[v3,02/11] credential: add WWW-Authenticate header to cred requests

Commit Message

Matthew John Cheetham Nov. 2, 2022, 10:09 p.m. UTC

From: Matthew John Cheetham <[e-mail]>

Add the value of the WWW-Authenticate response header to credential
requests. Credential helpers that understand and support HTTP
authentication and authorization can use this standard header (RFC 2616
Section 14.47 [1]) to generate valid credentials.

WWW-Authenticate headers can contain information pertaining to the
authority, authentication mechanism, or extra parameters/scopes that are
required.

The current I/O format for credential helpers only allows for unique
names for properties/attributes, so in order to transmit multiple header
values (with a specific order) we introduce a new convention whereby a
C-style array syntax is used in the property name to denote multiple
ordered values for the same property.

In this case we send multiple `wwwauth[]` properties where the order
that the repeated attributes appear in the conversation reflects the
order that the WWW-Authenticate headers appeared in the HTTP response.

[1] https://datatracker.ietf.org/doc/html/rfc2616#section-14.47

Signed-off-by: Matthew John Cheetham <[e-mail]>
---
 Documentation/git-credential.txt | 17 ++++++++++++++++-
 credential.c                     | 12 ++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

Patch

diff --git a/Documentation/git-credential.txt b/Documentation/git-credential.txt
index f18673017f5..791a57dddfb 100644
--- a/Documentation/git-credential.txt
+++ b/Documentation/git-credential.txt
@@ -113,7 +113,13 @@  separated by an `=` (equals) sign, followed by a newline.
 The key may contain any bytes except `=`, newline, or NUL. The value may
 contain any bytes except newline or NUL.
 
-In both cases, all bytes are treated as-is (i.e., there is no quoting,
+Attributes with keys that end with C-style array brackets `[]` can have
+multiple values. Each instance of a multi-valued attribute forms an
+ordered list of values - the order of the repeated attributes defines
+the order of the values. An empty multi-valued attribute (`key[]=\n`)
+acts to clear any previous entries and reset the list.
+
+In all cases, all bytes are treated as-is (i.e., there is no quoting,
 and one cannot transmit a value with newline or NUL in it). The list of
 attributes is terminated by a blank line or end-of-file.
 
@@ -160,6 +166,15 @@  empty string.
 Components which are missing from the URL (e.g., there is no
 username in the example above) will be left unset.
 
+`wwwauth[]`::
+
+	When an HTTP response is received by Git that includes one or more
+	'WWW-Authenticate' authentication headers, these will be passed by Git
+	to credential helpers.
+	Each 'WWW-Authenticate' header value is passed as a multi-valued
+	attribute 'wwwauth[]', where the order of the attributes is the same as
+	they appear in the HTTP response.
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/credential.c b/credential.c
index 897b4679333..8a3ad6c0ae2 100644
--- a/credential.c
+++ b/credential.c
@@ -263,6 +263,17 @@  static void credential_write_item(FILE *fp, const char *key, const char *value,
 	fprintf(fp, "%s=%s\n", key, value);
 }
 
+static void credential_write_strvec(FILE *fp, const char *key,
+				    const struct strvec *vec)
+{
+	int i = 0;
+	const char *full_key = xstrfmt("%s[]", key);
+	for (; i < vec->nr; i++) {
+		credential_write_item(fp, full_key, vec->v[i], 0);
+	}
+	free((void*)full_key);
+}
+
 void credential_write(const struct credential *c, FILE *fp)
 {
 	credential_write_item(fp, "protocol", c->protocol, 1);
@@ -270,6 +281,7 @@  void credential_write(const struct credential *c, FILE *fp)
 	credential_write_item(fp, "path", c->path, 0);
 	credential_write_item(fp, "username", c->username, 0);
 	credential_write_item(fp, "password", c->password, 0);
+	credential_write_strvec(fp, "wwwauth", &c->wwwauth_headers);
 }
 
 static int run_credential_helper(struct credential *c,