Hi Sascha, On 12/3/25 9:59 AM, Sascha Hauer wrote: > On Tue, Dec 02, 2025 at 10:22:44AM +0100, Jonas Rebmann wrote: >> __decode_base64 generally writes the input in 3 bytes increments, >> corresponding to 4 bytes increments in the base64 input buffer. This >> means that in order to respect dst_len as the size of the output buffer, >> the case of exceeding dst_len within a loop iteration must be >> considered. >> >> In such a case, refrain from writing the last one or two bytes if that >> write would be past dst_len. >> >> Signed-off-by: Jonas Rebmann <[email protected]> >> --- >> lib/base64.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) > > I wonder if we should switch to the kernel functions from lib/base64.c > instead. They look much more straight forward than the busybox based > implementation.
Just need to take care to support base64url, which is needed for the JSON web token support. Cheers, Ahmad > > Sascha > >> >> diff --git a/lib/base64.c b/lib/base64.c >> index d5ab217528..3e29f0a56c 100644 >> --- a/lib/base64.c >> +++ b/lib/base64.c >> @@ -163,19 +163,19 @@ static int __decode_base64(char *p_dst, int dst_len, >> const char *src, bool url) >> */ >> if (count > 1) >> *dst++ = six_bit[0] << 2 | six_bit[1] >> 4; >> - if (count > 2) >> + if (count > 2 && dst_len > 1) >> *dst++ = six_bit[1] << 4 | six_bit[2] >> 2; >> - if (count > 3) >> + if (count > 3 && dst_len > 2) >> *dst++ = six_bit[2] << 6 | six_bit[3]; >> + /* last character was "=" */ >> + if (count != 0) >> + length += min(count - 1, dst_len); >> /* >> * Note that if we decode "AA==" and ate first '=', >> * we just decoded one char (count == 2) and now we'll >> * do the loop once more to decode second '='. >> */ >> dst_len -= count-1; >> - /* last character was "=" */ >> - if (count != 0) >> - length += count - 1; >> } >> ret: >> p_dst = dst; >> >> -- >> 2.51.2.535.g419c72cb8a >> >> > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
