[PATCH v6 1/2] fetch-pack: redact packfile urls in traces

["Ivan Frade via GitGitGadget" <gitgitgadget@gmail.com>]

From: Ivan Frade <ifrade@google.com>

In some setups, packfile uris act as bearer token. It is not
recommended to expose them plainly in logs, although in special
circunstances (e.g. debug) it makes sense to write them.

Redact the packfile URL paths by default, unless the GIT_TRACE_REDACT
variable is set to false. This mimics the redacting of the Authorization
header in HTTP.

Signed-off-by: Ivan Frade <ifrade@google.com>
---
 Documentation/git.txt  |  5 +++--
 fetch-pack.c           |  4 ++++
 pkt-line.c             | 39 +++++++++++++++++++++++++++++++-
 pkt-line.h             |  1 +
 t/t5702-protocol-v2.sh | 51 ++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 97 insertions(+), 3 deletions(-)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index d63c65e67d8..c91aa2737f0 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -832,8 +832,9 @@ for full details.
 
 `GIT_TRACE_REDACT`::
 	By default, when tracing is activated, Git redacts the values of
-	cookies, the "Authorization:" header, and the "Proxy-Authorization:"
-	header. Set this variable to `0` to prevent this redaction.
+	cookies, the "Authorization:" header, the "Proxy-Authorization:"
+	header and packfile URIs. Set this variable to `0` to prevent this
+	redaction.
 
 `GIT_LITERAL_PATHSPECS`::
 	Setting this variable to `1` will cause Git to treat all
diff --git a/fetch-pack.c b/fetch-pack.c
index a9604f35a3e..62ea90541c5 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1653,8 +1653,12 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				receive_wanted_refs(&reader, sought, nr_sought);
 
 			/* get the pack(s) */
+			if (git_env_bool("GIT_TRACE_REDACT", 1))
+				reader.options |= PACKET_READ_REDACT_URI_PATH;
 			if (process_section_header(&reader, "packfile-uris", 1))
 				receive_packfile_uris(&reader, &packfile_uris);
+			reader.options &= ~PACKET_READ_REDACT_URI_PATH;
+
 			process_section_header(&reader, "packfile", 0);
 
 			/*
diff --git a/pkt-line.c b/pkt-line.c
index 2dc8ac274bd..5a69ddc2e77 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -370,6 +370,31 @@ int packet_length(const char lenbuf_hex[4])
 	return (val < 0) ? val : (val << 8) | hex2chr(lenbuf_hex + 2);
 }
 
+static char *find_packfile_uri_path(const char *buffer)
+{
+	const char *URI_MARK = "://";
+	char *path;
+	int len;
+
+	/* First char is sideband mark */
+	buffer += 1;
+
+	len = strspn(buffer, "0123456789abcdefABCDEF");
+	if (len != (int)the_hash_algo->hexsz || buffer[len] != ' ')
+		return NULL; /* required "<hash>SP" not seen */
+
+	path = strstr(buffer + len + 1, URI_MARK);
+	if (!path)
+		return NULL;
+
+	path = strchr(path + strlen(URI_MARK), '/');
+	if (!path || !*(path + 1))
+		return NULL;
+
+	/* position after '/' */
+	return ++path;
+}
+
 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 						size_t *src_len, char *buffer,
 						unsigned size, int *pktlen,
@@ -377,6 +402,7 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 {
 	int len;
 	char linelen[4];
+	char *uri_path_start;
 
 	if (get_packet_data(fd, src_buffer, src_len, linelen, 4, options) < 0) {
 		*pktlen = -1;
@@ -427,7 +453,18 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 		len--;
 
 	buffer[len] = 0;
-	packet_trace(buffer, len, 0);
+	if (options & PACKET_READ_REDACT_URI_PATH &&
+	    (uri_path_start = find_packfile_uri_path(buffer))) {
+		const char *redacted = "<redacted>";
+		struct strbuf tracebuf = STRBUF_INIT;
+		strbuf_insert(&tracebuf, 0, buffer, len);
+		strbuf_splice(&tracebuf, uri_path_start - buffer,
+			      strlen(uri_path_start), redacted, strlen(redacted));
+		packet_trace(tracebuf.buf, tracebuf.len, 0);
+		strbuf_release(&tracebuf);
+	} else {
+		packet_trace(buffer, len, 0);
+	}
 
 	if ((options & PACKET_READ_DIE_ON_ERR_PACKET) &&
 	    starts_with(buffer, "ERR "))
diff --git a/pkt-line.h b/pkt-line.h
index 467ae013573..6d2a63db238 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -87,6 +87,7 @@ void packet_fflush(FILE *f);
 #define PACKET_READ_CHOMP_NEWLINE        (1u<<1)
 #define PACKET_READ_DIE_ON_ERR_PACKET    (1u<<2)
 #define PACKET_READ_GENTLE_ON_READ_ERROR (1u<<3)
+#define PACKET_READ_REDACT_URI_PATH      (1u<<4)
 int packet_read(int fd, char *buffer, unsigned size, int options);
 
 /*
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index d527cf6c49f..f01af2f2ed3 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -1107,6 +1107,57 @@ test_expect_success 'packfile-uri with transfer.fsckobjects fails when .gitmodul
 	test_i18ngrep "disallowed submodule name" err
 '
 
+test_expect_success 'packfile-uri path redacted in trace' '
+	P="$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+	rm -rf "$P" http_child log &&
+
+	git init "$P" &&
+	git -C "$P" config "uploadpack.allowsidebandall" "true" &&
+
+	echo my-blob >"$P/my-blob" &&
+	git -C "$P" add my-blob &&
+	git -C "$P" commit -m x &&
+
+	git -C "$P" hash-object my-blob >objh &&
+	git -C "$P" pack-objects "$HTTPD_DOCUMENT_ROOT_PATH/mypack" <objh >packh &&
+	git -C "$P" config --add \
+		"uploadpack.blobpackfileuri" \
+		"$(cat objh) $(cat packh) $HTTPD_URL/dumb/mypack-$(cat packh).pack" &&
+
+	GIT_TRACE=1 GIT_TRACE_PACKET="$(pwd)/log" GIT_TEST_SIDEBAND_ALL=1 \
+	git -c protocol.version=2 \
+		-c fetch.uriprotocols=http,https \
+		clone "$HTTPD_URL/smart/http_parent" http_child &&
+
+	grep -F "clone< \\1$(cat packh) $HTTPD_URL/<redacted>" log
+'
+
+test_expect_success 'packfile-uri path not redacted in trace when GIT_TRACE_REDACT=0' '
+	P="$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+	rm -rf "$P" http_child log &&
+
+	git init "$P" &&
+	git -C "$P" config "uploadpack.allowsidebandall" "true" &&
+
+	echo my-blob >"$P/my-blob" &&
+	git -C "$P" add my-blob &&
+	git -C "$P" commit -m x &&
+
+	git -C "$P" hash-object my-blob >objh &&
+	git -C "$P" pack-objects "$HTTPD_DOCUMENT_ROOT_PATH/mypack" <objh >packh &&
+	git -C "$P" config --add \
+		"uploadpack.blobpackfileuri" \
+		"$(cat objh) $(cat packh) $HTTPD_URL/dumb/mypack-$(cat packh).pack" &&
+
+	GIT_TRACE=1 GIT_TRACE_PACKET="$(pwd)/log" GIT_TEST_SIDEBAND_ALL=1 \
+	GIT_TRACE_REDACT=0 \
+	git -c protocol.version=2 \
+		-c fetch.uriprotocols=http,https \
+		clone "$HTTPD_URL/smart/http_parent" http_child &&
+
+	grep -F "clone< \\1$(cat packh) $HTTPD_URL/dumb/mypack-$(cat packh).pack" log
+'
+
 test_expect_success 'http:// --negotiate-only' '
 	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
 	URI="$HTTPD_URL/smart/server" &&
-- 
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