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wind: Deny invalid UTF-8 encodings

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Codepoints above U+10FFFF and overlong encodings are considered invalid.
Unpaired surrogates are not, as these are known to be generated on
occasion — by Windows, for example.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
This commit is contained in:
Joseph Sutton
2023-07-12 13:04:56 +12:00
committed by Nico Williams
parent bf25b38c0a
commit a3878d3e9d
2 changed files with 32 additions and 15 deletions
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25
lib/wind/utf8.c
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@@ -39,13 +39,17 @@ utf8toutf32(const unsigned char **pp, uint32_t *out)
{
const unsigned char *p = *pp;
uint32_t c = *p;
uint32_t out_val;
if (c & 0x80) {
if ((c & 0xE0) == 0xC0) {
const uint32_t c2 = *++p;
if ((c2 & 0xC0) == 0x80) {
*out = ((c & 0x1F) << 6)
out_val = ((c & 0x1F) << 6)
| (c2 & 0x3F);
if (out_val < 0x80) {
return WIND_ERR_INVALID_UTF8;
}
} else {
return WIND_ERR_INVALID_UTF8;
}
@@ -54,9 +58,12 @@ utf8toutf32(const unsigned char **pp, uint32_t *out)
if ((c2 & 0xC0) == 0x80) {
const uint32_t c3 = *++p;
if ((c3 & 0xC0) == 0x80) {
*out = ((c & 0x0F) << 12)
out_val = ((c & 0x0F) << 12)
| ((c2 & 0x3F) << 6)
| (c3 & 0x3F);
if (out_val < 0x800) {
return WIND_ERR_INVALID_UTF8;
}
} else {
return WIND_ERR_INVALID_UTF8;
}
@@ -70,10 +77,13 @@ utf8toutf32(const unsigned char **pp, uint32_t *out)
if ((c3 & 0xC0) == 0x80) {
const uint32_t c4 = *++p;
if ((c4 & 0xC0) == 0x80) {
*out = ((c & 0x07) << 18)
out_val = ((c & 0x07) << 18)
| ((c2 & 0x3F) << 12)
| ((c3 & 0x3F) << 6)
| (c4 & 0x3F);
if (out_val < 0x10000) {
return WIND_ERR_INVALID_UTF8;
}
} else {
return WIND_ERR_INVALID_UTF8;
}
@@ -87,9 +97,16 @@ utf8toutf32(const unsigned char **pp, uint32_t *out)
return WIND_ERR_INVALID_UTF8;
}
} else {
*out = c;
out_val = c;
}
/* Allow unpaired surrogates (in the range 0xd800–0xdfff). */
if (out_val > 0x10ffff) {
return WIND_ERR_INVALID_UTF8;
}
*out = out_val;
*pp = p;
return 0;