util-lib,tests: rework unbase64 so that we skip over whitespace automatically (#7522)

Let's optimize things a bit, and instead of having to strip whitespace
first before decoding base64, let's do that implicitly while doing so.
Given that base64 was designed the way it was designed specifically to
be tolerant to whitespace changes, it's a good idea to do this
automatically and implicitly.

1 files changed, 96 insertions, 73 deletions

diff --git a/src/basic/hexdecoct.c b/src/basic/hexdecoct.c
index b61b032d9..689f51f4e 100644
--- a/src/basic/hexdecoct.c
+++ b/src/basic/hexdecoct.c
@@ -623,112 +623,135 @@ int base64_append(
                 return base64_append_width(prefix, plen, NULL, plen, p, l, width - plen - 1);
 }
 
-int unbase64mem(const char *p, size_t l, void **mem, size_t *_len) {
-        _cleanup_free_ uint8_t *r = NULL;
-        int a, b, c, d;
-        uint8_t *z;
+static int unbase64_next(const char **p, size_t *l) {
+        int ret;
+
+        assert(p);
+        assert(l);
+
+        /* Find the next non-whitespace character, and decode it. If we find padding, we return it as INT_MAX. We
+         * greedily skip all preceeding and all following whitespace. */
+
+        for (;;) {
+                if (*l == 0)
+                        return -EPIPE;
+
+                if (!strchr(WHITESPACE, **p))
+                        break;
+
+                /* Skip leading whitespace */
+                (*p)++, (*l)--;
+        }
+
+        if (**p == '=')
+                ret = INT_MAX; /* return padding as INT_MAX */
+        else {
+                ret = unbase64char(**p);
+                if (ret < 0)
+                        return ret;
+        }
+
+        for (;;) {
+                (*p)++, (*l)--;
+
+                if (*l == 0)
+                        break;
+                if (!strchr(WHITESPACE, **p))
+                        break;
+
+                /* Skip following whitespace */
+        }
+
+        return ret;
+}
+
+int unbase64mem(const char *p, size_t l, void **ret, size_t *ret_size) {
+        _cleanup_free_ uint8_t *buf = NULL;
         const char *x;
+        uint8_t *z;
         size_t len;
 
         assert(p || l == 0);
-        assert(mem);
-        assert(_len);
+        assert(ret);
+        assert(ret_size);
 
         if (l == (size_t) -1)
                 l = strlen(p);
 
-        /* padding ensures any base63 input has input divisible by 4 */
-        if (l % 4 != 0)
-                return -EINVAL;
-
-        /* strip the padding */
-        if (l > 0 && p[l - 1] == '=')
-                l--;
-        if (l > 0 && p[l - 1] == '=')
-                l--;
-
-        /* a group of four input bytes needs three output bytes, in case of
-           padding we need to add two or three extra bytes */
-        len = (l / 4) * 3 + (l % 4 ? (l % 4) - 1 : 0);
+        /* A group of four input bytes needs three output bytes, in case of padding we need to add two or three extra
+           bytes. Note that this calculation is an upper boundary, as we ignore whitespace while decoding */
+        len = (l / 4) * 3 + (l % 4 != 0 ? (l % 4) - 1 : 0);
 
-        z = r = malloc(len + 1);
-        if (!r)
+        buf = malloc(len + 1);
+        if (!buf)
                 return -ENOMEM;
 
-        for (x = p; x < p + (l / 4) * 4; x += 4) {
-                /* a == 00XXXXXX; b == 00YYYYYY; c == 00ZZZZZZ; d == 00WWWWWW */
-                a = unbase64char(x[0]);
+        for (x = p, z = buf;;) {
+                int a, b, c, d; /* a == 00XXXXXX; b == 00YYYYYY; c == 00ZZZZZZ; d == 00WWWWWW */
+
+                a = unbase64_next(&x, &l);
+                if (a == -EPIPE) /* End of string */
+                        break;
                 if (a < 0)
+                        return a;
+                if (a == INT_MAX) /* Padding is not allowed at at the beginning of a 4ch block */
                         return -EINVAL;
 
-                b = unbase64char(x[1]);
+                b = unbase64_next(&x, &l);
                 if (b < 0)
+                        return b;
+                if (b == INT_MAX) /* Padding is not allowed at the second character of a 4ch block either */
                         return -EINVAL;
 
-                c = unbase64char(x[2]);
+                c = unbase64_next(&x, &l);
                 if (c < 0)
-                        return -EINVAL;
+                        return c;
 
-                d = unbase64char(x[3]);
+                d = unbase64_next(&x, &l);
                 if (d < 0)
-                        return -EINVAL;
-
-                *(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
-                *(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
-                *(z++) = (uint8_t) c << 6 | (uint8_t) d;      /* ZZWWWWWW */
-        }
-
-        switch (l % 4) {
+                        return d;
 
-        case 3:
-                a = unbase64char(x[0]);
-                if (a < 0)
-                        return -EINVAL;
+                if (c == INT_MAX) { /* Padding at the third character */
 
-                b = unbase64char(x[1]);
-                if (b < 0)
-                        return -EINVAL;
+                        if (d != INT_MAX) /* If the third character is padding, the fourth must be too */
+                                return -EINVAL;
 
-                c = unbase64char(x[2]);
-                if (c < 0)
-                        return -EINVAL;
+                        /* b == 00YY0000 */
+                        if (b & 15)
+                                return -EINVAL;
 
-                /* c == 00ZZZZ00 */
-                if (c & 3)
-                        return -EINVAL;
-
-                *(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
-                *(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
-
-                break;
-        case 2:
-                a = unbase64char(x[0]);
-                if (a < 0)
-                        return -EINVAL;
+                        if (l > 0) /* Trailing rubbish? */
+                                return -ENAMETOOLONG;
 
-                b = unbase64char(x[1]);
-                if (b < 0)
-                        return -EINVAL;
+                        *(z++) = (uint8_t) a << 2 | (uint8_t) (b >> 4); /* XXXXXXYY */
+                        break;
+                }
 
-                /* b == 00YY0000 */
-                if (b & 15)
-                        return -EINVAL;
+                if (d == INT_MAX) {
+                        /* c == 00ZZZZ00 */
+                        if (c & 3)
+                                return -EINVAL;
 
-                *(z++) = (uint8_t) a << 2 | (uint8_t) (b >> 4); /* XXXXXXYY */
+                        if (l > 0) /* Trailing rubbish? */
+                                return -ENAMETOOLONG;
 
-                break;
-        case 0:
+                        *(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
+                        *(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
+                        break;
+                }
 
-                break;
-        default:
-                return -EINVAL;
+                *(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
+                *(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
+                *(z++) = (uint8_t) c << 6 | (uint8_t) d;      /* ZZWWWWWW */
         }
 
         *z = 0;
 
-        *mem = r;
-        r = NULL;
-        *_len = len;
+        if (ret_size)
+                *ret_size = (size_t) (z - buf);
+
+        *ret = buf;
+        buf = NULL;
 
         return 0;
 }