Subject: [PATCH v2] credential/wincred: erase matching creds only

From: "M Hickford via GitGitGadget" <[email-masked]>
Date: Wed, 26 Jul 2023 19:51:22 +0000

From: M Hickford <[email-masked]>

The credential erase request typically includes protocol, host, username
and password.

credential-wincred erases stored credentials that match protocol,
host and username, regardless of password.

This is confusing in the case the stored password differs from that
in the request. This case can occur when multiple credential helpers are
configured.

Only erase credential if stored password matches request (or request
omits password).

This fixes test "helper (wincred) does not erase a password distinct
from input" when t0303 is run with GIT_TEST_CREDENTIAL_HELPER set to
"wincred". This test was added in aeb21ce22e (credential: avoid
erasing distinct password, 2023-06-13).

Signed-off-by: M Hickford <[email-masked]>
---
    credential/wincred: erase more carefully
    
    Patch v2 expands the commit message

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1529%2Fhickford%2Ffix-wincred-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1529/hickford/fix-wincred-v2
Pull-Request: https://github.com/git/git/pull/1529

Range-diff vs v1:

 1:  d45c61d8f79 ! 1:  5e2aae38f72 credential/wincred: erase matching creds only
     @@ Metadata
       ## Commit message ##
          credential/wincred: erase matching creds only
      
     -    Fix test "helper ... does not erase a password distinct from input"
     -    introduced in aeb21ce22e (credential: avoid erasing distinct password,
     -    2023-06-13)
     +    The credential erase request typically includes protocol, host, username
     +    and password.
     +
     +    credential-wincred erases stored credentials that match protocol,
     +    host and username, regardless of password.
     +
     +    This is confusing in the case the stored password differs from that
     +    in the request. This case can occur when multiple credential helpers are
     +    configured.
     +
     +    Only erase credential if stored password matches request (or request
     +    omits password).
     +
     +    This fixes test "helper (wincred) does not erase a password distinct
     +    from input" when t0303 is run with GIT_TEST_CREDENTIAL_HELPER set to
     +    "wincred". This test was added in aeb21ce22e (credential: avoid
     +    erasing distinct password, 2023-06-13).
      
          Signed-off-by: M Hickford <[email-masked]>

 .../wincred/git-credential-wincred.c          | 20 +++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/contrib/credential/wincred/git-credential-wincred.c b/contrib/credential/wincred/git-credential-wincred.c
index 96f10613aee..4cd56c42e24 100644
--- a/contrib/credential/wincred/git-credential-wincred.c
+++ b/contrib/credential/wincred/git-credential-wincred.c
@@ -109,7 +109,18 @@ static int match_part_last(LPCWSTR *ptarget, LPCWSTR want, LPCWSTR delim)
 	return match_part_with_last(ptarget, want, delim, 1);
 }
 
-static int match_cred(const CREDENTIALW *cred)
+static int match_cred_password(const CREDENTIALW *cred) {
+	int ret;
+	WCHAR *cred_password = xmalloc(cred->CredentialBlobSize);
+	wcsncpy_s(cred_password, cred->CredentialBlobSize,
+		(LPCWSTR)cred->CredentialBlob,
+		cred->CredentialBlobSize / sizeof(WCHAR));
+	ret = !wcscmp(cred_password, password);
+	free(cred_password);
+	return ret;
+}
+
+static int match_cred(const CREDENTIALW *cred, int match_password)
 {
 	LPCWSTR target = cred->TargetName;
 	if (wusername && wcscmp(wusername, cred->UserName ? cred->UserName : L""))
@@ -119,7 +130,8 @@ static int match_cred(const CREDENTIALW *cred)
 		match_part(&target, protocol, L"://") &&
 		match_part_last(&target, wusername, L"@") &&
 		match_part(&target, host, L"/") &&
-		match_part(&target, path, L"");
+		match_part(&target, path, L"") &&
+		(!match_password || match_cred_password(cred));
 }
 
 static void get_credential(void)
@@ -134,7 +146,7 @@ static void get_credential(void)
 
 	/* search for the first credential that matches username */
 	for (i = 0; i < num_creds; ++i)
-		if (match_cred(creds[i])) {
+		if (match_cred(creds[i], 0)) {
 			write_item("username", creds[i]->UserName,
 				creds[i]->UserName ? wcslen(creds[i]->UserName) : 0);
 			write_item("password",
@@ -196,7 +208,7 @@ static void erase_credential(void)
 		return;
 
 	for (i = 0; i < num_creds; ++i) {
-		if (match_cred(creds[i]))
+		if (match_cred(creds[i], password != NULL))
 			CredDeleteW(creds[i]->TargetName, creds[i]->Type, 0);
 	}

base-commit: a80be152923a46f04a06bade7bcc72870e46ca09
-- 
gitgitgadget