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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729615758; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VDoKVxzboEyOZx7JDyIdlXgX6eUiunNnXmtg/ZwTIlk=; b=f13coFq2pK+lN51b2J3str8kjypkK+h4JwQPM03ZVlDyDh9B6h6f7xuV0drKAvU9asRfQ1 IYLzml8rxhyzrrRegNfSTPulKcbeAg08mdVpDjC2EZhCWISs9bzaPETeKMg25AiF45dN6E gK+t0qpjYzlywBGawCkyKa8dUlo/8js= X-MC-Unique: jp-gYhGgONWmZrwZfF9gGQ-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 2/9] block/ssh.c: Don't double-check that characters are hex digits Date: Tue, 22 Oct 2024 18:48:56 +0200 Message-ID: <20241022164903.282174-3-kwolf@redhat.com> In-Reply-To: <20241022164903.282174-1-kwolf@redhat.com> References: <20241022164903.282174-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" From: Peter Maydell In compare_fingerprint() we effectively check whether the characters in the fingerprint are valid hex digits twice: first we do so with qemu_isxdigit(), but then the hex2decimal() function also has a code path where it effectively detects an invalid digit and returns -1. This causes Coverity to complain because it thinks that we might use that -1 value in an expression where it would be an integer overflow. Avoid the double-check of hex digit validity by testing the return values from hex2decimal() rather than doing separate calls to qemu_isxdigit(). Since this means we now use the illegal-character return value from hex2decimal(), rewrite it from "-1" to "UINT_MAX", which has the same effect since the return type is "unsigned" but looks less confusing at the callsites when we detect it with "c0 > 0xf". Resolves: Coverity CID 1547813 Signed-off-by: Peter Maydell Reviewed-by: Kevin Wolf Message-ID: <20241008164708.2966400-3-peter.maydell@linaro.org> Reviewed-by: Richard Henderson Signed-off-by: Kevin Wolf --- block/ssh.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/block/ssh.c b/block/ssh.c index 871e1d4753..9f8140bcb6 100644 --- a/block/ssh.c +++ b/block/ssh.c @@ -364,7 +364,7 @@ static unsigned hex2decimal(char ch) return 10 + (ch - 'A'); } =20 - return -1; + return UINT_MAX; } =20 /* Compare the binary fingerprint (hash of host key) with the @@ -376,13 +376,15 @@ static int compare_fingerprint(const unsigned char *f= ingerprint, size_t len, unsigned c; =20 while (len > 0) { + unsigned c0, c1; while (*host_key_check =3D=3D ':') host_key_check++; - if (!qemu_isxdigit(host_key_check[0]) || - !qemu_isxdigit(host_key_check[1])) + c0 =3D hex2decimal(host_key_check[0]); + c1 =3D hex2decimal(host_key_check[1]); + if (c0 > 0xf || c1 > 0xf) { return 1; - c =3D hex2decimal(host_key_check[0]) * 16 + - hex2decimal(host_key_check[1]); + } + c =3D c0 * 16 + c1; if (c - *fingerprint !=3D 0) return c - *fingerprint; fingerprint++; --=20 2.47.0