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Revision 447ac906e189535e77dcb1f4bbe3f1bc917d4c12 authored by Patrick Steinhardt on 01 December 2022, 14:45:31 UTC, committed by Junio C Hamano on 05 December 2022, 06:14:16 UTC 
attr: fix out-of-bounds read with unreasonable amount of patterns
 
The `struct attr_stack` tracks the stack of all patterns together with
their attributes. When parsing a gitattributes file that has more than
2^31 such patterns though we may trigger multiple out-of-bounds reads on
64 bit platforms. This is because while the `num_matches` variable is an
unsigned integer, we always use a signed integer to iterate over them.

I have not been able to reproduce this issue due to memory constraints
on my systems. But despite the out-of-bounds reads, the worst thing that
can seemingly happen is to call free(3P) with a garbage pointer when
calling `attr_stack_free()`.

Fix this bug by using unsigned integers to iterate over the array. While
this makes the iteration somewhat awkward when iterating in reverse, it
is at least better than knowingly running into an out-of-bounds read.
While at it, convert the call to `ALLOC_GROW` to use `ALLOC_GROW_BY`
instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 34ace8b
Raw File
url.c 
#include "cache.h"
#include "url.h"

int is_urlschemechar(int first_flag, int ch)
{
	/*
	 * The set of valid URL schemes, as per STD66 (RFC3986) is
	 * '[A-Za-z][A-Za-z0-9+.-]*'. But use slightly looser check
	 * of '[A-Za-z0-9][A-Za-z0-9+.-]*' because earlier version
	 * of check used '[A-Za-z0-9]+' so not to break any remote
	 * helpers.
	 */
	int alphanumeric, special;
	alphanumeric = ch > 0 && isalnum(ch);
	special = ch == '+' || ch == '-' || ch == '.';
	return alphanumeric || (!first_flag && special);
}

int is_url(const char *url)
{
	/* Is "scheme" part reasonable? */
	if (!url || !is_urlschemechar(1, *url++))
		return 0;
	while (*url && *url != ':') {
		if (!is_urlschemechar(0, *url++))
			return 0;
	}
	/* We've seen "scheme"; we want colon-slash-slash */
	return (url[0] == ':' && url[1] == '/' && url[2] == '/');
}

static char *url_decode_internal(const char **query, int len,
				 const char *stop_at, struct strbuf *out,
				 int decode_plus)
{
	const char *q = *query;

	while (len) {
		unsigned char c = *q;

		if (!c)
			break;
		if (stop_at && strchr(stop_at, c)) {
			q++;
			len--;
			break;
		}

		if (c == '%' && (len < 0 || len >= 3)) {
			int val = hex2chr(q + 1);
			if (0 < val) {
				strbuf_addch(out, val);
				q += 3;
				len -= 3;
				continue;
			}
		}

		if (decode_plus && c == '+')
			strbuf_addch(out, ' ');
		else
			strbuf_addch(out, c);
		q++;
		len--;
	}
	*query = q;
	return strbuf_detach(out, NULL);
}

char *url_decode(const char *url)
{
	return url_decode_mem(url, strlen(url));
}

char *url_decode_mem(const char *url, int len)
{
	struct strbuf out = STRBUF_INIT;
	const char *colon = memchr(url, ':', len);

	/* Skip protocol part if present */
	if (colon && url < colon) {
		strbuf_add(&out, url, colon - url);
		len -= colon - url;
		url = colon;
	}
	return url_decode_internal(&url, len, NULL, &out, 0);
}

char *url_percent_decode(const char *encoded)
{
	struct strbuf out = STRBUF_INIT;
	return url_decode_internal(&encoded, strlen(encoded), NULL, &out, 0);
}

char *url_decode_parameter_name(const char **query)
{
	struct strbuf out = STRBUF_INIT;
	return url_decode_internal(query, -1, "&=", &out, 1);
}

char *url_decode_parameter_value(const char **query)
{
	struct strbuf out = STRBUF_INIT;
	return url_decode_internal(query, -1, "&", &out, 1);
}

void end_url_with_slash(struct strbuf *buf, const char *url)
{
	strbuf_addstr(buf, url);
	strbuf_complete(buf, '/');
}

void str_end_url_with_slash(const char *url, char **dest)
{
	struct strbuf buf = STRBUF_INIT;
	end_url_with_slash(&buf, url);
	free(*dest);
	*dest = strbuf_detach(&buf, NULL);
}
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