armor.c

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#include <linux/errno.h>

int ceph_armor(char *dst, const char *src, const char *end);
int ceph_unarmor(char *dst, const char *src, const char *end);

/*
 * base64 encode/decode.
 */

static const char *pem_key =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static int encode_bits(int c)
{
    return pem_key[c];
}

static int decode_bits(char c)
{
    if (c >= 'A' && c <= 'Z')
        return c - 'A';
    if (c >= 'a' && c <= 'z')
        return c - 'a' + 26;
    if (c >= '0' && c <= '9')
        return c - '0' + 52;
    if (c == '+')
        return 62;
    if (c == '/')
        return 63;
    if (c == '=')
        return 0; /* just non-negative, please */
    return -EINVAL;
}

int ceph_armor(char *dst, const char *src, const char *end)
{
    int olen = 0;
    int line = 0;

    while (src < end) {
        unsigned char a, b, c;

        a = *src++;
        *dst++ = encode_bits(a >> 2);
        if (src < end) {
            b = *src++;
            *dst++ = encode_bits(((a & 3) << 4) | (b >> 4));
            if (src < end) {
                c = *src++;
                *dst++ = encode_bits(((b & 15) << 2) |
                             (c >> 6));
                *dst++ = encode_bits(c & 63);
            } else {
                *dst++ = encode_bits((b & 15) << 2);
                *dst++ = '=';
            }
        } else {
            *dst++ = encode_bits(((a & 3) << 4));
            *dst++ = '=';
            *dst++ = '=';
        }
        olen += 4;
        line += 4;
        if (line == 64) {
            line = 0;
            *(dst++) = '\n';
            olen++;
        }
    }
    return olen;
}

int ceph_unarmor(char *dst, const char *src, const char *end)
{
    int olen = 0;

    while (src < end) {
        int a, b, c, d;

        if (src[0] == '\n') {
            src++;
            continue;
        }
        if (src + 4 > end)
            return -EINVAL;
        a = decode_bits(src[0]);
        b = decode_bits(src[1]);
        c = decode_bits(src[2]);
        d = decode_bits(src[3]);
        if (a < 0 || b < 0 || c < 0 || d < 0)
            return -EINVAL;

        *dst++ = (a << 2) | (b >> 4);
        if (src[2] == '=')
            return olen + 1;
        *dst++ = ((b & 15) << 4) | (c >> 2);
        if (src[3] == '=')
            return olen + 2;
        *dst++ = ((c & 3) << 6) | d;
        olen += 3;
        src += 4;
    }
    return olen;
}