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busybox-static.20467
wget-more-thorough-sanitization-of-other-side-s...
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File wget-more-thorough-sanitization-of-other-side-s-data.patch of Package busybox-static.20467
From: Denys Vlasenko <vda.linux@googlemail.com> Date: Mon Feb 12 16:46:13 2018 +0100 Subject: wget: more thorough sanitization of other side's data Patch-mainline: 3459024bf404af814cacfe90a0deb719e282ae62 Git-repo: https://git.busybox.net/busybox Git-commit: d997c35c7b02cd02e1bc476385cc6fb3d9357930 References: function old new delta get_sanitized_hdr - 156 +156 fgets_trim_sanitize - 128 +128 ftpcmd 129 133 +4 parse_url 461 454 -7 sanitize_string 14 - -14 wget_main 2431 2381 -50 fgets_and_trim 119 - -119 gethdr 163 - -163 ------------------------------------------------------------------------------ (add/remove: 2/3 grow/shrink: 1/2 up/down: 288/-353) Total: -65 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> Signed-off-by: Egbert Eich <eich@suse.de> --- networking/wget.c | 74 +++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 47 insertions(+), 27 deletions(-) diff --git a/networking/wget.c b/networking/wget.c index f3a923221..b5cf2c21f 100644 --- a/networking/wget.c +++ b/networking/wget.c @@ -325,15 +325,6 @@ static char *base64enc(const char *str) } #endif -static char* sanitize_string(char *s) -{ - unsigned char *p = (void *) s; - while (*p >= ' ') - p++; - *p = '\0'; - return s; -} - #if ENABLE_FEATURE_WGET_TIMEOUT static void alarm_handler(int sig UNUSED_PARAM) { @@ -396,22 +387,49 @@ static FILE *open_socket(len_and_sockaddr *lsa) return fp; } +/* We balk at any control chars in other side's messages. + * This prevents nasty surprises (e.g. ESC sequences) in "Location:" URLs + * and error messages. + * + * The only exception is tabs, which are converted to (one) space: + * HTTP's "headers: <whitespace> values" may have those. + */ +static char* sanitize_string(char *s) +{ + unsigned char *p = (void *) s; + while (*p) { + if (*p < ' ') { + if (*p != '\t') + break; + *p = ' '; + } + p++; + } + *p = '\0'; + return s; +} + /* Returns '\n' if it was seen, else '\0'. Trims at first '\r' or '\n' */ -static char fgets_and_trim(FILE *fp, const char *fmt) +static char fgets_trim_sanitize(FILE *fp, const char *fmt) { char c; char *buf_ptr; set_alarm(); - if (fgets(G.wget_buf, sizeof(G.wget_buf) - 1, fp) == NULL) + if (fgets(G.wget_buf, sizeof(G.wget_buf), fp) == NULL) bb_perror_msg_and_die("error getting response"); clear_alarm(); buf_ptr = strchrnul(G.wget_buf, '\n'); c = *buf_ptr; +#if 1 + /* Disallow any control chars: trim at first char < 0x20 */ + sanitize_string(G.wget_buf); +#else *buf_ptr = '\0'; buf_ptr = strchrnul(G.wget_buf, '\r'); *buf_ptr = '\0'; +#endif log_io("< %s", G.wget_buf); @@ -435,8 +453,10 @@ static int ftpcmd(const char *s1, const char *s2, FILE *fp) log_io("> %s%s", s1, s2); } + /* Read until "Nxx something" is received */ + G.wget_buf[3] = 0; do { - fgets_and_trim(fp, "%s\n"); + fgets_trim_sanitize(fp, "%s\n"); } while (!isdigit(G.wget_buf[0]) || G.wget_buf[3] != ' '); G.wget_buf[3] = '\0'; @@ -472,7 +492,7 @@ static void parse_url(const char *src_url, struct host_info *h) h->protocol = P_HTTP; } else { *p = ':'; - bb_error_msg_and_die("not an http or ftp url: %s", sanitize_string(url)); + bb_error_msg_and_die("not an http or ftp url: %s", url); } } else { // GNU wget is user-friendly and falls back to http:// @@ -527,13 +547,13 @@ static void parse_url(const char *src_url, struct host_info *h) */ } -static char *gethdr(FILE *fp) +static char *get_sanitized_hdr(FILE *fp) { char *s, *hdrval; int c; /* retrieve header line */ - c = fgets_and_trim(fp, " %s\n"); + c = fgets_trim_sanitize(fp, " %s\n"); /* end of the headers? */ if (G.wget_buf[0] == '\0') @@ -555,7 +575,7 @@ static char *gethdr(FILE *fp) /* verify we are at the end of the header name */ if (*s != ':') - bb_error_msg_and_die("bad header line: %s", sanitize_string(G.wget_buf)); + bb_error_msg_and_die("bad header line: %s", G.wget_buf); /* locate the start of the header value */ *s++ = '\0'; @@ -888,9 +908,9 @@ static void NOINLINE retrieve_file_data(FILE *dfp) if (!G.chunked) break; - fgets_and_trim(dfp, NULL); /* Eat empty line */ + fgets_trim_sanitize(dfp, NULL); /* Eat empty line */ get_clen: - fgets_and_trim(dfp, NULL); + fgets_trim_sanitize(dfp, NULL); G.content_len = STRTOOFF(G.wget_buf, NULL, 16); /* FIXME: error check? */ if (G.content_len == 0) @@ -1112,7 +1132,7 @@ static void download_one_url(const char *url) * Retrieve HTTP response line and check for "200" status code. */ read_response: - fgets_and_trim(sfp, " %s\n"); + fgets_trim_sanitize(sfp, " %s\n"); str = G.wget_buf; str = skip_non_whitespace(str); @@ -1123,7 +1143,7 @@ static void download_one_url(const char *url) switch (status) { case 0: case 100: - while (gethdr(sfp) != NULL) + while (get_sanitized_hdr(sfp) != NULL) /* eat all remaining headers */; goto read_response; @@ -1187,13 +1207,13 @@ However, in real world it was observed that some web servers /* Partial Content even though we did not ask for it??? */ /* fall through */ default: - bb_error_msg_and_die("server returned error: %s", sanitize_string(G.wget_buf)); + bb_error_msg_and_die("server returned error: %s", G.wget_buf); } /* * Retrieve HTTP headers. */ - while ((str = gethdr(sfp)) != NULL) { + while ((str = get_sanitized_hdr(sfp)) != NULL) { static const char keywords[] ALIGN1 = "content-length\0""transfer-encoding\0""location\0"; enum { @@ -1201,7 +1221,7 @@ However, in real world it was observed that some web servers }; smalluint key; - /* gethdr converted "FOO:" string to lowercase */ + /* get_sanitized_hdr converted "FOO:" string to lowercase */ /* strip trailing whitespace */ char *s = strchrnul(str, '\0') - 1; @@ -1213,14 +1233,14 @@ However, in real world it was observed that some web servers if (key == KEY_content_length) { G.content_len = BB_STRTOOFF(str, NULL, 10); if (G.content_len < 0 || errno) { - bb_error_msg_and_die("content-length %s is garbage", sanitize_string(str)); + bb_error_msg_and_die("content-length %s is garbage", str); } G.got_clen = 1; continue; } if (key == KEY_transfer_encoding) { if (strcmp(str_tolower(str), "chunked") != 0) - bb_error_msg_and_die("transfer encoding '%s' is not supported", sanitize_string(str)); + bb_error_msg_and_die("transfer encoding '%s' is not supported", str); G.chunked = 1; } if (key == KEY_location && status >= 300) { @@ -1229,7 +1249,7 @@ However, in real world it was observed that some web servers fclose(sfp); if (str[0] == '/') { free(redirected_path); - target.path = redirected_path = xstrdup(str+1); + target.path = redirected_path = xstrdup(str + 1); /* lsa stays the same: it's on the same server */ } else { parse_url(str, &target); @@ -1276,7 +1296,7 @@ However, in real world it was observed that some web servers /* It's ftp. Close data connection properly */ fclose(dfp); if (ftpcmd(NULL, NULL, sfp) != 226) - bb_error_msg_and_die("ftp error: %s", sanitize_string(G.wget_buf + 4)); + bb_error_msg_and_die("ftp error: %s", G.wget_buf); /* ftpcmd("QUIT", NULL, sfp); - why bother? */ } fclose(sfp);
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