From ebd64fcbd4f3858b6986ff1a048e3467d96841ab Mon Sep 17 00:00:00 2001
From: Harlen Stenn <stenn@ntp.org>
Date: Sat, 13 May 2023 05:23:33 UTC
Subject: [PATCH] mstolfp:make sure the buffer has enough room for the input extra characters

Conflict:NA
Reference:https://www.eecis.udel.edu/~ntp/ntp_spool//ntp4/ntp-4.2.8p15-3806-3807.patch

CVE-2023-26552, CVE-2023-26553, and CVE-2023-26554 are marked identical to CVE-2023-26551
https://github.com/spwpun/ntp-4.2.8p15-cves/issues/1

---
 include/ntp_fp.h        |   4 +-
 libntp/mstolfp.c        | 109 +++++++++++++++-------------------------
 2 files changed, 42 insertions(+), 71 deletions(-)

diff --git a/include/ntp_fp.h b/include/ntp_fp.h
index afd1f82..fe6e390 100644
--- a/include/ntp_fp.h
+++ b/include/ntp_fp.h
@@ -195,9 +195,9 @@ typedef u_int32 u_fp;
 	do { \
 		int32 add_f = (int32)(f); \
 		if (add_f >= 0) \
-			M_ADD((r_i), (r_f), 0, (uint32)( add_f)); \
+			M_ADD((r_i), (r_f), 0, (u_int32)( add_f)); \
 		else \
-			M_SUB((r_i), (r_f), 0, (uint32)(-add_f)); \
+			M_SUB((r_i), (r_f), 0, (u_int32)(-add_f)); \
 	} while(0)
 
 #define	M_ISNEG(v_i)			/* v < 0 */ \
diff --git a/libntp/mstolfp.c b/libntp/mstolfp.c
index 3dfc4ef..a428d17 100644
--- a/libntp/mstolfp.c
+++ b/libntp/mstolfp.c
@@ -14,86 +14,57 @@ mstolfp(
 	l_fp *lfp
 	)
 {
-	register const char *cp;
-	register char *bp;
-	register const char *cpdec;
-	char buf[100];
+	int        ch, neg = 0; 
+	u_int32    q, r;
 
 	/*
 	 * We understand numbers of the form:
 	 *
 	 * [spaces][-|+][digits][.][digits][spaces|\n|\0]
 	 *
-	 * This is one enormous hack.  Since I didn't feel like
-	 * rewriting the decoding routine for milliseconds, what
-	 * is essentially done here is to make a copy of the string
-	 * with the decimal moved over three places so the seconds
-	 * decoding routine can be used.
+	 * This is kinda hack.  We use 'atolfp' to do the basic parsing
+	 * (after some initial checks) and then divide the result by
+	 * 1000.  The original implementation avoided that by
+	 * hacking up the input string to move the decimal point, but
+	 * that needed string manipulations prone to buffer overruns.
+	 * To avoid that trouble we do the conversion first and adjust
+	 * the result.
 	 */
-	bp = buf;
-	cp = str;
-	while (isspace((unsigned char)*cp))
-	    cp++;
-	
-	if (*cp == '-' || *cp == '+') {
-		*bp++ = *cp++;
-	}
-
-	if (*cp != '.' && !isdigit((unsigned char)*cp))
-	    return 0;
-
-
-	/*
-	 * Search forward for the decimal point or the end of the string.
-	 */
-	cpdec = cp;
-	while (isdigit((unsigned char)*cpdec))
-	    cpdec++;
 
-	/*
-	 * Found something.  If we have more than three digits copy the
-	 * excess over, else insert a leading 0.
-	 */
-	if ((cpdec - cp) > 3) {
-		do {
-			*bp++ = (char)*cp++;
-		} while ((cpdec - cp) > 3);
-	} else {
-		*bp++ = '0';
+	while (isspace(ch = *(const unsigned char*)str))
+		++str;
+	switch (ch) {
+	    case '-': neg = TRUE;
+	    case '+': ++str;
+	    default : break;
 	}
 
-	/*
-	 * Stick the decimal in.  If we've got less than three digits in
-	 * front of the millisecond decimal we insert the appropriate number
-	 * of zeros.
-	 */
-	*bp++ = '.';
-	if ((cpdec - cp) < 3) {
-		size_t i = 3 - (cpdec - cp);
-		do {
-			*bp++ = '0';
-		} while (--i > 0);
-	}
+	if (!isdigit(ch = *(const unsigned char*)str) && (ch != '.'))
+		return 0;
+	if (!atolfp(str, lfp))
+		return 0;
 
-	/*
-	 * Copy the remainder up to the millisecond decimal.  If cpdec
-	 * is pointing at a decimal point, copy in the trailing number too.
+	/* now do a chained/overlapping division by 1000 to get from
+	 * seconds to msec. 1000 is small enough to go with temporary
+	 * 32bit accus for Q and R.
 	 */
-	while (cp < cpdec)
-	    *bp++ = (char)*cp++;
-	
-	if (*cp == '.') {
-		cp++;
-		while (isdigit((unsigned char)*cp))
-		    *bp++ = (char)*cp++;
-	}
-	*bp = '\0';
+	q = lfp->l_ui / 1000u;
+	r = lfp->l_ui - (q * 1000u);
+	lfp->l_ui = q;
 
-	/*
-	 * Check to make sure the string is properly terminated.  If
-	 * so, give the buffer to the decoding routine.
-	 */
-	if (*cp != '\0' && !isspace((unsigned char)*cp))
-	    return 0;
-	return atolfp(buf, lfp);
+	r = (r << 16) | (lfp->l_uf >> 16);
+	q = r / 1000u;
+	r = ((r - q * 1000) << 16) | (lfp->l_uf & 0x0FFFFu);
+	lfp->l_uf = q << 16;
+	q = r / 1000;
+	lfp->l_uf |= q;
+	r -= q * 1000u;
+
+	/* fix sign */
+	if (neg)
+		L_NEG(lfp);
+	/* round */
+	if (r >= 500)
+		L_ADDF(lfp, (neg ? -1 : 1));
+	return 1;
 }
-- 
2.33.0