67830784db
In 2.46, Git will support multistage authentication from credential helpers. This will allow Git and Git LFS to implement functionality like NTLM and Kerberos in the credential helper, which lets this functionality to work even if Git LFS doesn't support it natively. This requires two separate pieces of data. First, it involves a `state[]` field, which each credential helper can add to keep track of state. Second, it allows the usage of a boolean `continue` field, which indicates that the response is multistage and this is not the final stage. In order to make this work, we adjust a few things. First, we advertise the `state` capability. Additionally, we save and pass back the `state[]` fields that the credential helper may send to us. We also don't change the authentication scheme if the helper told us that this was a multistage response. Finally, we add a check to avoid a credential helper getting stuck in an infinite loop if it keeps handing back the same credentials.
377 lines
12 KiB
Go
377 lines
12 KiB
Go
package lfsapi
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import (
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"encoding/base64"
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"fmt"
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"net/http"
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"net/url"
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"os"
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"strings"
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"github.com/git-lfs/git-lfs/v3/creds"
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"github.com/git-lfs/git-lfs/v3/errors"
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"github.com/git-lfs/git-lfs/v3/lfshttp"
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"github.com/git-lfs/git-lfs/v3/tr"
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"github.com/rubyist/tracerx"
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)
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var (
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defaultEndpointFinder = NewEndpointFinder(nil)
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defaultMaxAuthAttempts = 3
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)
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// DoWithAuth sends an HTTP request to get an HTTP response. It attempts to add
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// authentication from netrc or git's credential helpers if necessary,
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// supporting basic authentication.
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func (c *Client) DoWithAuth(remote string, access creds.Access, req *http.Request) (*http.Response, error) {
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count := 0
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res, err := c.doWithAuth(remote, &count, access, req, nil)
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if errors.IsAuthError(err) {
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if len(req.Header.Get("Authorization")) == 0 {
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// This case represents a rejected request that
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// should have been authenticated but wasn't. Do
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// not count this against our redirection
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// maximum.
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newAccess := c.Endpoints.AccessFor(access.URL())
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tracerx.Printf("api: http response indicates %q authentication. Resubmitting...", newAccess.Mode())
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return c.DoWithAuth(remote, newAccess, req)
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}
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}
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return res, err
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}
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// DoWithAuthNoRetry sends an HTTP request to get an HTTP response. It works in
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// the same way as DoWithAuth, but will not retry the request if it fails with
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// an authorization error.
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func (c *Client) DoWithAuthNoRetry(remote string, access creds.Access, req *http.Request) (*http.Response, error) {
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count := 0
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return c.doWithAuth(remote, &count, access, req, nil)
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}
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// DoAPIRequestWithAuth sends an HTTP request to get an HTTP response similarly
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// to DoWithAuth, but using the LFS API endpoint for the provided remote and
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// operation to determine the access mode.
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func (c *Client) DoAPIRequestWithAuth(remote string, req *http.Request) (*http.Response, error) {
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operation := getReqOperation(req)
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apiEndpoint := c.Endpoints.Endpoint(operation, remote)
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access := c.Endpoints.AccessFor(apiEndpoint.Url)
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return c.DoWithAuth(remote, access, req)
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}
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func (c *Client) doWithAuth(remote string, count *int, access creds.Access, req *http.Request, via []*http.Request) (*http.Response, error) {
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if *count == defaultMaxAuthAttempts {
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return nil, fmt.Errorf("too many authentication attempts")
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}
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req.Header = c.client.ExtraHeadersFor(req)
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credWrapper, err := c.getCreds(remote, access, req)
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if err != nil {
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return nil, err
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}
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c.credContext.SetStateFields(credWrapper.Creds["state[]"])
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res, err := c.doWithCreds(req, count, credWrapper, access, via)
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if err != nil {
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if errors.IsAuthError(err) {
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multistage := credWrapper.Creds.IsMultistage()
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newMode, newModes, headers := getAuthAccess(res, access.Mode(), c.access, multistage)
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newAccess := access.Upgrade(newMode)
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if newAccess.Mode() != access.Mode() {
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c.Endpoints.SetAccess(newAccess)
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c.access = newModes
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}
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if credWrapper.Creds != nil {
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req.Header.Del("Authorization")
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if multistage && *count < defaultMaxAuthAttempts && res != nil && res.StatusCode == 401 {
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*count++
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} else {
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credWrapper.CredentialHelper.Reject(credWrapper.Creds)
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}
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}
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c.credContext.SetWWWAuthHeaders(headers)
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}
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}
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if res != nil && res.StatusCode < 300 && res.StatusCode > 199 {
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credWrapper.CredentialHelper.Approve(credWrapper.Creds)
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}
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return res, err
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}
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func (c *Client) doWithCreds(req *http.Request, count *int, credWrapper creds.CredentialHelperWrapper, access creds.Access, via []*http.Request) (*http.Response, error) {
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if access.Mode() == creds.NegotiateAccess {
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return c.doWithNegotiate(req, credWrapper)
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}
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req.Header.Set("User-Agent", lfshttp.UserAgent)
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client, err := c.client.HttpClient(req.URL, access.Mode())
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if err != nil {
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return nil, err
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}
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redirectedReq, res, err := c.client.DoWithRedirect(client, req, "", via)
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if err != nil || res != nil {
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return res, err
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}
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if redirectedReq == nil {
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return res, errors.New(tr.Tr.Get("failed to redirect request"))
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}
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return c.doWithAuth("", count, access, redirectedReq, via)
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}
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// getCreds fills the authorization header for the given request if possible,
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// from the following sources:
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//
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// 1. NTLM access is handled elsewhere.
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// 2. Existing Authorization or ?token query tells LFS that the request is ready.
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// 3. Netrc based on the hostname.
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// 4. URL authentication on the Endpoint URL or the Git Remote URL.
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// 5. Git Credential Helper, potentially prompting the user.
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//
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// There are three URLs in play, that make this a little confusing.
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//
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// 1. The request URL, which should be something like "https://git.com/repo.git/info/lfs/objects/batch"
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// 2. The LFS API URL, which should be something like "https://git.com/repo.git/info/lfs"
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// This URL used for the "lfs.URL.access" git config key, which determines
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// what kind of auth the LFS server expects. Could be BasicAccess,
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// NTLMAccess, NegotiateAccess, or NoneAccess, in which the Git Credential
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// Helper step is skipped. We do not want to prompt the user for a password
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// to fetch public repository data.
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// 3. The Git Remote URL, which should be something like "https://git.com/repo.git"
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// This URL is used for the Git Credential Helper. This way existing https
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// Git remote credentials can be re-used for LFS.
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func (c *Client) getCreds(remote string, access creds.Access, req *http.Request) (creds.CredentialHelperWrapper, error) {
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ef := c.Endpoints
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if ef == nil {
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ef = defaultEndpointFinder
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}
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operation := getReqOperation(req)
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apiEndpoint := ef.Endpoint(operation, remote)
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if access.Mode() != creds.NegotiateAccess {
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if requestHasAuth(req) || access.Mode() == creds.NoneAccess {
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return creds.CredentialHelperWrapper{CredentialHelper: creds.NullCreds, Input: nil, Url: nil, Creds: nil}, nil
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}
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credsURL, err := getCredURLForAPI(ef, operation, remote, apiEndpoint, req)
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if err != nil {
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return creds.CredentialHelperWrapper{CredentialHelper: creds.NullCreds, Input: nil, Url: nil, Creds: nil}, errors.Wrap(err, tr.Tr.Get("credentials"))
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}
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if credsURL == nil {
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return creds.CredentialHelperWrapper{CredentialHelper: creds.NullCreds, Input: nil, Url: nil, Creds: nil}, nil
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}
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credWrapper := c.getGitCredsWrapper(ef, req, credsURL)
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err = credWrapper.FillCreds()
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if err == nil {
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tracerx.Printf("Filled credentials for %s", credsURL)
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setRequestAuthWithCreds(req, credWrapper.Creds)
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}
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return credWrapper, err
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}
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// Negotiate only
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credsURL, err := url.Parse(apiEndpoint.Url)
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if err != nil {
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return creds.CredentialHelperWrapper{CredentialHelper: creds.NullCreds, Input: nil, Url: nil, Creds: nil}, errors.Wrap(err, tr.Tr.Get("credentials"))
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}
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// NTLM uses creds to create the session
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credWrapper := c.getGitCredsWrapper(ef, req, credsURL)
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return credWrapper, err
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}
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func (c *Client) getGitCredsWrapper(ef EndpointFinder, req *http.Request, u *url.URL) creds.CredentialHelperWrapper {
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return c.credContext.GetCredentialHelper(c.Credentials, u)
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}
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func getCredURLForAPI(ef EndpointFinder, operation, remote string, apiEndpoint lfshttp.Endpoint, req *http.Request) (*url.URL, error) {
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apiURL, err := url.Parse(apiEndpoint.Url)
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if err != nil {
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return nil, err
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}
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// if the LFS request doesn't match the current LFS url, don't bother
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// attempting to set the Authorization header from the LFS or Git remote URLs.
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if req.URL.Scheme != apiURL.Scheme ||
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req.URL.Host != apiURL.Host {
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return req.URL, nil
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}
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if setRequestAuthFromURL(req, apiURL) {
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return nil, nil
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}
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if len(remote) > 0 {
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if u := ef.GitRemoteURL(remote, operation == "upload"); u != "" {
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schemedUrl, _ := fixSchemelessURL(u)
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gitRemoteURL, err := url.Parse(schemedUrl)
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if err != nil {
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return nil, err
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}
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if gitRemoteURL.Scheme == apiURL.Scheme &&
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gitRemoteURL.Host == apiURL.Host {
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if setRequestAuthFromURL(req, gitRemoteURL) {
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return nil, nil
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}
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return gitRemoteURL, nil
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}
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}
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}
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return apiURL, nil
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}
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// fixSchemelessURL prepends an empty scheme "//" if none was found in
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// the URL and replaces the first colon with a slash in order to satisfy RFC
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// 3986 §3.3, and `net/url.Parse()`.
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//
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// It returns a string parse-able with `net/url.Parse()` and a boolean whether
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// or not an empty scheme was added.
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func fixSchemelessURL(u string) (string, bool) {
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if hasScheme(u) {
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return u, false
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}
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colon := strings.Index(u, ":")
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slash := strings.Index(u, "/")
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if colon >= 0 && (slash < 0 || colon < slash) {
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// First path segment has a colon, assumed that it's a
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// scheme-less URL. Append an empty scheme on top to
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// satisfy RFC 3986 §3.3, and `net/url.Parse()`.
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//
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// In addition, replace the first colon with a slash since
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// otherwise the colon looks like it's introducing a port
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// number.
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return fmt.Sprintf("//%s", strings.Replace(u, ":", "/", 1)), true
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}
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return u, true
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}
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var (
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// supportedSchemes is the list of URL schemes the `lfsapi` package
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// supports.
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supportedSchemes = []string{"ssh", "http", "https"}
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)
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// hasScheme returns whether or not a given string (taken to represent a RFC
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// 3986 URL) has a scheme that is supported by the `lfsapi` package.
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func hasScheme(what string) bool {
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for _, scheme := range supportedSchemes {
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if strings.HasPrefix(what, fmt.Sprintf("%s://", scheme)) {
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return true
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}
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}
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return false
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}
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func requestHasAuth(req *http.Request) bool {
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// The "Authorization" string constant is safe, since we assume that all
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// request headers have been canonicalized.
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if len(req.Header.Get("Authorization")) > 0 {
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return true
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}
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return len(req.URL.Query().Get("token")) > 0
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}
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func setRequestAuthFromURL(req *http.Request, u *url.URL) bool {
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if u.User == nil {
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return false
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}
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if pass, ok := u.User.Password(); ok {
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fmt.Fprintln(os.Stderr, tr.Tr.Get("warning: current Git remote contains credentials"))
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setRequestAuth(req, u.User.Username(), pass)
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return true
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}
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return false
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}
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func setRequestAuth(req *http.Request, user, pass string) {
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if len(user) == 0 && len(pass) == 0 {
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return
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}
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token := fmt.Sprintf("%s:%s", user, pass)
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auth := "Basic " + strings.TrimSpace(base64.StdEncoding.EncodeToString([]byte(token)))
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req.Header.Set("Authorization", auth)
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}
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func setRequestAuthWithCreds(req *http.Request, c creds.Creds) {
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authtype := creds.FirstEntryForKey(c, "authtype")
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credential := creds.FirstEntryForKey(c, "credential")
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if len(authtype) == 0 && len(credential) == 0 {
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user := creds.FirstEntryForKey(c, "username")
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pass := creds.FirstEntryForKey(c, "password")
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setRequestAuth(req, user, pass)
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return
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}
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auth := fmt.Sprintf("%s %s", authtype, credential)
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req.Header.Set("Authorization", auth)
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}
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func getReqOperation(req *http.Request) string {
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operation := "download"
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if req.Method == "POST" || req.Method == "PUT" {
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operation = "upload"
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}
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return operation
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}
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var (
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authenticateHeaders = []string{"Lfs-Authenticate", "Www-Authenticate"}
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)
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func getAuthAccess(res *http.Response, access creds.AccessMode, modes []creds.AccessMode, multistage bool) (creds.AccessMode, []creds.AccessMode, []string) {
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newModes := make([]creds.AccessMode, 0, len(modes))
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for _, mode := range modes {
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if multistage || access != mode {
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newModes = append(newModes, mode)
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}
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}
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headers := make([]string, 0)
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if res != nil {
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for _, headerName := range authenticateHeaders {
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headers = append(headers, res.Header[headerName]...)
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}
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supportedModes := make(map[creds.AccessMode]struct{})
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for _, headerName := range authenticateHeaders {
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for _, auth := range res.Header[headerName] {
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pieces := strings.SplitN(strings.ToLower(auth), " ", 2)
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if len(pieces) == 0 {
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continue
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}
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supportedModes[creds.AccessMode(pieces[0])] = struct{}{}
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}
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}
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for _, mode := range newModes {
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if _, ok := supportedModes[mode]; ok {
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return mode, newModes, headers
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}
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}
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}
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return creds.BasicAccess, newModes, headers
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}
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