MINOR: sample: add ub64dec and ub64enc converters

ub64dec and ub64enc are the base64url equivalent of b64dec and base64
converters. base64url encoding is the "URL and Filename Safe Alphabet"
variant of base64 encoding. It is also used in in JWT (JSON Web Token)
standard.
RFC1421 mention in base64.c file is deprecated so it was replaced with
RFC4648 to which existing converters, base64/b64dec, still apply.

Example:
  HAProxy:
    http-request return content-type text/plain lf-string %[req.hdr(Authorization),word(2,.),ub64dec]
  Client:
    Token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyIjoiZm9vIiwia2V5IjoiY2hhZTZBaFhhaTZlIn0.5VsVj7mdxVvo1wP5c0dVHnr-S_khnIdFkThqvwukmdg
    $ curl -H "Authorization: Bearer ${TOKEN}" http://haproxy.local
    {"user":"foo","key":"chae6AhXai6e"}
diff --git a/doc/configuration.txt b/doc/configuration.txt
index f21a29a..f242300 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -15660,11 +15660,14 @@
 b64dec
   Converts (decodes) a base64 encoded input string to its binary
   representation. It performs the inverse operation of base64().
+  For base64url("URL and Filename Safe Alphabet" (RFC 4648)) variant
+  see "ub64dec".
 
 base64
   Converts a binary input sample to a base64 string. It is used to log or
   transfer binary content in a way that can be reliably transferred (e.g.
-  an SSL ID can be copied in a header).
+  an SSL ID can be copied in a header). For base64url("URL and Filename
+  Safe Alphabet" (RFC 4648)) variant see "ub64enc".
 
 bool
   Returns a boolean TRUE if the input value of type signed integer is
@@ -16565,6 +16568,18 @@
   connections there are from a given address for example. See also the
   sc_trackers sample fetch keyword.
 
+ub64dec
+  This converter is the base64url variant of b64dec converter. base64url
+  encoding is the "URL and Filename Safe Alphabet" variant of base64 encoding.
+  It is also the encoding used in JWT (JSON Web Token) standard.
+
+  Example:
+    # Decoding a JWT payload:
+    http-request set-var(txn.token_payload) req.hdr(Authorization),word(2,.),ub64dec
+
+ub64enc
+  This converter is the base64url variant of base64 converter.
+
 upper
   Convert a string sample to upper case. This can only be placed after a string
   sample fetch function or after a transformation keyword returning a string
diff --git a/include/haproxy/base64.h b/include/haproxy/base64.h
index 1756bc0..ace6063 100644
--- a/include/haproxy/base64.h
+++ b/include/haproxy/base64.h
@@ -17,7 +17,9 @@
 #include <haproxy/api.h>
 
 int a2base64(char *in, int ilen, char *out, int olen);
+int a2base64url(const char *in, size_t ilen, char *out, size_t olen);
 int base64dec(const char *in, size_t ilen, char *out, size_t olen);
+int base64urldec(const char *in, size_t ilen, char *out, size_t olen);
 const char *s30tob64(int in, char *out);
 int b64tos30(const char *in);
 
diff --git a/reg-tests/sample_fetches/ubase64.vtc b/reg-tests/sample_fetches/ubase64.vtc
new file mode 100644
index 0000000..d6973e3
--- /dev/null
+++ b/reg-tests/sample_fetches/ubase64.vtc
@@ -0,0 +1,51 @@
+varnishtest "ub64dec sample fetche Test"
+
+#REQUIRE_VERSION=2.4
+
+feature ignore_unknown_macro
+
+haproxy h1 -conf {
+    defaults
+        mode http
+        timeout connect 1s
+        timeout client  1s
+        timeout server  1s
+
+    frontend fe
+        bind "fd@${fe}"
+				acl input hdr(encode) -m found
+        http-request return content-type text/plain hdr encode %[hdr(encode),ub64enc] hdr decode %[hdr(decode),ub64dec] if input
+        http-request return content-type text/plain hdr encode %[bin(14fb9c03d97f12d97e),ub64enc] hdr decode %[str(FPucA9l_Etl-),ub64dec,hex,lower] if !input
+
+} -start
+
+client c1 -connect ${h1_fe_sock} {
+    txreq -hdr "encode: f" -hdr "decode: Zg"
+    rxresp
+    expect resp.http.encode == "Zg"
+    expect resp.http.decode == "f"
+    txreq -hdr "encode: fo" -hdr "decode: Zm8"
+    rxresp
+    expect resp.http.encode == "Zm8"
+    expect resp.http.decode == "fo"
+    txreq -hdr "encode: foo" -hdr "decode: Zm9v"
+    rxresp
+    expect resp.http.encode == "Zm9v"
+    expect resp.http.decode == "foo"
+    txreq -hdr "encode: foob" -hdr "decode: Zm9vYg"
+    rxresp
+    expect resp.http.encode == "Zm9vYg"
+    expect resp.http.decode == "foob"
+    txreq -hdr "encode: fooba" -hdr "decode: Zm9vYmE"
+    rxresp
+    expect resp.http.encode == "Zm9vYmE"
+    expect resp.http.decode == "fooba"
+    txreq -hdr "encode: foobar" -hdr "decode: Zm9vYmFy"
+    rxresp
+    expect resp.http.encode == "Zm9vYmFy"
+    expect resp.http.decode == "foobar"
+    txreq
+    rxresp
+    expect resp.http.encode == "FPucA9l_Etl-"
+    expect resp.http.decode == "14fb9c03d97f12d97e"
+} -run
diff --git a/src/base64.c b/src/base64.c
index 53e4d65..5c4ab3a 100644
--- a/src/base64.c
+++ b/src/base64.c
@@ -19,11 +19,14 @@
 
 #define B64BASE	'#'		/* arbitrary chosen base value */
 #define B64CMIN	'+'
+#define UB64CMIN	'-'
 #define B64CMAX	'z'
 #define B64PADV	64		/* Base64 chosen special pad value */
 
 const char base64tab[65]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 const char base64rev[]="b###cXYZ[\\]^_`a###d###$%&'()*+,-./0123456789:;<=######>?@ABCDEFGHIJKLMNOPQRSTUVW";
+const char ubase64tab[65]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+const char ubase64rev[]="b##XYZ[\\]^_`a###c###$%&'()*+,-./0123456789:;<=####c#>?@ABCDEFGHIJKLMNOPQRSTUVW";
 
 /* Encodes <ilen> bytes from <in> to <out> for at most <olen> chars (including
  * the trailing zero). Returns the number of bytes written. No check is made
@@ -68,6 +71,48 @@
 	return convlen;
 }
 
+/* url variant of a2base64 */
+int a2base64url(const char *in, size_t ilen, char *out, size_t olen)
+{
+	int convlen;
+
+	convlen = ((ilen + 2) / 3) * 4;
+
+	if (convlen >= olen)
+		return -1;
+
+	/* we don't need to check olen anymore */
+	while (ilen >= 3) {
+		out[0] = ubase64tab[(((unsigned char)in[0]) >> 2)];
+		out[1] = ubase64tab[(((unsigned char)in[0] & 0x03) << 4) | (((unsigned char)in[1]) >> 4)];
+		out[2] = ubase64tab[(((unsigned char)in[1] & 0x0F) << 2) | (((unsigned char)in[2]) >> 6)];
+		out[3] = ubase64tab[(((unsigned char)in[2] & 0x3F))];
+		out += 4;
+		in += 3;
+		ilen -= 3;
+	}
+
+	if (!ilen) {
+		out[0] = '\0';
+		return convlen;
+	}
+
+	out[0] = ubase64tab[((unsigned char)in[0]) >> 2];
+	if (ilen == 1) {
+		out[1] = ubase64tab[((unsigned char)in[0] & 0x03) << 4];
+		out[2] = '\0';
+		convlen -= 2;
+	} else {
+		out[1] = ubase64tab[(((unsigned char)in[0] & 0x03) << 4) |
+		                    (((unsigned char)in[1]) >> 4)];
+		out[2] = ubase64tab[((unsigned char)in[1] & 0x0F) << 2];
+		out[3] = '\0';
+		convlen -= 1;
+	}
+
+	return convlen;
+}
+
 /* Decodes <ilen> bytes from <in> to <out> for at most <olen> chars.
  * Returns the number of bytes converted. No check is made for
  * <in> or <out> to be NULL. Returns -1 if <in> is invalid or ilen
@@ -138,6 +183,72 @@
 	return convlen;
 }
 
+/* url variant of base64dec */
+/* The reverse tab used to decode base64 is generated via /dev/base64/base64rev-gen.c */
+int base64urldec(const char *in, size_t ilen, char *out, size_t olen)
+{
+	unsigned char t[4];
+	signed char b;
+	int convlen = 0, i = 0, pad = 0, padlen = 0;
+
+	if (olen < ((ilen / 4 * 3)))
+		return -2;
+
+	switch (ilen % 4) {
+		case 0:
+			break;
+		case 2:
+			padlen = pad = 2;
+			break;
+		case 3:
+			padlen = pad = 1;
+			break;
+		default:
+			return -1;
+	}
+
+	while (ilen + pad) {
+		if (ilen) {
+			/* if (*p < UB64CMIN || *p > B64CMAX) */
+			b = (signed char) * in - UB64CMIN;
+			if ((unsigned char)b > (B64CMAX - UB64CMIN))
+				return -1;
+
+			b = ubase64rev[b] - B64BASE - 1;
+			/* b == -1: invalid character */
+			if (b < 0)
+				return -1;
+
+			in++;
+			ilen--;
+
+		} else {
+			b = B64PADV;
+			pad--;
+		}
+
+		t[i++] = b;
+
+		if (i == 4) {
+			/*
+			 * WARNING: we allow to write little more data than we
+			 * should, but the checks from the beginning of the
+			 * functions guarantee that we can safely do that.
+			 */
+
+			/* xx000000 xx001111 xx111122 xx222222 */
+			out[convlen]   = ((t[0] << 2) + (t[1] >> 4));
+			out[convlen + 1] = ((t[1] << 4) + (t[2] >> 2));
+			out[convlen + 2] = ((t[2] << 6) + (t[3] >> 0));
+
+			convlen += 3;
+			i = 0;
+		}
+	}
+	convlen -= padlen;
+
+	return convlen;
+}
 
 /* Converts the lower 30 bits of an integer to a 5-char base64 string. The
  * caller is responsible for ensuring that the output buffer can accept 6 bytes
diff --git a/src/sample.c b/src/sample.c
index 0c0f36e..04635a9 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -1567,6 +1567,24 @@
 	return 1;
 }
 
+static int sample_conv_base64url2bin(const struct arg *arg_p, struct sample *smp, void *private)
+{
+	struct buffer *trash = get_trash_chunk();
+	int bin_len;
+
+	trash->data = 0;
+	bin_len = base64urldec(smp->data.u.str.area, smp->data.u.str.data,
+			    trash->area, trash->size);
+	if (bin_len < 0)
+		return 0;
+
+	trash->data = bin_len;
+	smp->data.u.str = *trash;
+	smp->data.type = SMP_T_BIN;
+	smp->flags &= ~SMP_F_CONST;
+	return 1;
+}
+
 static int sample_conv_bin2base64(const struct arg *arg_p, struct sample *smp, void *private)
 {
 	struct buffer *trash = get_trash_chunk();
@@ -1585,6 +1603,24 @@
 	return 1;
 }
 
+static int sample_conv_bin2base64url(const struct arg *arg_p, struct sample *smp, void *private)
+{
+	struct buffer *trash = get_trash_chunk();
+	int b64_len;
+
+	trash->data = 0;
+	b64_len = a2base64url(smp->data.u.str.area, smp->data.u.str.data,
+			   trash->area, trash->size);
+	if (b64_len < 0)
+		return 0;
+
+	trash->data = b64_len;
+	smp->data.u.str = *trash;
+	smp->data.type = SMP_T_STR;
+	smp->flags &= ~SMP_F_CONST;
+	return 1;
+}
+
 static int sample_conv_sha1(const struct arg *arg_p, struct sample *smp, void *private)
 {
 	blk_SHA_CTX ctx;
@@ -4096,6 +4132,8 @@
 	{ "debug",  sample_conv_debug,     ARG2(0,STR,STR), smp_check_debug, SMP_T_ANY,  SMP_T_ANY },
 	{ "b64dec", sample_conv_base642bin,0,            NULL, SMP_T_STR,  SMP_T_BIN  },
 	{ "base64", sample_conv_bin2base64,0,            NULL, SMP_T_BIN,  SMP_T_STR  },
+	{ "ub64dec", sample_conv_base64url2bin,0,        NULL, SMP_T_STR,  SMP_T_BIN  },
+	{ "ub64enc", sample_conv_bin2base64url,0,        NULL, SMP_T_BIN,  SMP_T_STR  },
 	{ "upper",  sample_conv_str2upper, 0,            NULL, SMP_T_STR,  SMP_T_STR  },
 	{ "lower",  sample_conv_str2lower, 0,            NULL, SMP_T_STR,  SMP_T_STR  },
 	{ "length", sample_conv_length,    0,            NULL, SMP_T_STR,  SMP_T_SINT },