Re: [PATCH] credential/wincred: store oauth_refresh_token

>
> From: M Hickford <mirth.hickford@gmail.com>
>
> a5c7656 (credential: new attribute oauth_refresh_token) introduced
> a new confidential credential attribute for helpers to store.
>
> We encode the new attribute in the CredentialBlob, separated by
> newline:
>
>     hunter2
>     oauth_refresh_token=xyzzy
>
> This is extensible and backwards compatible. The credential protocol
> already assumes that attribute values do not contain newlines.
>
> Alternatives considered: store oauth_refresh_token in a wincred
> attribute. This would be insecure because wincred assumes attribute
> values to be non-confidential.
>
> Signed-off-by: M Hickford <mirth.hickford@gmail.com>
> ---
>     credential/wincred: store oauth_refresh_token
>
>     I'm not confident in C and found string manipulation difficult, so
>     please review carefully.
>
>     I tested on Linux, cross compiling with Zig make CC="zig cc -target
>     x86_64-windows-gnu" and tested make GIT_TEST_CREDENTIAL_HELPER=wincred
>     t0303-credential-external.sh (with a shell script git-credential-wincred
>     that wraps wine64 git-credential-wincred.exe "$@")
>
>     See also similar patch for credential-libsecret "[PATCH v4]
>     credential/libsecret: store new attributes"
>     https://lore.kernel.org/git/pull.1469.v4.git.git.1684306540947.gitgitgadget@gmail.com/T/#u
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1534%2Fhickford%2Fwincred-refresh-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1534/hickford/wincred-refresh-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/1534
>
>  .../wincred/git-credential-wincred.c          | 40 ++++++++++++++++---
>  t/t0303-credential-external.sh                |  1 +
>  2 files changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/contrib/credential/wincred/git-credential-wincred.c b/contrib/credential/wincred/git-credential-wincred.c
> index 96f10613aee..dc34283b85e 100644
> --- a/contrib/credential/wincred/git-credential-wincred.c
> +++ b/contrib/credential/wincred/git-credential-wincred.c
> @@ -35,7 +35,7 @@ static void *xmalloc(size_t size)
>  }
>
>  static WCHAR *wusername, *password, *protocol, *host, *path, target[1024],
> -       *password_expiry_utc;
> +       *password_expiry_utc, *oauth_refresh_token;
>
>  static void write_item(const char *what, LPCWSTR wbuf, int wlen)
>  {
> @@ -128,6 +128,11 @@ static void get_credential(void)
>         DWORD num_creds;
>         int i;
>         CREDENTIAL_ATTRIBUTEW *attr;
> +       WCHAR *secret;
> +       WCHAR *line;
> +       WCHAR *remaining_lines;
> +       WCHAR *part;
> +       WCHAR *remaining_parts;
>
>         if (!CredEnumerateW(L"git:*", 0, &num_creds, &creds))
>                 return;
> @@ -137,9 +142,17 @@ static void get_credential(void)
>                 if (match_cred(creds[i])) {
>                         write_item("username", creds[i]->UserName,
>                                 creds[i]->UserName ? wcslen(creds[i]->UserName) : 0);
> -                       write_item("password",
> -                               (LPCWSTR)creds[i]->CredentialBlob,
> -                               creds[i]->CredentialBlobSize / sizeof(WCHAR));
> +                       secret = xmalloc(creds[i]->CredentialBlobSize);
> +                       wcsncpy_s(secret, creds[i]->CredentialBlobSize, (LPCWSTR)creds[i]->CredentialBlob, creds[i]->CredentialBlobSize / sizeof(WCHAR));
> +                       line = wcstok_s(secret, L"\r\n", &remaining_lines);
> +                       write_item("password", line, wcslen(line));
> +                       while(line != NULL) {
> +                               part = wcstok_s(line, L"=", &remaining_parts);
> +                               if (!wcscmp(part, L"oauth_refresh_token")) {
> +                                       write_item("oauth_refresh_token", remaining_parts, wcslen(remaining_parts));
> +                               }
> +                               line = wcstok_s(NULL, L"\r\n", &remaining_lines);
> +                       }
>                         for (int j = 0; j < creds[i]->AttributeCount; j++) {
>                                 attr = creds[i]->Attributes + j;
>                                 if (!wcscmp(attr->Keyword, L"git_password_expiry_utc")) {
> @@ -148,6 +161,7 @@ static void get_credential(void)
>                                         break;
>                                 }
>                         }
> +                       free(secret);
>                         break;
>                 }
>
> @@ -158,16 +172,26 @@ static void store_credential(void)
>  {
>         CREDENTIALW cred;
>         CREDENTIAL_ATTRIBUTEW expiry_attr;
> +       WCHAR *secret;
> +       int wlen;
>
>         if (!wusername || !password)
>                 return;
>
> +       if (oauth_refresh_token) {
> +               wlen = _scwprintf(L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
> +               secret = xmalloc(sizeof(WCHAR) * wlen);
> +               _snwprintf_s(secret, sizeof(WCHAR) * wlen, wlen, L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
> +       } else {
> +               secret = _wcsdup(password);
> +       }
> +
>         cred.Flags = 0;
>         cred.Type = CRED_TYPE_GENERIC;
>         cred.TargetName = target;
>         cred.Comment = L"saved by git-credential-wincred";
> -       cred.CredentialBlobSize = (wcslen(password)) * sizeof(WCHAR);
> -       cred.CredentialBlob = (LPVOID)password;
> +       cred.CredentialBlobSize = wcslen(secret) * sizeof(WCHAR);
> +       cred.CredentialBlob = (LPVOID)_wcsdup(secret);
>         cred.Persist = CRED_PERSIST_LOCAL_MACHINE;
>         cred.AttributeCount = 0;
>         cred.Attributes = NULL;
> @@ -182,6 +206,8 @@ static void store_credential(void)
>         cred.TargetAlias = NULL;
>         cred.UserName = wusername;
>
> +       free(secret);
> +
>         if (!CredWriteW(&cred, 0))
>                 die("CredWrite failed");
>  }
> @@ -253,6 +279,8 @@ static void read_credential(void)
>                         password = utf8_to_utf16_dup(v);
>                 else if (!strcmp(buf, "password_expiry_utc"))
>                         password_expiry_utc = utf8_to_utf16_dup(v);
> +               else if (!strcmp(buf, "oauth_refresh_token"))
> +                       oauth_refresh_token = utf8_to_utf16_dup(v);
>                 /*
>                  * Ignore other lines; we don't know what they mean, but
>                  * this future-proofs us when later versions of git do
> diff --git a/t/t0303-credential-external.sh b/t/t0303-credential-external.sh
> index f028fd14182..51886b8e259 100755
> --- a/t/t0303-credential-external.sh
> +++ b/t/t0303-credential-external.sh
> @@ -45,6 +45,7 @@ test -z "$GIT_TEST_CREDENTIAL_HELPER_SETUP" ||
>  helper_test_clean "$GIT_TEST_CREDENTIAL_HELPER"
>
>  helper_test "$GIT_TEST_CREDENTIAL_HELPER"
> +helper_test_oauth_refresh_token "$GIT_TEST_CREDENTIAL_HELPER"
>
>  if test -z "$GIT_TEST_CREDENTIAL_HELPER_TIMEOUT"; then
>         say "# skipping timeout tests (GIT_TEST_CREDENTIAL_HELPER_TIMEOUT not set)"
>
> base-commit: 9e49351c3060e1fa6e0d2de64505b7becf157f28
> --
> gitgitgadget