ffmpeg | branch: master | Kevin Backhouse via RT <security-repo...@semmle.com> | Wed Feb 6 12:56:01 2019 +0000| [894995c41e0795c7a44f81adc4838dedc3932e65] | committer: Michael Niedermayer
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 <mich...@niedermayer.cc> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=894995c41e0795c7a44f81adc4838dedc3932e65 --- libavcodec/htmlsubtitles.c | 23 +++++++++++++++++++++-- 1 file 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] == '\\') _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
