From: Michael Tremer <michael.tremer@ipfire.org>
Date: Tue, 13 Jul 2021 13:41:36 +0000 (+0000)
Subject: util: Refactor unhexlify without using scanf
X-Git-Tag: 0.9.28~1027
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d0e6b2149d7352b2a7c26b2417c3a42b4e65e0d4;p=pakfire.git

util: Refactor unhexlify without using scanf

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/libpakfire/util.c b/src/libpakfire/util.c
index 3584f58e0..5c18f02ea 100644
--- a/src/libpakfire/util.c
+++ b/src/libpakfire/util.c
@@ -639,15 +639,44 @@ char* __pakfire_hexlify(const char* digest, const size_t length) {
 	return s;
 }
 
+static int parse_nibble(char nibble) {
+	// Handle digits
+	if (nibble >= '0' && nibble <= '9')
+		return nibble - '0';
+
+	// Handle lowercase letters
+	if (nibble >= 'a' && nibble <= 'f')
+		return 10 + nibble - 'a';
+
+	// Handle uppercase letters
+	if (nibble >= 'A' && nibble <= 'F')
+		return 10 + nibble - 'A';
+
+	// Error
+	return -1;
+}
+
 int __pakfire_unhexlify(unsigned char* dst, const size_t l, const char* src) {
-	const char* p = src;
+	if (!src) {
+		errno = EINVAL;
+		return 1;
+	}
 
-	for (unsigned int i = 0; i < l && *p; i++) {
-		int r = sscanf(p, "%02X", (unsigned int*)&dst[i]);
-		if (r != 1)
+	// Determine input length
+	const size_t length = strlen(src);
+
+	for (unsigned int i = 0, j = 0; i < length && j < l; i += 2, j++) {
+		int h = parse_nibble(src[i]);
+		int l = parse_nibble(src[i+1]);
+
+		// Check for invalid input
+		if (h < 0 || l < 0) {
+			errno = EINVAL;
 			return 1;
+		}
 
-		p += 2;
+		// Store result
+		dst[j] = h << 4 | l;
 	}
 
 	return 0;