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| author | Kevin Backhouse via RT <security-reports@semmle.com> | 2019-02-06 12:56:01 +0000 |
|---|---|---|
| committer | Michael Niedermayer <michael@niedermayer.cc> | 2019-02-17 10:29:42 +0100 |
| commit | 894995c41e0795c7a44f81adc4838dedc3932e65 (patch) | |
| tree | 9e44a81b7a109504fb2cedfd271ca79146dc8dcf | |
| parent | 1f00c97bc3475c477f3c468cf2d924d5761d0982 (diff) | |
| download | ffmpeg-894995c41e0795c7a44f81adc4838dedc3932e65.tar.gz | |
avcodec/htmlsubtitles: Fixes denial of service due to use of sscanf in inner loop for handling braces
Fixes: [Semmle Security Reports #19439]
Fixes: dos_sscanf2.mkv
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
| -rw-r--r-- | libavcodec/htmlsubtitles.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/libavcodec/htmlsubtitles.c b/libavcodec/htmlsubtitles.c index c0cfccfb16..d9221ba16b 100644 --- a/libavcodec/htmlsubtitles.c +++ b/libavcodec/htmlsubtitles.c @@ -24,6 +24,7 @@ #include "libavutil/common.h" #include "libavutil/parseutils.h" #include "htmlsubtitles.h" +#include <ctype.h> static int html_color_parse(void *log_ctx, const char *str) { @@ -44,14 +45,32 @@ static void rstrip_spaces_buf(AVBPrint *buf) buf->str[--buf->len] = 0; } +/* + * Fast code for scanning text enclosed in braces. Functionally + * equivalent to this sscanf call: + * + * sscanf(in, "{\\an%*1u}%n", &len) >= 0 && len > 0 + */ +static int scanbraces(const char* in) { + if (strncmp(in, "{\\an", 4) != 0) { + return 0; + } + if (!isdigit(in[4])) { + return 0; + } + if (in[5] != '}') { + return 0; + } + return 1; +} + /* skip all {\xxx} substrings except for {\an%d} and all microdvd like styles such as {Y:xxx} */ static void handle_open_brace(AVBPrint *dst, const char **inp, int *an, int *closing_brace_missing) { - int len = 0; const char *in = *inp; - *an += sscanf(in, "{\\an%*1u}%n", &len) >= 0 && len > 0; + *an += scanbraces(in); if (!*closing_brace_missing) { if ( (*an != 1 && in[1] == '\\') |