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lavf/url: rewrite ff_make_absolute_url() using ff_url_decompose().
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Also add and update some tests.

Change the semantic a little, because for filesytem paths
symlinks complicate things.
See the comments in the code for detail.

Fix trac tickets #8813 and 8814.
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@Cigaes
Cigaes committed Aug 12, 2020
1 parent d853293 commit 1201687
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Showing 4 changed files with 245 additions and 134 deletions.
60 changes: 59 additions & 1 deletion libavformat/tests/url.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,13 @@ static void test_decompose(const char *url)
static void test(const char *base, const char *rel)
{
char buf[200], buf2[200];
ff_make_absolute_url(buf, sizeof(buf), base, rel);
int ret;

ret = ff_make_absolute_url(buf, sizeof(buf), base, rel);
if (ret < 0) {
printf("%50s %-20s => error %s\n", base, rel, av_err2str(ret));
return;
}
printf("%50s %-20s => %s\n", base, rel, buf);
if (base) {
/* Test in-buffer replacement */
Expand Down Expand Up @@ -104,6 +110,58 @@ int main(void)
test("http://server/foo/bar", "/../../../../../other/url");
test("http://server/foo/bar", "/test/../../../../../other/url");
test("http://server/foo/bar", "/test/../../test/../../../other/url");
test("http://server/foo/bar", "file:../baz/qux");
test("http://server/foo//bar/", "../../");
test("file:../tmp/foo", "../bar/");
test("file:../tmp/foo", "file:../bar/");
test("http://server/foo/bar", "./");
test("http://server/foo/bar", ".dotfile");
test("http://server/foo/bar", "..doubledotfile");
test("http://server/foo/bar", "double..dotfile");
test("http://server/foo/bar", "doubledotfile..");

/* From https://tools.ietf.org/html/rfc3986#section-5.4 */
test("http://a/b/c/d;p?q", "g:h"); // g:h
test("http://a/b/c/d;p?q", "g"); // http://a/b/c/g
test("http://a/b/c/d;p?q", "./g"); // http://a/b/c/g
test("http://a/b/c/d;p?q", "g/"); // http://a/b/c/g/
test("http://a/b/c/d;p?q", "/g"); // http://a/g
test("http://a/b/c/d;p?q", "//g"); // http://g
test("http://a/b/c/d;p?q", "?y"); // http://a/b/c/d;p?y
test("http://a/b/c/d;p?q", "g?y"); // http://a/b/c/g?y
test("http://a/b/c/d;p?q", "#s"); // http://a/b/c/d;p?q#s
test("http://a/b/c/d;p?q", "g#s"); // http://a/b/c/g#s
test("http://a/b/c/d;p?q", "g?y#s"); // http://a/b/c/g?y#s
test("http://a/b/c/d;p?q", ";x"); // http://a/b/c/;x
test("http://a/b/c/d;p?q", "g;x"); // http://a/b/c/g;x
test("http://a/b/c/d;p?q", "g;x?y#s"); // http://a/b/c/g;x?y#s
test("http://a/b/c/d;p?q", ""); // http://a/b/c/d;p?q
test("http://a/b/c/d;p?q", "."); // http://a/b/c/
test("http://a/b/c/d;p?q", "./"); // http://a/b/c/
test("http://a/b/c/d;p?q", ".."); // http://a/b/
test("http://a/b/c/d;p?q", "../"); // http://a/b/
test("http://a/b/c/d;p?q", "../g"); // http://a/b/g
test("http://a/b/c/d;p?q", "../.."); // http://a/
test("http://a/b/c/d;p?q", "../../"); // http://a/
test("http://a/b/c/d;p?q", "../../g"); // http://a/g
test("http://a/b/c/d;p?q", "../../../g"); // http://a/g
test("http://a/b/c/d;p?q", "../../../../g"); // http://a/g
test("http://a/b/c/d;p?q", "/./g"); // http://a/g
test("http://a/b/c/d;p?q", "/../g"); // http://a/g
test("http://a/b/c/d;p?q", "g."); // http://a/b/c/g.
test("http://a/b/c/d;p?q", ".g"); // http://a/b/c/.g
test("http://a/b/c/d;p?q", "g.."); // http://a/b/c/g..
test("http://a/b/c/d;p?q", "..g"); // http://a/b/c/..g
test("http://a/b/c/d;p?q", "./../g"); // http://a/b/g
test("http://a/b/c/d;p?q", "./g/."); // http://a/b/c/g/
test("http://a/b/c/d;p?q", "g/./h"); // http://a/b/c/g/h
test("http://a/b/c/d;p?q", "g/../h"); // http://a/b/c/h
test("http://a/b/c/d;p?q", "g;x=1/./y"); // http://a/b/c/g;x=1/y
test("http://a/b/c/d;p?q", "g;x=1/../y"); // http://a/b/c/y
test("http://a/b/c/d;p?q", "g?y/./x"); // http://a/b/c/g?y/./x
test("http://a/b/c/d;p?q", "g?y/../x"); // http://a/b/c/g?y/../x
test("http://a/b/c/d;p?q", "g#s/./x"); // http://a/b/c/g#s/./x
test("http://a/b/c/d;p?q", "g#s/../x"); // http://a/b/c/g#s/../x

printf("\nTesting av_url_split:\n");
test2("/foo/bar");
Expand Down
261 changes: 132 additions & 129 deletions libavformat/url.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -149,146 +149,149 @@ int ff_url_decompose(URLComponents *uc, const char *url, const char *end)
return 0;
}

static void trim_double_dot_url(char *buf, const char *rel, int size)
static int append_path(char *root, char *out_end, char **rout,
const char *in, const char *in_end)
{
const char *p = rel;
const char *root = rel;
char tmp_path[MAX_URL_SIZE] = {0, };
char *sep;
char *node;

/* Get the path root of the url which start by "://" */
if (p && (sep = strstr(p, "://"))) {
sep += 3;
root = strchr(sep, '/');
if (!root)
return;
}

/* set new current position if the root node is changed */
p = root;
while (p && (node = strstr(p, ".."))) {
av_strlcat(tmp_path, p, node - p + strlen(tmp_path));
p = node + 3;
sep = strrchr(tmp_path, '/');
if (sep)
sep[0] = '\0';
else
tmp_path[0] = '\0';
char *out = *rout;
const char *d, *next;

if (in < in_end && *in == '/')
in++; /* already taken care of */
while (in < in_end) {
d = find_delim("/", in, in_end);
next = d + (d < in_end && *d == '/');
if (d - in == 1 && in[0] == '.') {
/* skip */
} else if (d - in == 2 && in[0] == '.' && in[1] == '.') {
av_assert1(out[-1] == '/');
if (out - root > 1)
while (out > root && (--out)[-1] != '/');
} else {
if (out_end - out < next - in)
return AVERROR(ENOMEM);
memmove(out, in, next - in);
out += next - in;
}
in = next;
}

if (!av_stristart(p, "/", NULL) && root != rel)
av_strlcat(tmp_path, "/", size);

av_strlcat(tmp_path, p, size);
/* start set buf after temp path process. */
av_strlcpy(buf, rel, root - rel + 1);

if (!av_stristart(tmp_path, "/", NULL) && root != rel)
av_strlcat(buf, "/", size);

av_strlcat(buf, tmp_path, size);
*rout = out;
return 0;
}

void ff_make_absolute_url(char *buf, int size, const char *base,
int ff_make_absolute_url(char *buf, int size, const char *base,
const char *rel)
{
char *sep, *path_query;
char *root, *p;
char tmp_path[MAX_URL_SIZE];

memset(tmp_path, 0, sizeof(tmp_path));
/* Absolute path, relative to the current server */
if (base && strstr(base, "://") && rel[0] == '/') {
if (base != buf)
av_strlcpy(buf, base, size);
sep = strstr(buf, "://");
if (sep) {
/* Take scheme from base url */
if (rel[1] == '/') {
sep[1] = '\0';
} else {
/* Take scheme and host from base url */
sep += 3;
sep = strchr(sep, '/');
if (sep)
*sep = '\0';
}
}
av_strlcat(buf, rel, size);
trim_double_dot_url(tmp_path, buf, size);
memset(buf, 0, size);
av_strlcpy(buf, tmp_path, size);
return;
URLComponents ub, uc;
char *out, *out_end, *path;
const char *keep, *base_path_end;
int use_base_path, simplify_path = 0, ret;

/* This is tricky.
For HTTP, http://server/site/page + ../media/file
should resolve into http://server/media/file
but for filesystem access, dir/playlist + ../media/file
should resolve into dir/../media/file
because dir could be a symlink, and .. points to
the actual parent of the target directory.
We'll consider that URLs with an actual scheme and authority,
i.e. starting with scheme://, need parent dir simplification,
while bare paths or pseudo-URLs starting with proto: without
the double slash do not.
For real URLs, the processing is similar to the algorithm described
here:
https://tools.ietf.org/html/rfc3986#section-5
*/

if (!size)
return AVERROR(ENOMEM);
out = buf;
out_end = buf + size - 1;

if (!base)
base = "";
if ((ret = ff_url_decompose(&ub, base, NULL) < 0) ||
(ret = ff_url_decompose(&uc, rel, NULL) < 0))
goto error;

keep = ub.url;
#define KEEP(component, also) do { \
if (uc.url_component_end_##component == uc.url && \
ub.url_component_end_##component > keep) { \
keep = ub.url_component_end_##component; \
also \
} \
} while (0)
KEEP(scheme, );
KEEP(authority_full, simplify_path = 1;);
KEEP(path,);
KEEP(query,);
KEEP(fragment,);
#undef KEEP
#define COPY(start, end) do { \
size_t len = end - start; \
if (len > out_end - out) { \
ret = AVERROR(ENOMEM); \
goto error; \
} \
memmove(out, start, len); \
out += len; \
} while (0)
COPY(ub.url, keep);
COPY(uc.url, uc.path);

use_base_path = URL_COMPONENT_HAVE(ub, path) && keep <= ub.path;
if (uc.path > uc.url)
use_base_path = 0;
if (URL_COMPONENT_HAVE(uc, path) && uc.path[0] == '/')
use_base_path = 0;
if (use_base_path) {
base_path_end = ub.url_component_end_path;
if (URL_COMPONENT_HAVE(uc, path))
while (base_path_end > ub.path && base_path_end[-1] != '/')
base_path_end--;
}
/* If rel actually is an absolute url, just copy it */
if (!base || strstr(rel, "://") || rel[0] == '/') {
memset(buf, 0, size);
trim_double_dot_url(buf, rel, size);
return;
}
if (base != buf)
av_strlcpy(buf, base, size);

/* Strip off any query string from base */
path_query = strchr(buf, '?');
if (path_query)
*path_query = '\0';

/* Is relative path just a new query part? */
if (rel[0] == '?') {
av_strlcat(buf, rel, size);
trim_double_dot_url(tmp_path, buf, size);
memset(buf, 0, size);
av_strlcpy(buf, tmp_path, size);
return;
}

root = p = buf;
/* Get the path root of the url which start by "://" */
if (p && strstr(p, "://")) {
sep = strstr(p, "://");
if (sep) {
sep += 3;
root = strchr(sep, '/');
if (!root)
return;
if (keep > ub.path)
simplify_path = 0;
if (URL_COMPONENT_HAVE(uc, scheme))
simplify_path = 0;
if (URL_COMPONENT_HAVE(uc, authority))
simplify_path = 1;
/* No path at all, leave it */
if (!use_base_path && !URL_COMPONENT_HAVE(uc, path))
simplify_path = 0;

if (simplify_path) {
const char *root = "/";
COPY(root, root + 1);
path = out;
if (use_base_path) {
ret = append_path(path, out_end, &out, ub.path, base_path_end);
if (ret < 0)
goto error;
}
if (URL_COMPONENT_HAVE(uc, path)) {
ret = append_path(path, out_end, &out, uc.path, uc.url_component_end_path);
if (ret < 0)
goto error;
}
} else {
if (use_base_path)
COPY(ub.path, base_path_end);
COPY(uc.path, uc.url_component_end_path);
}

/* Remove the file name from the base url */
sep = strrchr(buf, '/');
if (sep && sep <= root)
sep = root;

if (sep)
sep[1] = '\0';
else
buf[0] = '\0';
while (av_strstart(rel, "..", NULL) && sep) {
/* Remove the path delimiter at the end */
if (sep > root) {
sep[0] = '\0';
sep = strrchr(buf, '/');
}
COPY(uc.url_component_end_path, uc.end);
#undef COPY
*out = 0;
return 0;

/* If the next directory name to pop off is "..", break here */
if (!strcmp(sep ? &sep[1] : buf, "..")) {
/* Readd the slash we just removed */
av_strlcat(buf, "/", size);
break;
}
/* Cut off the directory name */
if (sep)
sep[1] = '\0';
else
buf[0] = '\0';
rel += 3;
}
av_strlcat(buf, rel, size);
trim_double_dot_url(tmp_path, buf, size);
memset(buf, 0, size);
av_strlcpy(buf, tmp_path, size);
error:
snprintf(buf, size, "invalid:%s",
ret == AVERROR(ENOMEM) ? "truncated" :
ret == AVERROR(EINVAL) ? "syntax_error" : "");
return ret;
}

AVIODirEntry *ff_alloc_dir_entry(void)
Expand Down
4 changes: 2 additions & 2 deletions libavformat/url.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -312,8 +312,8 @@ int ff_url_join(char *str, int size, const char *proto,
* @param base the base url, may be equal to buf.
* @param rel the new url, which is interpreted relative to base
*/
void ff_make_absolute_url(char *buf, int size, const char *base,
const char *rel);
int ff_make_absolute_url(char *buf, int size, const char *base,
const char *rel);

/**
* Allocate directory entry with default values.
Expand Down
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