advertisement, shallows are last
Tell a server that protocol v1 can be used by sending the http header
'Git-Protocol' with 'version=1' indicating this.
Also teach the apache http server to pass through the 'Git-Protocol'
header as an environment variable 'GIT_PROTOCOL'.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our trace handler is called by curl with a curl_infotype
variable to interpret its data field. For most types we
print the data and then break out of the switch. But for
CURLINFO_TEXT, we print data and then fall through to the
"default" case, which does the exact same thing (nothing!)
that breaking out of the switch would.
This is probably a leftover from an early iteration of the
patch where the code after the switch _did_ do something
interesting that was unique to the non-text case arms.
But in its current form, this fallthrough is merely
confusing (and causes gcc's -Wimplicit-fallthrough to
complain).
Let's make CURLINFO_TEXT like the other case arms, and push
the default arm to the end where it's more obviously a
catch-all.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Updates to the HTTP layer we made recently unconditionally used
features of libCurl without checking the existence of them, causing
compilation errors, which has been fixed. Also migrate the code to
check feature macros, not version numbers, to cope better with
libCurl that vendor ships with backported features.
* tc/curl-with-backports:
http: use a feature check to enable GSSAPI delegation control
http: fix handling of missing CURLPROTO_*
Currently, sha1_file.c and cache.h contain many functions, both related
to and unrelated to packfiles. This makes both files very large and
causes an unclear separation of concerns.
Create a new file, packfile.c, to hold all packfile-related functions
currently in sha1_file.c. It has a corresponding header packfile.h.
In this commit, the pack name-related functions are moved. Subsequent
commits will move the other functions.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Turn the version check into a feature check to ensure this functionality
is also enabled with vendor supported curl versions where the feature
may have been backported.
Signed-off-by: Tom G. Christensen <tgc@jupiterrise.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit aeae4db1 refactored the handling of the curl protocol
restriction support into a function but failed to add a version
check for older versions of curl that lack CURLPROTO_* support.
Add the missing check and at the same time convert it to a feature
check instead of a version based check. This is done to ensure that
vendor supported curl versions that have had CURLPROTO_* support
backported are handled correctly.
Signed-off-by: Tom G. Christensen <tgc@jupiterrise.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The http.{sslkey,sslCert} configuration variables are to be
interpreted as a pathname that honors "~[username]/" prefix, but
weren't, which has been fixed.
* jc/http-sslkey-and-ssl-cert-are-paths:
http.c: http.sslcert and http.sslkey are both pathnames
Back when the modern http_options() codepath was created to parse
various http.* options at 29508e1e ("Isolate shared HTTP request
functionality", 2005-11-18), and then later was corrected for
interation between the multiple configuration files in 7059cd99
("http_init(): Fix config file parsing", 2009-03-09), we parsed
configuration variables like http.sslkey, http.sslcert as plain
vanilla strings, because git_config_pathname() that understands
"~[username]/" prefix did not exist. Later, we converted some of
them (namely, http.sslCAPath and http.sslCAInfo) to use the
function, and added variables like http.cookeyFile http.pinnedpubkey
to use the function from the beginning. Because of that, these
variables all understand "~[username]/" prefix.
Make the remaining two variables, http.sslcert and http.sslkey, also
aware of the convention, as they are both clearly pathnames to
files.
Noticed-by: Victor Toni <victor.toni@gmail.com>
Helped-by: Charles Bailey <cbailey32@bloomberg.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A common pattern to free a piece of memory and assign NULL to the
pointer that used to point at it has been replaced with a new
FREE_AND_NULL() macro.
* ab/free-and-null:
*.[ch] refactoring: make use of the FREE_AND_NULL() macro
coccinelle: make use of the "expression" FREE_AND_NULL() rule
coccinelle: add a rule to make "expression" code use FREE_AND_NULL()
coccinelle: make use of the "type" FREE_AND_NULL() rule
coccinelle: add a rule to make "type" code use FREE_AND_NULL()
git-compat-util: add a FREE_AND_NULL() wrapper around free(ptr); ptr = NULL
Apply the result of the just-added coccinelle rule. This manually
excludes a few occurrences, mostly things that resulted in many
FREE_AND_NULL() on one line, that'll be manually fixed in a subsequent
change.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Stop including config.h by default in cache.h. Instead only include
config.h in those files which require use of the config system.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Allow the http.postbuffer configuration variable to be set to a
size that can be expressed in size_t, which can be larger than
ulong on some platforms.
* dt/http-postbuffer-can-be-large:
http.postbuffer: allow full range of ssize_t values
"http.proxy" set to an empty string is used to disable the usage of
proxy. We broke this early last year.
* sr/http-proxy-configuration-fix:
http: fix the silent ignoring of proxy misconfiguraion
http: honor empty http.proxy option to bypass proxy
Unfortunately, in order to push some large repos where a server does
not support chunked encoding, the http postbuffer must sometimes
exceed two gigabytes. On a 64-bit system, this is OK: we just malloc
a larger buffer.
This means that we need to use CURLOPT_POSTFIELDSIZE_LARGE to set the
buffer size.
Signed-off-by: David Turner <dturner@twosigma.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Earlier, the whole http.proxy option string was passed to curl without
any preprocessing so curl could complain about the invalid proxy
configuration.
After the commit 372370f167 ("http: use credential API to handle proxy
authentication", 2016-01-26), if the user specified an invalid HTTP
proxy option in the configuration, then the option parsing silently
fails and NULL will be passed to curl as a proxy. This forces curl to
fall back to detecting the proxy configuration from the environment,
causing the http.proxy option ignoring.
Fix this issue by checking the proxy option parsing result. If parsing
failed then print an error message and die. Such behaviour allows the
user to quickly figure the proxy misconfiguration and correct it.
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Curl distinguishes between an empty proxy address and a NULL proxy
address. In the first case it completely disables proxy usage, but if
the proxy address option is NULL then curl attempts to determine the
proxy address from the http_proxy environment variable.
According to the documentation, if the http.proxy option is set to an
empty string, git should bypass proxy and connect to the server
directly:
export http_proxy=http://network-proxy/
cd ~/foobar-project
git config remote.origin.proxy ""
git fetch
Previously, proxy host was configured by one line:
curl_easy_setopt(result, CURLOPT_PROXY, curl_http_proxy);
Commit 372370f167 ("http: use credential API to handle proxy
authentication", 2016-01-26) parses the proxy option, then extracts the
proxy host address and updates the curl configuration, making the
previous call a noop:
credential_from_url(&proxy_auth, curl_http_proxy);
curl_easy_setopt(result, CURLOPT_PROXY, proxy_auth.host);
But if the proxy option is empty then the proxy host field becomes NULL.
This forces curl to fall back to detecting the proxy configuration from
the environment, causing the http.proxy option to not work anymore.
Fix this issue by explicitly handling http.proxy being set the empty
string. This also makes the code a bit more clear and should help us
avoid such regressions in the future.
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These calls to snprintf should always succeed, because their
input is small and fixed. Let's use xsnprintf to make sure
this is the case (and to make auditing for actual truncation
easier).
These could be candidates for turning into heap buffers, but
they fall into a few broad categories that make it not worth
doing:
- formatting single numbers is simple enough that we can
see the result should fit
- the size of a sha1 is likewise well-known, and I didn't
want to cause unnecessary conflicts with the ongoing
process to convert these constants to GIT_MAX_HEXSZ
- the interface for curl_errorstr is dictated by curl
Signed-off-by: Jeff King <peff@peff.net>
When a redirected http transport gets an error during the
redirected request, we ignored the error we got from the server,
and ended up giving a not-so-useful error message.
* jt/http-base-url-update-upon-redirect:
http: attempt updating base URL only if no error
Reduce authentication round-trip over HTTP when the server supports
just a single authentication method.
* jk/http-auth:
http: add an "auto" mode for http.emptyauth
http: restrict auth methods to what the server advertises
When a redirected http transport gets an error during the
redirected request, we ignored the error we got from the server,
and ended up giving a not-so-useful error message.
* jt/http-base-url-update-upon-redirect:
http: attempt updating base URL only if no error
Reduce authentication round-trip over HTTP when the server supports
just a single authentication method.
* jk/http-auth:
http: add an "auto" mode for http.emptyauth
http: restrict auth methods to what the server advertises
http.c supports HTTP redirects of the form
http://foo/info/refs?service=git-upload-pack
-> http://anything
-> http://bar/info/refs?service=git-upload-pack
(that is to say, as long as the Git part of the path and the query
string is preserved in the final redirect destination, the intermediate
steps can have any URL). However, if one of the intermediate steps
results in an HTTP exception, a confusing "unable to update url base
from redirection" message is printed instead of a Curl error message
with the HTTP exception code.
This was introduced by 2 commits. Commit c93c92f ("http: update base
URLs when we see redirects", 2013-09-28) introduced a best-effort
optimization that required checking if only the "base" part of the URL
differed between the initial request and the final redirect destination,
but it performed the check before any HTTP status checking was done. If
something went wrong, the normal code path was still followed, so this
did not cause any confusing error messages until commit 6628eb4 ("http:
always update the base URL for redirects", 2016-12-06), which taught
http to die if the non-"base" part of the URL differed.
Therefore, teach http to check the HTTP status before attempting to
check if only the "base" part of the URL differed. This commit teaches
http_request_reauth to return early without updating options->base_url
upon an error; the only invoker of this function that passes a non-NULL
"options" is remote-curl.c (through "http_get_strbuf"), which only uses
options->base_url for an informational message in the situations that
this commit cares about (that is, when the return value is not HTTP_OK).
The included test checks that the redirect scheme at the beginning of
this commit message works, and that returning a 502 in the middle of the
redirect scheme produces the correct result. Note that this is different
from the test in commit 6628eb4 ("http: always update the base URL for
redirects", 2016-12-06) in that this commit tests that a Git-shaped URL
(http://.../info/refs?service=git-upload-pack) works, whereas commit
6628eb4 tests that a non-Git-shaped URL
(http://.../info/refs/foo?service=git-upload-pack) does not work (even
though Git is processing that URL) and is an error that is fatal, not
silently swallowed.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This variable needs to be specified to make some types of
non-basic authentication work, but ideally this would just
work out of the box for everyone.
However, simply setting it to "1" by default introduces an
extra round-trip for cases where it _isn't_ useful. We end
up sending a bogus empty credential that the server rejects.
Instead, let's introduce an automatic mode, that works like
this:
1. We won't try to send the bogus credential on the first
request. We'll wait to get an HTTP 401, as usual.
2. After seeing an HTTP 401, the empty-auth hack will kick
in only when we know there is an auth method available
that might make use of it (i.e., something besides
"Basic" or "Digest").
That should make it work out of the box, without incurring
any extra round-trips for people hitting Basic-only servers.
This _does_ incur an extra round-trip if you really want to
use "Basic" but your server advertises other methods (the
emptyauth hack will kick in but fail, and then Git will
actually ask for a password).
The auto mode may incur an extra round-trip over setting
http.emptyauth=true, because part of the emptyauth hack is
to feed this blank password to curl even before we've made a
single request.
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
By default, we tell curl to use CURLAUTH_ANY, which does not
limit its set of auth methods. However, this results in an
extra round-trip to the server when authentication is
required. After we've fed the credential to curl, it wants
to probe the server to find its list of available methods
before sending an Authorization header.
We can shortcut this by limiting our http_auth_methods by
what the server told us it supports. In some cases (such as
when the server only supports Basic), that lets curl skip
the extra probe request.
The end result should look the same to the user, but you can
use GIT_TRACE_CURL to verify the sequence of requests:
GIT_TRACE_CURL=1 \
git ls-remote https://example.com/repo.git \
2>&1 >/dev/null |
egrep '(Send|Recv) header: (GET|HTTP|Auth)'
Before this patch, hitting a Basic-only server like
github.com results in:
Send header: GET /repo.git/info/refs?service=git-upload-pack HTTP/1.1
Recv header: HTTP/1.1 401 Authorization Required
Send header: GET /repo.git/info/refs?service=git-upload-pack HTTP/1.1
Recv header: HTTP/1.1 401 Authorization Required
Send header: GET /repo.git/info/refs?service=git-upload-pack HTTP/1.1
Send header: Authorization: Basic <redacted>
Recv header: HTTP/1.1 200 OK
And after:
Send header: GET /repo.git/info/refs?service=git-upload-pack HTTP/1.1
Recv header: HTTP/1.1 401 Authorization Required
Send header: GET /repo.git/info/refs?service=git-upload-pack HTTP/1.1
Send header: Authorization: Basic <redacted>
Recv header: HTTP/1.1 200 OK
The possible downsides are:
- This only helps for a Basic-only server; for a server
with multiple auth options, curl may still send a probe
request to see which ones are available (IOW, there's no
way to say "don't probe, I already know what the server
will say").
- The http_auth_methods variable is global, so this will
apply to all further requests. That's acceptable for
Git's usage of curl, though, which also treats the
credentials as global. I.e., in any given program
invocation we hit only one conceptual server (we may be
redirected at the outset, but in that case that's whose
auth_avail field we'd see).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Update the error messages from the dumb-http client when it fails
to obtain loose objects; we used to give sensible error message
only upon 404 but we now forbid unexpected redirects that needs to
be reported with something sensible.
* jk/http-walker-limit-redirect:
http-walker: complain about non-404 loose object errors
http: treat http-alternates like redirects
http: make redirects more obvious
remote-curl: rename shadowed options variable
http: always update the base URL for redirects
http: simplify update_url_from_redirect
Finer-grained control of what protocols are allowed for transports
during clone/fetch/push have been enabled via a new configuration
mechanism.
* bw/transport-protocol-policy:
http: respect protocol.*.allow=user for http-alternates
transport: add from_user parameter to is_transport_allowed
http: create function to get curl allowed protocols
transport: add protocol policy config option
http: always warn if libcurl version is too old
lib-proto-disable: variable name fix
Update the error messages from the dumb-http client when it fails
to obtain loose objects; we used to give sensible error message
only upon 404 but we now forbid unexpected redirects that needs to
be reported with something sensible.
* jk/http-walker-limit-redirect:
http-walker: complain about non-404 loose object errors
Transport with dumb http can be fooled into following foreign URLs
that the end user does not intend to, especially with the server
side redirects and http-alternates mechanism, which can lead to
security issues. Tighten the redirection and make it more obvious
to the end user when it happens.
* jk/http-walker-limit-redirect-2.9:
http: treat http-alternates like redirects
http: make redirects more obvious
remote-curl: rename shadowed options variable
http: always update the base URL for redirects
http: simplify update_url_from_redirect
Add a from_user parameter to is_transport_allowed() to allow http to be
able to distinguish between protocol restrictions for redirects versus
initial requests. CURLOPT_REDIR_PROTOCOLS can now be set differently
from CURLOPT_PROTOCOLS to disallow use of protocols with the "user"
policy in redirects.
This change allows callers to query if a transport protocol is allowed,
given that the caller knows that the protocol is coming from the user
(1) or not from the user (0) such as redirects in libcurl. If unknown a
-1 should be provided which falls back to reading
`GIT_PROTOCOL_FROM_USER` to determine if the protocol came from the
user.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the creation of an allowed protocols whitelist to a helper
function. This will be useful when we need to compute the set of
allowed protocols differently for normal and redirect cases.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Always warn if libcurl version is too old because:
1. Even without a protocol whitelist, newer versions of curl have all
non-standard protocols disabled by default.
2. A future patch will introduce default "known-good" and "known-bad"
protocols which are allowed/disallowed by 'is_transport_allowed'
which older version of libcurl can't respect.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since commit 17966c0a6 (http: avoid disconnecting on 404s
for loose objects, 2016-07-11), we turn off curl's
FAILONERROR option and instead manually deal with failing
HTTP codes.
However, the logic to do so only recognizes HTTP 404 as a
failure. This is probably the most common result, but if we
were to get another code, the curl result remains CURLE_OK,
and we treat it as success. We still end up detecting the
failure when we try to zlib-inflate the object (which will
fail), but instead of reporting the HTTP error, we just
claim that the object is corrupt.
Instead, let's catch anything in the 300's or above as an
error (300's are redirects which are not an error at the
HTTP level, but are an indication that we've explicitly
disabled redirects, so we should treat them as such; we
certainly don't have the resulting object content).
Note that we also fill in req->errorstr, which we didn't do
before. Without FAILONERROR, curl will not have filled this
in, and it will remain a blank string. This never mattered
for the 404 case, because in the logic below we hit the
"missing_target()" branch and print nothing. But for other
errors, we'd want to say _something_, if only to fill in the
blank slot in the error message.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* ew/http-walker:
list: avoid incompatibility with *BSD sys/queue.h
http-walker: reduce O(n) ops with doubly-linked list
http: avoid disconnecting on 404s for loose objects
http-walker: remove unused parameter from fetch_object
The previous commit made HTTP redirects more obvious and
tightened up the default behavior. However, there's another
way for a server to ask a git client to fetch arbitrary
content: by having an http-alternates file (or a regular
alternates file, which is used as a backup).
Similar to the HTTP redirect case, a malicious server can
claim to have refs pointing at object X, return a 404 when
the client asks for X, but point to some other URL via
http-alternates, which the client will transparently fetch.
The end result is that it looks from the user's perspective
like the objects came from the malicious server, as the
other URL is not mentioned at all.
Worse, because we feed the new URL to curl ourselves, the
usual protocol restrictions do not kick in (neither curl's
default of disallowing file://, nor the protocol
whitelisting in f4113cac0 (http: limit redirection to
protocol-whitelist, 2015-09-22).
Let's apply the same rules here as we do for HTTP redirects.
Namely:
- unless http.followRedirects is set to "always", we will
not follow remote redirects from http-alternates (or
alternates) at all
- set CURLOPT_PROTOCOLS alongside CURLOPT_REDIR_PROTOCOLS
restrict ourselves to a known-safe set and respect any
user-provided whitelist.
- mention alternate object stores on stderr so that the
user is aware another source of objects may be involved
The first item may prove to be too restrictive. The most
common use of alternates is to point to another path on the
same server. While it's possible for a single-server
redirect to be an attack, it takes a fairly obscure setup
(victim and evil repository on the same host, host speaks
dumb http, and evil repository has access to edit its own
http-alternates file).
So we could make the checks more specific, and only cover
cross-server redirects. But that means parsing the URLs
ourselves, rather than letting curl handle them. This patch
goes for the simpler approach. Given that they are only used
with dumb http, http-alternates are probably pretty rare.
And there's an escape hatch: the user can allow redirects on
a specific server by setting http.<url>.followRedirects to
"always".
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We instruct curl to always follow HTTP redirects. This is
convenient, but it creates opportunities for malicious
servers to create confusing situations. For instance,
imagine Alice is a git user with access to a private
repository on Bob's server. Mallory runs her own server and
wants to access objects from Bob's repository.
Mallory may try a few tricks that involve asking Alice to
clone from her, build on top, and then push the result:
1. Mallory may simply redirect all fetch requests to Bob's
server. Git will transparently follow those redirects
and fetch Bob's history, which Alice may believe she
got from Mallory. The subsequent push seems like it is
just feeding Mallory back her own objects, but is
actually leaking Bob's objects. There is nothing in
git's output to indicate that Bob's repository was
involved at all.
The downside (for Mallory) of this attack is that Alice
will have received Bob's entire repository, and is
likely to notice that when building on top of it.
2. If Mallory happens to know the sha1 of some object X in
Bob's repository, she can instead build her own history
that references that object. She then runs a dumb http
server, and Alice's client will fetch each object
individually. When it asks for X, Mallory redirects her
to Bob's server. The end result is that Alice obtains
objects from Bob, but they may be buried deep in
history. Alice is less likely to notice.
Both of these attacks are fairly hard to pull off. There's a
social component in getting Mallory to convince Alice to
work with her. Alice may be prompted for credentials in
accessing Bob's repository (but not always, if she is using
a credential helper that caches). Attack (1) requires a
certain amount of obliviousness on Alice's part while making
a new commit. Attack (2) requires that Mallory knows a sha1
in Bob's repository, that Bob's server supports dumb http,
and that the object in question is loose on Bob's server.
But we can probably make things a bit more obvious without
any loss of functionality. This patch does two things to
that end.
First, when we encounter a whole-repo redirect during the
initial ref discovery, we now inform the user on stderr,
making attack (1) much more obvious.
Second, the decision to follow redirects is now
configurable. The truly paranoid can set the new
http.followRedirects to false to avoid any redirection
entirely. But for a more practical default, we will disallow
redirects only after the initial ref discovery. This is
enough to thwart attacks similar to (2), while still
allowing the common use of redirects at the repository
level. Since c93c92f30 (http: update base URLs when we see
redirects, 2013-09-28) we re-root all further requests from
the redirect destination, which should generally mean that
no further redirection is necessary.
As an escape hatch, in case there really is a server that
needs to redirect individual requests, the user can set
http.followRedirects to "true" (and this can be done on a
per-server basis via http.*.followRedirects config).
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
