Punycode decoding implementation

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9654)

crypto/build.info

@@ -78,6 +78,7 @@ SOURCE[../libcrypto]=$UTIL_COMMON \
         mem.c mem_sec.c \
         cversion.c info.c cpt_err.c ebcdic.c uid.c o_time.c o_dir.c \
         o_fopen.c getenv.c o_init.c init.c trace.c provider.c \
+        punycode.c \
         $UPLINKSRC
 SOURCE[../providers/libfips.a]=$UTIL_COMMON
 SOURCE[../providers/liblegacy.a]=$UTIL_COMMON

crypto/punycode.c

@@ -0,0 +1,338 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <stddef.h>
+#include <string.h>
+#include <stdio.h>
+#include <openssl/e_os2.h>
+#include "crypto/punycode.h"
+
+static const unsigned int base = 36;
+static const unsigned int tmin = 1;
+static const unsigned int tmax = 26;
+static const unsigned int skew = 38;
+static const unsigned int damp = 700;
+static const unsigned int initial_bias = 72;
+static const unsigned int initial_n = 0x80;
+static const unsigned int maxint = 0xFFFFFFFF;
+static const char delimiter = '-';
+
+#define LABEL_BUF_SIZE 512
+
+/*-
+ * Pseudocode:
+ *
+ * function adapt(delta,numpoints,firsttime):
+ *  if firsttime then let delta = delta div damp
+ *  else let delta = delta div 2
+ *  let delta = delta + (delta div numpoints)
+ *  let k = 0
+ *  while delta > ((base - tmin) * tmax) div 2 do begin
+ *    let delta = delta div (base - tmin)
+ *    let k = k + base
+ *  end
+ *  return k + (((base - tmin + 1) * delta) div (delta + skew))
+ */
+
+static int adapt(unsigned int delta, unsigned int numpoints,
+                 unsigned int firsttime)
+{
+    unsigned int k = 0;
+
+    delta = (firsttime) ? delta / damp : delta / 2;
+    delta = delta + delta / numpoints;
+
+    while (delta > ((base - tmin) * tmax) / 2) {
+        delta = delta / (base - tmin);
+        k = k + base;
+    }
+
+    return k + (((base - tmin + 1) * delta) / (delta + skew));
+}
+
+static ossl_inline int is_basic(unsigned int a)
+{
+    return (a < 0x80) ? 1 : 0;
+}
+
+/*-
+ * code points    digit-values
+ * ------------   ----------------------
+ * 41..5A (A-Z) =  0 to 25, respectively
+ * 61..7A (a-z) =  0 to 25, respectively
+ * 30..39 (0-9) = 26 to 35, respectively
+ */
+static ossl_inline int digit_decoded(const unsigned char a)
+{
+    if (a >= 0x41 && a <= 0x5A)
+        return a - 0x41;
+
+    if (a >= 0x61 && a <= 0x7A)
+        return a - 0x61;
+
+    if (a >= 0x30 && a <= 0x39)
+        return a - 0x30 + 26;
+
+    return -1;
+}
+
+/*-
+ * Pseudocode:
+ *
+ * function ossl_punycode_decode
+ *  let n = initial_n
+ *  let i = 0
+ *  let bias = initial_bias
+ *  let output = an empty string indexed from 0
+ *  consume all code points before the last delimiter (if there is one)
+ *    and copy them to output, fail on any non-basic code point
+ *  if more than zero code points were consumed then consume one more
+ *    (which will be the last delimiter)
+ *  while the input is not exhausted do begin
+ *    let oldi = i
+ *    let w = 1
+ *    for k = base to infinity in steps of base do begin
+ *      consume a code point, or fail if there was none to consume
+ *      let digit = the code point's digit-value, fail if it has none
+ *      let i = i + digit * w, fail on overflow
+ *      let t = tmin if k <= bias {+ tmin}, or
+ *              tmax if k >= bias + tmax, or k - bias otherwise
+ *      if digit < t then break
+ *      let w = w * (base - t), fail on overflow
+ *    end
+ *    let bias = adapt(i - oldi, length(output) + 1, test oldi is 0?)
+ *    let n = n + i div (length(output) + 1), fail on overflow
+ *    let i = i mod (length(output) + 1)
+ *    {if n is a basic code point then fail}
+ *    insert n into output at position i
+ *    increment i
+ *  end
+ */
+
+int ossl_punycode_decode(const char *pEncoded, const size_t enc_len,
+                         unsigned int *pDecoded, unsigned int *pout_length)
+{
+    unsigned int n = initial_n;
+    unsigned int i = 0;
+    unsigned int bias = initial_bias;
+    size_t processed_in = 0, written_out = 0;
+    unsigned int max_out = *pout_length;
+
+    unsigned int basic_count = 0;
+    unsigned int loop;
+
+    for (loop = 0; loop < enc_len; loop++) {
+        if (pEncoded[loop] == delimiter)
+            basic_count = loop;
+    }
+
+    if (basic_count > 0) {
+        if (basic_count > max_out)
+            return 0;
+
+        for (loop = 0; loop < basic_count; loop++) {
+            if (is_basic(pEncoded[loop]) == 0)
+                return 0;
+
+            pDecoded[loop] = pEncoded[loop];
+            written_out++;
+        }
+        processed_in = basic_count + 1;
+    }
+
+    for (loop = processed_in; loop < enc_len;) {
+        unsigned int oldi = i;
+        unsigned int w = 1;
+        unsigned int k, t;
+        int digit;
+
+        for (k = base;; k += base) {
+            if (loop >= enc_len)
+                return 0;
+
+            digit = digit_decoded(pEncoded[loop]);
+            loop++;
+
+            if (digit < 0)
+                return 0;
+            if ((unsigned int)digit > (maxint - i) / w)
+                return 0;
+
+            i = i + digit * w;
+            t = (k <= bias) ? tmin : (k >= bias + tmax) ? tmax : k - bias;
+
+            if ((unsigned int)digit < t)
+                break;
+
+            if (w > maxint / (base - t))
+                return 0;
+            w = w * (base - t);
+        }
+
+        bias = adapt(i - oldi, written_out + 1, (oldi == 0));
+        if (i / (written_out + 1) > maxint - n)
+            return 0;
+        n = n + i / (written_out + 1);
+        i %= (written_out + 1);
+
+        if (written_out > max_out)
+            return 0;
+
+        memmove(pDecoded + i + 1, pDecoded + i,
+                (written_out - i) * sizeof *pDecoded);
+        pDecoded[i] = n;
+        i++;
+        written_out++;
+    }
+
+    *pout_length = written_out;
+    return 1;
+}
+
+/*
+ * Encode a code point using UTF-8
+ * return number of bytes on success, 0 on failure
+ * (also produces U+FFFD, which uses 3 bytes on failure)
+ */
+static int codepoint2utf8(unsigned char *out, unsigned long utf)
+{
+    if (utf <= 0x7F) {
+        /* Plain ASCII */
+        out[0] = (unsigned char)utf;
+        out[1] = 0;
+        return 1;
+    } else if (utf <= 0x07FF) {
+        /* 2-byte unicode */
+        out[0] = (unsigned char)(((utf >> 6) & 0x1F) | 0xC0);
+        out[1] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);
+        out[2] = 0;
+        return 2;
+    } else if (utf <= 0xFFFF) {
+        /* 3-byte unicode */
+        out[0] = (unsigned char)(((utf >> 12) & 0x0F) | 0xE0);
+        out[1] = (unsigned char)(((utf >> 6) & 0x3F) | 0x80);
+        out[2] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);
+        out[3] = 0;
+        return 3;
+    } else if (utf <= 0x10FFFF) {
+        /* 4-byte unicode */
+        out[0] = (unsigned char)(((utf >> 18) & 0x07) | 0xF0);
+        out[1] = (unsigned char)(((utf >> 12) & 0x3F) | 0x80);
+        out[2] = (unsigned char)(((utf >> 6) & 0x3F) | 0x80);
+        out[3] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);
+        out[4] = 0;
+        return 4;
+    } else {
+        /* error - use replacement character */
+        out[0] = (unsigned char)0xEF;
+        out[1] = (unsigned char)0xBF;
+        out[2] = (unsigned char)0xBD;
+        out[3] = 0;
+        return 0;
+    }
+}
+
+/*-
+ * Return values:
+ * 1 - ok, *outlen contains valid buf length
+ * 0 - ok but buf was too short, *outlen contains valid buf length
+ * -1 - bad string passed
+ */
+
+int ossl_a2ulabel(const char *in, char *out, size_t *outlen)
+{
+    /*-
+     * Domain name has some parts consisting of ASCII chars joined with dot.
+     * If a part is shorter than 5 chars, it becomes U-label as is.
+     * If it does not start with xn--,    it becomes U-label as is.
+     * Otherwise we try to decode it.
+     */
+    char *outptr = out;
+    const char *inptr = in;
+    size_t size = 0;
+    int result = 1;
+
+    unsigned int buf[LABEL_BUF_SIZE];      /* It's a hostname */
+    if (out == NULL)
+        result = 0;
+
+    while (1) {
+        char *tmpptr = strchr(inptr, '.');
+        size_t delta = (tmpptr) ? (size_t)(tmpptr - inptr) : strlen(inptr);
+
+        if (strncmp(inptr, "xn--", 4) != 0) {
+            size += delta + 1;
+
+            if (size >= *outlen - 1)
+                result = 0;
+
+            if (result > 0) {
+                memcpy(outptr, inptr, delta + 1);
+                outptr += delta + 1;
+            }
+        } else {
+            unsigned int bufsize = LABEL_BUF_SIZE;
+            unsigned int i;
+
+            if (ossl_punycode_decode(inptr + 4, delta - 4, buf, &bufsize) <= 0)
+                return -1;
+
+            for (i = 0; i < bufsize; i++) {
+                unsigned char seed[6];
+                size_t utfsize = codepoint2utf8(seed, buf[i]);
+                if (utfsize == 0)
+                    return -1;
+
+                size += utfsize;
+                if (size >= *outlen - 1)
+                    result = 0;
+
+                if (result > 0) {
+                    memcpy(outptr, seed, utfsize);
+                    outptr += utfsize;
+                }
+            }
+
+            if (tmpptr != NULL) {
+                *outptr = '.';
+                outptr++;
+                size++;
+                if (size >= *outlen - 1)
+                    result = 0;
+            }
+        }
+
+        if (tmpptr == NULL)
+            break;
+
+        inptr = tmpptr + 1;
+    }
+
+    return result;
+}
+
+/*-
+ * a MUST be A-label
+ * u MUST be U-label
+ * Returns 0 if compared values are equal
+ * 1 if not
+ * -1 in case of errors
+ */
+
+int ossl_a2ucompare(const char *a, const char *u)
+{
+    char a_ulabel[LABEL_BUF_SIZE];
+    size_t a_size = sizeof(a_ulabel);
+
+    if (ossl_a2ulabel(a, a_ulabel, &a_size) <= 0) {
+        return -1;
+    }
+
+    return (strcmp(a_ulabel, u) == 0) ? 0 : 1;
+}

include/crypto/punycode.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef OSSL_CRYPTO_PUNYCODE_H
+# define OSSL_CRYPTO_PUNYCODE_H
+
+
+int ossl_punycode_decode (
+	const char *pEncoded,
+	const size_t enc_len,
+	unsigned int *pDecoded,
+	unsigned int *pout_length
+);
+
+int ossl_a2ulabel(const char *in, char *out, size_t *outlen);
+
+int ossl_a2ucompare(const char *a, const char *u);
+#endif