>From e5adcd97b5196e29991b524237381a0202a60659 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Sun, 9 Feb 2025 10:07:19 -0500 Subject: [PATCH] iconv: fix erroneous input validation in EUC-KR decoder as a result of incorrect bounds checking on the lead byte being decoded, certain invalid inputs which should produce an encoding error, such as "\xc8\x41", instead produced out-of-bounds loads from the ksc table. in a worst case, the loaded value may not be a valid unicode scalar value, in which case, if the output encoding was UTF-8, wctomb would return (size_t)-1, causing an overflow in the output pointer and remaining buffer size which could clobber memory outside of the output buffer. bug report was submitted in private by Nick Wellnhofer on account of potential security implications. --- src/locale/iconv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/locale/iconv.c b/src/locale/iconv.c index 9605c8e9..008c93f0 100644 --- a/src/locale/iconv.c +++ b/src/locale/iconv.c @@ -502,7 +502,7 @@ size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restri if (c >= 93 || d >= 94) { c += (0xa1-0x81); d += 0xa1; - if (c >= 93 || c>=0xc6-0x81 && d>0x52) + if (c > 0xc6-0x81 || c==0xc6-0x81 && d>0x52) goto ilseq; if (d-'A'<26) d = d-'A'; else if (d-'a'<26) d = d-'a'+26; -- 2.21.0 >From c47ad25ea3b484e10326f933e927c0bc8cded3da Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 12 Feb 2025 17:06:30 -0500 Subject: [PATCH] iconv: harden UTF-8 output code path against input decoder bugs the UTF-8 output code was written assuming an invariant that iconv's decoders only emit valid Unicode Scalar Values which wctomb can encode successfully, thereby always returning a value between 1 and 4. if this invariant is not satisfied, wctomb returns (size_t)-1, and the subsequent adjustments to the output buffer pointer and remaining output byte count overflow, moving the output position backwards, potentially past the beginning of the buffer, without storing any bytes. --- src/locale/iconv.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/locale/iconv.c b/src/locale/iconv.c index 008c93f0..52178950 100644 --- a/src/locale/iconv.c +++ b/src/locale/iconv.c @@ -545,6 +545,10 @@ size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restri if (*outb < k) goto toobig; memcpy(*out, tmp, k); } else k = wctomb_utf8(*out, c); + /* This failure condition should be unreachable, but + * is included to prevent decoder bugs from translating + * into advancement outside the output buffer range. */ + if (k>4) goto ilseq; *out += k; *outb -= k; break; -- 2.21.0