Date: Fri, 17 Dec 2021 10:18:42 +0200
From: Timo Teras <timo.teras@iki.fi>
To: "Jan Hendrik Farr" <git@jfarr.cc>
Cc: ~alpine/apk-tools@lists.alpinelinux.org
Subject: Re: [PATCH 1/1] libfetch: Allow special characters in http basic
 auth
Message-ID: <20211217101842.5f83dc3d@vostro>
In-Reply-To: <ee832554-1af5-47cd-a60a-81903b2e7a84@www.fastmail.com>
References: <20211213212929.925-1-git@jfarr.cc>
	<20211214213430.029b34c5@vostro>
	<e4a2e0eb-762f-41e7-92ce-0c58023f280d@www.fastmail.com>
	<20211215082220.71dbc443@vostro>
	<ee832554-1af5-47cd-a60a-81903b2e7a84@www.fastmail.com>
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Hi!

Committed with whitespace fixes. Somehow tabs were converted to spaces
in the patch you sent and it did not apply cleanly.

Thank you!
Timo

On Thu, 16 Dec 2021 23:34:38 +0100
"Jan Hendrik Farr" <git@jfarr.cc> wrote:

> Hi,
> 
> this version will allow unencoded colons in the password. I modified
> fetch_pctdecode to allow the callee to specify at what characters it
> should stop. For the username it stops at ":" or "@" and for the
> password just at "@". I prefer this behavior over giving people an
> error. While it will allow some invalid credentials this is actually
> the same behavior as curl + this won't brake current setups.
> 
> With kind regards, Jan
> 
> 
> 
> 
> 
> 
> Currently, special characters in the username or password are not
> handled correctly (when set in $http_proxy and $https_proxy). They
> should be percent encoded in the environment variables then decoded
> by libfetch and reencoded using base64. This implementation is mainly
> taken from the current FreeBSD source and adapted to the apk-tools
> version of libfetch.
> ---
>  libfetch/fetch.c | 80
> ++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 67
> insertions(+), 13 deletions(-)
> 
> diff --git a/libfetch/fetch.c b/libfetch/fetch.c
> index 45c92aa..526ba86 100644
> --- a/libfetch/fetch.c
> +++ b/libfetch/fetch.c
> @@ -354,7 +354,58 @@ fetchCopyURL(const struct url *src)
>  }
> 
>  /*
> - * Split an URL into components. URL syntax is:
> + * Return value of the given hex digit.
> + */
> +static int
> +fetch_hexval(char ch)
> +{
> +
> +       if (ch >= '0' && ch <= '9')
> +               return (ch - '0');
> +       else if (ch >= 'a' && ch <= 'f')
> +               return (ch - 'a' + 10);
> +       else if (ch >= 'A' && ch <= 'F')
> +               return (ch - 'A' + 10);
> +       return (-1);
> +}
> +
> +/*
> + * Decode percent-encoded URL component from src into dst, stopping
> at end
> + * of string or one of the characters contained in brk.  Returns a
> pointer
> + * to the unhandled part of the input string (null terminator,
> specified
> + * character).  No terminator is written to dst (it is the caller's
> + * responsibility).
> + */
> +static const char *
> +fetch_pctdecode(char *dst, const char *src, const char *brk, size_t
> dlen) +{
> +       int d1, d2;
> +       char c;
> +       const char *s;
> +
> +
> +
> +       for (s = src; *s != '\0' && !strchr(brk, *s); s++) {
> +               if (s[0] == '%' && (d1 = fetch_hexval(s[1])) >= 0 &&
> +                   (d2 = fetch_hexval(s[2])) >= 0 && (d1 > 0 || d2 >
> 0)) {
> +                       c = d1 << 4 | d2;
> +                       s += 2;
> +               } else if (s[0] == '%') {
> +                       /* Invalid escape sequence. */
> +                       return (NULL);
> +               } else {
> +                       c = *s;
> +               }
> +               if (!dlen)
> +                       return NULL;
> +               dlen--;
> +               *dst++ = c;
> +       }
> +       return (s);
> +}
> +
> +/*
> + * Split a URL into components. URL syntax is:
>   * [method:/][/[user[:pwd]@]host[:port]/][document]
>   * This almost, but not quite, RFC1738 URL syntax.
>   */
> @@ -428,25 +479,28 @@ find_user:
>         p = strpbrk(URL, "/@");
>         if (p != NULL && *p == '@') {
>                 /* username */
> -               for (q = URL, i = 0; (*q != ':') && (*q != '@'); q++)
> {
> -                       if (i >= URL_USERLEN) {
> -                               url_seterr(URL_BAD_AUTH);
> -                               goto ouch;
> -                       }
> -                       u->user[i++] = *q;
> +               q = URL;
> +               q = fetch_pctdecode(u->user, q, ":@", URL_USERLEN);
> +               if (q == NULL) {
> +                       url_seterr(URL_BAD_AUTH);
> +                       goto ouch;
>                 }
> 
>                 /* password */
>                 if (*q == ':') {
> -                       for (q++, i = 0; (*q != '@'); q++) {
> -                               if (i >= URL_PWDLEN) {
> -                                       url_seterr(URL_BAD_AUTH);
> -                                       goto ouch;
> -                               }
> -                               u->pwd[i++] = *q;
> +                       q = fetch_pctdecode(u->pwd, q + 1, "@",
> URL_PWDLEN); +
> +                       if (q == NULL) {
> +                               url_seterr(URL_BAD_AUTH);
> +                               goto ouch;
>                         }
>                 }
> 
> +               if (*q != '@') {
> +                       url_seterr(URL_BAD_AUTH);
> +                       goto ouch;
> +               }
> +
>                 p++;
>         } else {
>                 p = URL;
> --
> 2.34.1