varnish-cache/lib/libvarnish/venc.c
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/*-
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 * Copyright (c) 2020 Varnish Software AS
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 * All rights reserved.
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 *
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 * Author: Poul-Henning Kamp <phk@phk.freebsd.dk>
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 *
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 * SPDX-License-Identifier: BSD-2-Clause
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 *
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 */
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#include "config.h"
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#include <stdint.h>
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#include <string.h>
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#include <sys/types.h>
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#include "vdef.h"
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#include "vas.h"
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#include "vrt.h"
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#include "venc.h"
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#include "vsb.h"
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/*
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 * Yes: Cumbersome.  But if "..." syntax is used, C adds a NUL
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 */
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static const char base64_enc[64] = {
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    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
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    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
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    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
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    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
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    'o', 'p', 'r', 'q', 's', 't', 'u', 'v',
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    'w', 'x', 'y', 'z', '0', '1', '2', '3',
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    '4', '5', '6', '7', '8', '9', '+', '/'
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};
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/*
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 * Encode base64 (RFC4648 section 4) into VSB.
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 */
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void
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VENC_Encode_Base64(struct vsb *dst, const void *src, size_t len)
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{
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        const uint8_t *p = src;
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        uint32_t u;
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        char w[4];
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        AN(dst);
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        AN(src);
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        for (; len >= 3; len -= 3, p += 3) {
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                u = (p[0] << 16) | (p[1] << 8) | p[2];
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                w[3] = base64_enc[u & 0x3f];
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                u >>= 6;
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                w[2] = base64_enc[u & 0x3f];
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                u >>= 6;
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                w[1] = base64_enc[u & 0x3f];
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                u >>= 6;
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                w[0] = base64_enc[u & 0x3f];
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                if (VSB_bcat(dst, w, sizeof w))
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                        break;
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        }
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        if (len) {
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                memset(w, '=', sizeof w);
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                u = (p[0] << 16);
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                if (len == 2)
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                    u |= (p[1] << 8);
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                w[0] = base64_enc[(u >> 18) & 0x3f];
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                w[1] = base64_enc[(u >> 12) & 0x3f];
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                if (len == 2)
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                        w[2] = base64_enc[(u >> 6) & 0x3f];
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                VSB_bcat(dst, w, sizeof w);
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        }
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}
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#define BV 64
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static const uint8_t base64_dec[256] = {
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, 62, BV, BV, BV, 63,
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    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, BV, BV, BV,  0, BV, BV,
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    BV,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
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    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, BV, BV, BV, BV, BV,
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    BV, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV,
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    BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV, BV
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};
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struct venc_state {
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        unsigned                n;
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        unsigned                f;
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        uint8_t                 w;
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        struct vsb              *vsb;
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        const uint8_t           *tbl;
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};
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static const char *
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venc_decode_base64(struct venc_state *ves, const char *b, const char *e)
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{
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        unsigned i;
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        AN(ves);
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        AN(ves->vsb);
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        AN(ves->tbl);
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        AN(b);
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        if (e == NULL)
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                e = strchr(b, '\0');
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        assert(e >= b);
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        for (; b < e; b++) {
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                i = ves->tbl[*(const uint8_t*)b];
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                if (i == BV)
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                        return (b);
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                if (*b == '=' && ves->n < 2)
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                        return (b);
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                else if (*b == '=')
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                        ves->f++;
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                else if (ves->f)
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                        return (b - 1);
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                if (ves->f && ves->w)
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                        return (b - 1);
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                switch(++ves->n) {
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                case 1:
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                        ves->w = i << 2;
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                        break;
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                case 2:
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                        ves->w |= i >> 4;
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                        VSB_putc(ves->vsb, ves->w);
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                        ves->w = i << 4;
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                        break;
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                case 3:
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                        ves->w |= i >> 2;
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                        if (!ves->f)
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                                VSB_putc(ves->vsb, ves->w);
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                        ves->w = i << 6;
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                        break;
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                case 4:
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                        ves->w |= i;
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                        if (!ves->f)
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                                VSB_putc(ves->vsb, ves->w);
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                        ves->w = 0;
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                        ves->n = 0;
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                        break;
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                default:
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                        WRONG("Wrong turn in venc_decode_base64()");
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                }
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        }
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        return (NULL);
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}
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/*
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 * Decode base64 (RFC4648 section 4) into VSB.
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 *
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 * Returns NULL on success.
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 * Returns pointer to offending input character on failure.
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 */
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const char *
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VENC_Decode_Base64(struct vsb *dst, const char *b, const char *e)
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{
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        struct venc_state ves;
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        const char *rv;
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        memset(&ves, 0, sizeof ves);
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        ves.vsb = dst;
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        ves.tbl = base64_dec;
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        rv = venc_decode_base64(&ves, b, e);
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        if (rv)
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                return (rv);
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        if (ves.n)
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                return (e);
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        return (NULL);
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}