Merge branch 'ef/win32-cred-helper'

Credential helper for Win32 to allow access to the keychain of
the logged-in user.

* ef/win32-cred-helper:
  contrib: add win32 credential-helper

2 files changed, 371 insertions, 0 deletions

diff --git a/contrib/credential/wincred/Makefile b/contrib/credential/wincred/Makefile
new file mode 100644
index 0000000000..bad45ca47a
--- /dev/null
+++ b/contrib/credential/wincred/Makefile
@@ -0,0 +1,14 @@
+all: git-credential-wincred.exe
+
+CC = gcc
+RM = rm -f
+CFLAGS = -O2 -Wall
+
+-include ../../../config.mak.autogen
+-include ../../../config.mak
+
+git-credential-wincred.exe : git-credential-wincred.c
+	$(LINK.c) $^ $(LOADLIBES) $(LDLIBS) -o $@
+
+clean:
+	$(RM) git-credential-wincred.exe
diff --git a/contrib/credential/wincred/git-credential-wincred.c b/contrib/credential/wincred/git-credential-wincred.c
new file mode 100644
index 0000000000..cbaec5f24b
--- /dev/null
+++ b/contrib/credential/wincred/git-credential-wincred.c
@@ -0,0 +1,357 @@
+/*
+ * A git credential helper that interface with Windows' Credential Manager
+ *
+ */
+#include <windows.h>
+#include <stdio.h>
+#include <io.h>
+#include <fcntl.h>
+
+/* common helpers */
+
+static void die(const char *err, ...)
+{
+	char msg[4096];
+	va_list params;
+	va_start(params, err);
+	vsnprintf(msg, sizeof(msg), err, params);
+	fprintf(stderr, "%s\n", msg);
+	va_end(params);
+	exit(1);
+}
+
+static void *xmalloc(size_t size)
+{
+	void *ret = malloc(size);
+	if (!ret && !size)
+		ret = malloc(1);
+	if (!ret)
+		 die("Out of memory");
+	return ret;
+}
+
+static char *xstrdup(const char *str)
+{
+	char *ret = strdup(str);
+	if (!ret)
+		die("Out of memory");
+	return ret;
+}
+
+/* MinGW doesn't have wincred.h, so we need to define stuff */
+
+typedef struct _CREDENTIAL_ATTRIBUTEW {
+	LPWSTR Keyword;
+	DWORD  Flags;
+	DWORD  ValueSize;
+	LPBYTE Value;
+} CREDENTIAL_ATTRIBUTEW, *PCREDENTIAL_ATTRIBUTEW;
+
+typedef struct _CREDENTIALW {
+	DWORD                  Flags;
+	DWORD                  Type;
+	LPWSTR                 TargetName;
+	LPWSTR                 Comment;
+	FILETIME               LastWritten;
+	DWORD                  CredentialBlobSize;
+	LPBYTE                 CredentialBlob;
+	DWORD                  Persist;
+	DWORD                  AttributeCount;
+	PCREDENTIAL_ATTRIBUTEW Attributes;
+	LPWSTR                 TargetAlias;
+	LPWSTR                 UserName;
+} CREDENTIALW, *PCREDENTIALW;
+
+#define CRED_TYPE_GENERIC 1
+#define CRED_PERSIST_LOCAL_MACHINE 2
+#define CRED_MAX_ATTRIBUTES 64
+
+typedef BOOL (WINAPI *CredWriteWT)(PCREDENTIALW, DWORD);
+typedef BOOL (WINAPI *CredUnPackAuthenticationBufferWT)(DWORD, PVOID, DWORD,
+    LPWSTR, DWORD *, LPWSTR, DWORD *, LPWSTR, DWORD *);
+typedef BOOL (WINAPI *CredEnumerateWT)(LPCWSTR, DWORD, DWORD *,
+    PCREDENTIALW **);
+typedef BOOL (WINAPI *CredPackAuthenticationBufferWT)(DWORD, LPWSTR, LPWSTR,
+    PBYTE, DWORD *);
+typedef VOID (WINAPI *CredFreeT)(PVOID);
+typedef BOOL (WINAPI *CredDeleteWT)(LPCWSTR, DWORD, DWORD);
+
+static HMODULE advapi, credui;
+static CredWriteWT CredWriteW;
+static CredUnPackAuthenticationBufferWT CredUnPackAuthenticationBufferW;
+static CredEnumerateWT CredEnumerateW;
+static CredPackAuthenticationBufferWT CredPackAuthenticationBufferW;
+static CredFreeT CredFree;
+static CredDeleteWT CredDeleteW;
+
+static void load_cred_funcs(void)
+{
+	/* load DLLs */
+	advapi = LoadLibrary("advapi32.dll");
+	credui = LoadLibrary("credui.dll");
+	if (!advapi || !credui)
+		die("failed to load DLLs");
+
+	/* get function pointers */
+	CredWriteW = (CredWriteWT)GetProcAddress(advapi, "CredWriteW");
+	CredUnPackAuthenticationBufferW = (CredUnPackAuthenticationBufferWT)
+	    GetProcAddress(credui, "CredUnPackAuthenticationBufferW");
+	CredEnumerateW = (CredEnumerateWT)GetProcAddress(advapi,
+	    "CredEnumerateW");
+	CredPackAuthenticationBufferW = (CredPackAuthenticationBufferWT)
+	    GetProcAddress(credui, "CredPackAuthenticationBufferW");
+	CredFree = (CredFreeT)GetProcAddress(advapi, "CredFree");
+	CredDeleteW = (CredDeleteWT)GetProcAddress(advapi, "CredDeleteW");
+	if (!CredWriteW || !CredUnPackAuthenticationBufferW ||
+	    !CredEnumerateW || !CredPackAuthenticationBufferW || !CredFree ||
+	    !CredDeleteW)
+		die("failed to load functions");
+}
+
+static char target_buf[1024];
+static char *protocol, *host, *path, *username;
+static WCHAR *wusername, *password, *target;
+
+static void write_item(const char *what, WCHAR *wbuf)
+{
+	char *buf;
+	int len = WideCharToMultiByte(CP_UTF8, 0, wbuf, -1, NULL, 0, NULL,
+	    FALSE);
+	buf = xmalloc(len);
+
+	if (!WideCharToMultiByte(CP_UTF8, 0, wbuf, -1, buf, len, NULL, FALSE))
+		die("WideCharToMultiByte failed!");
+
+	printf("%s=", what);
+	fwrite(buf, 1, len - 1, stdout);
+	putchar('\n');
+	free(buf);
+}
+
+static int match_attr(const CREDENTIALW *cred, const WCHAR *keyword,
+    const char *want)
+{
+	int i;
+	if (!want)
+		return 1;
+
+	for (i = 0; i < cred->AttributeCount; ++i)
+		if (!wcscmp(cred->Attributes[i].Keyword, keyword))
+			return !strcmp((const char *)cred->Attributes[i].Value,
+			    want);
+
+	return 0; /* not found */
+}
+
+static int match_cred(const CREDENTIALW *cred)
+{
+	return (!wusername || !wcscmp(wusername, cred->UserName)) &&
+	    match_attr(cred, L"git_protocol", protocol) &&
+	    match_attr(cred, L"git_host", host) &&
+	    match_attr(cred, L"git_path", path);
+}
+
+static void get_credential(void)
+{
+	WCHAR *user_buf, *pass_buf;
+	DWORD user_buf_size = 0, pass_buf_size = 0;
+	CREDENTIALW **creds, *cred = NULL;
+	DWORD num_creds;
+	int i;
+
+	if (!CredEnumerateW(L"git:*", 0, &num_creds, &creds))
+		return;
+
+	/* search for the first credential that matches username */
+	for (i = 0; i < num_creds; ++i)
+		if (match_cred(creds[i])) {
+			cred = creds[i];
+			break;
+		}
+	if (!cred)
+		return;
+
+	CredUnPackAuthenticationBufferW(0, cred->CredentialBlob,
+	    cred->CredentialBlobSize, NULL, &user_buf_size, NULL, NULL,
+	    NULL, &pass_buf_size);
+
+	user_buf = xmalloc(user_buf_size * sizeof(WCHAR));
+	pass_buf = xmalloc(pass_buf_size * sizeof(WCHAR));
+
+	if (!CredUnPackAuthenticationBufferW(0, cred->CredentialBlob,
+	    cred->CredentialBlobSize, user_buf, &user_buf_size, NULL, NULL,
+	    pass_buf, &pass_buf_size))
+		die("CredUnPackAuthenticationBuffer failed");
+
+	CredFree(creds);
+
+	/* zero-terminate (sizes include zero-termination) */
+	user_buf[user_buf_size - 1] = L'\0';
+	pass_buf[pass_buf_size - 1] = L'\0';
+
+	write_item("username", user_buf);
+	write_item("password", pass_buf);
+
+	free(user_buf);
+	free(pass_buf);
+}
+
+static void write_attr(CREDENTIAL_ATTRIBUTEW *attr, const WCHAR *keyword,
+    const char *value)
+{
+	attr->Keyword = (LPWSTR)keyword;
+	attr->Flags = 0;
+	attr->ValueSize = strlen(value) + 1; /* store zero-termination */
+	attr->Value = (LPBYTE)value;
+}
+
+static void store_credential(void)
+{
+	CREDENTIALW cred;
+	BYTE *auth_buf;
+	DWORD auth_buf_size = 0;
+	CREDENTIAL_ATTRIBUTEW attrs[CRED_MAX_ATTRIBUTES];
+
+	if (!wusername || !password)
+		return;
+
+	/* query buffer size */
+	CredPackAuthenticationBufferW(0, wusername, password,
+	    NULL, &auth_buf_size);
+
+	auth_buf = xmalloc(auth_buf_size);
+
+	if (!CredPackAuthenticationBufferW(0, wusername, password,
+	    auth_buf, &auth_buf_size))
+		die("CredPackAuthenticationBuffer failed");
+
+	cred.Flags = 0;
+	cred.Type = CRED_TYPE_GENERIC;
+	cred.TargetName = target;
+	cred.Comment = L"saved by git-credential-wincred";
+	cred.CredentialBlobSize = auth_buf_size;
+	cred.CredentialBlob = auth_buf;
+	cred.Persist = CRED_PERSIST_LOCAL_MACHINE;
+	cred.AttributeCount = 1;
+	cred.Attributes = attrs;
+	cred.TargetAlias = NULL;
+	cred.UserName = wusername;
+
+	write_attr(attrs, L"git_protocol", protocol);
+
+	if (host) {
+		write_attr(attrs + cred.AttributeCount, L"git_host", host);
+		cred.AttributeCount++;
+	}
+
+	if (path) {
+		write_attr(attrs + cred.AttributeCount, L"git_path", path);
+		cred.AttributeCount++;
+	}
+
+	if (!CredWriteW(&cred, 0))
+		die("CredWrite failed");
+}
+
+static void erase_credential(void)
+{
+	CREDENTIALW **creds;
+	DWORD num_creds;
+	int i;
+
+	if (!CredEnumerateW(L"git:*", 0, &num_creds, &creds))
+		return;
+
+	for (i = 0; i < num_creds; ++i) {
+		if (match_cred(creds[i]))
+			CredDeleteW(creds[i]->TargetName, creds[i]->Type, 0);
+	}
+
+	CredFree(creds);
+}
+
+static WCHAR *utf8_to_utf16_dup(const char *str)
+{
+	int wlen = MultiByteToWideChar(CP_UTF8, 0, str, -1, NULL, 0);
+	WCHAR *wstr = xmalloc(sizeof(WCHAR) * wlen);
+	MultiByteToWideChar(CP_UTF8, 0, str, -1, wstr, wlen);
+	return wstr;
+}
+
+static void read_credential(void)
+{
+	char buf[1024];
+
+	while (fgets(buf, sizeof(buf), stdin)) {
+		char *v;
+
+		if (!strcmp(buf, "\n"))
+			break;
+		buf[strlen(buf)-1] = '\0';
+
+		v = strchr(buf, '=');
+		if (!v)
+			die("bad input: %s", buf);
+		*v++ = '\0';
+
+		if (!strcmp(buf, "protocol"))
+			protocol = xstrdup(v);
+		else if (!strcmp(buf, "host"))
+			host = xstrdup(v);
+		else if (!strcmp(buf, "path"))
+			path = xstrdup(v);
+		else if (!strcmp(buf, "username")) {
+			username = xstrdup(v);
+			wusername = utf8_to_utf16_dup(v);
+		} else if (!strcmp(buf, "password"))
+			password = utf8_to_utf16_dup(v);
+		else
+			die("unrecognized input");
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	const char *usage =
+	    "Usage: git credential-wincred <get|store|erase>\n";
+
+	if (!argv[1])
+		die(usage);
+
+	/* git use binary pipes to avoid CRLF-issues */
+	_setmode(_fileno(stdin), _O_BINARY);
+	_setmode(_fileno(stdout), _O_BINARY);
+
+	read_credential();
+
+	load_cred_funcs();
+
+	if (!protocol || !(host || path))
+		return 0;
+
+	/* prepare 'target', the unique key for the credential */
+	strncat(target_buf, "git:", sizeof(target_buf));
+	strncat(target_buf, protocol, sizeof(target_buf));
+	strncat(target_buf, "://", sizeof(target_buf));
+	if (username) {
+		strncat(target_buf, username, sizeof(target_buf));
+		strncat(target_buf, "@", sizeof(target_buf));
+	}
+	if (host)
+		strncat(target_buf, host, sizeof(target_buf));
+	if (path) {
+		strncat(target_buf, "/", sizeof(target_buf));
+		strncat(target_buf, path, sizeof(target_buf));
+	}
+
+	target = utf8_to_utf16_dup(target_buf);
+
+	if (!strcmp(argv[1], "get"))
+		get_credential();
+	else if (!strcmp(argv[1], "store"))
+		store_credential();
+	else if (!strcmp(argv[1], "erase"))
+		erase_credential();
+	/* otherwise, ignore unknown action */
+	return 0;
+}