From fd19a3d195be23e8d9d0d66576b96ea25eea8323 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 29 Jul 2015 16:58:32 +0100 Subject: PKCS#7: Improve and export the X.509 ASN.1 time object decoder Make the X.509 ASN.1 time object decoder fill in a time64_t rather than a struct tm to make comparison easier (unfortunately, this makes readable display less easy) and export it so that it can be used by the PKCS#7 code too. Further, tighten up its parsing to reject invalid dates (eg. weird characters, non-existent hour numbers) and unsupported dates (eg. timezones other than 'Z' or dates earlier than 1970). Signed-off-by: David Howells Reviewed-by: David Woodhouse --- crypto/asymmetric_keys/x509_cert_parser.c | 87 +++++++++++++++++++++++-------- 1 file changed, 66 insertions(+), 21 deletions(-) (limited to 'crypto/asymmetric_keys/x509_cert_parser.c') diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c index 849fd760923e..af71878dc15b 100644 --- a/crypto/asymmetric_keys/x509_cert_parser.c +++ b/crypto/asymmetric_keys/x509_cert_parser.c @@ -472,60 +472,105 @@ int x509_process_extension(void *context, size_t hdrlen, return 0; } -/* - * Record a certificate time. +/** + * x509_decode_time - Decode an X.509 time ASN.1 object + * @_t: The time to fill in + * @hdrlen: The length of the object header + * @tag: The object tag + * @value: The object value + * @vlen: The size of the object value + * + * Decode an ASN.1 universal time or generalised time field into a struct the + * kernel can handle and check it for validity. The time is decoded thus: + * + * [RFC5280 ยง4.1.2.5] + * CAs conforming to this profile MUST always encode certificate validity + * dates through the year 2049 as UTCTime; certificate validity dates in + * 2050 or later MUST be encoded as GeneralizedTime. Conforming + * applications MUST be able to process validity dates that are encoded in + * either UTCTime or GeneralizedTime. */ -static int x509_note_time(struct tm *tm, size_t hdrlen, - unsigned char tag, - const unsigned char *value, size_t vlen) +int x509_decode_time(time64_t *_t, size_t hdrlen, + unsigned char tag, + const unsigned char *value, size_t vlen) { + static const unsigned char month_lengths[] = { 31, 29, 31, 30, 31, 30, + 31, 31, 30, 31, 30, 31 }; const unsigned char *p = value; + unsigned year, mon, day, hour, min, sec, mon_len; -#define dec2bin(X) ((X) - '0') +#define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; }) #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; }) if (tag == ASN1_UNITIM) { /* UTCTime: YYMMDDHHMMSSZ */ if (vlen != 13) goto unsupported_time; - tm->tm_year = DD2bin(p); - if (tm->tm_year >= 50) - tm->tm_year += 1900; + year = DD2bin(p); + if (year >= 50) + year += 1900; else - tm->tm_year += 2000; + year += 2000; } else if (tag == ASN1_GENTIM) { /* GenTime: YYYYMMDDHHMMSSZ */ if (vlen != 15) goto unsupported_time; - tm->tm_year = DD2bin(p) * 100 + DD2bin(p); + year = DD2bin(p) * 100 + DD2bin(p); + if (year >= 1950 && year <= 2049) + goto invalid_time; } else { goto unsupported_time; } - tm->tm_year -= 1900; - tm->tm_mon = DD2bin(p) - 1; - tm->tm_mday = DD2bin(p); - tm->tm_hour = DD2bin(p); - tm->tm_min = DD2bin(p); - tm->tm_sec = DD2bin(p); + mon = DD2bin(p); + day = DD2bin(p); + hour = DD2bin(p); + min = DD2bin(p); + sec = DD2bin(p); if (*p != 'Z') goto unsupported_time; + mon_len = month_lengths[mon]; + if (mon == 2) { + if (year % 4 == 0) { + mon_len = 29; + if (year % 100 == 0) { + year /= 100; + if (year % 4 != 0) + mon_len = 28; + } + } + } + + if (year < 1970 || + mon < 1 || mon > 12 || + day < 1 || day > mon_len || + hour < 0 || hour > 23 || + min < 0 || min > 59 || + sec < 0 || sec > 59) + goto invalid_time; + + *_t = mktime64(year, mon, day, hour, min, sec); return 0; unsupported_time: - pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n", - tag, (int)vlen, (int)vlen, value); + pr_debug("Got unsupported time [tag %02x]: '%*phN'\n", + tag, (int)vlen, value); + return -EBADMSG; +invalid_time: + pr_debug("Got invalid time [tag %02x]: '%*phN'\n", + tag, (int)vlen, value); return -EBADMSG; } +EXPORT_SYMBOL_GPL(x509_decode_time); int x509_note_not_before(void *context, size_t hdrlen, unsigned char tag, const void *value, size_t vlen) { struct x509_parse_context *ctx = context; - return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen); + return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen); } int x509_note_not_after(void *context, size_t hdrlen, @@ -533,7 +578,7 @@ int x509_note_not_after(void *context, size_t hdrlen, const void *value, size_t vlen) { struct x509_parse_context *ctx = context; - return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen); + return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen); } /* -- cgit v1.2.3-55-g7522